vvEPA
United States
Environmental Protection
Agency
Office of Acid Deposition,
Environmental Monitoring and
Quality Assurance
Washington DC 20460
EPA/600/4-86/009
February 1986
Research and Development
Eastern Lake Survey
Phase I
Analytical Methods
Manual
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EPA 600/4-86/009
February 1986
Eastern Lake Survey
Phase I
Analytical Methods Manual
A Contribution to the
National Acid Precipitation Assessment Program
**
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
Environmental Monitoring Systems Laboratory - Las Vegas, NV 89114
Environmental Research Laboratory - Corvallls, OR 97333
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NOTICE
The information in this document has been funded wholly or in part by the U.S. Environmental Protection
Agency (EPA) under Contract No. 68-03-3249 and 68-03-3050 to Lockheed Engineering and Management Services
Company, Inc., No. 68-02-3889 to Radian Corporation, No. 68-03-3246 to Northrop Services, Inc., and Interagency
Agreement No. 40-1441-84 with the U.S. Department of Energy. It has been approved for publication as an EPA
document.
Mention of corporation names, trade names or commercial products does not constitute endorsement or rec-
ommendation for use.
This document has been published previously. As part of the AERP Technical Information Program, this docu-
ment has been repackaged and retitled to clearly identify its relationship to other documents produced for the
Eastern Lake Survey. The document contents and reference number have not changed. Proper citation of this
document remains:
Hillman, D. C., J. F. Potter, and S. J. Simon. National Surface Water Survey, Eastern Lake Survey (Phase I -
Synoptic Chemistry) Analytical Methods Manual. EPA-600/4-86-009, U.S. Environmental Protection Agency, Las
Vegas, NV, 1986.
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ABSTRACT
The National Surface Water Survey of the National Acid Precipitation Assessment Program is a three-phase
project to evaluate the current water chemistry of lakes and streams, determine the status of fisheries and other
biotic resources, and select regionally representative surface waters for a long-term monitoring program to
study changes in aquatic resources. The Eastern Lake Survey is part of Phase I of the National Surface Water
Survey lake study.
The U.S. Environmental Protection Agency requires that data collection activities be based on a program which
ensures that the resulting data are of known quality and are suitable for the purpose for which they are intended.
In addition, it is necessary that the data obtained be consistent and comparable throughout the survey. For
these reasons, the same reliable, detailed analytical methodology must be available to and used by all analysts
participating in the study.
This manual provides details of the analytical methods and internal qual ity control used to process and analyze
samples for the Eastern Lake Survey. The determinations and methods described are the following:
Parameter
1. Acidity
2. Alkalinity
3. Aluminum, total
4. Aluminum, total extractable
5. Ammonium, dissolved
6. Calcium, dissolved
7. Chloride, dissolved
8. Fluoride, total dissolved
9. Inorganic carbon, dissolved
10. Iron, dissolved
11. Magnesium, dissolved
12. Manganese, dissolved
13. Nitrate, dissolved
14. Organic carbon, dissolved
15. pH
16. Phosphorus, total
17. Potassium, dissolved
18. Silica, dissolved
19. Sodium, dissolved
20. Sulfate, dissolved
21. Specific conductance
22. True color
23. Turbidity
Method
Titration with Gran analysis
Titration with Gran analysis
202.2 AAS (furnace)
Extraction with 8-hydroxyquinoline into MIBKfollowed by
AAS (furnace)
Automated colorimetry (phenate)
AAS (flame) or ICPES
Ion chromatography
Ion-selective electrode and meter
Instrumental (acidification, CO2generation, IR detection)
AAS (flame) or ICPES
AAS (flame) or ICPES
AAS (flame) or ICPES
Ion chromatography
Instrumental (uv-promoted oxidation, CO2generation, IR
detection)
pH electrode and meter
Automated colorimetry (phosphomolybdate)
AAS (flame)
Automated colorimetry (molybdate blue)
AAS (flame)
Ion chromatography
Conductivity cell and meter
Comparison to Platinum-Cobalt color standards
Instrumental (nephelometer)
Hi
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TABLE OF CONTENTS
Section Page
Notice ii
Abstract iii
Figures xii
Tables xiii
Acknowledgement xiv
1.0 INTRODUCTION 1
1.1 Background 1
1.2 Physical Parameters and Analytes Measured 3
1.2.1 CO2 Acidity (acidity) 3
1.2.2 Alkalinity 3
1.2.3 Aluminum, Total Extractable 3
1.2.4 Aluminum, Total 3
1.2.5 Dissolved Inorganic Carbon 3
1.2.6 Dissolved Ions (Na, K, Ca, Mg, Fe, Mn, NH4+, F, CI', SO/.and NO3)... 4
1.2.7 Dissolved Organic Carbon 4
1.2.8 Dissolved Silica (SiO2) 5
1.2.9 pH 5
1.2.10 Specific Conductance 5
1.2.11 Total Phosphorus 5
1.2.12 True Color 5
1.2.13 Turbidity 5
1.3 References 5
2.0 FIELD OPERATIONS 6
2.1 Personnel 6
2.2 Daily Operation 6
2.2.1 Activities Before Sample Arrival 6
2.2.2 Activities Following Sample Arrival 6
2.3 Determination of DIG 14
2.3.1 Scope and Application 14
2.3.2 Summary of Method 17
2.3.3 Interferences 17
2.3.4 Safety 17
iv
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2.3.5 Apparatus and Equipment
2.3.6 Reagents and Consumable Materials
2.3.7 Sample Collection, Preservation, and Storage
2.3.8 Calibration and Standardization
2.3.9 Quality Control
2.3.10 Procedure
2.3.1 1 Calculations
2.3.12 Reporting
2.4 Determination of pH
2.4.1 Scope and Application
2.4.2 Summary of Method
2.4.3 interferences
2.4.4 Safety
2.4.5 Apparatus and Equipment ,
2.4.6 Reagents and Consumable Materials
2.4.7 Sample Collection, Preservation, and Storage
2.4.8 Calibration and Standardization
2.4.9 Quality Control
2.4.10 Procedure
2.4.1 1 Calculations
2.4.12 Reporting
2.5 Determination of Turbidity
2.5.1 Scope and Application
2.5.2 Summary of Method
2.5.3 Interferences
2.5.4 Safety
2.5.5 Apparatus and Equipment
2.5.6 Reagents and Consumable Materials
2.5.7 Sample Collection, Preservation, and Storage
2.5.8 Calibration and Standardization
2.5.9 Quality Control
2.5.10 Procedure
2.5.1 1 Calculations
2.5.12 Reporting
2.6 Determination of True Color
2.6.1 Scope and Application
2.6.2 Summary of Method
2.6.3 interferences
2.6.4 Safety
2.6.5 Apparatus and Equipment
2.6.6 Reagents and Consumable Materials
2.6.7 Sample Collection, Preservation, and Storage
2.6.8 Calibration and Standardization
17
17
17
18
18
20
20
20
20
20
20
20
20
20
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23
23
25
25
25
25
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29
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2.6.9 Quality Control 29
2.6.10 Procedure 29
2.6.11 Calculations 29
2.6.12 Reporting 29
2.7 Aliquot and Split Sample Preparation 29
2.7.1 Summary 29
2.7.2 Safety 29
2.7.3 Apparatus and Equipment 29
2.7.4 Reagents and Consumable Materials 31
2.7.5 Procedure 31
2.8 References 33
3.0 ANALYTICAL LABORATORY OPERATIONS 35
3.1 Summary of Operations 35
3.2 Sample Receipt and Handling 35
3.3 Sample Analysis 36
3.4 Internal Quality Control Requirements 36
3.4.1 Method Quality Control 36
3,4.2 Overall Internal Quality Control 40
3.5 Data Reporting 42
3.6 References 43
4.0 DETERMINATION OF ACIDITY, ALKALINITY, AND pH 46
4.1 Scope and Application 46
4.2 Summary of Method 46
4.3 Interferences 46
4.4 Safety 46
4.5 Apparatus and Equipment 46
4.6 Reagents and Consumable Materials 47
4.7 Sample Collection, Preservation, and Storage 48
4.8 Calibration and Standardization 48
4.8.1 Standardization of HCI Titrant 48
4.8.2 Standardization of NaOH Titrant 49
4.8.3 Calibration and Characterization of Electrodes 52
4.9 Quality Control 54
4.9.1 Duplicate Analysis 54
4.9.2 Blank Analysis 54
4.9.3 pH QCCS 55
4.9.4 Comparison of Initial Titration pH Values 55
4.9.5 Comparison of Calculated Alkalinity and Measured Alkalinity 55
4.9.6 Comparison of Calculated Acidity and Measured Acidity 56
4.9.7 Comparison of Calculated Total Carbonate and Measured Total
Carbonate 57
4.10 Procedure 58
4.10.1 Acid Titration 57
vi
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4.10.2 Base Titration
4.10.3 Air-Equilibrated pH Measurement
4.11 Calculations
4.11.1 Initial Calculations
4.1 1 .2 Calculation Procedure
4.11.3 Calculation Procedure B
4.11.4 Calculation Procedure C
4.12 Precision and Accuracy
4.13 References
5.0 DETERMINATION OF AMMONIUM
5.1 Scope and Application
5.2 Summary of Method
5.3 Interferences
5.4 Safety
5.5 Apparatus and Equipment
5.6 Reagents and Consumable Materials
5.7 Sample Collection, Preservation, and Storage
5.8 Calibration and Standardization
5.9 Quality Control
5.10 Procedure
5.11 Calculations
5.12 Precision and Accuracy
5.13 References
6.0 DETERMINATION OF CHLORIDE, NITRATE, AND SULFATE BY ION
CHROMATOGRAPHY
6.1 Scope and Application
6.2 Summary of Method
6.3 Interferences
6.4 Safety
6.5 Apparatus and Equipment
6.6 Reagents and Consumable Materials
6.7 Sample Collection, Preservation, and Storage
6.8 Calibration and Standardization
6.9 Quality Control
6.10 Procedure
6.11 Calculations
6.12 Precision and Accuracy
6.13 References
7.0 DETERMINATION OF DISSOLVED ORGANIC CARBON AND DISSOLVED
INORGANIC CARBON
7.1 Scope and Application
7.2 Summary of Method
7.3 Interferences
58
58
58
59
60
61
62
63
64
65
65
65
65
65
65
65
66
66
66
67
67
67
67
70
70
70
70
71
71
71
72
72
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73
74
74
74
74
Vll
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7.4 Safety
7.5 Apparatus and Equipment
7.6 Reagents and Consumable Materials
7.7 Sample Collection, Preservation, and Storage ,
7.8 Calibration and Standardization
7.8.1 DOC Calibration
7.8.2 DIG Calibration
7.9 Quality Control
7.10 Procedure
7.10.1 DOC Analysis
7.10.2 DIG Analysis
7.11 Calculations
7.12 Precision and Accuracy
7.12.1 DOC
7.12.2 DIG
7.13 References
8.0 DETERMINATION OF TOTAL DISSOLVED FLUORIDE BY ION-SELECTIVE
ELECTRODE
8.1 Scope and Application
8.2 Summary of Method
8.3 Interferences
8.4 Safety
8.5 Apparatus and Equipment
8.6 Reagents and Consumable Materials
8.7 Sample Collection, Preservation, and Storage
8.8 Calibration and Standardization
8.9 Quality Control
8.10 Procedure
8.11 Calculations
8.12 Precision and Accuracy
8.13 References
9.0 DETERMINATION OF TOTAL PHOSPHORUS
9.1 Scope and Application
9.2 Summary of Method
9.3 Interferences
9.4 Safety
9.5 Apparatus and Equipment
9.6 Reagents and Consumable Materials
9.7 Sample Collection, Preservation, and Storage
9.8 Calibration and Standardization
9.9 Quality Control
9.10 Procedure
9.1 1 Calculations
74
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75
76
76
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77
78
78
78
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79
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82
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83
83
84
84
85
85
85
85
87
via
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9.12 Precision and Accuracy 87
9.13 References 88
10.0 DETERMINATION OF DISSOLVED SILICA 89
10.1 Scope and Application 89
10.2 Summary of Method 89
10.3 Interferences , 89
10.4 Safety 89
10.5 Apparatus and Equipment 89
10.6 Reagents and Consumable Materials 90
10.7 Sample Collection, Preservation, and Storage 90
10.8 Calibration and Standardization 90
10.9 Quality Control 91
10.10 Procedure 91
10.11 Calculations , 93
10.12 Precision and Accuracy 93
10.13 References 93
11.0 DETERMINATION OF SPECIFIC CONDUCTANCE 94
11.1 Scope and Application 94
11.2 Summary of Method 94
11.3 Interferences , _ 94
11.4 Safety 94
11.5 Apparatus and Equipment 94
11.6 Reagents and Consumable Materials 95
11.7 Sample Collection, Preservation, and Storage 95
11.8 Calibration and Standardization 95
11.9 Quality Control 95
11.10 Procedure 95
11.11 Calculations 96
11.12 Precision and Accuracy 96
11.13 References 96
12.0 DETERMINATION OF METALS (Al, Ca, Fe, K, Mg, Mn, Na) BY ATOMIC ABSORPTION
SPECTROSCOPY 97
12.1 Scope and Application 97
12.2 Summary of Method 98
12.3 Definitions 98
12.4 Interferences 99
12.4.1 Direct Aspiration 99
12.4.2 Flameless Atomization 99
12.5 Safety 100
12.6 Apparatus and Equipment ,. 100
12.7 Reagents and Consumable Materials , 100
12.8 Sample Collection, Preservation, and Storage 101
12.9 Calibration and Standardization 101
ix
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12.10 Quality Control 101
12.11 Procedure 101
12.11.1 Flame Atomic Absorption Spectroscopy 103
12.11.2 Furnace Atomic Absorption Spectroscopy 103
12.11.3 Procedure for Determination of Total Aluminum 103
12.11.4 Procedure for Determination of Total Extractable Aluminum 105
12.11.5 Procedure for Determination of Dissolved Calcium 106
12.11.6 Procedure for Determination of Dissolved Iron 107
12.11.7 Procedure for Determination of Dissolved Magnesium 108
12.11.8 Procedure for Determination of Dissolved Manganese 109
12.11.9 Procedure for Determination of Dissolved Potassium 110
12.11.10 Procedure for Determination of Dissolved Sodium 111
12.12 Calculations 112
12.13 References 112
13.0 DETERMINATION OF DISSOLVED METALS (Ca, Fe, Mg, Mn) BY INDUCTIVELY
COUPLED PLASMA EMISSION SPECTROSCOPY 113
13.1 Scope and Application 113
13.2 Summary of Method 113
13.3 Interferences , 114
13.3.1 Spectra! Interferences 114
13.3.2 Physical Interferences 115
13.3.3 Chemical Interferences 115
13.3.4 Interference Tests 115
13.4 Safety 116
13.5 Apparatus and Equipment 116
13.6 Reagents and Consumable Materials 116
13.7 Sample Handling, Preservation, and Storage 117
13.8 Calibration and Standardization 117
13.9 Quality Control 117
13.10 Procedure 118
13.11 Calculations 118
13.12 Precision and Accuracy 118
13.13 References 118
APPENDICES
A CLEANING OF PLASTICWARE A-1
B BLANK DATA FORMS B-1
C EXAMPLES OF CALCULATIONS REQUIRED FOR ALKALINITY AND ACIDITY
DETERMINATIONS C-1
1.0 HCI Standardization C-1
2.0 NaOH Standardization C-2
2.1 Initial NaOH Standardization with KHP C-2
2.2 Standardization Check C-4
2.3 Routine NaOH Standardization with Standardized HCI C-7
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3.0 Electrode Calibration C-8
4.0 Blank Analysis - Alkalinity Determination C-10
5.0 Sample Analysis , C-13
5.1 Titration Data C-13
5.2 Initial Estimate of V, C-14
5.3 Initial Estimate of V2, Alkalinity, Acidity, and Carbonate C-14
5.4 Refined Estimates of Vn and V2 C-14
5.5 New Estimates of Alkalinity, Acidity, and Carbonate C-17
5.6 Comparison of Latest Two Estimates of Total Carbonate C-17
6.0 Quality Control Calculations .,., C-19
6.1 Comparison of Calculated Alkalinity and Measured Alkalinity C-19
6.2 Comparison of Calculated Acidity and Measured Acidity C-19
6.3 Comparison of Calculated Total Carbonate and Measured Total Carbonate.... C-20
xi
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Figures
Number Page
1.1 Organizational Diagram of the National Surface Water Survey and the Years
During Which Field Activities are to be Initiated 2
2.1 Flow Scheme of Daily Field Station Activities 10
2.2 Field Sample Label 11
2.3 Aliquot and Audit Sample Labels 12
2.4 NSWS Form 2 - BatcWQC Field Data , 13
2.5 NSWS Form 3 - Shipping 15
2.6 Data Flow Scheme 16
2.7 Flow Scheme for DIG Determinations 19
2.8 Schematic of pH Measurement System 21
2.9 pH Sample Chamber 22
2.10 Flow Scheme for pH Determinations 24
2,11 Flow Scheme for Turbidity Determinations 27
5.1 Ammonia Manifold AAl 68
5.2 Ammonia Manifold AAll 69
9.1 Total Phosphorus Manifold 86
10.1 Silica Manifold , 92
12.1 Standard Addition Plot 102
jew
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Tables
Table Page
1.1 Required Minimum Analytical Detection Limits, Expected Ranges, and Intra-
Jab Relative Precision 4
2.1 Field Station Equipment List 7
2.2 List of Sample Codes 14
2.3 Aliquot Descriptions 30
2.4 Split Sample Descriptions 30
3.1 List of Aliquots, Containers, Preservatives, and Corresponding Parameters
to be Measured 35
3.2 List of Holding Times 36
3.3 List of Parameters and Corresponding Measurement Methods 37
3.4 Summary of Internal Method Quality Control Checks 38
3.5 Maximum Control Limits for Quality Control Samples 39
3.6 Factors to Convert mg/L to Meq/L 41
3.7 Chemical Reanalysis Criteria 42
3.8 Conductance Factors of Ions 43
3.9 List of Data Forms 44
3.10 National Surface Water Survey Data Qualifiers 45
4.1 List of Calculation Procedures for Combinations of Initial V1 and pH* 59
4.2 List of Frequently Used Equations and Constants 60
6.1 Suggested Concentration of Dilute Calibration Standards 72
6.2 Typical 1C Operating Conditions 73
6.3 Single-Operator Accuracy and Precision 73
9.1 Percent Recovery of Total P in the Presence of SiO2 83
9.2 Precision of the Method for Natural Water Samples 87
9.3 Precision and Accuracy of the Method for Analyst Prepared Standards.... 87
12.1 Atomic Absorption Concentration Ranges 97
13.1 Recommended Wavelengths and Estimated Instrumental Detection
Limits 113
13.2 Analyte Concentration Equivalents (mg/L) Arising from Interferences at the
100-mg/L Level 114
13.3 Interference and Analyte Elemental Concentrations Used for Interference
Measurements in Table 13.2 115
13.4 ICP Precision and Accuracy Data 118
xiii
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ACKNOWLEDGEMENT
Contributions provided by the following individuals were essential to the completion of this methods manual
and are gratefully acknowledged: Mark Peden (Illinois State Water Survey), Kevin Cabbie, Lynn Creelman, Sevda
Drouse, Janice Engels, Marianne Faber, Henry Kerfool, and Frank Morris (Lockheed Engineering and Manage-
ment Services Company, Inc.), James Kramer (McMaster University), John Lawrence (National Water Research
Institute), Bruce LaZerte (Ontario Ministry of the Environment), John Nims (State of Maine, Department of Envi-
ronmental Protection), Charles Driscoll and Gary Schafron (Syracuse University), Dixon Landers (State Univer-
sity of New York), Howard May (U.S. Geological Survey), Peter Campbell (University of Quebec), Richard Wright
(University of Virginia), and David Brakke (Western Washington University).
XIV
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SECTION 1
INTRODUCTION
The National Surface Water Survey (NSWS) is divided into two major components (Figure 1.1), the
National Lake Survey (NLS) and the National Stream Survey (NSS), each of which has three phases.
1.1 BACKGROUND
Phase I of the Eastern Lake Survey (ELS-I) is part of the NSWS and involves a synoptic chemical
survey of 1,800 lakes in the Eastern United States. The NSWS program is part of the National Acid
Precipitation Assessment Program (NAPAP). One of the responsibilities of NAPAP is to assess the
extent and severity to which aquatic resources within the U.S. are at risk due to effects of acidic
deposition. The NSWS was initiated at the request of the Administrator of EPA when it became
apparent that existing data could not be used to quantitatively assess the present chemical and
biological status of surface waters in the U.S.
Extrapolation of existing data, largely compiled through individual studies, to the regional or
national scale was limited because studies were often biased in terms of site selection. Additionally,
many previous studies were incomplete with respect to the chemical variables of interest, inconsis-
tent relative to sampling/analytical methodologies, or highly variable in terms of data quality.
The ELS-1 was designed to alleviate uncertainty in making regional assessments based on existing
data by:
(1) providing data from a subset of lakes which are characteristic of the overall population of lakes
within a region;
(2) using standardized methods in collection of chemical data;
(3) measuring a complete set of variables thought to influence or be influenced by surface-water
acidification;
(4) providing data which can be used to statistically investigate relationships among chemical
variables on a regional basis; and
(5) providing reliable estimates of the chemical status of lakes within a region of interest.
The U.S. Environmental Protection Agency (EPA) requires that data collection activities be based on
a program which ensures that the resulting data are of known quality and are suitable for the purpose
for which they are intended. The EPA's goals in designing the ELS-I were to clearly identify ELS-I
objectives; identify intended uses and users of the data; develop an overall conceptual and practical
approach to meeting the objectives; develop an appropriate survey design; identify the quality of
data needed; develop analytical protocols and quality assurance/quality control (QA/QC) proce-
dures; test the approach through a "pilot" or feasibility study; and revise and modify the approach
and methodology as needed.
Using these criteria as guidelines, ELS-I was designed to provide statistically comparable data which
could be extrapolated with a known degree of confidence to a regional or national scale. The concep-
tual approach to the survey emphasized that the data would not be used to ascribe observed effects
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NATIONAL SURFACE WATER SURVEY (NSWS)
NATIONAL LAKE SURVEY (NLS)
NATIONAL STREAM SURVEY (NSS)
PHASE I
Synoptic Chemistry
Eastern Survey (1984)
I
PHASE I
Synoptic Chemistry
Western Survey (1985)
PHASE I
Pilot Survey
(1985)
PHASE II
Temporal
Variability
(1986-87)
PHASE II
Biological
Resources
(1986-87)
PHASE I Synoptic Survey
(1986)
PHASE III
Long-Term Monitoring
(1988-95)
PHASE II
Temporal
Variability
(1987-89)
PHASE II
Biological
Resources
(1987-89)
I
PHASE III
Long-Term Monitoring
(1988-95)
Figure 1.1. Organizational Diagram of the National Surface Water Survey and the Years During Which
Field Activities are to be Initiated.
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to acidic deposition phenomena. Rather, the survey's intent was to provide information for develop-
ing of correlative, not cause-and-effect, relationships through large-scale monitoring activities.
The conceptual approach to the program was developed by EPA personnel and cooperating scien-
tists. Planning for the ELS-I began in October 1983, The research plan for the National Surface Water
Survey, National Lake Survey Phase I (U.S. EPA, 1984) was initially reviewed late in 1983 by 100 scien-
tists who have expertise in the areas of study. Fifty scientists discussed the plan during a workshop
held in December; suggested modifications were incorporated by March 1984. The Research Plan
was submitted to members of the American Statistical Association (ASA) for review in June 1984; a
final ASA review was conducted in October.
The National Surface Water Survey Eastern Lake Survey (Phase I - Synoptic Chemistry) Quality
Assurance Plan (Drouse' et al., 1986) provides details of the extensive external and internal QA and
QC activities.
This manual provides details of the analytical methods and internal QC used to process and analyze
the lake samples. Details of the actual sampling and on-site lake analyses are provided in the field
operations report (Morris et ai., 1986).
1.2 PHYSICAL PARAMETERS AND ANALYTES MEASURED
The constituents and parameters to be measured, along with a rationale for each, are listed below.
Table 1.1 lists the required detection limits, relative precision goals, and expected concentration
ranges.
1.2.1 CO2 A cidity (acidity)
CO2 acidity is the base neutralizing capacity (BNC, the quantity of OH ions reacted over a given pH
range during a base titration) of a carbonate system. The lakes sampled for the NSWS can generally
by described by a carbonate system, i.e., a sample in which the soluble reacting protoiytes are the
carbonate species (H2CO3, HCO3~, and CO32~") as well as H + and OH". In conjunction with alkalinity,
this measurement is useful in refining calculations for both alkalinity and acidity. (An iterative calcu-
lation procedure is performed. During each iteration, improved values for alkalinity and acidity are
generated).
1.2.2 Alkalinity
Alkalinity is the acid neutralizing capacity (ANC, the quantity.'of H ions reacted over a given pH range
during an acid titration) of a carbon ate system. Because of its inherent relationship to buffering
capacity, alkalinity is an important variable in acid deposition studies.
. 1.2.3 Aluminum, Total Extractable
The determination of total extractable aluminum provides an estimate of dissolved aluminum and
includes most mononuclear aluminum species. Aluminum is considered to be highly toxic, espe-
cially to fish. Knowing its concentration is important in assessing the biological environment of a
lake.
1.2.4 Aluminum, Total
Total aluminum is an estimate of the potential aluminum pool available to the biological environ-
ment.
7.2.5 Dissolved Inorganic Carbon
The field determination of dissolved inorganic carbon (DIG) is useful in determining the degree of
dissolved C02 saturation in a lake. Both the field and lab determinations of DIG (combined with pH)
are useful in QA/QC calculations.
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Parameter3
Acidity
Alkalinity
A1 , Total Extractable
A1, Total
Ca
C1"
DIG
DOC
F, Total
Fe
K
Mg
Mn
Ma
NH4 +
N03~
P, Total
pH, Field
pH, Lab
s,o.
S04 "
Specific Conductance
True Color
Turbidity
Units
^ueq/L
Meq/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
pH units
pH units
mg/L
mg/L
MS/cm
PCUe
NTU
Required
Detection
Limit
0.005
0.005
0.01
0.01
0.05
0.1
0.005
0.01
0.01
0.01
0.01
0.01
0.01
0.005
0.002
0.05
0.05
d
0
2
Expected
Range
10-150
-100-1000
0.005-1.0
0.005-1.0
0.5-20
0.2-10
0.05-15
0.1-50
0.01-0.2
0.01-5
0.1-1
0.1-7
0.01-5
0.5-7
0.01-2
0.01-5
0.005-0.07
3-8
3-8
2-25
1-20
5-1000
0-200
2-15
Relative
Intralab
Precision Goal (%)"
10
10
10(A1>0.01
10(A1>0.01
5
5
10
5 (DOO5)
5
10
5
5
10
5
5
10
10(P>0 01)
+ 0.1C
±0.5°
5
5
1
±5C
10
), 20(A1<0.01)
), 20(A1<0.01)
10(DOC<5)
, 20(P<0.01)
a Dissolved ions and metals are being determined, except where noted.
b Unless otherwise noted, this is the relative precision at concentrations above 10 times instrumental detection limits
0 Absolute precision goal is in terms of applicable units.
d Blank must be <0.9/uS/cm.
e = platinum - cobalt units.
Table 1.1, Required Minimum Analytical Detection Limits, Expected Ranges, and Intralab Relative
Precision.
1,2.6 Dissolved Ions (Na, K, Ca, Mg, Fe, Mn, NH/, F~, CI', SO/', and NO3')
The determination of major ions is necessary in order to chemically characterize a lake. For example,
fluoride is important as an aluminum chelator.
The determinations are also valuable in QA/QC calculations for mass ion and conductivity balances.
1.2.7 Dissolved Organic Carbon
Dissolved organic carbon (DOC) determination is necessary to establish a relationship with color
and to estimate the concentration of organic acids. Also, DOC is important as a natural chelator of
aluminum.
4
~T
-------
1.2.8 Dissolved Silica (
The absence or existence of dissolved silica is an important factor controlling diatom blooms, and it
assists in identifying trophic status. It is also an indication of mineral weathering.
1.2.9 pH
pH is a general and direct indication of free hydrogen ion concentration.
7.2.70 Specific Conductance
The specific conductance of lake water is a general indication of its ionic strength and is related to
buffering capacity.
1.2.11 Total Phosphorus
Total phosphorus is an indicator of potentially available nutrients for phytoplankton productivity and
overall trophic status.
1.2.72 True Color
True color indicates the presence of organic acids and DOC. Substances which impart color may also
be important natural chelators of aluminum.
1.2.13 Turbidity
Turbidity is a measure of suspended material in a water column.
1.3 REFERENCES
Drouse', S. K., D. C. Hillman, L W. Creelman, and S. J. Simon, 1986. National Surface Water Survey.
Eastern Lake Survey (Phase I - Synoptic Chemistry) Quality Assurance Plan. U.S. Environmental
Protection Agency, Las Vegas.
Morris, F. A., D. V. Peck, D. C. Hillman, K. J. Cabbie, M. B. Bonoff, S. L Pierett, 1986. National Surface
Water Survey. Eastern Lake Survey (Phase I - Synoptic Chemistry) Field Operations Report. U.S.
Environmental Protection Agency, Las Vegas.
U.S. Environmental Protection Agency, 1984. National Surface Water Survey. National Lake Survey -
Phase I. NAPAP Project Reference No. E-23. U.S. EPA, Office of Research and Development,
Washington, D.C.
-------
SECTION 2
FIELD OPERATIONS
Field operations are based at fully equipped mobile field laboratories, or field stations. A list of equip-
ment contained in the field station is given in Table 2.1. Lake samples, collected by sampling crews,
are delivered to the field station for preliminary analysis, processing, and shipment to analytical
laboratories for more detailed analysis.
The activities of the field station crew are described in this section. Sampling crew activities are
described elsewhere (Morris et al., 1986).
2.1 PERSONNEL
The field station is staffed by a five-person crew consisting of a coordinator, supervisor, and three
analysts. The coordinator is responsible for the overall operation of the field station including coordi-
nation with the sampling crews, communication with the EPA's Environmental Monitoring Systems
Laboratory in Las Vegas, Nevada (EMSL-LV), sample tracking and logistics, data forms, and safety.
The supervisor, with the assistance of the analysts, is responsible for field station measurements
and sample processing.
2.2 DAILY OPERATION
The field station operates each day that samples are collected. The daily field station activities {out-
lined in Figure 2.1) are based upon samples arriving at about 4:00 p.m. each day. The daily operations
are divided into activities that are conducted before sample arrival (discussed in section 2.2.1) and
activities that are conducted following sample arrival (discussed in section 2.2.2).
2,2.1 Activities Before Sample Arrival
Prior to sample arrival, the reagents for determining DIG, determining pH, and preparing aliquot 2
(total extractable Al) are prepared as described in sections 2.3, 2.4, and 2.7, respectively. Also, the
carbon analyzer, pH meter, and nephelometer are calibrated as described in sections 2.3,2.4, and 2.5,
respectively.
2.2.2 Activities Following Sample Arrival
After samples are delivered by the sampling crews, the steps outlined in Figure 2.1 are performed.
The first step, performed by the coordinator, involves organizing the samples into a batch. The next
five steps (aliquot preparation and pH, DIG, color, and turbidity determinations) are performed simul-
taneously by the supervisor and three analysts. Finally, after all measurements and processing are
finished, the data forms are completed, the samples are packed, and the forms and samples are
shipped to their destinations. These steps are detailed in sections 2.2.2.1 through 2.2.2.4.
2.2.2.1 Sample Identification and Batch Organization
Three types of samples (routine, duplicate, and blank) are collected and delivered to the field station.
The sample type is indicated on the sample label (Figure 2.2). The samples collected on a given day
are organized into a batch, consisting of 20 to 30 samples, which includes all the routine, duplicate,
-------
1. Mobile Lab Equipment with
a. Electrical and water inputs
b. Water outlet
c. Source of water meeting ASTM Type I specifications (such as Barnstead
NANOpure 40 Millipore Milli-RO/Super-Q System)
d. Heating/cooling system
e. Freezer
f. Laminar flow hood delivering class 100 air
g. Solvent storage cabinet
h. Standard laboratory countertops and sink
i. analytical balance and plastic weighing boats
2. Centrifuge (capable of holding four 50-mL tubes) . - 1
3. Clean 4-L Cubitainers - 30/day
4. Clean Nalgene Amber Wide-Mouth Bottles
a. 500-mL (Nalgene No. 2106-0016) - 30/day
b. 250-mL (Nalgene No. 2106-0008) - 60/day
c. 125-mL (Nalgene No9. 2106-0004) - 90/day
5. Total Extractable Aluminum Supplies
a. Clean 50-mL graduated centrifuge tubes with sealing caps (Fisher No.
05-538-55A) - 30/day
b. Clean 10-mL centrifuge tubes (Nalgene 3119-0010) - 30/day
c. Clean sealing caps for 10-mL centrifuge tubes (Nalgene 3131-0013) - 30/day
d. HPLC-grade methyl isobutyl ketone (MIBK) - 180 mL/day
e. Sodium acetate (Alfa ultrapure) - 80 g/month
f. 8-hydroxyquinoline (99+% purity) - 30 g/month
g. NH4OH (30% - Baker Instra-Analyzed grade) - 750 mL/month
h. Clean 1-L, 500-mL, and 100-mL volumetric flasks - 5 of each
i. Glacial acetic acid (Baker Instra-analyzed grade) -100 mL/month
j. Hydrochloric acid (12 M - Baker Instra-Analyzed grade) -500 mL/month
k. Phenol-red indicator solution (0.04% w/v - American Scientific Products
5720) -1 L
I. 2.00-mL Repipet dispenser - 2/station
m. 3.00-mL Repipet dispenser top for 1-gallon bottle -2/station
n. 5.00-mL Repipet dispenser - 2/station
o. 100-mL reagent bottle with dropper (Nalgene 2411-0060) - 2/station
p. Polystryene graduated cylinders (25-, 100-, 250-ml sizes) - 2 each/station
6. Color Determination Kit (Hach Model (CO-1) - 2
7. Color Kit Spare Supplies
a. Color disc (Hach No. 2092-00) - 2
b. Color viewing tube (Hach No. 1730-00) - 10
c. Hollow polyethylene stoppers (Hach No. 14480-74) - 10
8. Filtration Apparatus and Supplies
a. Membrane filters, 0.45 jum, 47mm diameter (Gelman No. 60173)
(package of 100) - 7 pkg/week
b. Teflon or plastic forceps - 5
c. Fisher filtrator -n low form (fisher 09-788) - 3
d. Acrylic vacuum chambers (custom made) - 6
e. Clean filter holder (Nalgene No. 310-4000) - 12
f. Spare rubber stoppers (Fisher No. 09-788-2) - 6
g. Vacuum pump with regulator (Millipore No. xx5500000) - 1
Table 2.1. Field Station Equipment List.
7
-------
9. Hydrolab Model 4041 (spare)
10. Hydrolab Supplies
a. Spare probe
b. Spare cable (200 m)
c. Membrane/KC1 kit (high sensitivity)
d. Calibration standards
e. Miscellaneous tools
11. Disposable Gloves (talc-free)
12. Preservation Supplies
a: Repipet Jr. (0.1 ml)
b. Indicating pH paper (Whatman Type CS No. 2626-990 range 1.8-38)
c. HN03 and H2S04 (Baker Ultrex grade or Seaster Ultrapure grade)
13. Frozen Freeze Gel Packs - daily use (reuseable)
- shipping
14. Styrofoam-Lined Shipping Containers
15. Field Data Forms, Shipping Forms, Batch, etc.
16, Buoys (spare)
17. Color Blindness Test Kit
18. DIG Determination Supplies
a. Dohrman DC-80 carbon analyzer
b. 50-mL polypropylene syringes - station use
- field use
c. "Mininert" syringe valves - station use
- field use
d. Zero-grade nitrogen gas
e. .Anhydrous Na2COj (ACS Primary Standard Grade
f. Syringe membrane filters (Gelman Acrodisc 4218, 0.45 m)
g. Spare carbon analyzer parts (nuts, ferrules, tubing, etc.)
19. Field Station pH Supplies
a. pH meter (Orion Model 611)
b. Orion Ross epoxy body combination pH electrode
c. Filling solution for Ross combination pH electrode (pack of 6 bottles)
d. pH sample chamber
e. Certified 0.100 N H2S04
f. Ringstand (to hold pH apparatus) and clamps
g. NBS-traceable pH buffers (pH 4 and 7)
n. 50-mL disposable beakers
20. Turbidimeter (Monitek Model 21)
21. Turbidimeter Supplies
a. 5-, 10-, 20-, 50-, 1QO-, 200-NTU standards
b. Cuvettes
22. Class 100 air Filtration Filters
,23. Spare Water Treatment Cartridges
-1
-2
- 1
- 1
-2
-2
- 6 packs/week
- 50 mL/week
- 25/day
- 30/40 sample batch
- 4/day
2
-1
1
50
1/sample
20
70
1 cylinder/month
500g
1/sample
-2
-6
-2
-2
-2L
-2
- 2 L of each/month
-200
-1
1 L of each
10
6
6
Table 2.1. Field Station Equipment List (Continued).
8
-------
24. Coolers - 4
25. Depth Finder (spare) - 1
26. Clean 20-L Cubitainers with Spigots -5
27. Digital Micropipets (5-40 /u L, 40-200 ju L, 200-1,000 n L, 1,000-5,000 yu L) - 1 of each
28. Micropipet Metal-Free Pipet Tips (in four sizes corresponding to micropipet
sizes in item 27) ' -2 cases (1,000 tips/case)
of each size
Table 2.1. Field Station Equipment List (Concluded).
and blank samples collected on that day as well as audit samples (inserted daily at field station) and
split samples (prepared daily by the field station from the routine, duplicate, and blank samples).
After organization, a unique batch ID number is assigned to each batch and is recorded on the labels
(and corresponding aliquot labels) of all samples in the batch. Next, an ID number is randomly
assigned to each sample as follows:
Routine Samples. Three sample containers are filled at each lake, namely, two syringes (for DIG and
pH determination) and a cubitainer. One ID number is assigned to all three containers and is recorded
on each container label.
Duplicate and Blank Samples. ID numbers are assigned in the same manner as for the routine sam-
ples. (Note: There are no syringe samples for the blank.)
Split Samples. One ID number is assigned and recorded on the cubitainer label of the samples which
are split.
Field Audit Samples. One 2-L field audit sample (received each day from a central source) is inserted
into each day's batch of samples. The field audit sample is assigned an ID number in the same man-
ner as a routine sample and the number is recorded on the label (Figure 2.3a).
Lab Audit Samples. One lab audit sample (received from a central source) is included in each day's
batch. A single lab audit sample consists of a set of seven aliquots. Each aliquot has a temporary
label (Figure 2.3b) listing the aliquot number, audit sample code, preservative amount, and shipping
date. The lab audit sample is then assigned batch and sample ID numbers in the same manner as for
a routine sample. An aliquot label (Figure 2.3c) is attached to each aliquot, and the batch and sample
ID numbers are recorded on the label, as are the date and amount of preservative added.
After the batch and sample ID numbers have been assigned and recorded on each sample label, the
same information is recorded on Form 2, Batch/QC Field Data. (Figure 2.4). Codes necessary to com-
plete the form are given in Table 2.2.
NOTE 1: The ID numbers are randomly assigned to all samples in a batch. Furthermore, ID numbers
run consecutively from 1 to the number of samples in the batch. Audit samples must not always be
assigned the same ID number.
NOTE 2: Field audit samples are processed exactly like routine lake samples. Lab audit samples
receive no field treatment other than labeling and shipping.
NOTE 3: After Form 2 is completed, the temporary label on the lab audit sample (seven aliquots) is
removed and placed in the lab audit logbook.
-------
BEFORE SAMPLE ARRIVAL
1. Prepare reagents for
a. Total extractable Al
b. DIG
c. pH
2. Warm up and calibrate instruments
a. Turbidimeter
b. Carbon analyzer
c. pH meter
1
SAMPLES
FOLLOWING SAMPLE
ARRIVAL
1. Insert required audit samples, assign
batch and ID numbers, start batch form
2. Determine DIG
3. Prepare aliquots
4. Measure pH
5. Measure turbidity
6. Determine true color
7. Complete batch and shipping forms
8. Ship samples
9. Distribute data
Figure 2.1, Flow scheme of daily field station activities.
10
-------
Lake ID
Date
Sampled
Crew ID
Time
Sampled
Sample Type (Check One)
Routine _
Duplicate _.
Blank _
Batch ID
Sample ID
Figure 2-2. Field Sample Label.
11
-------
FIELD AUDIT SAMPLE
Radian ID No.
Date
Shipped
Code
Batch
Date
Received
ID
a. Field Audit Sample Label
Aliquot
Batch ID
Sample ID
Date Sampled
Preservative
Amount
Parameters
LAB AUDIT SAMPLE
Aliquot No.
Date Shipped Date Received
Code
Preservative Amount
b. Lab Audit Sample Label
NOTE: The aliquot no.,
preservative, and parameters are
preprinted on the seven aliquot
labels.
c. Aliquot Labels
Figure 2.3. Aliquot and Audit Sample Labels.
12
-------
NSWS
FORM 2
DATE RECEIVED
BY DATA MQT.
ENTERED
RE-ENTERED
BATCH/QC FIELD DATA
ATCH ID .
NO. SAMPLES
IN BATCH
STATION ID _
LAB TO WHICH
.ATCH SENT _
DATE SHIPPED
CHEW ID.
DATE SAMPLED.
AIR-SILL NO.
FIELD STATION
MANAGER ___
SAMPLE
10
LAKE
ID
SAMPLE
CODE
VALUE OCCS
STATION >M
OCCS LIMITS
UCL-JLL
LCLlil.
VALUE OCCS
TURBIDITY (NTU)
OCCS LIMITS
UCL
LCL - 4-S
"VALUE" "bee?
COLOR
UPHA
UNITS)
VALUE
SPUT
cooes
(E.C/U
01
02
O4
OS
06
09
13
16
IS
19
20
2 I
_LL
23
2S
26
COMMENTS:
HTTE - ORNLCOPY
YELLOW- FIELD COPY
PINK - EMSL-LV COPY
Figure 2.4. NSWS Form 2 - Batch/QC Field Data.
13
-------
Sample Type
Code
Description
Normal
Audit
R
D
B
TD
F L 1 -1
Split
Routine Lake Sample
Duplicate Lake Sample
Field Bank Sample
Field Station (Trailer) Duplicate
Radian ID Number
Concentrate Lot Number
Concentration Level
(L = low, H = high, N = natural)
Type of Audit Sample
= field audit sample \
= lab audit sample l
= performance evaluation sample/
A split sample consists of two sets of aliquots. Each set has the same ID
number as assigned in Section 2.2.2, so there is one ID number
associated with each split sample. However, for a split sample the letter
E (or N or C, depending on where it is shipped) is recorded under the
Split Code column on Form 2.
Shipping destination of split sample (N = Norwegian lab, C = Canadian
lab, E = EPA Corvallis lab)
Table 2.2. List of Sample Codes.
2.2.2.2 Determination of DIG, pH, Turbidity, and True Color
These parameters are measured as described in sections 2.3, 2.4, 2.5, and 2.6, respectively.
2.2.2.3 Aliquot and Split Sample Preparation
Seven aliquots are prepared from each sample (routine, duplicate, or blank), each with the same
batch and sample ID numbers. The details for preparing each aliquot are provided in section 2.7. The
preparation of "split" samples is also described in section 2.7.
2.2.2.4 Form Completion, Sample Shipment, and Data Distribution
After a batch has been completely processed, the supervisor records all analytical data on Form 2
(Figure 2.4). The coordinator then reviews and signs the form. Next, each aliquot is sealed in a plastic
bag and is packed in a Styrofoam-lined shipping container, along with 7 to 10 frozen freeze-gel packs
(to maintain aliquots at 4°C). A shipping form (Figure 2.5) is then completed and enclosed with each
container and shipped by overnight delivery to its destination. Finally, copies of Forms 1 (a form
completed by sampling crew for each sample), 2, and 3 are sent to the locations indicated in Figure
2.6.
2.3 DETERMINATION OF DIG
2.3.7 Scope and Application
This method is applicable to the determination of DIG in natural surface waters and is written specifi-
cally for the NSWS. DIG is determined in NSWS mobile field laboratories using a Dohrman DC-80
Carbon Analyzer. For this reason, the method has been written assuming that the DC-80 is being used
(Xertex - Dohrman Corp., 1984).
The method detection limit (MDL) for DIG determined from replicate analyses of a calibration blank
(approximately 0.1 mg/L DIG) is 0.1 mg/L DIG.
14
-------
NATIONAL SURFACE WATEP. SURVEY
SAMPLE MANAGEMENT OFFICE
P.O. BCKSIS
ALEXANDRIA. VA 22314
news
FORM 9
SHIPPING
RECEIVED BY _______
IF MOOUPLETE MMEOIATELr MOTIFYi
SAMPLE MANAGEMENT OFFICE
(703)557-2490
FROM
(STATION 0>i
SAMPLE
10
01
02
09
04
OS
OC
07
OS
09
10
1 1
12
13
14
IS
16
17
IS
IS
20
21
22
23
24
25
2«
27
29
2»
30
1
TO
;LAS>I
(Ft
2
ALOUD
HSTA1
3
BATCH
10
TSSH0
WNUSI
4
DATE
no
LONLY)
S
SAMPt
6
LEO
7
DATE SUPPED DATE RECEIVED
Aff M,L "*0. _ ______
SAMPLE CONOtTION UPON LAS RECEIPT
(raRLAaus£OM.r>
--
QUALIFIERS,
Vt AUOUOT 8H»PEO
Ml ALIQUOT MSSMG OUE TO OESTROVEO SAMPLE
WHTTE - FIELD COW
PtK-LAACOPY
YELLOW - SMO COPY
SOLD - LAS COPY F« RETURN TO SMO
Figure 2.5. NSWS Form 3 - Shipping.
15
-------
ANALYTICAL
LABORATORY
Form 3 (2 copies)
FIELD
STATION
(Keeps 1 copy
of Forms 1,
2, and 3)
Form 3 (1 copy)
SAMPLE
MANAGEMENT
OFFICE
Form 3
QA
MANAGER
(EMSL-Las Vegas)
Forms 1 and 2
DATA
BASE
(Oak Ridge)
Forms 1 and 2
Figure 2.6. Data Flow Scheme.
16
-------
A 1.00-mL sample volume was used to determine the MDL The applicable analyte concentration
range is 0.1 to 50 mg/L DIG.
2.3.2 Summary of Method
Samples for DIG determination are collected and sealed at the lake sites in syringes. At the field
station, a syringe filter is attached to the syringe and sample is filtered into the sample loop of the
DC-80, The sample is subsequently injected into a reaction chamber containing 5 per cent phos-
phoric acid. The carbonates (DIG) in the sample react with the acid to form CO2, which is sparged
from the reaction chamber with a nitrogen gas carrier stream. The CO2 in the carrier stream is then
detected and quantified (in terms of DIG) by an infrared (IR) C02 analyzer.
2.3.3 Interferences
No interferences are known.
2.3.4 Safety
The calibration standards, sample types, and most reagents used in this method pose no hazard to
the analyst. Protective clothing (lab coat and gloves) and safety glasses must be used when handling
concentrated phosphoric acid.
The nitrogen cylinder must be secured in an upright position. The line pressure must be kept below 40
psi.
2.3.5 Apparatus and Equipment
Dohrman DC-80 Carbon Analyzer equipped with High Sensitivity Sampler (1.00-mL loop).
Reagent bottles for DIG standards (equipped with three-valve cap to permit storage under a CO2-
free atmosphere, Rainin No. 45-3200).
0.45-m syringe filters.
60-mL plastic syringes.
Luer-Lok syringe valves.
2.3.6 Reagents and Consumable Materials
Nitrogen Gas (99.9 percent). CO2-free.
Phosphoric Acid(5 percent v/v). Carefully add 50 ml_ concentrated phosphoric acid (H3PO4, sp gr
1.71) to 500 ml_ water. Mix well and dilute to 1,000 mL with water.
Stock DIC Quality Control Sample Solution. Weekly, open a fresh ampule of anhydrous, primary
standard grade sodium carbonate (Na2CO3) and dissolve 8.825 g in water, then dilute to 1.000 L
Store at 4°C in a special reagent bottle under a CCyfree atmosphere.
Stock DIC Calibration Standard Solution. Biweekly, open a fresh ampule of anhydrous, primary
standard grade Na2CO3 and dissolve 8.825 g in water, then dilute to 1.000 L. Store at 4°C in a
special reagent bottle under a CO2-free atmosphere.
Water. Water used in all preparations must conform to ASTM specifications for Type I water
(ASTM, 1984). Such water is obtained from the Millipore Milli-Q water system.
2.3.7 Sample Collection, Preservation, and Storage
Samples are collected and sealed in 60-mL plastic syringes. They are stored at 4°C until use.
17
-------
2.3.8 Calibration and Standardization
Step 1 - Set up and operate the DC-80 according to the manufacturer's instructions.
Sfep 2 - Prepare the calibration standard (10.00 mg/L DIG) daily by diluting 5.000 mL of the stock DIG
calibration standard to 500.00 mL with fresh water. Store in a special reagent bottle under a CCyfree
atmosphere.
Step 3 - Erase previous calibration. Load the sample loop with the 10.00-mg/L DIG calibration stand-
ard by flushing with 7 to 10 mLsolution. Inject and start the analysis. When the analysis is complete,
repeat the process twice more.
Step 4 - Calibrate the analyzer by pushing the calibrate button. This completes the calibration. Sam-
ple results are output directly in mg/L DIG.
2.3.9 Quality Control
QC procedures are outlined in Figure 2.7 and are described in sections 2.3.9.1 through 2.3.9.5.
2.3.9.1 Initial Calibration Verification and Linearity Check
Immediately after calibration, analyze two QC samples to ensure the calibration validity and linearity.
Daily, prepare a 2.00-mg/L and a 20.00-mg/L DIG QC sample by diluting 1.000 and 10.00 mL of the stock
DIG QC sample, respectively, to 500.00 mL with fresh water. Store each DIG QC sample in a special
reagent bottle under a CO2-free atmosphere.
Analyze the QC samples. The results must be 2.0 ± 0.2 and 20.0 ± 0.5 mg/L DIG. If the results do not
fall within these ranges, a problem exists in the calibration, standard preparation, or QC sample
preparation. The problem must be resolved prior to sample analysis, and the QC samples must be
reanalyzed. Acceptable results must be obtained before continuing.
2.3.9.2 Continuing Calibration Verification
To check for calibration drift, analyze the 2.00-mg/L DIG QC sample after every 10 samples and after
the last sample. The measured value must be 2.0 ± 0.2 mg/L DIG. If it is not, repeat the calibration and
reanalyze all samples analyzed since the last acceptably analyzed QC sample.
2.3.9.3 Calibration Blank Analysis
After the initial calibration, analyze a fresh calibration blank. It must contain less than 0.1 mg/L DIG. If
it does not, check the water system and repeat the calibration procedure (including preparation of
standards).
2.3.9.4 Duplicate Analysis
To determine the analytical precision, analyze one sample per batch in duplicate.
2.3.9.5 Detection Limit Determination
Determine the detection limit by analyzing 20 blank samples. The detection limit is defined as three
times the standard deviation.
2.3.10 Procedure
Step 7 - Check that the DC-80 is equilibrated and a stable baseline has been achieved.
Step 2 - Prepare calibration standard and calibrate the analyzer.
Step 3 - Perform the necessary QC analyses. Proceed with sample analysis if acceptable results are
obtained.
Step 4 - Place a syringe valve on the sample syringe and filter 7 to 10 mL of sample directly into the
sample loop. Inject the sample and start the analysis. Discard the syringe filter after a single use.
18
-------
Prepare calibration and
QC standards.
±
Performs initial calibration
(three 10-mg/L analyses).
I
Make initial calib. linearity check
1. Analyze 2 mg/L QC sample
2. Analyze 20 mg/L QC sample
YES
I
Are measured values
2.0 ± 0.2 and 20.0 ± 0.5 mg/L?
±
Record value in
logbook, and record
value for 2.00 mg/L
QC sample on Form 2.
YES
Analyze calibration blank.
Is value <0.1 mg/L?
Record value in logbook.
Analyze up to 10 sample.
iSL/
I
Check instrument operation
and standard preparation.
i it U L
NO
NO
(2)
Record sample result
and unacceptable QA
result on Form 2.
NO
Does enough volume
remain of previous
samples for reanalysis'
Analyze 2.00 mg/L QC sample.
Is measured value 2.0 ± 0.2?
YES
Record QC result and
previous sample results
on Form 2.
(1) Analyze one sample per batch in duplicate.
(2) Reanalyze samples associated with unacceptable QA result.
Figure 2.7. Flow Scheme for DIC Determinations.
19
-------
Step 5 - Thirty seconds after injection, switch the valve to the load position and load the next sample.
The analysis time for a single sample is 3 to 4 minutes.
Step 6 - At the end of the day, rinse the sample loop with water. Keep the power to the IR analyzer on at
all times.
2.3.77 Calculations
No calculations are necessary. Sample results are output on the printer directly in mg/L DIG.
2.3.72 Reporting
Record the batch and sample ID numbers directly on the printer output. Similarly identify QC sam-
ples. Attach the printout to the logbook. Record the sample and QC data on Form 2.
2.4 DETERMINATION OF pH
2.47 Scope and Application
This method is applicable to the determination of pH in surface waters of low ionic strength and is
written specifically for the NSWS. The pH is determined in the field stations using an Orion Model 611
pH meter and an Orion Ross combination pH electrode. As a result, the method has been written
assuming that the Orion meter and electrode are used (Orion, 1983).
The applicable pH range is 3 to 11.
2.4.2 Summary of Method
Samples for pH determination are collected and sealed in syringes at the lake site. At the field sta-
tion, pH is measured in a closed system to prevent atmospheric exposure. The measurement is per-
formed by attach ing the sample syringe to the pH sample chamber (Figures 2.8 and 2.9), injecting
sample, and determining pH using a pH meter and electrode.
2.4.3 Interferences
No interferences are known.
2.4.4 Safety
The calibration standards, sample types, and reagents used in this method pose no hazard to the
analyst. Protective clothing (lab coat and gloves) and safety glasses must be used when handling
sulfuric acid.
2.4.5 Apparatus and Equipment
Orion Model 611 pH meter
Orion Ross combination pH electrode
pH sample chamber
60-mL plastic syringes
Luer-Lok syringe valves
2.4.6 Reagents and Consumable Materials
pH Calibration Buffers (pH 4 and 7). Commercially available pH calibration buffers (NBS-trace-
able) at pH values of 4 and 7.
20
-------
Figure 2.8. Schematic of pH Measurement System.
-------
TO
WASTE
INLET
Figure 2.9. pH Sample Chamber.
22
-------
Potassium Chloride (3 M). Dissolve 75 g KCI in 1 L of water.
Stock pH Quality Control Sample Solution (0.1 OON /^SO^. Commercially available certified
standard sulfuric acid at a concentration of 0.100N.
Water. Water used in all preparations must conform to ASTM specifications for Type I water
(ASTM, 1984). It is obtained from the Millipore Milli-Q water system.
2.4.7 Sample Collection, Preservation, and Storage
Samples are collected and sealed in 60-mL plastic syringes. They are stored at 4°C until used.
2.4.8 Calibration and Standardization
Weekly, calibrate the temperature function of the pH meter and electrode using a two-point calibra-
tion (4°C and room temperature) following the manufacturer's instructions.
Daily, calibrate the pH function of the pH meter and electrode using a two-point calibration (pH 7 and
4) following the manufacturer's instructions. Generally, the calibration involves setting the meter
calibration control while measuring pH 7 buffer and the slope control while measuring pH 4 buffer.
After calibration, the calibration accuracy is checked as described in the following procedure:
Step 1 - Copiously rinse the electrode with water. Immerse in 20 mL pH 7 buffer and stir for 30 to 60
seconds. Discard and replace with an additional 40 mL pH 7 buffer. While the solution is gently
stirred, measure and record the pH.
Step 2 - Repeat step 1 using the pH 4 buffer.
Step 3 - Compare the pH values obtained for the pH 7 and 4 buffers in steps 1 and 2 to the certified
values of the buffers. If either observed value differs from the certified value by more than ± 0.02 pH
units, repeat the electrode calibration. If acceptable results cannot be obtained, replace the elec-
trode.
2.4.9 Quality Control
QC procedures are outlined in Figure 2.10 and are described in sections 2.4.9.1 through 2.4.9.4.
2.4.9.1 pH QC Check Sample
Daily, prepare a pH QC check sample (pH QCCS) by diluting 1 .000 mL of the 0.100N H2SO4 to 1.000 L
with water.
2.4.9.2 Initial pH QC Check
Immediately after calibration, analyze the pH QCCS using the procedure described in section 2.4.8.3.
The observed pH must be 4.0 ± 0.1 pH unit. If it is not, repeat the calibration process (section 2.4.8),
then repeat the measurement on a fresh pH QCCS. If an acceptable result is still not obtained, con-
sult the manufacturer's troubleshooting guide for the meter and electrode. Lake samples must not be
analyzed until an acceptable value for the pH QCCS is obtained.
2.4.9.3 Continuing pH QC Check
In order to check for calibration drift, the pH QCCS sample is analyzed after every five samples and
after the last sample. The measured valve must be 4.0 ± 0.1 pH unit. If it is not, recalibrate the elec-
trode and meter and reanalyze all samples analyzed since the last acceptably analyzed pH QCCS.
2.4.9.4 Duplicate Analysis
To determine the analytical precision, analyze one sample per batch in duplicate.
23
-------
Perform initi
i
Is QCCS with
\
J
f
YES
i
Record on Form 2.
\ i
i
Record QCCS value on
Form 2 and note sample
ID numbers associated
with unacceptable
QCCS.
'
'
Measure pH of 5 samples.
Record on Form 2.
(1)
Record on
Form 2.
i QCCS within 0.1 pH unit?
YES
J
NO
(2)
YES
NO
Does enough volume
previously analyzed lake
samples remain for
reanalysis?
oTx
ike X
(1) Measure 1 sample per batch in duplicate (same syringe).
(2) Previous samples must be reanalyzed after unacceptable QCCS is obtained.
Figure 2.10. Flow Scheme for pH Determinations.
24
-------
2,4.10 Procedure
Step 1 - Calibrate the pH meter and electrode.
Step 2 - Perform the required QC analysis. Proceed with sample analyses if acceptable results are
obtained.
Step 3 - Clamp a pH sample chamber to a ringstand. Rinse thoroughly with water.
Step 4 - Equilibrate the sample syringes to room temperature.
Step 5 - Attach a sample syringe to the sample chamber. Fill the chamber with sample. Rinse the
electrode in the top of the chamber for 15 to 30 seconds. Drain the chamber and repeat. Refill the
chamber with sample and loosely insert the electrode. Flush with 5 to 10 mL sample to expel air
bubbles, then lightly seal the chamber. Measure and record the sample pH and temperature. Monitor
the pH reading. Record the reading when it stabilizes (± 0.02 pH unit/minute, usually about 1 to 5
minutes). Slowly inject 5 mL sample over a 60-second period. Measure the pH and record when sta-
ble. Repeat the 5-mL injections until successive pH readings are within 0.03 pH units.
Step 6 - Rinse the sample chamber and electrode copiously with water between samples.
Step 7 - At the end of the day, store the electrode in 3 M KCI.
2.4.11 Calculations
No calculations are required.
2.4.72 Reporting
Record the raw data in the pH logbook, and record the final sample pH value on Form 2. Also record
the initial and continuing QC results on Form 2.
2.5 DETERMINATION OF TURBIDITY
2.5,1 Scope and Application
This method is applicable to the determination of turbidity in natural surface waters and is written
specifically for the NSWS. Turbidity is determined in the field stations using a Monitek Model 21
nephelometer. As a result, the method has been written assuming that the Monitek nephelometer is
used (Monitek, 1977).
The applicable turbidity range is 0 to 200 NTUs.
2.5.2 Summary of Method
Samples are collected at the lake site in Cubitainers. At the field station the sample turbidity is mea-
sured directly in NTU's, using a calibrated nephelometer.
2.5.3 Interferences
Air bubbles in the sample cuvette interfere with the determination and cause a positive bias.
2.5.4 Safety
The calibration standards and sample types pose no hazard to the analyst.
2.5.5 Apparatus and Equipment
Monitek Model 21 nephelometer
Sample cuvettes
25
-------
2.5.6 Reagents and Consumable Materials
Turbidity Calibration Standard (10 NTU). Commercially available certified turbidity standard.
Turbidity Quality Control Samples (1.7,5,20,50,100, and200 NTU). Commercially available certi-
fied turbidity standards.
2.5.7 Sample Collection, Preservation, and Storage
Lake samples are collected in plastic Cubitainers and are stored at 4°C until use.
2.5.8 Calibration and Standardization
Step 1 - Turn on the nephelometer power and lamp. Allow to warm up for 15 to 30 minutes.
Step 2 - Set the nephelometer range switch to 20. Zero the instrument with the zero knob.
Step 3- Place the 10.0-NTU calibration standard in the instrument. Calibrate by setting the reading to
10.0 with the calibrate knob.
2.5.9 Quality Control
QC procedures are outlined in Figure 2.11 and are described in sections 2.5.9.1 through 2.5.9.3.
2.5.9.1 Initial Calibration Verification and Linearity Check
Immediately after calibration, analyze the 1.7-, 5.0-, and 20.0-NTU QC samples to ensure the calibra-
tion validity and linearity. The measured values must be 1.7 ± 0.3, 5.0 ± 0.5, and 20.0 ± 1.0. If the
measured values are unacceptable, the calibration must be repeated. Ensure that the instrument is
warmed up and that the cuvettes are clean. Acceptable results must be obtained prior to sample
analysis.
2.5.9.2 Continuing Calibration Check
After every eight samples and after the last sample reanalyze the 5.0-NTU QC sample. The measured
value must be 5.0 ± 0.5 NTU. If it is not, recalibrate the instrument and re analyze all samples ana-
lyzed since the last acceptably analyzed QC sample.
2.5.9.3 Duplicate Analysis
In order to determine the analytical precision, analyze one sample per batch in duplicate.
2.5.70 Procedure
Step 1 - Warm up the nephelometer.
Step 2 - Calibrate the nephelometer.
Step 3 - Analyze the QC samples. Proceed with the sample analysis if acceptable results are
obtained.
Step 4 - Allow the sample Cubitainer to reach room temperature. Gently swirl sample Cubitainers to
mix and distribute any particles which may have settled out during sample transport. Care must be
taken to avoid agitation-induced air bubbles, which interfere with the measurement. Rinse the nephe-
lometer cuvette with two 5-mL portions of sample, then fill (approximately 25 mL sample). Wipe the
cuvette with a Kimwipe, insert the cuvette into the nephelometer, and measure the turbidity on range
20. (Note: Fingerprints, bubbles, smudges, etc., must be avoided because they will affect the accu-
racy of the system.) The turbidity of a sample is not expected to exceed 20 NTU; however, if this
occurs, the sample must be analyzed on range 200. In this case, a QC sample with a turbidity greater
than the sample must be analyzed (50-, 100-, or 200-NTU QC samples are available). Acceptable
results for the QC samples are 50 ± 2.5, 100 ± 5, and 200 ± 10, respectively. If an acceptable QC
26
-------
Perform initial calibration!
Range: 20
Cal. Std.: 10 NTU
Make calibration linearity check
1. Analyze 1.7-NTU QC sample.
2. Analyze 5-NTU QC sample.
3. Analyze 20-NTU QC sample.
YES / Are measured values
1.7 ± 0.3,5.0 ± 0.5,
20.0 ± 1.0
Record values in logbook,
and record value for 5-NTU
standard on Form 2.
(1)
Analyze up to 8 samples.
Record results in logbook.
Record QC result and
previous sample results on
Form 2.
YES
NO
Check instrument
operation, standard
concentrations, etc.
Samples associated
with unacceptable QC
must be reanalyzed
when acceptable QC is
obtained.
Analyze 5-NTU QC sample.
measured value 5 ± 0.5 NTU?
/
NO
(1) Analyze one sample per batch in duplicate.
Figure 2.11. Flow Scheme for Turbidity Determinations.
27
-------
value is not obtained, the turbidimeter must be recalibrated on range 200 using a 100-NTU QC stand-
ard, and the sample must be reanalyzed. If the sample turbidity exceeds 200 NTU, the sample must be
diluted 1:10 with filtered sample and must be reanalyzed on range 200 as stated above. The turbidity
of the original sample is calculated by multiplying the turbidity of the dilute sample by the dilution
factor.
Step 5 - Rinse cuvette thoroughly with water between samples.
2.5.17 Calculations
No calculations are required.
2.5.72 Reporting
Record the sample and QC data in the turbidity logbook and on Form 2. Report only the QC data for
the 5.O-NTU QC sample on Form 2.
2.6 DETERMINATION OF TRUE COLOR
2.6.7 Scope and Application
This method is applicable to the determination of true color in natural surface waters and is written
specifically forthe NSWS. True color is determined in the field station using a Hach Color Determina-
tion Kit. As a result, the method has been written assuming that the Hach Color Determination Kit is
used.
The applicable color range is 0 to 200 APHA platinum-cobalt color units (PCUs) (APHA, 1985; U.S.
EPA, 1983).
2.6.2 Summary of Method
Samples are collected at the lake site in Cubitainers. At the field station, the true color is determined
after centrifuging a sample and comparing its color to APHA color standards.
2,6.3 Interferences
No interferences are known.
2.6.4 Safety
The sample types pose no hazard to the analyst.
2.6.5 Apparatus and Equipment
Hach Model CO-1 Color Determination Kit
Sample cuvettes
2.6.6 Reagents and Consumable Materials
Water. Water used to rinse cuvettes must conform to ASTM specifications for Type I water
(ASTM, 1984). It is obtained from the Millipore Milli-Q water system.
2.6.7 Sample Collection, Preservation, and Storage
Lake samples are collected in plastic Cubitainers and stored at 4°C until use.
28
-------
2.6.8 Calibration and Standardization
The color kit contains permanent color standards. No calibration is necessary.
2.6.9 Quality Control
Duplicate Analysis. To determine the analytical precision, analyze one sample per batch in duplicate.
2.6.10 Procedure
Step 1 - Allow the samples to reach room temperature.
Step 2 - Centrifuge a 50-mL sample to remove turbidity. Rinse a sample cuvette with three 5-mL por-
tions of centrifuged sample. Fill the cuvette with sample, and cap it. Determine the color using the
color kit follow ing the manufacturer's instructions.
Step 3 - Rinse the sample cuvette thoroughly with water between samples.
2.6.77 Calculations
No calculations are necessary.
2.6.72 Reporting
Record the sample data in the color logbook and on Form 2.
2.7 ALIQUOT AND SPLIT SAMPLE PREPARATION
2.7.7 Summary
Lake samples are collected in 4-L Cubitainers. From each sample, seven aliquots are prepared. Each
is processed in a different manner according to which analytes will be determined in the aliquot.
In addition to the seven aliquots, split samples are also prepared from some lake samples. Split
samples are similar to the aliquots but are sent to noncontract laboratories (i.e., laboratories not
under contract to perform the NSWS analyses) for the purposes of international cooperation and
exploratory analyses.
A brief description of the seven aliquots is given in Table 2.3 and of the split samples in Table 2.4.
2.7.2 Safety
The sample types and most reagents used in preparing aliquots pose no hazard to the analyst. Pro-
tective clothing (lab coat and gloves) and safety glasses must be used when handling concentrated
sulfuric, nitric, hydrochloric, and glacial acetic acids and concentrated ammonium hydroxide. The
use of hydrochloric and acetic acids and of ammonium hydroxide should be restricted to the hood.
MIBK is a highly flammable organic solvent and must be kept away from ignition sources. Also, MIBK
vapor is irritating to the eyes, nose, and throat. Exposure to the vapor may cause temporary irritation.
Liquid MIBK is also an irritant. If spilled on skin or in eyes, wash affected area thoroughly with water
until irritation stops. The use of MIBK should be restricted to the hood. If it must be used outside of
the hood, organic vapor masks should be worn.
2.7.3 Apparatus and Equipment
Filtration Apparatus. Includes filter holder, vacuum chamber, and vacuum pumps.
29
-------
Aliquot
1
2
3
4
5
6
7
Container Description
250 ml
(acid-washed)
10 mL
(acid-washed)
250 ml
(not acid-washed)
125 ml
(acid-washed)
500 mL
(not acid-washed)
125 mL
(acid-washed)
125 mL
(acid-washed)
Description
Filtered sample acidified with HN03 to a
pH<2
MIBK-Hydroxyquinoline extract
Filtered sample
Filtered sample acidified with H2S04 to a
pH<2
Raw unfiltered sample
Unfiltered sample acidified with H2S04 to a pH <2
Unfiltered sample acidified with HN03 to
apH<2
Table 2.3. Aliquot Descriptions.
Split
EPA-Corvallis
Norwegian6
Canadian11
Container Description
250 mL
(acid-washed)
500 mL
(not acid-washed)
250 mLc
(not acid-washed)
250 mLc
(acid-washed)
250 mLd
(not acid-washed)
125 ml"
(not acid-washed)
Number
All samples3
90
115
115
115
115
Descriptions
Filtered sample acidified with HN03 to a pH < 2
Raw unfiltered sample
Raw unfiltered sample
Raw unfiltered sample acidified with HN03 to a pH <2
Raw unfiltered sample
Raw unfiltered sample
a Except when there is insufficient sample due to other splits.
b Sample to be taken in the Northeast.
c Sent to Ontario Ministry of the Environment, Rexdale, Ontario, Canada.
d Sent to Canada Center for Inland Waters, Burlington, Ontario, Canada.
Table 2.4. Split Sample Descriptions.
30
-------
2.7.4 Reagents and Consumable Materials
Ammonium Hydroxide (1 M)--Carefully add 20 ml_concentrated ammonium hydroxide (NH4OH, 5
M, Baker Instra-Analyzed grade or equivalent) to 80 mL water, then dilute to 100 mL
Hydrochloric Acid (2.5 M)--Carefully add 208 mL concentrated hydrochloric acid (HCI, 12 M,
Baker Instra-Analyzed grade or equivalent) to 500 mL water, then dilute to 1.0 L.
8-hydroxyquinoline Solution (10 g/L)--Dissolve 5 g 8-hydroxyquinoline (99 percent plus purity) in
12.5 mL glacial acetic acid (HOAc, Baker Instra-Analyzed grade or equivalent), then dilute to 500
mL with water.
8-hydroxyquinoline/Sodium Acetate Reagent (HOx Reagent)--Prepare daily by mixing in order, 30
mL 1.0 M NaOAc, 150 mL water, and 30 mL 8 hydroxyquinoline solution.
NH4 + /NH3 Buffer Solution (pH 8.3)--Adjust the pH of 21 mL concentrated NH4OH (5 M, Baker
Instra-Analyzed grade or equivalent) to 8.3 with 2.5 M HCI (test the pH with indicating pH paper),
then add an additional 32 mL of the NH4OH. If the total volume is less than 100 mL, dilute to 100
mL with water.
NOTE: Prepare the buffer solution in a hood. Add the HCI to the solution slowly to minimize forma-
tion of dense, white fumes (the fumes are corrosive and can cause NH4+ and Cl- contamination in
samples).
Nitric Acid (HNO3,12 M, Baker Ultrex grade or equivalent).
Phenol Red Indicator Solution (4 percent w/v).
Sodium Acetate (NaOAc, 1.0 M) - Dissolve 8.20 g sodium acetate (Alfa ultrapure grade or equiva-
lent) in water, then dilute to 100 mL.
Sulfuric Acid (H2SO4,18 M, Baker Ultrex grade or equivalent).
Water - Water used in all preparations must conform to ASTM specifications for Type I water
(ASTM, 1984). It is obtained from the Millipore Milli-Q water system.
Aliquot Bottles - Clean aliquot bottles are required for the split samples and the seven aliquots
prepared from each sample (see Tables 2.3 and 2.4 for the size and quantity required). The bottles
are cleaned (using the procedure in Appendix A) and are supplied by an out side contractor.
Indicating pH Paper (Range 8 to 9 and 1 to 3)
Membrane Filters (0.45-m pore size)
2.7.5 Procedure
Preparation of the seven aliquots and split samples is described in this section. All filtrations and
aliquot 2 preparation are performed in the laminar-flow clean work station.
2.7.5.1 Preparation of Aliquots 1 and 4
Step 1 - Complete aliquot labels for aliquots 1 and 4 and attach to containers. Assemble the filtration
apparatus with a waste container as a collection vessel. Thoroughly rinse the filter holder and mem-
brane filter in succession with 20 to 40 mL water, 20 mL 5 percent HNO3 (Baker Instra-Analyzed
grade), and 40 to 50 mL water.
Step 2 - Rinse the filter holder and membrane with 10 to 15 mL of the sample to be filtered.
Step 3 - Replace the waste container with the aliquot 1 container. Reapply vacuum (vacuum pressure
must not exceed 12 in. Hg), and filter 10 to 15 mL of sample. Remove the vacuum. Rinse the aliquot 1
container with the 15 mL of filtered sample by slowly rotating the bottle so that the sample touches
all surfaces. Discard the rinse sample and replace the container under the filter holder.
31
-------
Step 4 - Filter sample into the container until full.
Step 5 - Transfer filtered sample into the aliquot 4 container (previously labeled) after first rinsing the
container with 10 to 15 ml_ filtered sample.
Step 6 - Return the aliquot 1 container to the filtration apparatus and collect additional filtered sam-
ple until the container is full.
If it is necessary to replace a membrane (due to clogging) before adequate filtered sample has been
obtained, rinse the new membrane with 15 to 20 ml_ water, 10 to 15 mL 5 percent HNO3, 40 to 50 mL
water, and 10 to 15 mL sample prior to collecting additional sample.
Step 7 - Between samples, remove the membrane and thoroughly rinse the filter holder with water.
Step 8 - Preserve by adding concentrated HNO3 to aliquot 1 and con centrated H2SO4 to aliquot 4 in
0.100-mL increments until the pH < 2 (U.S. EPA, 1983). Check the pH by placing a drop of sample on
indicating pH paper using a clean plastic pipet tip. Record on the aliquot label the volume of acid
added.
Step 9 - Store aliquots 1 and 4 at 4°C until ready to ship.
2.7.5.2 Preparation of Aliquot 2 - Total Extractable Aluminum (Barnes, 1975)
Step 1 - Obtain a filtered portion of sample from the analyst perform ing filtrations.
Step 2 - Rinse a clean, plastic 50-mL graduated centrifuge tube with three 10-mL portions of the
filtered sample, then fill to the 25.0-mL mark.
Step 3 - Add two to three drops phenol red indicator, 5.0 mL HOx reagent, and 2.0 mL NH4 + /NH3
buffer. Shake for 5 seconds. This should adjust the pH to 8.3 and the solution should turn red. If it
does not turn red, rapidly adjust the pH by dropwise addition of 1 M NH4OH until the solution color
changes to red. Add 10.0 mL MIBK, cap, and shake vigorously for 10 seconds using a rapid, end-to-
end motion. (Note: Successful extraction depends on good agitation.) This entire process should
take about 15 to 20 seconds. Open tube carefully after shaking, because pressure builds up.
Step 4 - Centrifuge the sample to hasten separation of the aqueous and organic layers, then transfer
the MIBK layer with a 5-mL micropipet to a 10-mL centrifuge tube. Securely cap tube.
Step 5 - Complete a label for aliquot 2 and attach label to the container.
Step 6 - Store the 10-mL tube containing aliquot 2 at 4°C in the dark until ready to ship.
Step 7 - Discard the 50-mL centrifuge tube after a single use.
2.7.5.3 Preparation of Aliquot 3
Filtered sample for aliquot 3 is obtained similarly to that for aliquots 1 and 4, except that the filter
holder used to filter aliquot 3 is never allowed to come into contact with nitric acid. This is CRUCIAL
in preventing nitrate contamination. Previous experience indicates that even the most scrupulous
water rinses did not remove all traces of a nitric acid rinse. Blanks still contained measurable nitrate.
Step 1 - Soak filter holders for 24 hours in deionized water prior to first use.
Step 2 - Complete an aliquot 3 label and attach label to the aliquot bottle. Assemble the filtration
apparatus with a waste container as a collection vessel. Thoroughly rinse the filter holder and mem-
brane filter with three 25-mL portions water, followed by 10 to 15 mL sample to be filtered.
Step 3 - Replace the waste container with the aliquot 3 container and filter an additional 15 mL
sample. Remove the container and rinse by slowly rotating the bottle so that the sample touches all
surfaces. Discard the rinse sample and replace the container under the filter holder.
Step 4 - Filter sample into the container until full.
32
-------
If it is necessary to replace a membrane (due to clogging), rinse the membrane with three 20-mL
portions water followed by 15 ml_ sample before collecting additional sample.
Step 5 - Between samples, remove the membrane and thoroughly rinse the filter holder with water.
Step 6 - Store at 4°C until ready to ship.
2.7.5.4 Preparation of Aliquots 5, 6, and 7
Aliquots 5, 6, and 7 are unfiltered aliquots.
Step 1 - Complete aliquot 5, 6, and 7 labels and attach to the appropriate aliquot bottles. Transfer 15
to 20 mL sample to aliquot bottle and rinse by slowly rotating bottle so that sample touches all sur
faces. Discard rinse.
Step 2 - Fill aliquot bottle with unfiltered sample. Fill aliquot 5 bottle so that no headspace exists.
Step 3 - Preserve by adding concentrated HNO3 to aliquot 7 and concentrated H2SO4 to aliquot 6 in 0.100-
mL increments until pH < 2 (U.S. EPA, 1983). Check the pH by placing a drop of sample on indicating pH
paper using a clean plastic pipet tip. Record the volume of acid added on the aliquot label.
Step 4 - Store at 4°C until ready to ship.
2.7.5.5 Preparation of Split Samples
Three different split samples are prepared, depending upon their destination (Canada, EPA-Corvallis,
or Norway). Descriptions of each split are listed in Table 2.4.
EPA Corvallis splits. Prepare a split sample for Corvallis from all samples following the proce-
dure for aliquot 1 preparation, with the exception that only 125 mL of sample need be filtered and
collected. When sample volume limitations exist, other sample splits take precedence. Record
the split code "E" on Form 2.
Norwegian splits. Prepare a split sample for Norway from 90 samples in the Northeast (as
directed by the QA manager) following the procedure for aliquot 5 preparation. Record the split
code "N" on Form 2.
Canadian splits. Prepare four split samples for Canada from 115 samples in the Northeast (as
directed by the QA manager) following the procedure below:
a. Splits C1, C3, and C4--Prepare following aliquot 5 procedure, except reduce volume and con-
tainer size (not acid-washed) to 250 mL. (C4 requires only 125 mL sample.)
b. Split C2-Prepare following aliquot 7 procedure, except increase volume and container size
(acid-washed) to 250 mL
c. Split C4--Prepare following aliquot 5 procedure.
d. Record the split code "C" on Form 2.
2.8 REFERENCES
American Public Health Association, 1985. Standard Methods for the Examination of Water and Was-
tewater, 16th ed., APHA, Washington.
American Society for Testing and Materials, 1984b. Annual Book of ASTM Standards, Vol. 11.01,
Standard Specification for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia,
Pennsylvania.
Barnes, R. B., 1975. The Determination of Specific Forms of Aluminum in Natural Water. Chem. Geol.
v. 15, pp. 177-191.
Monitek, Inc., 1977. Model 21 Laboratory Nephelometer, Preliminary Operating and Maintenance
Instructions. Hayward, California.
33
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Morris, F. A., D. V. Peck, D. C. Hillman, K. J. Cabbie, M. B. Bonoff, S. L Pierett, 1986. National Surface
Water Survey. Eastern Lake Survey (Phase I -- Synoptic Chemistry) Field Operations Report.
U.S. Environmental Protection Agency, Las Vegas.
Orion Research Incorporated, 1983. Instruction Manual - Model 611 pH/milli volt manual. Orion, Cam-
bridge, Massachusetts.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes. EPA-600/4-79-020. U.S. EPA, Cincinnati, Ohio.
Xertex-Dohrman Corporation, 1984. DC-80 Automated Laboratory Total Organic Carbon Analyzer
Systems Manual, 6th ed. Xertex-Dohrman, Santa Clara, California.
34
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SECTION 3
ANALYTICAL LABORATORY OPERATIONS
3.1 SUMMARY OF OPERATIONS
Samples are shipped from the field stations to the contract analytical laboratories for analysis. Each
sample consists of seven aliquots, each processed in a different manner depending on the analytes
for which the aliquot will be analyzed. A brief description of each aliquot and its corresponding analy-
tes is given in Table 3.1.
After receipt, the analytes in each sample are quantified. The analyses must occur within the pre-
scribed holding times (listed in Table 3.2) or a penalty is assessed against the lab. Strict QC require-
ments must be followed throughout the analyses. Finally, the sample results must be reported in the
proper format, on a timely basis, for entry in the NSWS data base.
3.2 SAMPLE RECEIPT AND HANDLING
Samples are shipped to the contract laboratory by overnight delivery service. Upon receipt, measure
the temperature inside the shipping container and record the temperature on the shipping form. Log
in samples and ensure that the samples listed on the shipping form have actually been received.
Note anything unusual (such as leaking samples) on the shipping form.
Store sample aliquots 2,3,4,5 and 6 in the dark at 4°C when not in use. The samples must be stored at
4°C for 6 months or until notified by the QA manager.
Clean all labware that comes into contact with the sample (such as autosampler vials, beakers, etc.)
as described in Appendix A.
Aliquot'
1
2
3
4
5
6
7
a Aliquots 2,
Container
250 ml
10 ml
250 mL
125 ml
500ml
125 ml
125 ml
3, 4, 5, and 6 must be
Preservative and
Description
Filtered, pH<2 with HN03
MIBK-HQ extract
Filtered
Filtered, pH<2with H2S04
Unfiltered
Unfiltered, pH<2 with H2S04
Unfiltered, pH <2 with HN03
stored at 4°C in the dark.
Parameters
Ca, Mg, K, Na, Mn, Fe
Total extractable Al
Cl~, F", S042~, N03", Si02
DOC, NH4+
pH, acidity, alkalinity, specific conductance, QIC
Total P
Total Al
Table 3.1. List of Aliquots, Containers, Preservatives, and Corresponding Parameters to be Measured.
35
-------
Holding
Time Parameter
7 days N03",a pH," Total extractable Al
14 days Alkalinity, acidity, specific conductance, DIG, DOC
28 days Total P, NH4+, Cf, S042", F, Si02
6 months ° Ca, Mg, K, Na, total Al, Mn, Fe
a Although the EPA (U.S. EPA, 1983) recommends that nitrate in unpreserved samples (un-acidified) be determined within 48
hours of collection, evidence exists (Peden, 1981 and APHA et. al., 1985) that nitrate is stable for 2 to 4 weeks if stored in the
darkat4°C.
b Although the EPA (U.S. EPA, 1983) recommends that pH be measured immediately after sample collection, evidence exists
(McQuaker et. al., 1983) that it is stable for up to 15 days if stored at 4°C and sealed from the atmosphere. Seven days is
specified here as an added precaution. The pH is also measured in a sealed sample at the field station within 12 hours of sample
collection.
c Although the EPA (U.S. EPA, 1983) recommends a 6-month holding time for these metals, this study requires that al of the
metals be determined within 28 days This is to ensure that significant changes do not occur and to obtain data in a timely
manner.
Table 3,2. List of Holding Times.
3.3 SAMPLE ANALYSIS
The analytes to be determined in each sample and corresponding measurement techniques are
listed in Table 3.3, and the method protocols are provided in sections 4 through 13. Each analyte must
be determined within the hold ing times listed in Table 3.2.
3.4 INTERNAL QUALITY CONTROL REQUIREMENTS
QC is an integral part of sample analysis. Method QC requirements common to all methods are
detailed in this section. QC requirements specific to a single method are detailed in the description
for that method.
3.4.7 Method Quality Control
Each method contains specific QC steps which must be performed to ensure data quality. Table 3.4 is
a brief summary of the required QC checks as well as control limits and corrective actions for QC
checks outside control limits. QC steps common to all (or most) of the methods are detailed in sec-
tions 3.4.1.1 through 3.4.1.4, while QC steps specific to a single method are detailed in the method
protocol.
3.4.1.1 Calibration Verification QC Check Sample
After performing the calibration step for a method, verify the calibration (to ensure proper standard
preparation, etc.) prior to sample analysis by analyzing a calibration QC check sample (QCCS). The
QCCS is a known sample containing the analyte of interest at a concentration in the low- to mid-
calibration range. Furthermore, the QCCS must be independent of the calibration standards.
For each batch of samples, analyze the calibration QCCS immediately after calibration, after every
10 sample analyses, and after the final sample analysis. Plot the measured analyte concentration in
36
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Parameter
Method
1. Acidity
2. Alkalinity
3. Aluminum, total
4. Aluminum, total extractable
5. Ammonium, dissolved
6. Calcium, dissolved
7. Chloride, dissolved
8. Fluoride, total dissolved
9. Inorganic carbon, dissolved
10. Iron, dissolved
11 Magnesium, dissolved
12. Manganese, dissolved
13. Nitrate, dissolved
14. Organic carbon, dissolved
15. pH
16. Phosphorus, total
17. Potassium, dissolved
18. Silica, dissolved
19. Sodium, dissolved
20. Sulfate, dissolved
21. Specific conductance
Titration with Gran analysis
Titration with Gran analysis
202.2 AAS (furnace)
Extraction with 8-hydroxyquinoline into MIBK followed by AAS (furnace)
Automated colorimetry (phenate)
AAS (flame) or 1CPES
Ion cnrqmatography
Ion-selective electrode and meter
Instrument (acidification, C02 generation, IR detection)
AAS (flame) or ICPES
AAS (flame) or ICPES
AAS (flame) or ICPES
Ion cnromatography
Instrument (uv-promoted oxidation, C02 generation, IR detection)
pH electrode and meter
Automated colorimetry (phosphomolybdate)
AAS (flame)
Automated colorimetry (molybdate blue)
AAS (flame)
Ion chromatography
Conductivity cell and meter
Table 3.3. List of parameters and Corresponding Measurement Methods.
the QCCS on a control chart and develop the 95 percent and 99 percent confidence intervals. The 99
percent confidence interval must be within the limits given in Table 3.5. (The limits in Table 3.5 may be
used as initial limits until enough data are obtained to generate a control chart.) If the 99 percent
confidence interval is not within those limits, a problem exists with the experimental technique or the
QCCS itself.
The measured analyte concentration in the QCCS must be within the 99 percent confidence interval.
An acceptable result must be obtained prior to continuing sample determinations. If unacceptable
results are obtained, repeat the calibration step and reanalyze all samples analyzed since the last
acceptably analyzed QCCS.
3.4.1.2 Detection Limit Determination and Verification
Determine the detection limit weekly for all parameters (except pH alkalinity, acidity, and specific
conductance for which the term detection limit does not apply). For the NSWS, the detection limit is
defined as three times the standard deviation of 10 nonconsecutive reagent or calibration blank anal-
yses. In the case where a signal is not obtained for a blank analysis (such as in ion chromatographic
analyses or autoanalyzer analyses), a low concentration standard (concentration about three to four
times the detection limit) is analyzed rather than a blank. Detection limits must not exceed the values
listed in Table 1.1. If a detection limit is not met, refine the analytical technique and optimize any
instrumentation variables until the detection limit is achieved.
To verify the detection limit for the determination of metals and total P daily, analyze a detection limit
QCCS after calibration and prior to sample analysis. The detection limit QCCS must contain the
analyte of interest at two to three times the detection limit. The measured concentration must be
within 20 percent of the true concentration. If it is not, the detection limit is questionable. Determine
the detection limit as described above.
3.4.1.3 Blank Analysis
Once per batch analyze a calibration blank as a sample. The calibration blank is defined as a "O" mg/
37
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Parameter or Method
QC Check
Control Limits
Corrective Action3
Acidity, Alkalinity, pH
1. Titrant standardization cross-check.
2. Electrode calibration (Nernstian
response check).
3. pH QCCS (pH 4 and 10) analysis.
4. Blank analysis (salt spike).
5. Duplicate analysis.
6. Protolyte comparison.
1. Relative difference < 5%.
2. Slope = 1.00 ± 0.05.
3. pH 4 = 4.00 ± 0.05.
4. IBIankJ<10/*eq/L
5. RSD<10%.
6. See method (Section 4).
1. Restandardize titranfs.
2. Recalibrate or replace electrode.
3. Recalibrate electrode.
4. Prepare fresh KCI spike solution.
5. Refine analytical technique. Analyze
another duplicate.
6. See method (Section 4).
lons(Cf, F", NH4+, N03~,
so42-),
Metals (Al, Ca, Fe, K, Mg, Mn,
Na),
Si02, Total P, DIG, DOC
Specific Conductance
1a. Initial QCCS analysis (calibration and
verification).
b. Continuing QCCS analysis (every 10
samples).
2a. Detection limit determination (weekly).
b. DL QCCS analysis (daily, metals, and
total P only).
3. Blank analysis.
4. Duplicate analysis.
5. Matrix spike (except total ext. Al, DIG,
and sp. cond.).
6. Resolution test (1C only).
1a, b. The lesser of the 99% Cl or value
given in Table 3.5
2a. DL < values in Table 1.1.
b. % Recovery = 100 ±20%.
3a. Blank <2 x DL (except sp. cond.).
b. Blank <0.9 S/cm (sp. cond. only).
4. Duplicate precision (BSD) < values
given in Table 1.1.
5. % Recovery = 100 ± 15%.
6. Resolution >60%.
1a. Prepare new standards and recalibrate.
b. Recalibrate. Reanalyze associated
samples.
2a, b. Optimize instrumentation and
technique.
3a, b. Determine and eliminate
contamination source. Prepare fresh
blank solution. Reanalyze associated
samples.
4. Investigate and eliminate source of
imprecision. Analyze another duplicate.
5. Analyze 2 additional spikes. If one or
both outside control limits, analyze
sample batch by method of standard
additions.
6. Clean or replace separator column.
Recalibrate.
Assuming QC check is outside control limits.
Tabie 3.4. Summary of Internal Method Quality Control Checks.
-------
Parameter
Al, total extractable
Al, total
Ca
cr
DIG
DOC
F", total
Fe
K
Mg
Mn
Na
NH4+
N03"
P, total
Si02
S042~
Specific conductance
Maximum Control Limit for QC Sample (% Deviation from
Theoretical Concentration of QC Sample)
±20%
±20%
± 5%
± 5%
±10%
±10%
± 5%
±10%
± 5%
± 5%
±10%
± 5%
±10%
±10%
±20%
± 5%
± 5%
± 2%
Table 3.5. Maximum Control Limits for Quality Control Samples.
L standard (contains only the matrix of the calibration standards). The measured concentration of
the calibration blank must be less than twice the instrumental detection limit. If not, the blank is
contaminated or the calibration is in error at the low end. Prior to sample analysis, investigate and
eliminate any contamination source and repeat the calibration.
Prepare and analyze a reagent blank for the three methods which require sample preparation (dis-
solved SiO2, total P, and total Al). A reagent blank contains all the reagents (in the same quantities)
used in preparing a real sample for analysis. Process in the same manner (digestions, etc.) as a real
sample. The measured concentration of the reagent blank must be less than twice the required
detection limit (Table 1.1). If it is not, the reagent blank is contaminated. Investigate and eliminate the
contamination source. Prepare and analyze a new reagent blank and apply the same criteria. Reana-
lyze all samples associated with the contaminated blank when the contamination is eliminated. Con-
tact the QA manager if a contaminated reagent blank problem cannot be rectified.
Prepare one reagent blank with each set of samples processed at one time. For example, if two sam-
ple batches are processed together, only one reagent blank is necessary. Report the concentration of
the single reagent blank for both batches. On the other hand, if a sample batch is split into groups
that are processed at different times, a reagent blank is necessary for each group. In this case, report
all reagent blank values for the batch. (Identify in a cover letter which reagent blank values are associ-
ated with which samples.)
3.4.1.4 Duplicate Sample Analysis
Prepare and analyze one sample per batch in duplicate. If possible, for duplicate analysis choose a
sample containing analyte at a concentration greater than five times the detection limit. Calculate
the relative standard deviation (RSD) between duplicates. The duplicate precision (RSD) must not
39
-------
exceed the value given in Table 1.1. If duplicate RSD values fall outside the values given in Table 1.1, a
problem exists (such as instrument malfunction, calibration drift, etc.). After finding and resolving
the problem, analyze a second sample in duplicate. Acceptable duplicate sample results must be
obtained prior to continuing sample analysis.
% RSD = _JL_ x 100
x
s = / 2 (x- x)2 \ 1/2
(2 (x - x)" \
n-1 )
3.4.1.5 Matrix Spike Analysis
Prepare one matrix spike with each batch by spiking a portion of a sample with a known quantity of
analyte. The spike concentration must be the larger of two times the endogenous level or ten times
the required detection limit. Also, the volume of the spike added must be negligible (less than or
equal to 0.001 of the sample aliquot volume). Calculate the percent recovery of the spike as follows:
measured measured
(measured measureu »
concentration concentration \
of sample of unspiked I
plus spike sample /
plus spike sample
% spike recovery = x 100
(actual concentration
of spike added)
The spike recovery must be 100 ± 15 percent. If the recovery is not acceptable, spike and analyze two
additional, different samples. If either recovery is unacceptable, analyze the entire batch by the
method of standard additions. The method of standard addition involves analyzing the sample, sam-
ple plus a spike at about the endogenous level, and sample plus a spike at about twice the endoge-
nous level.
NOTE: Matrix spikes for graphite furnace atomic absorption spectroscopy (GFAA) analyses may not
be added directly in the furnace.
The concentration of the matrix spike must not exceed the instrument linear dynamic range. For this
reason, the matrix spike concentration for furnace analyses must be chose n judiciously and may be
different than suggested above.
Similarly, care must be taken to avoid exceeding the linear range when performing standard addi-
tions for GFAA analyses. The samples may be diluted and the spike levels may be adjusted so that
the linear range is not exceeded.
3.4.2 Overall Internal Quality Control
Once each parameter in a sample has been determined, two procedures exist for checking the cor-
rectness of analyses. These procedures are outlined in sections 3.4.2.1 and 3.4.2.2.
3.4.2.1 Anion-Cation Balance
Theoretically, the acid neutralizing capacity (ANC) of a sample equals the difference between the
concentration (eq/L) of cations and the anions in a sample (Kramer, 1982). In practice, this is rarely
true due to analytical variability and to ions that are present but not measured. For each sample,
calculate the percent ion difference (%ID) as follows:
40
-------
% Ion Difference =
ANC + 2 anions - 2 cations
Tl
x 100
Tl (Total ion strength) = 2 anions + 2 cations + ANC + 2 [H+]
anions = [C\~\ + [F] + [N03~] + [SO/']
cations =
ANC = [ALK]
[H+] = (10-pH) x 106 /ueq/L
All concentrations are expressed as microequivalents/liter ( ju eq/L). Table 3.6 lists factors for converting
mg/L to /ueq/L for each of the parameters.
The %ID must not exceed the limits given in Table 3.7. An unacceptable value for %ID indicates the
presence of unmeasured ions or an analytical error in the sample analysis. For the surface waters
sampled, the ions included in the %ID calculation are expected to account for 90 to 100 percent of
the ions in a sample. Note that the ANC term in the calculation accounts for protolyte ions that are
not specifically determined (such as organic acids and bases).
Examine the data from samples that do not meet the %ID criteria for possible causes of unaccepta-
ble % ID. Often, the cause is improper data reporting (misplaced decimal point, incorrect data reduc-
tion, switched sample ID's, etc.). After examining the data, redetermine any parameter that is sus-
pect. If an explanation for the poor %ID cannot be found and the problem cannot be corrected,
contact the QA manager at EMSL-Las Vegas for further guidance.
3.4.2.2 Conductivity Balance
Estimate the specific conductance of a sample by summing the equivalent conductances for each
measured ion. Calculate the equivalent conductance for each ion by multiplying the ion concentra-
tion by the appropriate factor in Table 3.8 (only major ions are included in the calculation). Calculate
the percent conductance difference (%CD) as follows:
% Conductance Difference =
calculated cond. - measured cond.
measured conductance
x 100
Ion
Ca2+
cr
r
K+
Mg2+
Ha+
NH4+
S042'
Factor
(/ueq/L per mg/L)
49.9
28.2
52.6
25.6
82.3
43.5
55.4
16.1
20.8
Figure 3.6. Factors to Convert mg/L to
41
-------
A. Anion-Cation Balance
Maximum
Total Ion Strength (/*eq/L) % Ion Difference3
< 50 60
>50<100 30
>100 15
B. Specific Conductance
Maximum
Measured Conductance ( S/cm) % Conductance Difference3
<5 50
>5<30 30
>30 20
If the absolute value of the percent difference exceeds these values, the sample is reanalyzed. When reanalysis is indicated,
the data for each parameter are examined for possible analytical error. Any suspect results are then redetermmed and the above
percent differences are recalculated (Peden, 1981). If the differences ae still unacceptable or no suspect data are identified,
the QA manager should be contacted for guidance.
Table 3.7. Chemical Reanalysis Criteria.
The %CD must not exceed the limits listed in Table 3.7. As with the % ID calculation, an unacceptable
value for % CD indicates either the presence of unmeasured ions or an analytical error in the sample
analysis. For the surface waters sampled, the ions included in the %CD calculation are expected to
account for 90 to 100 percent of the ions in a sample. However, in contrast to the %1D calculation,
there is no term in the %CD calculation to account for protolytes not specifically determined.
Examine the data from samples that do not meet the %CD criteria for possible causes of the unac-
ceptable %CD, such as improper data reporting or analysis. The presence or absence of unmeasured
protolytes can be tested by the procedures described in section 4. Note that the absence of unmea-
sured protolytes is positive evidence that the %CD exceeds the maximum difference due to analyti-
cal error. Redetermine any parameterthat is identified as suspect. If an explanation for the poor %CD
cannot be found and the problem cannot be corrected, contact the QA manager at EMSL-Las Vegas
for further guidance.
3.5 DATA REPORTING
Record the results from each method on the data form indicated in Table 3.9 (blank data forms are
included in Appendix B). Report results to the number of decimal places in the actual detection limit.
However, report no more than four significant figures. Sample results from reanalyzed samples
(occasionally samples are reanalyzed for QC reasons) are annotated by the letter R. Results obtained
by standard additions are annotated by the letter G. These and other data qualifiers are listed in Table
3.10. After the forms are completed, the laboratory manager must sign them, indicating he has
reviewed the data and that the samples were analyzed exactly as described in this manual. All devia-
tions from the manual require the authorization of the QA manager prior to sample analysis.
42
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Ion
Specific
Conductance
OuS/cm at 25 °C)
per mg/L
Ion
Specific
Conductance
at 25 °C)
per mg/L
Ca
cr
co3
H +
2+
2-
HC03"
Mg2+
2.60
2.14
2.82
3.5 x 105
(per mole/L)
0.715
3.82
2-
Na+
NH4+
S04:
N03
K+
OH~
2.13
4.13
1.54
1.15
1.84
1.92 x 105
(per mole/L)
[H+]moles/L = 10~pH
pH = pH determined at V = 0 of the acidity titration.
[OH'
HC0
C0
5.080[DIC(mg/L)][H+]K1
4.996 [DIC(mg/L)] K, K2
fH + l2 4. fH + l K + K K
= 4.4453 x 10~7
= 4.6881 x 10
,-11
APHA et. al., 1985 and Weast, 1972.
Table 3.8. Conductance Factors of Ions3.
3.6 REFERENCES
American Public Health Association, American Water Works Association, and Water Pollution Con-
trol Federation, 1985. Standard Methods for the Examination of Water and Wastewater, 16th Ed.
APHA, Washington, D.C.
Kramer, J. R., 1982. Alkalinity and Acidity. In: R. A. Minear, L H. Keith (eds.), Water Analysis. Vol. 1.
Inorganic Species, Part 1. Academic Press, Orlando, Florida.
McQuaker, N. R., P. D. Kluckner, and D. K. Sandberg, 1983. Chemical Analysis of Acid Precipitation:
pH and Acidity Determinations. Environ. Sci. Technol., v. 17 n. 7, pp. 431-435.
43
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Peden, M. E., 1981. Sampling, Analytical, and Quality Assurance Protocols for the National Atmo-
spheric Deposition Program. Paper presented at October 1981 ASTM D-22 Symposium and
Workshop on Sampling and Analysis of Rain. ASTM, Philadelphia, Pennsylvania.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes. EPA-600/4-79-020. U.S. EPA, Cincinnati, Ohio.
Weast, R. C. (ed.), 1972. CRC Handbook of Chemistry and Physics, 53rd Ed. CRC Press, Cleveland,
Ohio.
Data Form Description
11 Summary of sample results
12a QCCS pH results
13 Alkalinity and acidity results
14a QC data for alkalinity and acidity analysis
15a Specific conductance (measured and calculated)
16a Anion-cation balance calculations
17 Ion chromatography resolution test form
18 QA (detection limits)
19 Sample holding times summary
20 Blank and QCCS results
21 Matrix spike results
22 Duplicate results
23 Standard addition results
a Form is not required but is recommended for internal lab use.
Copies of raw data must be submitted as requested by the program manager. All original raw data must be retained by the lab
until notified otherwise. Raw data include data system printouts, chromatograms, notebooks, QC charts, standard preparation
data, and all information pertinent to sample analysis.
Table 3.9. List of Data Forms.
44
-------
Qualifier Indicates
F Result outside QA criteria (with consent of QA manager)
G Result obtained from method of standard additions
H Holding time exceeded criteria (Form 19 only)
J Result not available; insufficient sample volume shipped
K Result not available; entire aliquot not shipped
L Result not available; analytical interference
M Result not available; sample lost or destroyed by lab
N Not required
P Result outside QA criteria, but insufficient volume for reanalysis
Q Result outside QA criteria
R Result from reanalysis
S Contamination suspected
T Leaking container
U Result not required by procedure
V Anion-cation balance outside criteria due to DOC
W % Difference (%D) calculation (Form 14) outside criteria due to high DOC
Y Available for miscellaneous comments
2 Available for miscellaneous comments
Table 3.10. National Surface Water Survey Data Qualifiers.
45
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SECTION 4
DETERMINATION OF ACIDITY, ALKALINITY, AND pH
4.1 SCOPE AND APPLICATION
This procedure is applicable to the determination of pH, alkalinity, and acidity in weakly buffered
natural waters of low ionic strength. The terms alkalinity and acidity refer to the acid neutralizing
capacity (ANC) and base neutralizing capacity (BNC) of systems which are based on the carbonate
ion system. (The soluble reacting species are H2CO3, HCO3", and CO32~.) For calculation purposes, it
is assumed that the lakes in this survey are represented by a carbonate ion system; hence, the alka-
linity and acidity definitions are made in relation to the carbonate ion species (Kramer, 1982; Butler,
1982).
4.2 SUMMARY OF METHOD
Samples are titrated with standardized acid and base while monitoring and recording the pH. The
acidity (Acy) and alkalinity (Alk) are determined by analyzing the titration data using a modified Gran
analysis technique (Kramer, 1982; Butler, 1982; Kramer, 1984; Gran, 1952).
The Gran analysis technique defines the Gran functions Ft and F2 based upon sample volume, acid
(base) volume added, and carbonate dissociation constants. The Gran functions are calculated for
several data pairs (volume of titrant added, resulting pH) from a titration. The data pairs are chosen so
that they cross the alkalinity and acidity equivalence points. When the Gran functions are plotted
versus volume of titrant added, the linear portion of each curve can be interpolated to the equiva-
lence point.
The pH is determined prior to the start of the titrations with the electrode used during the titration.
(U.S. EPA, 1983; McQuaker et al., 1983; NBS, 1982).
The air-equilibrated pH is determined similarly after equilibrating the sample with 300 ppm CO2 in air.
Air equilibration is expected to normalize pH values by factoring out the day-to-day and seasonal
fluctuations in dissolved CO2 concentrations.
4.3 INFERENCES
No interferences are known.
4.4 SAFETY
The standards, sample types, and most reagents pose no hazard to the analyst. Protective clothing
(lab coat and gloves) and safety glasses must be used when handling concentrated acids and bases.
Gas cylinders must be secured in an upright position.
4.5 APPARATUS AND EQUIPMENT
pH/mV Meter-A digital pH/mV meter capable of measuring pH to ±0.01 pH unit, potential to ±1
mV, and temperature to ± 0.5°C must be used, it must also have automatic temperature compen-
sation capability.
46
-------
pH Electrodes - High-quality, low-sodium glass pH and reference electrodes must be used. (Gel-
type reference electrodes must not be used.) A combination electrode is recommended (such as
the Orion Ross combination pH electrode or equivalent), and the procedure is written assuming
one is used.
Buret - A microburet capable of precisely and accurately delivering 10 to 50 ML must be used
(relative error and standard deviation less than 1 percent).
NOTE: A commercial titration instrument meeting the same specifications may be used in
place of the pH/mV meter, pH electrodes, and buret.
Teflon-coated Stir Bars
Variable-Speed Magnetic Stirrer
Plastic Gas Dispersion Tube
NOTE: Glass dispersion tubes must not be used because they can add alkalinity to a sample.
Plastic dispersion tubes are available in most fish-aquarium supply stores.
4.6 REAGENTS AND CONSUMABLE MATERIALS
Carbon Dioxide Gas (300 ppm CO2 in Air) - Certified Standard Grade
Hydrochloric Acid Titrant, (0.01 N HCI) - Add 0.8 ml_ concentrated hydrochloric acid (HCI, 12N,
ACS reagent grade or equivalent) to 500 mL water, then dilute to 1.00 L with water. Standardize as
described in section 4.8.1.
Nitrogen Gas (N2) - CO2-free
Potassium Chloride Solution (0.10 M KCI) - Dissolve 7.5 g KCI (Alfa Ultrapure or equivalent) in
water, then dilute to 1.00 L with water.
Potassium Hydrogen Phthalate (KHP) - Dry 5 to 10 g KHP (ACS-certified primary standard grade
or equivalent) at 110°C for 2 hours, then store in a desiccator.
pH Calibration Buffers (pH 4,7, and 10) - NBS-traceable pH buffers at pH values of 4, 7, and 10.
pH QC Samples (pH 4 and 10) - pH 4 QC sample - dilute 1.00 ml standardized 0.01 N HCI titrant to
100.00 mL with water. The theoretical pH is calculated by
N
pH = -log
(INHCI \
100 )
pH 10 QC sample - Dilute 1.00 mLof the standardized 0.01 N NaOH titrant to 100.00 mL with water.
The theoretical pH is calculated by
N
pH = 14 + log
('^NaOH \
100 )
Sodium Carbonate (Na2CO3) - Dry 5 to 10 g Na2CO3 (ACS certified primary standard grade or
equivalent) at 110°C for 2 hours, then store in a desiccator.
Sodium Hydroxide Stock Solution (50 percent w/v NaOH) - Dissolve 100 g NaOH (ACS reagent
grade orequivalent) in 100 mL water. After cooling and allowing any precipitate to settle (may be
hastened by centrifugation), transfer the supernatant to a polyethylene bottle. Store tightly
capped and avoid atmospheric exposure.
47
-------
Sodium Hydroxide Titrant (0.01 N NaOH) - Dilute 0.6 to 0.7 ml_ 50 percent NaOH to 1.0 L with
water. Standardize as described in section 4.8.2.
Water - Water used to prepare reagents and standards must conform to ASTM specifications for
Type I water (ASTM, 1984).
4.7 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
The sample for which acidity, alkalinity, and pH is to be determined is delivered to the lab in a 500-mL
amber polyethylene bottle (aliquot 5). Store at 4°C and minimize atmospheric exposure.
4.8 CALIBRATIONS AND STANDARDIZATION
4.8.7 Standardization of HCI Titrant
Step 1 - Weigh about 1 g anhydrous Na2CO3 to the nearest 0.1 mg, dissolve in water, men dilute to
1.000 L Calculate the concentration by the following equation.
wt. Na2CO3 g 1
NNa2CO3 = x.
106.00 g 1 mole IL
- x -
mole 2 eq
NOTE: This solution is to be freshly prepared just before use.
Step 2 - Calibrate the pH meter and electrode as recommended by the manufacturer.
Step 3 - Pipet 1 .00 mL standard Na2CO3 plus 40.00 ml_ CO2-free water into a clean, dry titration vessel.
Add a Teflon-coated stir bar and stir at a medium speed (no visible vortex).
Step 4 - Immerse the pH electrode and record the pH when a stable reading is obtained.
Step 5 - Add a known volume of the HCI titrant and record the pH when a stable reading is obtained.
Use the following table as a guide to the volume of titrant that should be added in different pH ranges:
Maximum Volume Increment
pH of HCI Titrant (mL)
>7.5 0.2
4-7.5 0.1
< 4 .. 0.2
Continue the titration until the pH < 4. Obtain at least seven data points in the range pH 4 to 7.
Step 6 - Calculate F1b for each data pair (volume acid added, pH) with pH in the range 4 to 7:
[VSC / [H*]^ + 2 K! K2 \ Kw ]
^V)( trf + tr]Kl + Kl «2 )+^T" [H]J
F1b = Gran function
Vs = Initial sample volume = 41.00 mL
V = Volume of HCI added in mL
C = N Na2CO3/(2 x dilution factor)
K1 = 4.4463 x 10"7
K2 = 4.6881 x 10'11
Kw = 1.0123 x 10'14
48
-------
Step 7- Plot F1 b versus V. Using the points on the linear portion of the plot, perform a linear regres-
sion of F1b on V to obtain the coefficients of the line
F1b = a + bV
The correlation coefficient should exceed 0.999. If it does not, re examine the plot to make sure only
points on the linear portion are used in the linear regression.
Step 8 - Calculate the equivalence volume, V^ by
V, = -alb
then calculate the HCI normality by
N Na2CO3 x Na2CO3
NHCI =
Step 9 - Repeat the titration and calculation three times (steps 3 through 8). Calculate an average
NHC|and standard deviation. The BSD must be less than 2 percent. If it is not, the entire standardiza-
tion must be repeated until it is less than 2 percent.
Step 70 - The concentration of every new batch of HCI titrant must be cross checked using the proce-
dure described in Section 4.8.2.2.
Step 11 - Store in a clean polyethylene bottle. Although the HCI titrant is stable, it must be restandar-
dized monthly.
NOTE: An example of an HCI standardization is given in Appendix C.
4.8.2 Standardization of NaOH Titrant
Every batch of NaOH titrant is initially standardized against KHP (section 4.8.2.1) and the standardi-
zation cross-checked against standardized HCI titrant (section 4.8.2.2). Thereafter, it is restandar-
dized daily against the HCI titrant (section 4.8.2.3).
4.8.2.1 Initial NaOH Standardization
Step 1 -Weigh about 0.2 g KHP to the nearest 0.1 mg, dissolve in water, then dilute to 1.000 L. Calcu-
late the normality of the solution by the following equation.
wt. KHPg 1
NKHP = x
204.22 g 1 L
eq
Step 2 - Calibrate the pH electrode and meter as recommended by the manufacturer.
Purge the titration vessel with CO2-free nitrogen, then pipet 5.00 mL standard KHP solution and 20.00
ml CO2-f ree water into the vessel. Maintain a CO2-f ree atmosphere above the sample throughout the
titration. Add a Teflon stir bar and stir at a medium speed (no visible vortex).
Step 3 - Immerse the pH electrode and record the reading when it stabilizes.
Step 4 - Titrate with the 0.01 N NaOH using the increments specified in the table below. Record the
volume and pH (when stable) between additions. Continue the titration until the pH >10. Obtain at
least four data points in the pH range 5 to 7 and four data points in the pH range 7 to 10.
49
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Maximum Volume Increment
pH of NaOH Titrant (mL)
<5 0.10
5 to 9 0.05
> 9 0.2
Step 5 - Calculate F3b for each data pair (volume added, pH) with a pH 5-10.
VSC
(Vs + V) [H+]2 + [H+]K, + Id K2
\ Kw ]
|+[H+] --
/ [H+] J
F1b = Gran function
Vs = Initial sample volume = 25.00 mL
V = Volume of NaOH added (mL)
C = N KHP corrected for initial dilution = N
KHP/5
[H+] = 10~pH
K1 = 1.3 x 10"3
K2 = 3.9 x 10~6
Kw = 1.01 x 10"14
StepS - Plot F3b versus V. Using the points on the linear portion of the plot, perform a linear regression
of F3b on V to obtain the coefficients of the line
F3b = a + bV.
The correlation coefficient should exceed 0.999. If it does not, examine the plot to ensure that only
points on the linear portion are used in the linear regression.
Step 7 - Calculate the equivalence volume, V3, by
V3 = -alb
then calculate the NaOH normality by
N KHP x VKHP
N
NaOH
Step 8 - Perform the titration and calculation a total of three times. Calculate an average NNaOH and
standard deviation. The RSD must be less than 2 percent. If not, the entire standardization must be
repeated until the RSD is less than 2 percent.
4.8.2.2 NaOH-HCI Standardization Cross-Check
Step 1 - Purge a titration vessel with CO2-freenitrogen, then pipet 0.500 mL of 0.01 N NaOH and 25.00
mL of CO2-free water into the vessel. Maintain a CO2-free atmosphere above the sample. Add a Teflon
stir bar and stir at a medium speed.
Step 2 - Immerse the pH electrode and record the reading when it stabilizes.
Step 3 - Titrate with the standardized 0.01 N HCI using the increments specified in the table below.
Record the volume and pH (when stable) between additions. Continue the titration until the pH is less
than 3.5. Obtain at least seven data points in the pH range 4 to 10.
50
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Maximum Volume Increment
pH of HCITitrant(mL)
>10 0.2
10 to 4 0.05
< 4 0.2
Step 4 - Calculate F^ for each data pair (V, pH) with a pH 4 to 10.
F1 = (VS + V) / -
' * o / ri I 4-"I
F1b = Gran function
Vs = Initial sample volume = 25.5 mL
V = Volume of HCI added (mL)
Kw=1.01 x 1Q-14
StepS- Plot FT versus V. Using the points on the linear portion of the plot, perform a linear regression
of R| on V to obtain the co efficients of the line
FT = a + bV
The correlation coefficient should exceed 0.999. If not, reexamine the plot to ensure that only points
on the linear portion are used in the linear regression.
Step 6 - Calculate the equivalence volume, V^ by
V, = -alb
then calculate the HCI normality (designated as N'Ha) by
N'HCI = Na°H*
VNaOH = 0.500
Step 7 - Calculate the absolute relative percent difference (RPD) between N'HC|HC and NHCn (normal-
ity determined in section 4.8.1) by
RPD =
N'HCI
x 100
0.5(N'HC, + NHCI)
The absolute RPD must be less than 5 percent. If not, then a problem exists in the acid and/or the base
standardization (bad reagents, out-of-calibration burets, etc.). The problem must be identified and
both procedures 4.8.1 and 4.8.2 must be repeated until the RPD calculated above is less than 5 per-
cent.
4.8.2.3 Daily NaOH Standardization
Step 1 - Calibrate the pH meter and electrode as recommended by the manufacturer.
Step 2 - Purge the titration vessel with C02-f ree nitrogen, then pipet 1.000 mL NaOH titrant plus 25.00
mL CO2-free water into the vessel. Maintain a CO2-free nitrogen atmosphere above the sample.
(Smaller volumes of NaOH may be used. A known volume of CO2-f ree water should be added to bring
solution to a convenient volume.) Add a Teflon stir bar and stir at a medium speed.
Step 3 - Immerse the pH electrode and record the reading when it stabilizes.
51
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Step 4 - Titrate with the standardized HCI titrant using the increments specified in the table below.
Record the volume and pH (when stable) between additions. Continue the titration until the pH < 4.
Obtain at least seven data points in the pH range 4 to 10.
Maximum Volume Increment
pH of HCI Titrant (mL)
>10 0.2
4 to 10 0.05
< 4 0.2
Step 5 - Calculate F, for each data pair (volume acid added, pH) with a pH 4 to 10:
(Kw
TFFT
F1b = Gran function
Vs = Initial sample volume = 26.00 mL
V = Volume of HCI added
Kw=1.01 x ID'14
Step 6-Plot FT versus V. Using the points on the linear portion of the plot, perform a linear regression
of FT on V to obtain the co efficients of the line
FT = a + bV.
The correlation coefficient should exceed 0.999. If it does not, reexamine the plot to make sure that
only points on the linear portion are used in the linear regression.
Step 7 - Calculate the equivalence volume, V1( by
V, = -alb
then calculate the NaOH normality by
NHCI x VT
N
NaOH
V
NaOH
Step 8 - Perform the titration and calculation twice more (steps 2 through 7). Calculate an average
^NaoH ancl standard deviation. The RSD must be less than 2 percent. If it is not, the entire standardiza-
tion must be repeated until the RSD is less than 2 percent.
Because the NaOH titrant can readily deteriorate through exposure to the air, every effort must be
made to prevent its exposure to the air at all times. Furthermore, it must be standardized daily or
before every major work shift. Store in a linear polyethylene or Teflon container with a CO2-free atmo-
sphere, e.g., under CO2-free air, nitrogen, or argon.
NOTE: An example of NaOH standardization is given in Appendix C.
4.8.3 Calibration and Characterization of Electrodes
Separate electrodes must be used for the acid and base titration. Each new electrode pair must be
rigorously evaluated for Nernstian response, using the procedure described in section 4.8.3.1, prior
to analyzing samples. After the initial electrode evaluation, the electrodes are calibrated daily using
the procedure in section 4.8.3.2.
52
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4.8.3.1 Rigorous Calibration Procedure
This procedure calibrates (in terms of H ion concentration) and evaluates the Nernstian response of
an electrode. Also, it familiarizes the analyst with the electrode's characteristic response time.
Step 7 - Following the manufacturer's instructions, calibrate the electrode and meter used for acid
titrations with pH 7 and 4 buffer solutions and the electrode used for base titrations with pH 7 and 10
buffer solutions.
Step 2 - Prepare a blank solution by pipetting 50.00 mL CO2-free water and 0.50 mL 0.10M KCI into a
titration vessel. Add a Teflon stir bar and stir at a medium speed using a magnetic stirrer.
Step 3 - Titrate the blank with standardized 0.01 N HCI using the increments specified in the table
below. Continue the titration until the pH is 3.3 to 3.5. Record the pH between each addition, noting
the time required for stabilization. Obtain at least seven data points that have a pH less than 4.
Maximum Volume Increment
pH of HCI Titrant (mL)
> 4 0.050
< 4 0.3
Step 4 - Prepare a fresh aliquot of water and 0.1 OM KCI as in step 2.
Step 5 - Under a CO2-free atmosphere, titrate the blank with standardized 0.01 N NaOH using the
increments specified in the table below.
Maximum Volume Increment
pH of NaOH Titrant (mL)
<10 0.10
>10 0.20
Continue the titration until the pH is 10.5 to 11. Record the pH between each addition. Obtain at least
10 data points between pH 9 and 10.5.
Step 6 - For each titration, calculate the pH for each data point using pH = -log [H+]. [H+] is calcu-
lated by
acid titration
base titration
VACA
[H+] = ineq/L
Vs + VA
[H+] = ineq/L
VA = acid volume (in mL)
CA = HCI concentration in eq/L
Vs = sample volume = 50.5 mL
Kw = 1.01 x 10-14
VB = base volume (in mL)
CB = NaOH concentration in eq/L
(VBCB \
Vs + VB I
53
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Step 7 - For each titration, plot the measured pH versus the calculated pH (designated as pH*).
Perform a linear regression on each plot to obtain the coefficients of the line
pH = a + b(pH*)
The plots must be linear with b = 1.00 ± 0.05 and r > 0.999. Typically, some nonlinearity exists in the
pH region 6 to 8. This is most likely due to small errors in titrant standardization, impure salt solu-
tions, or atmospheric CO2 contamination. The nonlinear points should not be used in the linear
regression.
If the plots are not linear and do not meet the specifications above, the electrode should be consid-
ered suspect. The electrode characterization must then be repeated. If unacceptable results are still
obtained, the electrode must be replaced.
Step 8 - The plots for both titrations should be coincident. Combine the data from both titrations and
perform a linear least squares analysis on the combined data to obtain new estimates for the coeffi-
cients of
pH = a + b(pH*)
The electrodes are now calibrated. Do not move any controls on the meter.
If the two plots are not coincident (i.e., the coefficients a and b do not overlap), the characterization
must be repeated. If the plots are still not coincident, the electrode must be replaced.
4.8.3.2 Daily Calibration Procedure
Generally, the calibration curve prepared above is stable from day to day. This daily calibration is
designed to verify the calibration on a day-to-day basis.
Step 1 - Copiously rinse the electrode with water. Immerse it in 20 mL of pH 7 buffer and stir for 1 to 2
minutes. Discard the buffer and replace with an additional 40 mL of pH 7 buffer. While the solution is
gently stirred, measure the pH. Adjust the pH meter calibration knob until the pH is equal to the
theoretical pH of the buffer. Record the theoretical pH and final, measured pH reading. (The two
values should be identical).
Step 2 - Copiously rinse the electrode with water. Immerse it in 20 mLof pH 4 QC sample and stir for 1
to 2 minutes. Discard the sample and replace with an additional 40 mil pH 4 QC sample. While the
solution is stirred, measure and record the pH. From the calibration curve of pH versus pH*, deter-
mine the pH* for the observed pH. Compare pH* to the theoretical pH of the QC sample. The two
values must agree within ± 0.05 pH unit. If the two values do not agree, the rigorous calibration proce-
dure (section 4.8.3.1) must be performed prior to sample analysis.
Step 3 - Repeat step 2 with the pH 10 QC sample. This sample must be kept under a CCyfree atmo-
sphere when in use, or acceptable results may not be obtained.
4.9 QUALITY CONTROL
4.9.1 Duplicate Analysis
Analyze one sample per batch in duplicate. The duplicate precision (expressed as an RSD) must be
less than or equal to 10 percent. If the duplicate precision is unacceptable (RSD > 10 percent), then a
problem exists in the experimental technique. Determine and eliminate the cause of the poor preci-
sion prior to continuing sample analysis.
4.9.2 Blank Analysis
Determine the alkalinity in one blank per batch. The calculations are described in section 4.11.1. The
absolute value of the alkalinity must be less than or equal to 10 /u eq/L If it is not, contamination is
indicated. Determine and eliminate the contamination source (often the source will be the water or
KCI) prior to continuing sample analysis.
54
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4.9.3 pH QCCS
Prior to analysis of the first sample in a shift and every five samples thereafter, the appropriate pH QC
sample (pH 4 QC for acid titrations and pH 10 QC for base titrations) must be analyzed using the
following procedure. Copiously rinse the electrode with deionized water. Immerse it in 20 mL of QC
sample and stir it for 30 to 60 seconds. Discard the sample and replace with an additional 40 mL of QC
sample. While the solution is gently stirred, measure and record the pH. From the calibration curve of
pH versus pH *, determine the pH *. If the pH * and theoretical pH of the QC sample differ by more than
± 0.05 pH unit, stop the analysis and repeat the rigorous electrode calibration (Section 4.8.3.1). Previ-
ously analyzed samples (up to last acceptable QC sample) must be reanalyzed. Acceptable values of
pH* are reported on Form 12.
4.9.4 Comparison ol Initial Titration pH Values
The values for measured pH at Vtitrant = O (before KCI spike) of the acid and base titrations should be
within ± 0.1 pH unit. If they are not, check operation to ensure that cross-contamination is not occur-
ring.
For a sample with Alk ^ -15 /*eq/L, calculate a value for alkalinity as follows:
= 106 x 10-pH* (pH at V = O)
(The pH at V,,,rant = O is taken from the acid titration.) If Alk differs from [Alk]co by more than ± 10
L then check the electrode operation and calibration.
4.9.5 Comparison of Calculated Alkalinity and Measured Alkalinity
A value for Alk can be calculated from a sample's DIG concentration and pH. Two sets of pH and DIG
values are obtained in the lab, (1) pH* at V = O of the base titration and the associated DIG concentra-
tion, and (2) pH of the air-equilibrated sample and the associated DIG concentration. Each set can be
used to calculate a value for Alk. The calculated values for Alk can then be compared to the measured
value of Alk. The comparison is useful in checking both the validity of assuming a carbonate system
and the possibility of analytical error. Alk is calculated from pH and DIG as follows:
[Alk]Ci = calculated Alk from initial pH and DIG at time of base titration
[Alk]C2 = calculated Alk from air-equilibrated pH and DIG
DIG
- - + -- [H+] x 106
[DIG / [hTJK, + 2 K1 K2 x Kw n
- / - \+ -- [H+]
12,011 \ [H + ]2 + [H + ]K,K2 I [H+] J
DIG = DIC in mg/L (the factor 1 2,01 1 converts
mg/L to moles/L)
[H+] =1Q-pH
K, =4.4463 x 1Q-7at25°C
K2 = 4.6881 x 10'11 at 25°C
Kw =1.0023 x 10-14at25°C
[Alk]01 and [Alk]C2 are compared as follows:
For[Alk]c1 <100 //eq/L, the following condition applies
[Alk]c1 - [Alk]C2
For [Alk]c1 > 100 jueq/L, the following condition applies
55
-------
[Alk]G1 - [Alk]C2
x100
«Alk]c1 + [Alk]C2)/2
If either of the above conditions is not satisfied, then thepH and DIG values are suspect and must be
remeasured. It is very important that the pH and DIG be measured as closely together in time as
possible. If they are not measured closely in time, acceptable agreement between [Alk]^ and [Alk]p2
may not be obtained. When acceptable values for [Alk]c1 and [Alk]C2 are obtained, their average is
compared to the measured Alk as described below.
For [Alk]c.avg <100 Meq/L, then the difference "D" and the acceptance window "w" are
D = [Aik]c.avg - Alk and w = 15 /ueq/L
For [Alk]c.avg >100 /ueq/L, then
[Alk]c.avg - Alk
D = x 100 and w =10%
[Alk]c.avg
If ID! w, then an analytical problem exists in the pH determination, DIG
determination, or acid titration (such as titrant concentration). In this case the problem must be iden-
tified and the sample must be reanalyzed.
4.9.6 Comparison of Calculated Acidity and Measured Acidity
Just as for alkalinity, pH and DIG values can be used to calculate an Acy value. Since the Acy of a
sample changes with changing DIG, only the initial pH and DIG values measured at the beginning of
the base titration are used to calculate an Acy value. This calculated Acy is then compared to the
measured Acy value. Acy is calculated by
[DIG / [H ] KI K£ V Kyy "I
/ \+[H + ] x 1Q6
12,011 \ [H+]2 + [H+]K, + K^z / [H+]J
[AcyJC is compared to Acy as described below.
For[Acy]C <100 Meq/L, then
D = [AcyjC - Acy and w = 10 /ueq/L
For[Acy]C >100 /ueq/L, then
[Acy]c - Acy
D = x 100 and w =10%
[Acy]c
If fDI w, then an analytical problem exists in the pH determination, DIG determination, or base titra-
tion (such as titrant concentration). In this case the problem must be identified and the sample must
be reanalyzed.
56
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4.9.7 Comparison of Calculated Total Carbonate and Measured Total Carbonate
If the assumption of a carbonate system is valid, the sum of Alk plus Acy is equal to the total carbon-
ate. This assumption can be checked by calculating the total carbonate from the DIG, then compar-
ing the calculated total carbonate to the measured estimate of total carbonate (the sum of Alk plus
Acy). The total carbonate is calculated by
Cc( Mmole/L) = DIG (mg/L) x 83.26 (/u mole/mg)
Cc is compared to (Alk + Acy) as follows:
ForCC<100 Mmole/L, then
D = Cc - (Alk + Acy) and w = 10 jumole/L
ForCc >100 /umole/L, then
Cc - (Alk + Acy)
D = x 100 and w =10%
Cc
If KD! w, an analytical problem exists. It must be iden-
tified and the sample must be reanalyzed.
4.10 PROCEDURE
An acid titration (section 4.10.1) and a base titration (section 4.10.2) are necessary to determine the
acidity and alkalinity of a sample. As part of each titration, the sample pH is determined. The air-
equilibrated pH is determined in a separate sample portion (section 4.10.3).
4.70.1 Acid Titration
Step 1 - Allow a sealed water sample (aliquot 5) to reach ambient temperature.
Step 2- Copiously rinse the electrode with deionized water, then immerse in 10 to 20 mL sample. Stir
for 30 to 60 seconds.
Step 3 - Pipet 40.00 mL of sample into a clean, dry titration flask. Add a clean Teflon stir bar and place
on a magnetic stirrer. Stir at a medium speed (no visible vortex).
Step 4 - Immerse the pH electrode and read pH. Record pH on Forms 11 and 13 when the reading
stabilizes (1 to 2 minutes). This is the initial measured pH at Vtltran, = 0.
StepS-Add 0.40mL 0.1 M KCI. Read and record the pH on Form 13. This is the initial measured pH at
Vtitrant = ^ a^er addition of KCI spike.
Step 6 - Add increments of 0.01 N HCI as specified in the table below. Record the volume of HCI added
and the pH when a stable reading is obtained. Adjust the volume increment of titrant so that readings
can be taken at pH values of 4.5 and 4.2. Continue the titration until the pH is between 3.3 and 3.5.
Obtain at least six data points that have a pH less than 4.
Maximum Volume Increment
pH of HCI Titrant (mL)
>9 0.1
7.0 to 9.0 0.025
5.5 to 7.0 0.1
4.5 to 5.5 0.05
3.75 to 4.50 0.1
< 3.75 0.3
57
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4.70.2 Base Titration
Step 1 - Take a portion of aliquot 5 at this time for DIG determination. If the DIG is not determined
immediately, the sample must be kept sealed from the atmosphere. A simple way to do this is to
withdraw the sample for DIG using a syringe equipped with a syringe valve. By closing the valve, the
sample is sealed from the atmosphere (syringe valves that fit standard Luer-Lok syringes are availa-
ble from most chromatography supply companies).
Step 2 - Purge the titration vessel with CO2-free air, N2, or Ar.
Step 3 - Copiously rinse the electrode with deionized water, then immerse in 10 to 20 mL sample for 30
to 60 seconds.
Step 4 - Pipet 40.00 mL sample into the CCyfree titration vessel. Maintain a CCyfree atmosphere
above the sample. Do not bubble the N2(or other CO2-free gas) through the sample. Add a clean Teflon
stir bar and place on a magnetic stirrer. Do not turn stirrer on at this point.
Step 5 - Immerse the pH electrode, read pH, and record pH on Forms 11 and 13 when pH stabilizes.
This is the initial measured pH at Vtltrant = 0.
Step 6 - Add 0.40 mL 0.10M KCI. Stir for 10 to 15 seconds. Read pH, and record pH on Form 13.
Step 7 - Add 0.025 mL of 0.01 N NaOH and begin gentle stirring (no visible vortex). Record the NaOH
volume and pH when it stabilizes. Continue the titration by adding increments of NaOH as specified
below until the pH >11. Record the volume of NaOH added and the pH after each addition. Obtain at
least 10 data points in the pH region 9 to 10.5. If the initial sample pH is less than 7, obtain at least 5
data points below pH 8.
Maximum Volume Increment
pH of NaOH Titrant (mL)
<5
5 to 7
7 to 9
9 to 10
10 to 10.5
>10.5
0.025
0.050
0.025
0.10
0.30
1.00
4.70.3 Air-Equilibrated pH Measurement
Step 1 - Allow the sealed sample (aliquot 5) to reach ambient temperature.
Step 2- Copiously rinse the electrode with deionized water, then immerse in 10 to 20 mL sample. Stir
for 30 to 60 seconds.
Step 3 - Pipet 20 to 40 mL sample into a clean, dry titration flask. Add a clean Teflon stir bar and place
on a magnetic stirrer. Stir at a medium speed.
Step 4 - Bubble standard gas containing 300 ppm CO2 through the sample for 20 minutes. Measure
and record the pH.
Step 5 - Take a subsample at this time for DIG determination. The sub sample must be kept sealed
from the atmosphere prior to analysis. The DIG should be measured as soon as possible.
4.11 CALCULATIONS
During the titrations, any substance which reacts with the acid or base is titrated. However, for calcu-
lations, it is assumed that the samples represent carbonate systems and that the only reacting spe-
58
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cies are H+, OH , H2CO3, HCO3, and CO32. Using this assumption, the two parameters "Alkalinity"
(Alk) and "CO2-Acidity" (Acy) are calculated. The validity of the assumption is checked as described
in sections 4.9.6 through 4.9.8. Note that for blank samples only the initial calculations are required
(section 4.11.1).
The theory behind the calculations is available elsewhere (Kramer, 1982; Butler, 1982; Kramer, 1984).
Examples of the calculations are given in Appendix C.
4.77.7 Initial Calculations
Step 1 - From the calibration curve of measured pH versus calculated pH (pH*), determine pH* for
each pH value obtained during both the acid and base titrations. Next, convert all pH* values to
hydrogen ion concentrations using the equation
[H+] = 10-pH*
Step 2 - Using the acid titration data, calculate the Gran function F1a for each data pair (Va, pH*) in
which pH* <4:
Fia = (Vs +Va)[H+]
Vs = Total initial sample volume (40.00 + 0.400) ml
Va = Cumulative volume of acid titrant added
Step 3 - Plot F1a versus Va. The data should be on a straight line with the equation
F1a = a + bV
Step 4 - Perform a linear regression of F1a on Va to determine the correlation coefficient (r) and the
coefficients a and b. The coefficient r should exceed 0.999. If it does not, examine the data to ensure
that only data on the linear portion of the plot were used in the regression. If any outliers are detected,
repeat the regression analysis. Calculate an initial estimate of the equivalence volume (V^ by
Vi = -alb
Further calculations are based on this initial estimate of V^ and the initial sample pH*. Table 4.1
below lists the appropriate calculation procedure for the various combinations of V-, and initial sam-
ple pH*.
Sample Description
Initial V1 Initial pH*
<0
> 0 <76
>0 >7.6
Calculation
Procedure
A
B
C
Section No.
4.11.2
4.11.3
4.11.4
Table 4.1. List of Calculation Procedures for Combinations of Initial V1 and pH*.
59
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NOTE: For blank analyses, calculate Alk by Alk = V-, Ca/Vsa. Further calculations are not necessary.
Throughout the calculations, there are several equations and constants that are frequently used.
These are listed in Table 4.2.
4.77,2 Calculation Procedure A (Initial V, <0)
Step 1 - From the basetitration data, determine which data set (V, pH*) has the pH* nearest (but not
exceeding) a pH = 8.2. As an initial estimate, set the equivalence volume V2 equal to the volume of
this data set. Next, calculate initial estimates of Alk, Acy, and C by
Alk =
Ca = concentration of acid titrant
Vsa = original sample volume (acid titration)
V,
Acy =
V
sb
Cb = concentration of base titrant
VSb = original sample volume (base titration)
C = total carbonate = Alk + Acy
No Equation
ECttH + ljK! + 2 K,K2) Kw
.
+ 2 + m +
1 1 2
EC([H + ]2-K1K2)
[H + ]2 + [H + ]K! + KtK2
.*,]
KW "1
[H + ] J
Vs = Total initial sample volume
Constants3 V = Cumulative volume of titrant added
and C = Total carbonate expressed in moles/ L
variable [H + ] = Hydrogen ion concentration
descriptions K1 = 4.4463 x 10~7 at 25°C
K2 = 4.6881 x 10M1at25°C
Kw= 1.0023 x 10"14at25°C
"Constants are taken from Butler, 1982
Table 4.2. List of Frequently Used Equations and Constants.
60
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Step 2 - Calculate the Gran function F1c for the first 7 to 8 points of the base titration using equation 1 ,
Table 4.2. Plot Flc versus Vb. Perform a linear regression with the points lying on the linear portion of
the plot. Determine the coefficients of the line F1c = a + bV. The coefficient r should exceed 0.999. If it
does not, examine the plot to ensure that only points on the linear portion are used. From the co
efficients, calculate a new estimate of \A, by
V, - -a/b
Step 3 - Calculate the Gran function F2c (equation 2, Table 4.2) for data from the base titration across
the current estimate of V2. (Use the first 4 to 6 sets with a volume less than V2 and the first 6 to 8 sets
greater than V2.) Plot F2c versus Vb. The data should lie on a straight line with the equation F2c = a +
bV. Perform a linear regression of F2o on Vb and determine the coefficients of the line. If r <0.999
reexamine the data to ensure that only points on the linear portion were used in the regression.
Calculate a new estimate of V2 by
V2 = -a/b
Step 4- Calculate new estimates of Alk, Acy, and C using the new estimates of \A, and V2(an asterisk
indicates a new value).
-VA V2Cb
Alk* = - ; Acy* = - - ; C* = Alk + Acy
Vsb Vsb
Step 5 - Compare the latest two values for total carbonate. If
C-C"
> 0.001
C + C
then calculate a new estimate for C by
C(new) = (C + C*)/2
Step 6 - Using the new value for C, repeat the calculations for the Gran functions and for new values
of C. Continue repeating the calculations until the relative difference between C and G* is less than
0.001.
Step 7- When the expression is less than 0.001, convert the final values for Alk, Acy, and C to /*eq/L
by
Alk( Meq/L) = Alk(eq/L) x 106
Acy ( Meq/L) = Acy (eq/L) x 106
C( jueq/L) = C(eq/L) x 106
4.11.3 Calculation Procedure B (Initial V1 >0, Initial pH* < 7.6)
Step 1 - From the base titration data, determine which data set (V, pH*) has the pH* nearest, but not
exceeding, 8.2. As an initial estimate, set the equivalence volume V2 equal to the volume of this data
set. Next calculate initial estimates of Alk, Acy, and C by
V,Ca V2Cb
Alk = - ; Acy = - ; C = Alk + Acy
Vsa Vsb
Step 2 - Calculate the Gran function F1c (equation 1) for data sets from the acid titration with vol-
umes across the current estimate of V^ (use the first 4 to 6 sets with volumes less than Vn and the first
6 to 8 sets with volumes greater than V,). Plot F1c versus Va. The data should lie on a line with the
equation F1c = a + bV. Perform a linear regression of F1c on Va and determine the coefficients of the
line.
61
-------
If r does not exceed 0.999, reexamine the data to ensure that no outliers were used in the regression.
Calculate a new estimate for V, by
V1 = -alb
Step 3 - Calculate the Gran function F2c(equation 2) for data sets from the base titration with volumes
across the current estimate of V2. (Use the first 4 to 6 sets with volumes less than V2 and the first 6 to 8
sets with volumes greater than V2). Plot F2c versus Vb. The data should lie on a line with the equation
F2o = a + bV. Perform a linear regression of F2c on Vb and determine the coefficients of the line. If r
does not exceed 0.999, reexamine the data to ensure that only data on the linear portion were inclu-
ded in the regression. Calculate a new estimate for V2 by
V2 = -a/b
Step 4 - Calculate new estimates of Alk, Acy, and C using the latest estimates of V-, and V2.
ViCa V2Cb
Alk* = ; Acy* = ; C* = Alk + Acy
Vsa Vsb
Step 5 - Compare the latest two values for total carbonate. If
C-C*
C + C*
then calculate a new estimate of C by
> 0.001
C(new) = (C + C*)/2
Step 6 - Using the new value of C, repeat the calculations for the Gran functions and for new values of
C (steps 2 through 5). Continue repeat ing the calculations until the above expression is less than
0.001.
When the expression is less than 0.001, convert the final values for AIK, Acy, and C to yueq/L by
Alk( A«eq/L) = Alk(eq/L) x 106
Acy ( Mq/L) = Acy (eq/L) x 106
C ( /0, Initial pH* >7.6)
Step 1 - Obtain an initial estimate of the equivalence volume V2 by follow ing the procedure in step 2 if
the initial sample pH* >8.2. If the initial sample pH* <8.2, then follow the procedure in step 3.
Step 2 - From the acid titration data, determine which data set (V, pH*) has the pH* nearest, but not
exceeding, 8.2. As an initial estimate, set the equivalence volume V2 equal to the volume of this data
set. Go to step 4.
Step 3 - Using data sets from the acid titration with pH * values across a pH = 7 (use 4 to 6 sets with a
pH* <7 and 4 to 6 sets with a pH* > 7), calculate the Gran function F2a by
Step 4 - Plot F2a versus Va. The data should lie on a straight line with the equation F2a = a + bV.
Perform a linear regression of F2a on Va. The coefficient r should exceed 0.999. If it does not, reex-
amine the plot to ensure that only data on the linear portion were used in the calculation. Calculate a
new estimate for V2 by
62
-------
V2 = -alb
Step 5 - Calculate estimates of Alk, Acy, and C by
V1Ca -V2Ca
Alk = - ; Acy = - ; C = Alk + Acy
V "s
sa
Step 6 - Calculate the Gran function F1c (equation 1) for data sets from the acid titration with volumes
across the current estimate of V^ (use the first 4 to 6 sets with volumes less than V1 and the first 6 to 8
sets with volumes greater than V^. Plot F1c versus Va. The data should lie on a straight line with the
equation F1c = a + bV. Per form a linear regression of F1c on Va and determine the coefficients of the
line. The coefficient r should exceed 0.999. If it does not, reexamine the plot to ensure that only data
on the linear portion were included in the regression. Calculate a new estimate for \^ by
V, = -alb
Step 7 - Calculate the Gran function F2c (equation 2) for data sets from the acid titration with volumes
across the current estimate of V2(use the first 4 to 6 sets with volumes less than V2 and the first 6 to 8
sets with volumes greater than V2). Plot F2c versus Va. The data should lie on a straight line with the
equation F2c = a + bV. Perform a linear regression of F2c on Va and determine the coefficients of the
line. The coefficient r should exceed 0.999. If it does not, reexamine the plot to ensure that only data
on the linear portion were included in the regression. Calculate a new estimate of V2 by
V2 = -alb
Step 8 - Calculate new estimates of Alk, Acy, and C using the latest estimates of V1 and V2.
ViCa -V2Ca
Alk* = - ; Acy* = - ; C* = Alk + Acy
Vsa Vsa
Step 9 - Compare the latest two values for total carbonate. If
C-C*
0.001
C + C*
then calculate a new estimate of C by
C(new) = (C + C*)/2
Step 10 - Using this new value of C, repeat the calculations in steps 6 through 9. Continue repeating
the calculations until the above expression is less than 0.001.
Step 11- When the expression is less than 0.001, convert the final values for Alk, Acy, and C to //eq/L
by
Alk ( Meq/L) = Alk (eq/L) x 106
Acy( Meq/L) = Acy (eq/L) x 106
C( Meq/L) = C(eq/L) x 106
4.12 PRECISION AND ACCURACY
In a multiple lab study using 115 lake samples containing 10-1000 Meq/L alkalinity, 10-200 /zeq/L
acidity, and pH values in the range 4-8, the overall duplicate precision was 1.1 percent rsd, 9.0 percent
rsd, and +0.06 pH units, respectively (note that this is the overall within lab duplicate precision).
63
-------
In a multiple lab study using two synthetic simulated lake samples con taining 116 and 464
ANC respectively, the percent recoveries obtained were 96 percent (n = 57) and 103 percent (n = 57),
respectively.
4.13 REFERENCES
American Society for Testing and Materials, 1984. Annual Book of ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
Butler, J. N., 1982. Carbon Dioxide Equilibria and Their Applications. Addison-Wesley Publications,
Reading, Massachusetts,
Gran, G., 1952. Determination of the Equivalence Point in Potentiometric Titrations. Part II. Analyst,
v. 77, pp. 661-671.
Kramer, J. R., 1982. Alkalinity and Acidity. In: R. A. Minear and L. H. Keith (eds.), Water Analysis, Vol. 1.
Inorganic Species, Part 1. Academic Press, Orlando, Florida.
Kramer, J. R., 1984. Modified Gran Analysis for Acid and Base Titrations. Environmental Geochemis-
try Report No. 1984-2. McMaster University, Hamilton, Ontario, Canada.
McQuaker, N. R., P. D. Kluckner, and D. K. Sandberg, 1983. Chemical Analysis of Acid Precipitation:
pH and Acidity Determinations. Environ. Sci. Technol., v. 17, n. 7, pp. 431-435.
National Bureau of Standards, 1982. Simulated Precipitation Reference Materials, IV. NBSIR 82-2581.
U.S. Department of Commerce - NBS, Washington, D.C.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes, Method 150.1, pH. EPA-600/4-79-020. U.S. EPA, Cincinnati, Ohio.
64
-------
SECTION 5
DETERMINATION OF AMMONIUM
5.1 SCOPE AND APPLICATION
This method covers the determination of ammonia in natural surface waters in the range of 0.01 to 2.6
mg/L NH4+. This range is for photometric measurements made at 630 to 660 nm in a 15-mm or 50-mm
tubular flow cell. Higher concentrations can be determined by sample dilution. Approximately 20 to
60 samples per hour can be analyzed.
5.2 SUMMARY OF METHOD
Alkaline phenol and hypochlorite react with ammonia to form an amount of indophenol blue that is
proportional to the ammonium concentration. The blue color formed is intensified with sodium nitro-
prusside (U.S. EPA, 1983).
5.3 INTERFERENCES
Calcium and magnesium ions may be present in concentration sufficient to cause precipitation prob-
lems during analysis. A 5 percent EDTA solution is used to prevent the precipitation of calcium and
magnesium ions.
Sample turbidity may interfere with this method. Turbidity is removed by filtration at the field station.
Sample color that absorbs in the photo metric range used also interferes.
5.4 SAFETY
The calibration standards, sample types, and most reagents used in this method pose no hazard to
the analyst. Use protective clothing (lab coat and gloves) and safety glasses when preparing
reagents.
5.5 APPARATUS AND EQUIPMENT
Technicon AutoAnalyzer Unit (AAI or AAII) consisting of sampler, manifold (AAI) or analytical
cartridge (AAII), proportioning pump, heating bath with double-delay coil (AAI), colorimeter
equipped with 15-mm tubular flow cell and 630- to 660-nm filters, recorder, and digital printer for
AAII (optional).
5.6 REAGENTS AND CONSUMABLE MATERIALS
Water-Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
Sulfuric Acid (5N), Air Scrubber Solution-Carefully add 139 mL concentrated sulfuric acid to
approximately 500 mL ammonia-free water. Cool to room temperature and dilute to 1 L with
water.
Sodium Phenolate Solution-Using a 1-L Erlenmeyer flask, dissolve 83 g phenol in 500 mL water.
In small increments, cautiously add with agitation 32 g NaOH. Periodically cool flask under
flowing tap water. When cool, dilute to 1 L with water.
65
-------
Sodium Hypochlorite Solution-Dilute 150 mL of a bleach solution containing 5.25 percent
NaOCI (such as "Clorox") to 500 mL with water. Available chlorine level should approximate 2 to
3 percent. Clorox is a proprietary product, and its formulation is subject to change. The analyst
must remain alert to detecting any variation in this product significant to its use in this proce-
dure. Due to the instability of this product, storage over an extended period should be avoided.
Disodium Ethylenediamirte-Tetraacetate (EDTA) (5 percent w/v)-Dissolve 50 g EDTA (disodium
salt) and approximately six pellets NaOH in 1 L water.
Sodium Nitroprusside (0.05 percent w/v)--Dissolve 0.5 g sodium nitro prusside in 1 L deionized
water.
NH4 + Stock Standard Solution (1,000 mg/L)--Dissolve 2.9654 g anhydrous ammonium chloride,
NH4CI (dried at 105°C for 2 hours) in water, and dilute to 1,000 mL.
Standard Solution A (10.00 mg/L NH4+)--Dilute 10.0 mL NH4+ stock standard solution to 1,000
mL with water.
Standard Solution B (1.000 mg/L NH4"l")--Dilute 10.0 mL standard solution A to 100.0 mL with
water.
Using standard solutions A and B, prepare (fresh daily) the following standards in 100-mL volu-
metric flasks:
NH4+ mL Standard
(mg/L) Solution/100m L
Solution B
0.01 1.0
0.02 2.0
0.05 5.0
0.10 10.0
NH4+ mL Standard
(mg/L) Solution /1QOmL
SolutionA
0.20 2.0
0.50 5.0
0.80 8.0
1.00 10.0
1.50 15.0
2.00 20.0
5.7 Sample Collection, Preservation, and Storage
Samples are collected, filtered, and preserved (addition of H2SO4 until pH <2) in the field. The sam-
ples must be stored in the dark at 4°C when not in use.
5.8 CALIBRATION AND STANDARDIZATION
Analyze the series of ammonium standards as described in Section 5.10. Prepare a calibration, curve
by plotting the peak height versus standard concentration.
5.9 QUALITY CONTROL
The required QC is described in Section 3.4.
66
-------
5.10 PROCEDURE
Since the intensity of the color used to quantify the concentration is pH-dependent, the acid concen-
tration of the wash water and the standard ammonium solutions should approximate that of the
samples. For example, if the samples have been preserved with 2 ml_ concentrated H2SO4/L, the
wash water and standards should also contain 2 ml concentrated H2SO4/L
Step 1 - Fora working range of 0.01 to 2.6 mg/L NH4+ (AAI), set up the manifold as shown in Figure
5.1. For a working range of 0.01 to 1.3 mg/L NH4+ (AAII), set up the manifold as shown in Figure 5.2.
Higher concentrations may be accommodated by sample dilution.
Step 2 - Allow both colorimeter and recorder to warm up for 30 minutes. Obtain a stable baseline with
all reagents, feeding distilled water through sample line.
Sfep 3 - For the AAI system, sample at a rate of 20/hr, 1:1. For the AAII use a 60/hr 6:1 cam with a
common wash.
Step 4 - Load sampler tray with unknown samples.
Step 5 - Switch sample line from water to sampler and begin analysis.
Step 6 - Dilute and reanalyze samples with an ammonia concentration exceeding the calibrated
concentration range.
5.11 CALCULATIONS
Compute concentration of samples by comparing sample peak heights with calibration curve.
Report results in mg/L NH4 + .
5.12 PRECISION AND ACCURACY
In a single laboratory (EMSL-Cincinnati), using surface-water samples at concentrations of 1.41,
0.77, 0.59, and 0.43 mg NH3-N/L, the standard deviation was ±0.005 (U.S. EPA, 1983).
In a single laboratory (EMSL-Cincinnati), using surface-water samples at concentrations of 0.16 and
1.44 mg NH3-N/L, recoveries were 107 percent and 99 percent, respectively (U.S. EPA, 1983). These
recoveries are statistic ally significantly different from 100 percent.
5.13 REFERENCES
American Society for Testing and Materials, 1984. Annual Book of ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes, Method 350.1, Ammonia Nitrogen. EPA 600/4-79-020. U.S. EPA, Cincinnati, Ohio.
67
-------
Wash Water ^
To Sampler
SM = Small Mixing Coil ~"
LM - Large Mixing Coil SM
oooo ___
LM
oooooooo _^
w
LM
oooooooo
SM 1
_ , 000° J ^
Heating f \ 1 -____ ^
Bath37°c( J A I
V/ 1 1
1 r1
1 / _ _
^ *J
Colorimeter
15mm Flow Cell
650 - 660 nm Filter
Proportioning
Pump
i
P B
G G
R R
G G
W W
W W
R R
P P
-nl/min
2.9 Wash
2.0 Sample
0.8 EDTA
2.0 Air*
0.6 Phenolate
0.6 Hypochlorite
0.6 Nitroprusside
2.5
1 Waste
corder
* Schrubbed Through
5N H2SO4
0
Sampler
20/hr.
1:1
Figure 5.1. Ammonia Manifold AAI.
-------
Heating
Bath
50°C
Wash Water
To Sampler
OOOO
Proportioning
Pump
G
ml/min
2.0 Wash
W
Black
Blue
0.23 Air*
0.42 Sample
0.8 EDTA
0.42 Phenolate
0.32 Hypochlorite
0.42 Nitroprusside
Waste
Sampler
60/hr.
6:1
Colorimeter
15 mm Flow Cell
650 - 660 nm Filter
* Schrubbed Through
5N H2SO4
Figure 5.2. Ammonia Manifold AAI.
-------
SECTION 6
DETERMINATION OF CHLORIDE, NITRATE, AND SULFATE
BY ION CHROMATOGRAPHY
6.1 SCOPE AND APPLICATION
This method is applicable to the determination of chloride, nitrate, and sulfate in natural surface
waters by ion chromatography (1C). It is restricted to use by or under the supervision of analysts
experienced in the use of ion chromatography and in the interpretation of the resulting ion chromato-
gram.
6.2 SUMMARY OF METHOD
Samples are analyzed by 1C. 1C is a liquid chromatographic technique that combines ion exchange
chromatography, eluent suppression, and conductimetric detection.
A filtered sample portion is injected into an ion chromatograph. The sample is pumped through a
precolumn, separator column, suppressor column, and a conductivity detector. The precolumn and
separator column are packed with a low-capacity anion exchange resin. The sample anions are sepa-
rated in these two columns based on their affinity for the resin exchange sites.
The suppressor column reduces the conductivity of the eluent to a low level and converts the sample
anions to their acid form. Typical reactions in the suppressor column are:
Na+ HCO3" + R - H , H2CO3 + R - Na
(High-conductivity eluant) (Low conductivity)
Na+ A~ + R- H HA + R-Na
Three types of suppressor columns are available: the packed-bed suppressor, the fiber suppressor,
and the micromembrane suppressor. The packed bed suppressor contains a high-capacity cation
exchange resin in The hydrogen form. It is consumed during analysis and must be periodically regen-
erated off-line. The latter two suppressors are based on cation exchange membranes. These sup-
pressors are continuously regenerated through out the analysis. Also, their dead volume is substan-
tially less than that of a packed-bed suppressor. For these two reasons, the latter two suppressors
are preferred.
The separated anions in their acid form are measured using a conductivity cell. Anion identification
is based on retention time. Quantification is performed by comparing sample peak heights to a cali-
bration curve generated from known standards (ASTM, 1984a; O'Dell et al., 1984; Topol and Ozdemir,
1981).
6.3 INTERFERENCES
Interferences can be caused by substances with retention times that are similar to and overlap those
of the anion of interest. The lake samples are not expected to contain any interfering species. Large
amounts of an anion can interfere with the peak resolution of an adjacent anion. Sample dilution or
spiking can be used to solve most interference problems.
70
-------
The water dip or negative peak that elutes near, and can interfere with, the chloride peak can be
eliminated by the addition of the concentrated eluant so that the eluant and sample matrix are simi-
lar.
Method interferences may be caused by contaminants in the reagent water, reagents, glassware, and
other sample processing apparatus that lead to discrete artifacts or elevated baselines in ion chro-
matograms.
Samples that contain particles larger than 0.45 microns and reagent solutions that contain particles
larger than 0.20 microns require filtration to prevent damage to instrument columns and flow sys-
tems.
6.4 SAFETY
Normal, accepted laboratory safety practices should be followed during reagent preparation and
instrument operation. The calibration standards, samples, and most reagents pose no hazard to the
analyst. Protective clothing and safety glasses should be worn when handling concentrated sulfuric
acid.
6.5 APPARATUS AND EQUIPMENT
Ion Chromatograph-Analytical system complete with ion chromatograph and all accessories
(conductivity detector, autosampler, data recording system, etc.).
Anion Preseparator and Separator Columns-Dionex Series AG-4A and AS-4A are recommended
for use with the 2000i ion chromatographs. AG-3 and AS-3 columns are recommended for older
ion chromatographs.
Suppressor Column - Dionex AFS fiber suppressor or AMMS membrane suppressor is recom-
mended.
6.6 REAGENTS AND CONSUMABLE MATERIALS
Unless stated otherwise, all chemicals must be ACS reagent grade or better. Also, salts used in prep-
aration of standards must be dried at 105°C for 2 hours and stored in a desiccator.
Deionized Water - Water must meet the specifications for Type I Reagent Water given in ASTM D
1193(ASTM, 1984b).
Eluant Solution (0.0028M NaHCO3/0.0020M Na2CO2) - Dissolve 0.94 g sodium bicarbonate
(NaHCO3) and 0.85 g sodium carbonate (Na2CO3) in water and dilute to 4 L This eluant strength
may be adjusted for different columns according to the manufacturer's recommendations.
Fiber Suppressor Regenerant (0.025N H2SO4) - Add 2.8 ml_ concentrated sulfuric acid (H2SO4,
Baker Ultrex grade or equivalent) to 4 L water.
Stock Standard Solutions - Store stock standards in clean polyethylene bottles (cleaned with-
out acid using procedure in Appendix A) at 4°C. Prepare monthly.
a. Bromide Stock Standard Solution (1,000 mg/L Br") - Dissolve 1.2877 g sodium bromide (NaBr)
in water and dilute to 1.000 L.
b. Chloride Stock Standard Solution (200 mg/L Cl~) - Dissolve 0.3297 g sodium chloride (NaCI) in
water and dilute to 1.000 L.
c. Fluoride Stock Standard Solution (1,000 mg/L F") - Dissolve 2.2100 g sodium fluoride (NaF) in
water and dilute to 1.000 L.
d. Nitrate Stock Standard Solution (200 mg/L NO3~) - Dissolve 0.3261 g potassium nitrate
(KNO3) in water and dilute to 1.000 L
71
-------
e. Phosphate Stock Standard Solution (1,000 mg/L P) - Dissolve 4.3937 g potassium phosphate
(KH2PO4) in water and dilute to 1.000 L.
f. Sulfate Stock Standard Solution (1,000 mg/L SO42~) - Dissolve 1.8141 g potassium sulfate
(K2SO4) in water and dilute to 1.000 L.
Mixed Resolution Sample (1 mg/L F', 2 mg/L Cl~, 2 mg/L NO3", 2 mg/L P, 2 mg/L Br~, 5 mg/L SO42~)
Prepare by appropriate mixing and dilution of the stock standard solutions.
6.7 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
Samples are collected and filtered in the field. Store samples at 4°C when not in use.
6.8 CALIBRATION AND STANDARDIZATION
Each day (or work shift) for each analyte, analyze a blank and a series of standards which bracket the
expected analyte concentration range as described in section 6.10. Prepare the standards daily by
quantitative dilution of the stock standard solutions. Suggested concentrations for the dilute stand-
ards are given in Table 6.1.
Prepare a calibration curve for each analyte by plotting peak height versus standard concentration.
6.9 QUALITY CONTROL
General QC procedures are described in section 3.4.
After calibration, perform a resolution test. Analyze the mixed standard containing fluoride, chloride,
nitrate, phosphate, bromide, and sulfate. Resolution between adjacent peaks must equal or exceed
60 percent. If it is not, replace or clean the separator column and repeat calibration.
6.10 PROCEDURE
Step 1 - Set up the 1C for operation. Typical operating conditions for a Dionex 2010i 1C are given in
Table 6.2. Other conditions may be used depending upon the columns and system selected.
Step 2 - Adjust detector range to cover the concentration range of samples.
Step 3 - Load injection loop (manually or via an autosampler) with the sample (or standard) to be
analyzed. Load five to ten times the volume required to thoroughly flush the sample loop. Inject the
sample. Measure and record (manually or with a data system) the peak heights for each analyte.
Step 4- Dilute and reanalyze samples with an analyte concentration exceeding the calibrated con-
centration range.
Standard
1
2
3
4
5
6
cr
0
0.200
0.10
0.50
1.00
3.00
Concentration (mg/L)
N03"
0
0.200
0.10
0.50
1.00
3.00
S042'
0
0.20
0.50
2.00
5.00
10.00
Table 6.1. Suggested Concentration of Dilute Calibration Standards.
72
-------
1C: Dionex 20101 Sample Loop Size: 250 /u
Precolumrr AG-4A
Separator Colum: AS-4A
Suppressor Column: AMMS
Eluant: 0.75mM NaHC)3/2.0mM Na2C03
Eluant Flow Rate: 2.0 mL/min
Regenerant: 0.025N H2S04
Regenerant Flow Rate: 3 mL/min
Jon Typical Retention Time (min)
C1~ 1.8
N03" 4.9
S042' 8.1
Table 6.2. Typical 1C Operating Conditions.
6.11 CALCULATIONS
Compute the sample concentration by comparing the sample peak height with the calibration curve.
Report results in mg/L.
6.12 PRECISION AND ACCURACY
Typical single operator results for surface water analyses are listed in Table 6.3 (O'Dell et al., 1984).
6.13 REFERENCES
American Society for Testing and Materials, 1984a. Annual Book of ASTM Standards, Vol. 11.01,
Standard Test Method for Anions in Water by Ion Chromatography, D4327-84. ASTM, Philadel-
phia, Pennsylvania.
American Society for Testing and Materials, 1984b. Annual Book of ASTM Standards, Vol. 11.01,
Standard Specification for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia,
Pennsylvania.
O'Dell, J. W., J. D. Pfaff, M. E. Gales, and G. D. McKee, 1984. Technical Addition to Methods for the
Chemical Analysis of Water and Wastes, Method 300.0, The Determination of Inorganic Anions
in Water by Ion Chromatography. EPA-600/4-85-017. U.S. Environmental Protection Agency, Cin-
cinnati, Ohio.
Topol, L E., and S. Ozdemir, 1984. Quality Assurance Handbook for Air Pollution Measurement Sys-
tems: Vol. V. Manual for Precipitation Measurement Systems, Part II. Operations and Mainte-
nance Manual. EPA-600/4-82-042b. U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina.
Ion
cr
N0~3
so%
Spike
(mg/L)
1.0
0.5
10.0
Number of
Replicates
7
7
7
Mean %
Recovery
105
100
112
Standard
Deviation (mg/L)
0.14
0.0058
0.71
a The chromatographic conditions used by O'Dell were slightly different than those listed in Table 6.2. However, the results are
typical of what is expected.
Table 6.3. Single-Operator Accuracy and Precision (O'Dell et al., 1984)a.
73
-------
SECTION 7
DETERMINATION OF DISSOLVED ORGANIC CARBON
AND DISSOLVED INORGANIC CARBON
7.1 SCOPE AND APPLICATION
This method is applicable to the determination of DIG and DOC in natural surface waters, and it is
written assuming that a Dohrman-Xertex DC-80 Analyzer is used. However, any instrumentation hav-
ing similar operating characteristics may also be used.
The method is applicable over the concentration range 0.1 to 30 mg/L DIG or DOC. The method detec-
tion limit is about 0.8 mg/L DOC and 0.1 mg/L DIG, as determined from replicate analyses of a blank
sample.
7.2 SUMMARY OF METHOD
Two samples, aliquots 4 and 5, are sent to the lab for analysis. Aliquot 4 is filtered and preserved in the
field (acidified to pH <2 with H2SO4). It is analyzed for DOC. Aliquot 5 is an unfiltered sample. It is
filtered and analyzed for DIG.
DOC is determined (after external sparging to remove DIC) by ultraviolet promoted persulfate oxida-
tion, followed by IR detection. DIC is determined directly by acidifying to generate CO2followed by IR
detection (U.S. EPA, 1983; Xertex-Dohrman, 1984).
7.3 INTERFERENCES
No interferences are known.
7.4 SAFETY
The sample types, standards, and most reagents pose no hazard to the analyst. Protective clothing
(lab coat) and safety glasses should be worn when preparing reagents and operating the instrument.
7.5 APPARATUS AND EQUIPMENT
Disposable plastic Luer-Lok syringes (for DIC samples) equipped with Luer-Lok syringe valves.
Carbon Analyzer - This method is based on the Dohrman DC-80 Carbon Analyzer equipped with
a high-sensitivity sampler. The essential components of the instrument are a sample injection
valve, UV-reaction chamber, IR detector, and integrator. The injection valve should have a 5- to 7-
mL sample loop and should permit injection with a standard Luer-Lok syringe. Other instru-
ments having similar performance characteristics may also be used.
Reagent Bottle for Standard Storage - Heavy-wall borosilicate glass bottle with three two-way
valves in the cap. Suitable suppliers include (but are not limited to) Rainin Instrument Co. (Cata-
log No. 45-3200) and Anspec Co. (Catalog No. H8332).
74
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7.6 REAGENTS AND CONSUMABLE MATERIALS
DOC Calibration Stock Solution (2,000 mg/L DOC) - Dissolve 0.4250 g potassium hydrogen
phthalate (KHR primary standard grade, dried at 105°C for 2 hours) in water, add 0.10 ml phos-
phoric acid (ACS reagent grade), and dilute to 100.00 ml with water. Store in an amber bottle at
4°C. Prepare monthly.
Dilute Daily DOC Calibration Solutions - Using micropipets and volumetric pipets, prepare the
following calibration standards daily.
a. 0.500 mg/L DOC - dilute 0.125 mL DOC stock solution plus 0.5 ml_ phosphoric acid to 500.00
mL with water.
b. 1.000 mg/L DOC - dilute 0.250 mL DOC stock solution plus 0.5 mL phosphoric acid to 500.00
mL with water.
c. 5.000 mg/L DOC - dilute 1.250 mL DOC stock solution plus 0.5 mL phosphoric acid to 500.00
mL with water.
d. 10.00 mg/L DOC - dilute 2.500 mL DOC stock solution plus 0.5 mL phosphoric acid to 500.00
mL with water.
e. 30.00 mg/L DOC - dilute 3.750 mL DOC stock solution plus 0.25 mL phosphoric acid to 250.00
mL with water.
Store in amber bottles at 4°C.
DOC QC Stock Solution (1,000 mg/L DOC) - Dissolve 0.5313 g KHP in water, add 0.25 mL phos-
phoric acid, then dilute to 250.00 mL with water. Store in an amber bottle at 4°C. The QC stock
solution must be prepared using an independent source of KHP. Prepare monthly.
Dilute Daily DOC QC Solutions - Prepare the following QC samples daily.
a. 0.500 mg/L DOC (Detection Limit QC Sample - DL QCCS) - dilute 0.250 mL QC stock solution
plus 0.5 mL phosphoric acid to 500.00 mL with water.
b. 10.00 mg/L DOC - dilute 2.500 mL QC stock solution plus 0.25 mL phosphoric acid to 250.00
mL with water.
c. 30.00 mg/L DOC - dilute 3.000 mL QC stock solution plus 0.1 mL phosphoric acid to 100.00 mL
with water. Store in amber bottles at 4°C.
DIG Calibration Stock Solution (2,000 mg/L DIG) - Dissolve 4.4131 g sodium carbonate (Na2CO3,
primary standard grade, freshly dried at 105°C for 2 hours) in water and dilute to 250.00 mL with
water. Store in a tightly capped bottle under a CO2-free atmosphere. Prepare weekly.
Dilute DIG Calibration Solutions - Prepare the following calibration standards daily. Store in
tightly capped bottles under a CO2-free atmosphere.
a. 0.500 mg/L DIC - dilute 0.250 mL DIG stock solution to 1.000 L with water.
b. 1.000 mg/L DIC - dilute 0.250 mL DIC stock solution to 500.00 mL with water.
c. 5.000 mg/L DIC - dilute 1.250 mL DIC stock solution to 500.00 mL with water.
d. 10.00 mg/L DIC - dilute 2.500 mL DIC stock solution to 500.00 mL with water.
f. 30.00 mg/L DIC - dilute 3.750 mL DIC stock solution to 250.00 mL with water.
DIC QC Stock Solution (1,000 mg/L DIC) - Dissolve 2.2065 g Na2CO3 in water and dilute to 250.00
mL with water. Store in a tightly capped bottle under a CO2-free atmosphere. The QC stock solu-
tion must be prepared using an independent source of Na2CO3.
Dilute DIC QC Solutions - Prepare the following QC samples daily.
75
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a. 0.500 mg/L DIG (Detection Limit QC Sample - DLQCCS) - dilute 0.250 ml_ QC stock solution to
500.00 mL with water.
b. 10.00 mg/L DIG - dilute 2.500 mL QC stock solution to 250.00 mL with water.
c. 30.00 mg/L DIG - dilute 3.000 mL QC stock solution to 100.00 mL with water.
Potassium Persulfate Reagent (2 percent w/v) - Dissolve 20 g potassium persulfate (K2S2O8,
ACS reagent grade or better) in water, add 2.0 mL phosphoric acid, then dilute to 1.0 L with water.
This reagent is used for DOC analyses.
Phosphoric Acid Reagent (5 percent v/v) - Dilute 50.0 mL concentrated phosphoric acid (ACS
reagent grade) to 1.0 L with water. This reagent is used for DIG analyses.
Water - Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
7.7 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
The sample for DOC analysis (aliquot 4) is collected, filtered, and preserved in the field (pH adjusted
to less than 2 with sulfuric acid). Store at 4°C when not in use.
The sample for DIG analysis (aliquot 5) is collected in the field and is not filtered or preserved. Store at
4°C and minimize atmospheric exposure.
7.8 CALIBRATION AND STANDARDIZATION
7.8.7 DOC Calibration
7.8.1.1 Set-up
Set up the instrument according to the manufacturer's instructions. Adjust all liquid and gas flow
rates. Turn on UV lamp and allow the system to stabilize. The IR detector must warm up for at least 2
hours. For best results, leave the IR detector on at all times.
7.8.1.2 Routine Calibration
For the range of interest (0 to 30 mg/L DOC) the instrument is designed to be calibrated with a single
10.00 mg/L DOC standard. The linearity of the calibration is chec'ked with the QC samples. If accept-
able results are not obtained for the QC samples, the instrument must be calibrated using the proce-
dure in section 7.8.1.3.
Step 1 - Sparge the 10.00-mg/L calibration standard for 5 to 6 minutes with CO2-free gas.
Step 2 - Following the instructions in the operating manual, calibrate the instrument using three
replicate analyses of the 10.00-mg/L standard.
Step 3 - Analyze a system blank and a reagent blank. Both must contain less than 0.1 rng/L DOC. If
either contains more DOC, then the water is contaminated. In this case, all standards and reagents
must be prepared again with DOC-free water, and the instrument must be recalibrated.
Step 4 - After sparging for 5 to 6 minutes, analyze the 0.500, 10.00, and 30.00 mg/L QC samples.
Acceptable results are 0.50 ± 0.10, 10.0 ± 0.5, and 30.0 ± 1.5 mg/L, respectively. If acceptable
results are not obtained for all QC samples, the instrument calibration is in adequate (nonlinear). In
this case, recalibrate the instrument using the procedure in section 7.8.1.3.
7.8.1.3 Nonroutine Calibration
If the inherent instrument calibration procedure is inadequate (nonlinear over the range of interest),
then the instrument must be calibrated manually. This is done by analyzing a series of calibration
standards and generating a calibration curve by plotting instrument response versus standard con-
76
-------
centration. Sample concentrations are then determined by inverse interpolation. The procedure is
outlined in steps 1 through 5.
Step 1 - Sparge the 0.500, 1.000, 5.000, 10.00, and 30.00 mg/L DOC calibration standard for 5 to 6
minutes with CO2-free gas.
Step 2 - Erase the instrument calibration (if present). Analyze each standard and record the uncali-
brated response.
Step 3 - Plot the response versus standard concentration. Draw or calculate (using linear regression)
the best calibration curve.
Step 4 - Analyze a system blank and a reagent blank. From their response and the calibration curve
determine their concentrations. Both must contain less than 0.1 mg/L DOC. If either contains more
than 0.1 mg/L DOC, then the water is contaminated. In this case, the standards and reagents must be
prepared again using DOC-free water, and the instrument must be recalibrated.
Step 5 - After sparging for 5 to 6 minutes, analyze the 0.500 and 10.00 mg/L QC samples. From their
response and the calibration curve, determine the concentration of each QC sample. Acceptable
results are 0.5 ± 0.1 and 10.0 ± 0.5 mg/L, respectively. If unacceptable results are obtained, the
calibration standards must be prepared again and reanalyzed. Acceptable results must be obtained
prior to sample analysis.
7.8.2 DIC Calibration
7.8.2.1 Set-up
Set up 'ihe instrument according to the manfacturer's instructions. Adjust all liquid and gas flow
rates, using 5 percent phosphoric acid as the reagent. Do not turn on the UV lamp. Allow the system
to stabilize.
7.8.2.2 Routine Calibration
The calibration procedure is identical to that for DOC (section 7.8.1.2) with the exception that the DIC
standards are not sparged prior to analysis.
7.8.2.3 Nonroutine Calibration
The nonroutine calibration procedure is identical to that for DOC (section 7.8.1.3) with the exception
that the DIC standards are not sparged prior to analysis.
7.9 QUALITY CONTROL
In addition to the QC inherent in the calibration procedures (section 7.8), the QC procedures
described in section 3.4 must be performed.
7.10 PROCEDURE
7.10.1 DOC Analysis
Step 1 - Calibrate the carbon analyzer for DOC.
Step 2 - Sparge samples with CO2-free gas for 5 to 6 minutes (sparge gas should have a flow of 100 to
200 cc/min). Load and analyze the sample as directed by the instrument operating manual.
7.10.2 DIC Analysis
NOTE: For QA reasons, it is very important that the DIC is measured at the same time pH is measured
(section 4).
Calibrate the carbon analyzer for DIC.
77
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7.10.2.1 Routine Determination
Rinse a clean syringe with sample. Withdraw a fresh sample portion into the syringe. Attach a
syringe filter (0.45 n m) and simultaneously filter the sample and inject it into the carbon analyzer.
Analyze as directed by the instrument operating manual.
7.10.2.2 Air-Equilibrated Determination
As described in section 4.10.3, equilibrate the sample with 300 ppm CO2 in air. Rinse a. clean syringe
with the air-equilibrated sample. Withdraw a fresh portion of the air-equilibrated sample and attach a
syringe filter (0.45 //m). Simultaneously filter and inject the sample into the carbon analyzer. Analyze
as directed by the instrument operating manual.
7.11 CALCULATIONS
If the routine calibration procedure is satisfactory, the instrument outputs the sample results directly
in mg/L. DOC or DIG calculations are not necessary.
If a calibration curve is necessary, determine the sample concentration by comparing the sample
response to the calibration curve. Report results as mg/L DOC or DIG.
7.12 PRECISION AND ACCURACY
7.12.1 DOC
In a single laboratory (EMSL-Cincinnati), using raw river water, centrifuged river water, drinking water,
and the effluent from a carbon column which had concentrations of 3.11, 3.10,1.79, and 0.07 mg/L
total organic carbon respectively, the standard deviations from 10 replicates were 0.13,0.03,0.02, and
0.02 mg/L, respectively (U.S. EPA, 1983).
In a single laboratory (EMSL-Cincinnati), using potassium hydrogen phthalate in distilled water at
concentrations between 5.0 and 1.0 mg/L total organic carbon, recoveries were 80 percent and 91
percent, respectively (U.S. EPA, 1983).
7.12.2 DIC
In a multiple lab study using two lake samples containing 0.42 and 9.9 mg/L DIC respectively, the
relative standard deviations were 19 percent (n = 41) and 5.2 percent (n = 7), respectively.
In a single laboratory (EMSL-Las Vegas), using sodium carbonate in deionized water at concentra-
tions of 0.150, 0.500, 2.00, and 30.00 mg/L DIC, recoveries were 94,101,100, and 98 percent, respec-
tively.
7.13 REFERENCES
American Society for Testing and Materials, 1984. Annual Book of ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes, Method 415.2, Organic Carbon, Total (low level) (UV promoted, persulfate oxidation).
EPA-600/4-79-020. U.S. EPA, Cincinnati, Ohio.
Xertex-Dohrman Corporation, 1984. DC-80 Automated Laboratory Total Organic Carbon Analyzer
Systems Manual, 6th Ed. Xertex-Dohrman, Santa Clara, California.
78
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SECTION 8
DETERMINATION OF TOTAL DISSOLVED FLUORIDE
BY ION-SELECTIVE ELECTRODE
8.1 SCOPE AND APPLICATION
This method is applicable to the determination of total dissolved fluoride in natural surface waters,
using a fluoride ion-selective electrode (ISE). The applicable concentration range is 0.005 to 2 mg/L
fluoride (F~).
8.2 SUMMARY OF METHOD
The total dissolved fluoride in a sample is determined electrometrically using a fluoride ion-selective
electrode, after addition to the sample of a total ionic strength buffer solution (TISAB). The TISAB
adjusts sample ionic strength and pH and breaks up fluoride complexes.
The potential of the fluoride ISE varies logarithmically as a function of the fluoride concentration. A
calibration curve is prepared by measuring the potential of known fluoride standards (after TISAB
addition) and plott ing the potential versus fluoride concentration (on a semi-log scale). Sample con-
centrations are determined by comparing the sample potential to the calibration curve.
This method is based on existing methods (U.S. EPA, 1983; Barnard and Nordstrom, 1982; Bauman,
1971; LaZerte, 1984; Kissa, 1983; Warner and Bressan, 1973).
8.3 INTERFERENCES
The electrode potential is partially a function of temperature. As a result, standards and samples
must be equilibrated to the same temperature (± 1 °C).
The sample pH must be in the range 5 to 7 to avoid complexation of fluoride by hydronium (pH < 5)
and hydroxide (pH >7). The addition of TISAB to samples and standards ensures that the pH is
maintained in the correct range.
Polyvalent cations may interfere by complexing fluoride, thereby preventing detection by the elec-
trode. The TISAB solution contains a decomplexing agent to avoid potential interferences from poly-
valent cations.
Fluoride is ubiquitous. Good laboratory practices and extra care must be used in order to minimize
contamination of samples and standards.
8.4 SAFETY
The sample types, calibration standards, and most reagents pose no hazard to the analyst. Protect-
ive clothing (lab coat and gloves) and safety glasses must be worn when handling concentrated
sodium hydroxide.
8.5 APPARATUS AND EQUIPMENT
Digital electrometer (pH/mV meter) with expanded mV scale capable of reading 0.1 mV
Combination Reference - Fluoride ion selective electrode
79
-------
Thermally isolated magnetic stirrer and Teflon-coated stir bar
8.6 REAGENTS AND CONSUMABLE MATERIALS
Unless otherwise specified, all chemicals must be ACS reagent grade or better. Use only plasticware
(cleaned as described in Appendix A) for reagent preparation.
TISAB Solution - To approximately 500 ml_ water in a 1-L beaker, add 57 ml_ glacial acetic acid
(Baker Ultrex grade or equivalent), 4 g CDTA*, and 58 g sodium chloride (NaCI, ultrapure). Stir to
dissolve, and cool to room temperature. Adjust the pH of the solution to between 5.0 and 5.5 with
5N NaOH (about 150 mL will be required). Transfer the solution to a 1 L volumetric flask and dilute
to the mark with water. Transfer to a clean polyethylene (LPE) bottle. (Note: Alternatively, com-
mercially available TISAB solution may be used.)
Sodium Hydroxide Solution (5N NaOH) - Dissolve 200 g NaOH in water, cool, then dilute to 1 L.
Store in a tightly sealed LPE bottle.
Fluoride Calibration Solutions
a. Concentrated Fluoride Calibration Stock Solution (1,000 mg/L F") - Dissolve 0.2210 g of
sodium fluoride (NaF, ultrapure, dried at 110°C for 2 hours and stored in a desiccator) in water
and dilute to 100.00 mL Store in a clean LPE bottle.
b. Dilute Fluoride Calibration Stock Solution (10.00 mg/L F') - Dilute 1.000 mL of the concen-
trated fluoride calibration stock solution to 100.00 mL with water.
c. Dilute Fluoride Working Standards - Using micropipets and volumetric pipets, prepare daily
a series of dilute working standards in the range 0.0-2 mg/L F" by quantitatively diluting
appropriate volumes of the 10.00 mg/L F~ solution and TISAB solution to 50.00 mL. The follow
ing series may be used:
Resulting F"
mL of Concentration When
mL of 10.00 mg/L F" Diluted to
TISAB Solution 50.00 mL (mg/L)
5.00 0.000 0.0000
5.00 0.0500 0.0100
5.00 0.100 0.0200
5.00 0.250 0.0500
5.00 0.500 0.100
5.00 2.50 0.500
5.00 10.00 2.000
Water - Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
8.7 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
Samples are collected and filtered in the field and are shipped to the lab in LPE bottles. Store at 4°C
when not in use.
8.8 CALIBRATION AND STANDARDIZATION
Step 1 - Allow the electrometer to warm up, and ensure that the fluoride ISE contains adequate
internal filling solution.
Step 2 - With the electrometer set to measure mV, analyze the dilute fluoride working standards (in
order of increasing concentration, beginning with the blank), using the procedure described in steps
3 through 5.
80
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Step 3- Prior to use and between determinations, rinse the electrode with water until a potential of at
least 200 mV is obtained. Blot dry to avoid carryover.
Step4- Place 20.00 ml of standard in a clean 30-mL plastic beaker. Add a clean Teflon-coated stir bar,
place on a magnetic stirrer, and stir at medium speed.
Step 5 - Immerse the electrode in the solution to just above the stir bar and observe the potential.
Record the potential when a stable reading is obtained (potential drift less than 0.1 mV/minute).
Record the time required to obtain the reading. (It may take 15 to 30 minutes to obtain a stable reading
for the low standards.)
Step 6 - Prepare a calibration curve on semi-logarithmic graph paper. Plot the concentration of F~ (in
mg/L) on the log axis versus the electrode potential on the linear axis. Determine the slope of the line
in the linear portion of the plot. The measured slope should be within ±10 per cent of the theoretical
slope (obtained from the electrode manual). If it is not, the electrode is not operating properly. Con-
sult the electrode manual for guidance. (Note: The calibration curve may be nonlinear below 0.05 mg/
L)
8.9 QUALITY CONTROL
The required QC procedures are described in Section 3.4.
8.10 PROCEDURE
NOTE: Use only plasticware when performing fluoride determinations. Clean using the acid-free
washing procedure described in Appendix A.
Step 1 - Allow samples and standards to equilibrate at room temperature.
Step 2 - Analyze fluoride standards and prepare calibration curve as described in section 8.8.
Step 3 - Prior to use and between determinations, rinse the electrode with water until a potential of at
least 200 mV is obtained. Blot dry to avoid carryover.
Step 4- Place 10.00 ml_ of sample in a clean 30-mL plastic beaker. Add a clean Teflon-coated stir bar,
place on a magnetic stirrer, and stir at a medium speed. Add 1.00 ml_ of TISAB to beaker. Record the
reading when a stable potential is obtained (drift is less than 0.1 mV/minute). Also record the time
required to reach the stable reading. (It may take as much as 15 to 30 minutes.) This assists the
analyst in detecting electrode problems.
Step 5 - At the end of the day, thoroughly rinse the electrode and store it in deionized water.
8.11 CALCULATIONS
Compute the sample concentration by comparing the sample potential reading to the calibration
curve. Report results in mg/L.
8.12 PRECISION AND ACCURACY
A synthetic sample containing 0.85 mg/L fluoride and no interferences was analyzed by 111 analyst;
the mean result was 0.84 mg/L and the standard deviation was 0.03 mg/L (U.S. EPA, 1983).
A synthetic sample containing 0.75 mg/L fluoride, 2.5 mg/L polyphosphate, and 300 mg/L alkalinity
was analyzed by 111 analysts; the mean result was 0.75 mg/L fluoride and the standard deviation was
0.036 (U.S. EPA, 1983).
81
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8.13 REFERENCES
American Society for Testing and Materials, 1984. Annual Book of ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
Barnard, W. R., and D. K. Nordstrom, 1982. Fluoride in Precipitation -1. Methodology with the Fluoride-
Selective Electrode. Atmos. Environ., v. 16, pp. 99-103.
Bauman, E. W., 1971. Sensitivity of the Fluoride-Selective Electrode Below the Micromolar Range.
Anal. Chim. Acta, v. 54, pp. 189-197.
Kissa, E., 1983. Determination of Fluoride at Low Concentrations with the Ion-Selective Electrode.
Anal. Chem., v. 55, pp. 1445-1448.
LaZerte, B. D., 1984. Forms of Aqueous Aluminum in Acidified Catchments of Central Ontario: A
Methodological Analysis. Can. J. Fish Aquat. Sci., v. 41, n. 5, pp. 766-776.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes, Method 340.2, Fluoride (Potentiometric, Ion Selective Electrode). EPA-600/4-79-020. U.S.
EPA, Cincinnati, Ohio.
Warner, T. B., and D. J. Bressan, 1973. Direct Measurement of Less Than 1 Part-Per-Billion Fluoride in
Rain, Fog, and Aerosols with an Ion Selective Electrode. Anal. Chim. Acta, v. 63, pp. 165-173.
82
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SECTION 9
DETERMINATION OF TOTAL PHOSPHORUS
9.1 SCOPE AND APPLICATION
This method may be used to determine concentrations of total phosphorus in natural surface waters
in the range from 0.001 to 0.200 mg/L P.
Samples preserved with HgCI2 should not be analyzed using this method.
9.2 SUMMARY OF METHOD
All forms of phosphorus, including organic phosphorus, are converted to orthophosphate by an acid-
persulfate digestion.
Orthophosphate ion reacts with ammonium molybdate in acidic solution to form phosphomolybdic
acid, which upon reduction with ascorbic acid produces an intensely colored blue complex. Anti-
mony potassium tartrate is added to increase the rate of reduction (Skougstad et al., 1979; Gales et
al., 1966; Murphy and Riley, 1962).
9.3 INTERFERENCES
Barium, lead, and silver interfere by forming a precipitate. There is a positive interference from silica
when the silica-to-total-phosphorus ratio exceeds about 400:1 (Table 9.1).
HgCi2-NaCI-preserved samples give inconsistent results and therefore should not be used.
9.4 SAFETY
The calibration standards, sample types, and most reagents used in this method pose no hazard to
the analyst. Use protective clothing (lab coat and gloves) and safety glasses when handling concen-
trated sulfuric acid.
Use proper care when operating the autoclave. Follow manufacturer's safety precautions.
Si02 (mg/L)
Total P mg/L
0.200
0.100
0.050
0.010
0.005
0.002
HgC12-NaC1-preserved samples
20
98
103
104
144
160
550
give inconsistent
15
100
104
133
140
350
results and
10
100
102
122
120
250
therefore should
5
102
102
111
120
250
not be used.
1
101
103
102
100
100
100
Table 9.1. Percent Recovery of Total P in the Presence of SiO2 (Skougstad et al., 1979).
83
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9.5 APPARATUS AND EQUIPMENT
Autoclave
Technicon AutoAnalyzer II, consisting of sampler, cartridge manifold, proportioning pump, heat-
ing bath, colorimeter, voltage stabilizer, recorder, and printer With this equipment the following
operating conditions have been found satisfactory for the range from 0.001 to 0.200 mg/L P:
Absorption cell - 50 mm
Wavelength - 880 nm
Cam - 30/h (1:1) Heating bath temperature - 37.5°C.
Glass tubes with plastic caps, disposable - 18 mm by 150 mm.
9.6 REAGENTS AND CONSUMABLE MATERIALS
All reagents must be ACS reagent grade or equivalent.
Ammonium Molybdate Solution (35,6 g/L) - Dissolve 40 g ammonium molybdate
((NH4)6Mo7024.4H2O) in 800 mL water and dilute to 1 L.
Ascorbic Acid Solution (18 g/L)- Dissolve 18 g ascorbic acid (C6H8Q8) in 800 mL water and dilute
to 1 L.
Antimony Potassium Tartrate Solution (3 g/L) - Dissolve 3.0 g antimony potassium tartrate
(K(SbO)C4H404.1/2H20) in 800 mL water and dilute to 1 L.
Combined Working Reagent - Combine reagents in the order listed below. (This reagent is stable
for about 8 hours. The stability is increased if kept at 4°C):
50 mL Sulfuric acid, 2.45M
15 mL Ammonium molybdate solution
30 mL Ascorbic acid solution
5 mL Antimony potassium
tartrate solution
Phosphate Stock Standard Solution (100 mg/L P) - Dissolve 0.4394 g potassium acid phosphate
(KH2PO4, dried for 12 to 16 hours over concentrated H2SO4, sp gr 1.84) in water and dilute to 1,000
mL
Phosphate Standard Solution I (10.00 mg/L P) - Quantitatively dilute 100.0 mL phosphate stock
standard solution to 1,000 mL with water.
Phosphate Standard Solution II (1.000 mg/L P) - Quantitatively dilute 10.00 mL phosphate stock
standard solution to 1,000 mL with water.
Dilute Phosphate Working Standards - Prepare a blank and 1,000 mL each of a series of working
standards by appropriate quantitative dilution of phosphate standard solutions I and II. For
example:
84
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Total P
Phosphate Phosphate concentration
standard standard in working
solution II Solution I standard
(ml) (ml) (mg/L)
0.0 0.0 0.000
1.00 0.001
5.00 0.005
10.00 0.010
5.0 0.050
10.0 0.100
20.0 0.200
Potassium Persulfate Solution (4 g/L) - Dissolve 4.0 g potassium persulfate (K2S2O8) in water
and dilute to 1 L
Sulfuric Acid (2.45M) - Slowly, and with constant stirring and cooling, add 136 ml_ concentrated
sulfuric acid (sp gr 1.84) to 800 ml_ water. Cool, and dilute to 1 L with water.
Sulfuric Acid (0.45M) - Slowly, and with constant stirring and cooling, add 25.2 mL concentrated
sulfuric acid (sp gr 1.84) to 800 mL water. Cool, and dilute to 1 L with water.
Sulfuric Acid-Persulfate Reagent, (1 + 1)-Mix equal volumes of 0.45M sulfuric acid and potas-
sium persulfate solution.
Water Diluent - Add 1.0 mL Levor IV to 1 L water.
Water - Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
9.7 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
Samples are collected and preserved in the field (addition of H2SO4 until the pH < 2). Store samples
at 4°C when not in use.
9.8 CALIBRATION AND STANDARDIZATION
Analyze the series of total P standards as described in section 9.10.
Prepare a calibration curve by plotting the peak height versus standard concentration.
9.9 QUALITY CONTROL
The required QC is described in Section 3.4.
9.10 PROCEDURE
NOTE: It is critical that the colorimeter is optically peaked prior to first analysis.
Step 1 - Mix each sample, pipet a volume of it containing less than 0.002 mg total P (10.0 mL maxi-
mum) into a disposable glass tube, and adjust the volume to 10.0 mL.
Step 2 - Prepare blank solution and sufficient standards, and adjust the volume of each to 10.0 mL.
Step 3 - Add 4.0 mL acid-persulfate reagent to samples, blank, and standards.
Step 4 - Place plastic caps gently on top of tubes but do not push down. Autoclave for 30 minutes at
15 psi pressure and 121°C. After the samples have cooled, the caps may be pushed down.
Step 5 - Set up manifold as shown in Figure 9.1.
85
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Coil No.
157-B273-(
)3
5-
turn coils
ooooo
37.5°C
Colorimeter
880 nm
50 mm cells ^
T
ooooo
Waste
r
1
t
To sampler 4
receptacle
! ^
0.03 in
0.32 mL/min
0.030 in
0.32 mL/min
0.035 in
0.42 mL/min
0.030 in
0.32 mL/min
0.073 in
2.00 mL/miln
0.040 in
0.60 mL/min
Air
Water
Sample
Combined
reagent
Wash
solution
Waste
1 Proportioning pump
J
Recorder
Sampler 4
30/h
i/i cam
Figure 9.1 Total Phosphorus Manifold
-------
Step 6 - Allow the colorimeter, recorder, and heating bath to warm up for at least 30 minutes or until
the temperature of the heating bath reaches 37.5°C. Zero the recorder baseline while pumping all
reagents through the system.
Step 7 - Beginning with the most concentrated standard, place a complete set of standards in the
first positions of the first sample tray, with blank solution between each standard. Fill remainder of
each tray alternately with unknown samples and blank solution.
Step 8 - Begin analysis. When the peak from the most concentrated standard appears on the
recorder, adjust the STD CAL control until the flat portion of the peak reads full scale. Using the
baseline control, adjust each blank in the tray to read zero as it is analyzed.
Step 9 - Dilute and reanalyze samples with a total P concentration exceeding the calibrated range.
9.11 CALCULATIONS
Compute the concentration of total P in each sample by comparing its peak height to the calibration
curve. Report results as mg/L P.
9.12 PRECISION AND ACCURACY
Data for the determination of the precision and accuracy of the method are given in Tables 9.2 and 9.3.
It is estimated that the RSD (coefficient of variation) of this method is 38 percent at 0.001 mg/L, 2.5
percent at 0.020 mg/L, and 2,2 percent at 0.144 mg/L.
Sample
4-065070
4-065080
4-066060
n
10
10
10
Mean
0.0347
0.1435
0.0902
Std. Dev.
0.0012
0.0031
0.0027
Rel. Std. Dev. (%)
3.34
2.16
2.99
Table 9.2. Precision of the Method for Natural Water Samples (Skougstad et al., 1979). (All data in
mg/L P).
Sample
0.040
0.030
0.020
0.004
0.001
n
9
10
10
9
9
Mean
0.0424
0.0322
0.0172
0.0033
0.0013
Std. Oev.
0.0007
0.0006
0.0004
0.0007
0.0005
Rel. Std. Dev. (%)
1.71
1.96
2.45
21.21
37.5
Table 9.3. Precision and Accuracy of the Method for Analyst-Prepared Standards (Skougstad et al.,
1979. (All data in mg/L P).
87
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9.13 REFERENCES
American Society for Testing and Materials, 1984. Annual Book of ASTM Standards, Vol. 11.01, Stand-
ardSpecificatton for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
Gales, M. E., Jr., E. C. Julian, and R. C. Kroner, 1966. Method for Quantitative Determination of Total
Phosphorus in Water. J. Am. Water Works Assoc., v. 58, pp. 1363-1368.
Murphy, J., and J. P. Riley, 1962. A Modified Single-Solution Method for the Determination of Phos-
phate in Natural Waters. Anal. Chim. Acta, v. 27, pp. 31-36.
Skougstad, M. W., M. J. Fishman, L. C. Friedman, D. E. Erdman, and S. S. Duncan (eds.), 1979. Method
I-4600-78, Automated Phosphomolybdate Colorimetric Method for Total Phosphorus. In: Meth-
ods for Determination of Inorganic Substances in Water and Fluvial Sediments: Techniques of
Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1.
U.S. Government Printing Office, Washington, D.C.
88
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SECTION 10
DETERMINATION OF DISSOLVED SILICA
10.1 SCOPE AND APPLICATION
This method is applicable for the determination of dissolved silica in natural surface waters in the
concentration range from 0.1 to 10 mg/L.
10.2 SUMMARY OF METHOD
The procedure specified utilizes automated technology and is based on existing methodology
(Skougstad et al., 1979).
Silica reacts with molybdate reagent in acid media to form a yellow silico molybdate complex. This
complex is reduced by ascorbic acid to form the molybdate blue color. The silicomolybdate complex
may form either as an alpha or beta polymorph, or as a mixture of both. Because the two poly morphic
forms have absorbance maxima at different wavelengths, the pH of the mixture is kept below 2.5, a
condition which favors formation of the beta polymorph (Govett, 1961; Mullen and Riley, 1955; Strick-
land, 1962).
A 1-hour digestion with 1.0M NaOH is required to ensure that all the silica is available for reaction
with the molybdate reagent.
10.3 INTERFERENCES
Interference from phosphate, which forms a phosphomolybdate complex, is suppressed by the addi-
tion of oxalic acid. Hydrogen sulfide must be removed by boiling the acidified sample prior to analy-
sis. Large amounts of iron interfere. However, neither hydrogen sulfide nor iron is expected in appre-
ciable quantities.
10.4 SAFETY
The calibration standards, samples, and most reagents used in this method pose no hazard to the
analyst. Use protective clothing (lab coat and gloves) and safety glasses when handling concen-
trated sulfuric acid and performing sample digestions.
10.5 APPARATUS AND EQUIPMENT
Technicon AutoAnalyzer II consisting of sampler, cartridge manifold, proportioning pump, color-
imeter, voltage stabilizer, recorder, and printer.
With this equipment the following operating conditions are recommended:
Absorption cell - 15 mm
89
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10.6 REAGENTS AND CONSUMABLE MATERIALS
Ammonium Molybdate Solution (9.4 g/L) - Dissolve 10 g ammonium molybdate
((NH4)6Mo4O24.4H40) in 0.05M H2SO4 and dilute to 1 L with 0.05M H2SO4. Filter and store in an
amber plastic container.
Ascorbic Acid Solution (17.6 g/L) - Dissolve 17.6 g ascorbic acid (C6H8O6) in 500 ml_ water con-
taining 50 ml_ acetone. Dilute to 1 L with water. Add 0.5 ml_ Levor IV solution. The solution is
stable for 1 week if stored at 4°C.
Hydrochloric Acid (50 percent v/v) - Slowly add 500 ml_ concentrated HCI to 500 mL water.
Hydrochloric Acid (2 percent v/v) - Add 10 mL (concentrated) HCI to 490 mL water.
Hydrofluoric Acid (HF, ACS reagent grade)
Levor IV Solution - Technicon No. 21-0332 or equivalent.
Oxalic Acid Solution (50 g/L) - Dissolve 50 g oxalic acid (C2H204.2H2O) in water and dilute to 1 L.
Silica Standard Solution (500 mg/L SiO2) - Dissolve 2.366 g sodium metasilicate (Na2SiO3.9H2O)
in water and dilute to 1.000 L. The concentration of this solution must be verified by standard
gravimetric analysis (described in section 10.8.1). Store in a plastic bottle.
Silica Working Standards - Prepare a blank and 500 mL each of a series of silica working stand-
ards by appropriate quantitative dilution of the silica stock standard solution. The following
series is suggested:
Silica
Silica Stock concentration
Standard in Working
solution (ml) standard (mg/L)
0.0 0
0.200 0.200
0.500 0.500
1.00 1.00
5.00 5.00
10.0 10.0
Sodium Hydroxide Solution (1.0M NaOH) - Dissolve 4 g sodium hydroxide (NaOH) in water and
dilute to 1 L
Sulfuric Acid Solution (0.05M H2SO4) (50% v/v H2SO4) - Cautiously add 2.8 mL concentrated
sulfuric acid (H2SO4, sp gr 1.84) to water and dilute to 1 L for 0.05M H2SO4 . Cautiously and slowly
add 500 mL H2SO4 to 500 mL water. Beware of excessive heat buildup.
Water - Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
10.7 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
Samples are collected and filtered in the field, then shipped to the lab. Store at 4°C when not in use.
10.8 CALIBRATION AND STANDARDIZATION
Verify the concentration of the silica stock standard solution using the gravimetric procedure
detailed in steps 1 through 7 (APHA, 1980).
Step 1 - Sample Evaporation: Add 5 rnLof 50 percent v/v HCI to 200.0 mL silica stock standard. Evapo-
rate to dryness in a 200-mL platinum evaporating dish, in several portions if necessary, on a water
90
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bath or suspended on an asbestos ring over a hot plate. Protect against contamination by atmo-
spheric dust. During evaporation, add a total of 15 mL 50 percent HCI in several portions. Evaporate
sample to dryness and place dish with residue in a 110°C oven or over a hot plate to bake for 30
minutes.
Step 2 - First Filtration: Add 5 ml of 50 percent HCI, warm, and add 50 mL hot water. While hot, filter
sample through an ashless medium-texture filter paper, decanting as much liquid as possible. Wash
dish and residue with hot 2 percent HCI and then with a minimum volume of water, until washings are
chloride-free. Save all washings. Set aside filter paper with its residue.
Step 3 - Second Filtration: Evaporate filtrate and washings from the above operations to dryness in
the original platinum dish. Bake residue in a 110°C oven or over a hot plate for 30 minutes. Repeat
steps in section 10.8.1.2. Use a separate filter paper and a rubber policeman to aid in transferring
residue from dish to filter.
Step 4 - Ignition: Transfer the two filter papers and residues to a covered platinum crucible, dry at
110°C, and ignite at 1,200°C to constant weight. Avoid mechanical loss of residue when first charring
and burning off the paper. Cool in desiccator, weigh, and repeat ignition and weighing until constant
weight is attained. Record weight of crucible and contents.
Step 5 - Volatilization with HF: Thoroughly moisten weighed residue with water. Add 4 drops of 50
percent v/v H2SO4 followed by 10 mL concentrated HF, measuring the latter in a plastic graduated
cylinder or pouring an estimated 10 mL directly from the reagent bottle. Slowly evaporate to dryness
over an air bath or hot plate in a hood, and avoid loss by splatter ing. Ignite crucible to constant
weight at 1,200°C. Record weight of crucible and contents.
Step 6 - Blank: Repeat steps 1 through 5 with a blank sample.
Step 7 - Perform the following calculations for both the standard and blank samples.
X = weight of crucible plus contents before HF treatment (mg)
Y = weight of crucible plus contents after HF treatment (mg)
Z = weight of silica in sample (mg) = X - Y
Step 8 - Calculate the silica concentration in the stock standard by:
mg SiQ2 _ Z (standard) - Z (blank) mg
L0.200 L
Step 9 - Analyze the series of silica standards as described in section 10.10 (including digestion).
Step 10 - Prepare a calibration curve by plotting the peak height versus standard concentration.
10.9 QUALITY CONTROL
The required QC is described in section 3.4.
10.10 PROCEDURE
Step 7 - Set up the AutoAnalyzer manifold (Figure 10.1).
Step 2 - Allow colorimeter and recorder to warm up for at least 30 minutes. Zero the recorder baseline
while pumping all reagents through the system.
Step 3 - Add 5.00 mL of 1.0M NaOH to 50.00 mL of sample. Digest for one hour.
Step 4 - Beginning with the most concentrated working standard, place a complete set of standards
in the first positions of the first sample tray, followed by a blank. Fill remainder of each sample tray
with unknown and QC samples.
91
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20-turn coil
22-turn coil
Colorimeter
660 nm
15-mm cell
Waste
To sampler 4
wash
receptacle
0.030 in
0.32 mL/min
0.035 in
0.42 mL/min
0.025 in
0.23 mL/min
0.030 in
0.32 mL/min
0.035 in
0.42 mL/min
0.073 in
2.00 mL/min
0.045 in
0.80 mL/mm
Air
Molybdate
Reagent
Sample
Oxalic
Acid
Ascorbic
Acid
Water
Waste
Proportioning pump
Recorder
Sampler 4
60/h
6/1 cm
Figure 10.1. Silica Manifold.
-------
Step 5 - Begin analysis. When the peak from the most concentrated working standard appears on the
recorder, adjust the STD CAL control until the flat portion of the curve reads full scale.
Step 6 - Dilute and reanalyze any sample with a concentration exceeding the calibrated range.
10.11 CALCULATIONS
Compute the silica concentration of each sample by comparing its peak height to the calibration
curve. Any baseline drift that may occur must be taken into account when computing the height of a
sample or standard peak. Report results as mg/L SiO2.
10.12 PRECISION AND ACCURACY
In a multiple lab study using 111 lake samples containing 0.05-10 mg/L SiO2 the duplicate relative
standard deviation was 1.6 percent (note that this is the overall within-lab precision).
In a multiple lab study using two synthetic, simulated lake samples containing 10.7 and 1.07 mg/L
SiO2 respectively, recoveries obtained were 88 (n = 21) and 95 (n = 21) percent, respectively.
10.13 REFERENCES
American Public Health Association, American Waterworks Association, and Water Pollution Con-
trol Foundation, 1980. Standard Methods for the Examination of Water and Wastewater, 15th Ed.
Part 425-Silica. APHA, Washington, D.C.
American Society for Testing and Materials, 1984. Annual Book of ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
Govett, G.J.S., 1961. Critical Factors in the Colorimetric Determination of Silica. Anal. Chim. Acta, v.
25, pp. 69-80.
Mullen, J. B., and J. P. Riley, 1955. The Colorimetric Determination of Silica with Special Reference to
Sea and Natural Waters. Anal. Chim. Acta, v. 12, pp. 162-176.
Skougstad, M. W., M. J. Fishman, L. C. Friedman, D. E. Erdman, and S. S. Duncan (eds.), 1979. Method
I-2700-78, Automated Molybdate Blue Colorimetric Method for Dissolved Silica. In: Methods for
Determination of Inorganic Substances in Water and Fluvial Sediments: Techniques of Water-
Resources Investigations of the United States Geological Survey, Book 5, Chapter A1. U.S. Gov-
ernment Printing Office, Washington, D.C.
Strickland, J.D.H., 1962. The Preparation and Properties of Silicomo lybdic Acid; I. The Properties of
Alpha Silicomolybdic Acid. J. Am. Chem. Soc., v. 74, pp. 852-857.
93
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SECTION 11
DETERMINATION OF SPECIFIC CONDUCTANCE
11.1 SCOPE AND APPLICATION
This method is applicable to natural surface waters of low ionic strength.
The majority of lakes sampled for the NSWS have a specific conductance in the range 10 to 100 AS/
cm.
11.2 SUMMARY OF METHOD
The specific conductance in samples is measured using a conductance meter and conductivity cell.
The meter and cell are calibrated using potassium chloride standards of known specific conduc-
tance (U.S. EPA, 1983).
Samples are preferably analyzed at 25°C. If they cannot be analyzed at 25°C, temperature correc-
tions are made and results are reported at 25°C.
11.3 INTERFERENCES
Temperature variations represent the major source of potential error in specific conductance deter-
minations. To minimize this error, calibration standards and samples must be measured at the same
temperature.
Natural surface waters contain substances (humic and fulvic acids, suspended solids, etc.) which
may build up on the conductivity cell. Such a buildup interferes with the operation of the cell and
must be removed periodically, following the cell manufacturer's recommendations.
11.4 SAFETY
The calibration standards and sample types pose no hazard to the analyst.
11.5 APPARATUS AND EQUIPMENT
Specific Conductance Meter - Digital meter with the following minimum specifications:
Range - 0.1 to 1000 M S/cm
Readability - 0.1 /iS/cm
Maximum Error - 1% of reading
Maximum Imprecision - 1% of reading
Conductivity Cell - High quality glass cell with a cell constant of 1.0 or 0.1. Cells containing
platinized electrodes are recommended.
Thermometer - NBS-traceable thermometer with a range of 0 to 40°C and divisions of 0.1 °C.
94
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11.6 REAGENTS AND CONSUMABLE MATERIALS
Potassium Chloride Stock Calibration Solution (0.01000M KCI) - Dissolve 0.7456 g potassium
chloride (KCI, ultrapure, freshly dried for two hours at 105°C and stored in a desiccator) in water
and dilute to 1.000 L Store in a tightly sealed LPE container.
Potassium Chloride Calibration Solution (0.001000M KCI) - Dilute 10.00 ml KCI stock calibration
solution to 100.00 mL with water. This solution has a theoretical specific conductance of 147.0 SI
cm at 25°C.
Potassium Chloride QC Solution (0.000500M KCI) - Dilute 5.00 mL 0.0100M KCI solution (indepen-
dent of the KCI stock calibration solution) to 100.00 mL with water. This solution has a theoretical
specific conductance of 73.9 M S/cm at 25°C.
Water - Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
11.7 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
The samples are collected in the field and shipped to the lab in LPE bottles without treatment. Store
at 4°C when not in use.
11.8 CALIBRATION AND STANDARDIZATION
Step 7 - Measure and record the specific conductance of the KCI calibration solution as described in
section 11.10.
Step 2 - Calculate the corrected cell constant, Kc, using the following equation:
Kc =
147.0 /uS/cm
KCIm
KCIm = measured specific conductance for
the KCI calibration solution.
The corrected cell constant, Kc, includes the calculation for the cell constant and the temperature
correction to 25°C.
11.9 QUALITY CONTROL
The required QC procedures are described in section 3.4.
11.10 PROCEDURE
Step 1 - Follow the manufacturer's instructions for the operation of the meter and cell.
Step 2 - Allow the samples and calibration standard to equilibrate to room temperature.
Step 3 - Measure the sample temperature. If different from the standard temperature, allow more
time for equilibration.
Step 4 - Rinse the cell thoroughly with water.
Step 5 - Rinse the cell with a portion of the sample to be measured. Immerse the electrode in a fresh
portion of sample and measure its specific conductance.
Step 6 - Rinse the cell thoroughly with water after use. Store in water.
If the readings become erractic, the cell may be dirty or need replatinizing. Consult the manufactur-
er's operating manual for guidance.
95
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11.11 CALCULATIONS
Calculate the corrected specific conductance (Sc) for each sample using the following equation:
Sc = (Kc)(Sm)
Kc = corrected cell constant
Sm = measured specific conductance
Report the results as specific conductance, M S/cm at 25°C.
11.12 PRECISION AND ACCURACY
Forty-one analysts in seventeen laboratories analyzed six synthetic samples containing increments
of inorganic salts, with the following results (U.S. EPA, 1983):
Accuracy, as
Increment
as Specific
Conductance
{ MS/cm)
100
106
808
848
1,640
1,710
Precision as
Standard
Deviations
( MS/cm)
7.55
8.14
66.1
79.6
106
119
Bias (%) Bias (
-2.02 - 2.0
-0.76 - 0.8
-3.63 -29.3
-4.54 -38.5
-5.36 -87.9
-5.08 -86.9
In a single laboratory (EMSL-Cincinnati) using surface-water samples with an average conductivity of 536
M S/cm at 25°C, the standard deviation was 6 M S/cm (U.S. EPA, 1983).
11.13 REFERENCES
American Society for Testing and Materials, 1984. Annual Bookof ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes, Method 120.1, Conductance. EPA-600/4-79-020. U.S. EPA, Cincinnati, Ohio.
96
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SECTION 12
DETERMINATION OF METALS (Al, Ca, Fe, K, Mg, Mn, Na)
BY ATOMIC ABSORPTION SPECTROSCOPY
12.1 SCOPE AND APPLICATION
Metals in solution may be readily determined by atomic absorption spectro scopy. The method is
simple, rapid, and applicable to the determination of Al, Ca, Fe, K, Mg, Mn, and Na in natural surface
waters.
Detection limits, sensitivity, and optimum ranges of the metals vary with the makes and models of
atomic absorption spectrophotometers. The data listed in Table 12.1, however, provide some indica-
tion of the actual con centration ranges measurable by direct aspiration (flame) and furnace tech-
niques. In the majority of instances the concentration range shown in the table for analysis by direct
aspiration may be extended much lower with scale expansion and, conversely, extended upward by
using a less sensitive wavelength or by rotating the burner head. Detection limits by direct aspiration
may also be extended through concentration of the sample and through solvent extraction tech-
niques. Lower concentrations may also be determined using the furnace techniques. The concentra-
tion ranges given in Table 12.1 are somewhat dependent on equipment such as the type of spectro-
photometer and furnace accessory, the energy source, and the degree of electrical expansion of the
output signal. When using furnace techniques, however, the analyst should be cautioned that chemi-
Flame
Optimum
Detection Sensi- Concentration Detection
Limit tivity Range Limit
Metal (mg/L) (mg/L) (mg/L) fcug/L)
Aluminum
Calcium
Iron
Magnesium
Manganese
Potassium
Sodium
0.1
0.01
0.03
0.001
0.01
0.01
0.002
1
0.08
0.12
0.007
0.05
0.04
0.015
5 to 50 3
0.2 to 7
0 3 to 5 1
0 2 to 0 5 1
0.1 to 3 0.2
0.1 to 2
0 03 to 1
1The concentrations shown are obtainable with any satisfactory atomic absorption spectrophotometer.
2For furnace sensitivity values, consult instrument operating manual.
3The listed furnace values are those expected when using a 20-^1 injection and normal gas flow, except
selenium where gas interrupt is used.
Furnace2
Optimum
Concentration
Range
(ug/L)
20 to 200
-
5 to 100
-
1 to 30
-
-
in the case of arsenic and
Table 12.1. Atomic Absorption Concentration Ranges1.
97
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cal reactions may occur at elevated temperatures, which may result in either suppression or
enhancement of the signal from the element being analyzed. To ensure valid data, the analyst must
examine each matrix for interference effects (matrix spike analysis) and, if detected, must analyze
the samples by the method of standard additions.
12.2 SUMMARY OF METHOD
In direct aspiration atomic absorption spectroscopy, a sample is aspirated and atomized in a flame. A
light beam from a hollow cathode lamp, whose cathode is made of the element to be determined, is
directed through the flame into a monochromator and onto a detector that measures the amount of
light absorbed. Absorption depends upon the presence of free unexcited ground state atoms in the
flame. Since the wavelength of the light beam is characteristic of only the metal being determined,
the light energy absorbed by the flame is a measure of the concentration of that metal in the sample.
This principle is the basis of atomic absorption spectroscopy.
When using the furnace technique in conjunction with an atomic absorption spectrophotometer, a
representative aliquot of a sample is placed in the graphite tube in the furnace, evaporated to dry-
ness, charred, and atomized. As a greater percentage of available analyte atoms are vaporized and
dissociated for absorption in the tube than the flame, the use of small sample volumes or detection
of low concentrations of elements is possible. The principle is essentially the same as with direct
aspiration atomic absorption except a furnace, rather than a flame, is used to atomize the sample.
Radiation from a given excited element is passed through the vapor containing ground state atoms
of that element. The intensity of the transmitted radiation decreases in proportion to the amount of
the ground state element in the vapor.
The metal atoms to be measured are placed in the beam of radiation by increasing the temperature of
the furnace, thereby causing the injected specimen to be volatilized. A monochromator isolates the
characteristic radiation from the hollow cathode lamp and a photosensitive device measures the
attenuated transmitted radiation.
Dissolved metals (Ca, Fe, K, Mg, Mn, and Na) are determined in a filtered sample (aliquot 1) by flame
atomic absorption spectroscopy (U.S. EPA, 1983).
Total Al is determined in an unfiltered sample (aliquot 7) after digestion by graphite furnace atomic
absorption spectroscopy (U.S. EPA, 1983).
Total extractable Al is determined in a sample that has been treated with 8-hydroxyquinoline and has
been extracted into MIBK (aliquot 2) by graphite furnace atomic absorption spectroscopy (Barnes,
1975; May et al., 1979; Driscoll, 1984).
12.3 DEFINITIONS
Optimum Concentration Range - This is a range, defined by limits expressed in concentration,
below which scale expansion must be used and above which curve correction should be consid-
ered. This range will vary with the sensitivity of the instrument and the operating conditions
employed.
Sensitivity - Sensitivity is the concentration in milligrams of metal per liter that produces an
absorption of 1 percent.
Dissolved Metals - Dissolved metals are those constituents (metals) which can pass through a
0.45- nm membrane filter.
Total Metals - The concentration of metals is determined on an unfiltered sample following
vigorous digestion.
98
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12.4 INTERFERENCES
72.4.7 Direct Aspiration
The most troublesome type of interference in atomic absorption spectrophotometry is usually
termed "chemical" and is caused by lack of absorption of atoms bound in molecular combination in
the flame. This phenomenon can occur when the flame is not sufficiently hot to dissociate the mole-
cule, as in the case of phosphate interference with magnesium, or because the dissociated atom is
immediately oxidized to a compound that will not dissociate further at the temperature of the flame.
The addition of lanthanum will overcome the phosphate interference in the magnesium and calcium
determinations. Similarly, silica interference in the determination of manganese can be eliminated
by the addition of calcium.
Chemical interferences may also be eliminated by separating the metal from the interfering material.
While complexing agents are primarily employed to increase the sensitivity of the analysis, they may
also be used to eliminate or reduce interferences.
lonization interferences occur when the flame temperature is sufficiently high to generate the
removal of an electron from a neutral atom, giving a positively charged ion. This type of interference
can generally be controlled by the addition, to both standard and sample solutions, of a large excess
of an easily ionized element.
Although quite rare, spectral interference can occur when an absorbing wavelength of an element
present in the sample but not being determined falls within the width of the absorption line of the
element of interest. The results of the determination will then be erroneously high, due to the contri-
bution of the interfering element to the atomic absorption signal. Also, interference can occur when
resonant energy from another element in a multi-element lamp or a metal impurity in the lamp cath-
ode falls within the bandpass of the slit setting, and that metal is present in the sample. This type of
interference may sometimes be reduced by narrowing the slit width.
72.4.2 Flameless Atomization
Although the problem of oxide formation is greatly reduced with furnace procedures because atomi-
zation occurs in an inert atmosphere, the technique is still subject to chemical and matrix interfer-
ences. The composition of the sample matrix can have a major effect on the analysis. It is this effect
which must be determined and taken into consideration in the analysis of each different matrix
encountered. To verify the absence of matrix or chemical interference, a matrix spike sample is ana-
lyzed using the following procedure. Withdraw from the sample two equal aliquots. To one of the
aliquots add a known amount of analyte and dilute both aliquots to the same predetermined volume.
(The dilution volume should be based on the analysis of the undiluted sample. Preferably, the dilution
should be 1:4 while keeping in mind the optimum concentration range of the analysis. Under no cir-
cumstances should the dilution be less than 1:1). The diluted aliquots should then be analyzed and
the unspiked results multiplied by the dilution factor should be compared to the original determina-
tion. Agreement of the results (within ! 10 percent) indicates the absence of interference. Comparison
of the actual signal from the spike to the expected response from the analyte in an aqueous standard
helps confirm the finding from the dilution analysis. Those samples which indicate the presence of
interference must be analyzed by the method of standard additions.
Gases generated in the furnace during atomization may have molecular absorption bands encom-
passing the analytical wavelength. When this occurs, either the use of background correction or
choosing an alternate wavelength outside the absorption band should eliminate this interference.
Background correction can also compensate for nonspecific broad-band absorption interference.
Interference from a smoke-producing sample matrix can sometimes be reduced by extending the
charring time at a higher temperature or utilizing an ashing cycle in the presence of air. Care must be
taken, however, to prevent loss of the element being analyzed.
99
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The chemical environment of the furnace may cause certain elements to form carbides at high tem-
peratures. This problem is greatly reduced and the sensitivity is increased with the use of pyrolyti-
cally coated graphite.
12.5 SAFETY
The calibration standards, sample types, and most reagents pose no hazard to the analyst. Use pro-
tective clothing (lab coat and gloves) and safety glasses when preparing reagents, especially when
concentrated acids and bases are used. The use of concentrated hydrochloric acid, ammonium
hydroxide solutions, and MIBK should be restricted to a hood.
Follow the manufacturer's safety precautions when operating the atomic absorption spectropho-
tometers.
Follow good laboratory practices when handling compressed gases.
12.6 APPARATUS AND EQUIPMENT
Atomic Absorption Spectrophotometer - The spectrophotometer used shall be a single- or dual-
channel, single-or double-beam instrument having a grating monochromator, photomultiplier
detector, adjustable slits, a wavelength range of 190 to 800 nm, and provisions for interfacing
with a strip chart recorder.
Burner - The burner recommended by the particular instrument manufacturer should be used.
For certain elements, the nitrous oxide burner is required.
Hollow Cathode Lamps - Single element lamps are preferred, but multi-element lamps may be
used. Electrodeless discharge lamps may also be used when available.
Graphite Furnace - Any furnace device capable of reaching the specified temperatures is satis-
factory.
Strip Chart Recorder - A recorder is strong ly recommended for furnace work so that there will be
a permanent record and any problems with the analysis such as drift, incomplete atomization,
losses during charring, changes in sensitivity, etc., can be easily recognized.
12.7 REAGENTS AND CONSUMABLE MATERIALS
General reagents used in each metal determination are listed in this section. Reagents specific to
particular metal determinations are listed in the particular procedure description for that metal.
Concentrated Hydrochloric Acid (12M HCI) - Ultrapure grade (Baker Instra Analyzed or equiva-
lent) is required.
HCI (1 percent v/v) - Add 5 ml_ concentrated HCI to 495 mL water.
Nitric Acid (0.5% v/v HNO3 - Ultrapure grade, Baker Instra-Analyzed or equivalent) - Carefully
dilute HNO3 in water in the ratio of 0.5 to 100.
Stock Standard Metal Solutions - Prepare as directed in the individual metal procedures. Com-
mercially available stock standard solutions may also be used.
Dilute Calibration Standards - Prepare a series of standards of the metal by dilution of the
appropriate stock metal solution to cover the concentration range desired.
Fuel and Oxidant - Commercial grade acetylene is generally acceptable. Air may be supplied
from a compressed air line, a laboratory compressor, or from a cylinder of compressed air.
Reagent grade nitrous oxide is also required for certain determinations. Standard, commer-
cially available argon and nitrogen are required for furnace work.
100
-------
Water - Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
12.8 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
Samples are collected and processed in the field. The sample for dissolved metals (aliquot 1) is fil-
tered through a 0.45- jum membrane filter then preserved by acidifying to a pH < 2 with nitric acid.
The sample for total Al analysis (aliquot 7) is preserved by acidifying to a pH < 2 with nitric acid. The
sample for total extractable Al (aliquot 2) is prepared by mixing a portion of sample with 8-hydroxy-
quinoline followed by extraction with MIBK.
After processing, the samples are shipped to the analytical laboratory. For aliquot 2 samples, it is the
MIBK layer from the extraction that is shipped.
12.9 CALIBRATION AND STANDARDIZATION
The calibration procedure varies slightly with the various atomic absorption instruments.
For each analyte, calibrate the atomic absorption instrument by analyzing a calibration blank and a
series of standards, following the instructions in the instrument operating manual.
The concentration of standards should bracket the expected sample concentration. However, the
linear range of the instrument should not be exceeded.
When indicated by the matrix spike analysis, the analytes must be quantified by the method of stand-
ard additions. In this method, equal volumes of sample are added to a deionized water blank and to
three standards containing different known amounts of the test element. The volume of the blank and
of each standard must be the same. The absorbance of each solution is determined and then plotted
on the vertical axis of a graph, with the concentrations of the known standards plotted on the hori-
zontal axis. When the resulting line is extrapolated to zero absorbance, the point of intersection of
the abscissa is the concentration of the unknown. The abscissa on the left of the ordinate is scaled
the same as on the right side, but in the opposite direction from the ordinate. An example of a plot so
obtained is shown in Figure 12.1. The method of standard additions can be very useful; however, for
the results to be valid the following limitations must be taken into consideration:
The absorbance plot of sample and standards must be linear over the concentration range of
concern. For best results, the slope of the plot should be nearly the same as the slope of the
aqueous standard curve. If the slope is significantly different (more than 20 percent) caution
should be exercised.
The effect of the interference should not vary as the ratio of analyte concentration to sample
matrix changes, and the standard addition should respond in a similar manner as the analyte.
The determination must be free of spectral interference and corrected for nonspecific back-
ground interference.
12.10 QUALITY CONTROL
The required QC procedures are described in section 3.4.
12.11 PROCEDURE
General procedures for flame and furnace atomic absorption analysis are given in sections 12.11.1
and 12.11.2. Detailed procedures for determining Al, Ca, Fe, K, Mg, Mn, and Na are given in sections
12.11.3 through 12.11.10.
101
-------
s
Zero
Absorbance
I Cone, of
Sample
AddnO
No Addn
AddrM
Addn of 50%
of Expected
Amount
Addn 2
Addn of 100%
of Expected
Amount
Addn 3
Addn of 150%
of Expected
Amount
Figure 12.1 Standard Addition Plot.
-------
12.11.1 Flame Atomic Absorption Spectroscopy
Differences among the various makes and models of satisfactory atomic absorption spectrophotom-
eters prevent the formulation of detailed instructions applicable to every instrument. The analyst
should follow the manufacturer's operating instructions for his particular instrument. In general,
after choosing the proper hollow cathode lamp for the analysis, the lamp should be allowed to warm
up for a minimum of 15 minutes unless operated in a double-beam mode. During this period, align the
instrument, position the monochromator at the correct wavelength, select the proper monochroma-
tor slit width, and adjust the hollow cathode current according to the manufacturer's recommenda-
tion. Subsequently, light the flame and regulate the flow of fuel and oxidant, adjust the burner and
nebulizer flow rate for maximum percent absorption and stability, and balance the photometer. Run a
series of standards of the element under analysis and calibrate the instrument. Aspirate the samples
and determine the concentrations either directly (if the instrument reads directly in concentration
units) or from the calibration curve.
12.11.2 Furnace Atomic Absorption Spectroscopy
Furnace devices (flameless atomization) are a most useful means of extending detection limits.
Because of differences among various makes and models of satisfactory instruments, no detailed
operating instructions can be given for each instrument. Instead, the analyst should follow the
instructions provided by the manufacturer of his particular instrument and use as a guide the temper-
ature settings and other instrument conditions listed in sections 12.11.3 through 12.11.10 (which are
the recommended ones for the Perkin-Elmer HGA-2100). In addition, the following points may be
helpful.
With flameless atomization, background correction becomes of high importance, especially below
350 nm. This is because certain samples, when atomized, may absorb or scatter light from the hollow
cathode lamp. These effects can be caused by the presence of gaseous molecular species, salt parti-
cles, or smoke in the sample beam. If no correction is made, sample absorbance will be greater than it
should be, and the analytical result will be erroneously high.
If during atomization all the analyte is not volatilized and removed from the furnace, memory effects
will occur. This condition is dependent on several factors, such as the volatility of the element and its
chemical form, whether pyrolytic graphite is used, the rate of atomization, and furnace design. If this
situation is detected through blank burns, the tube should be cleaned by operating the furnace at full
power for the required time period at regular intervals in the analytical scheme.
Some of the smaller size furnace devices, or newer furnaces equipped with feedback temperature
control (Instrumentation Laboratories MODEL 555, Perkin-Elmer MODELS HGA 2200 and HGA 76B,
and Varian MODEL CRA-90) employing faster rates of atomization, can be operated using lower atom-
ization temperatures for shorter time periods than those listed in this manual.
Although prior digestion of the sample in many cases is not required providing a representative ali-
quot of sample can be pipeted into the furnace, it provides for a more uniform matrix and possibly
lessens matrix effects.
Inject a measured microliter aliquot of sample into the furnace and atomize. If the concentration
found is greater than the highest standard, the sample should be diluted in the same acid matrix and
should be reanalyzed. The use of multiple injections can improve accuracy and can help detect fur-
nace pipetting errors.
12.11.3 Procedure for Determination of Total Aluminum
To determine total aluminum, a portion of sample is digested and digestate is analyzed for aluminum
by furnace atomic absorption Spectroscopy (U.S. EPA, 1983).
12.11.3.1 Preparation of Aluminum Standard Solutions
103
-------
Aluminum stock solution (1000 mg/L Al) - Carefully weigh 1.000 gram aluminum metal (analytical
reagent grade). Add 15 ml_ concentrated HCI and 5 mL concentrated HNO3 to the metal, cover the
beaker, and warm gently. When metal is completely dissolved, transfer solution quantitatively to a 1-L
volumetric flask and bring to volume with water. Alternatively, a commercially available, certified Al
standard may be used.
Prepare dilutions of the stock solution to be used as calibration standards at the time of analysis.
These solutions are also to be used for "standard additions."
The calibration standard should be prepared in 0.5 percent (v/v) HNO3.
12.11.3.2 Sample Preparation
The sample must be digested prior to analysis. Due to the low concentrations of analyte expected,
contamination from atmospheric sources can be a major problem. To avoid contamination, all prepa-
rations must be performed in a laminar flow hood.
Quantitatively transfer a 50.00 mL aliquot of the well-mixed sample to a Griffin beaker. Add 3.0 mL of
concentrated nitric acid. Place the beaker on a hot plate and cautiously evaporate to near dryness,
making certain that the sample does not boil. (DO NOT BAKE.) Allow the beaker to cool, then again
add 3.0 mL of concentrated nitric acid. Cover the beaker with a watch glass and return to the hot
plate. Increase the temperature of the hot plate until a gentle reflux action occurs. Continue reflux-
ing, adding acid as necessary, until the digestion is complete (indicated by a light-colored residue or
no change in appearance with continued refluxing). When complete, evaporate to near dryness.
Allow to cool. Add 0.5 mL of 50 percent nitric acid and warm slightly to dissolve any precipate or
residue resulting from evaporation. Wash down the beaker walls and watch glass with water. Quanti-
tatively filter the sample (to remove silicates and other insoluble materials) and adjust to 50.00 mL.
The sample is now ready for analysis.
12.11.3.3 Suggested Instrument Conditions (General)
Drying time and temperature - 30 seconds at 125°C
Ashing time and temperature - 30 seconds at 1300°C
Atomizing time and temperature - 10 seconds at 2700°C
Purge gas atmosphere - Argon
Wavelength - 309.3 nm
Other operating conditions should be set as specified by the particular instrument manufacturer.
NOTE 1: The above instrument conditions are for a Perkin-ElmerHGA 2100, based on the use of a 20 M L
injection, continuous flow purge gas, and nonpyrolytic graphite.
NOTE 2: Background correction may be required if the sample con tains a high level of dissolved
solids.
NOTE 3: It has been reported that chloride ion and that nitrogen used as a purge gas suppress the
aluminum signal. There fore, the use of halide acids and nitrogen as a purge gas should be avoided.
NOTE 4: The ashing temperature can be increased to 1,500 to 1,700°C by adding 30 M g magnesium
nitrate (Mg(NO3)2) (Manning et al., 1982).
NOTE 5: If blanks indicate that sample contamination is occuring, the use of Teflon labware is recom-
mended.
12.11.3.4 Analysis Procedure
Step 1 - Calibrate the instrument as directed by the instrument manufacturer.
Step 2 - Analyze the samples (including required QC samples).
104
-------
Step 3 - If a sample concentration exceeds the linear range, dilute (with acidic media) and reanalyze.
Report results as mg/L Al.
12.11.3.5 Precision and Accuracy
In a multiple lab study using 84 lake samples containing 0.03-5 mg/L Al the overall duplicate relative
standard deviation was 10.5 percent (note that this represents the overall within lab precision).
In a multiple lab study using synthetic, simulated lake samples containing 0.02 and 0.19 mg/L Al
respectively, recoveries of 115 (n = 21) and 103 (n = 21) precent were obtained.
12.11.4 Procedure for Determination ol Total Extractable Aluminum
Samples for extractable aluminum are prepared in the field and are obtained as the 8-hydroxyquino-
line complex in MIBK. The MIBK solution is analyzed for aluminum by graphite furnace atomic
absorption (GFAA) (Barnes, 1975; May et al., 1979; Driscoll, 1984).
12.11.4.1 Preparation of Reagents
Glacial acetic acid (HOAc, 18M) - Baker Ultrex grade or equivalent.
Ammonium hydroxide (NH4OH, 5M) - Baker Ultrex grade or equivalent.
Sodium acetate solution (NaOAc, 1 .OM) - Dissolve 8.2 g NaOAc (Alfa Ultrapure grade or equiva-
lent) in 100 mL water.
Methyl isobutyl ketone (MIBK) - HPLC grade or equivalent.
Phenol red indicator solution (0.04 percent w/v) - ACS reagent grade.
Hydrochloric acid (HCI, 12M) - Baker Ultrex grade or equivalent.
2.5 M HCI - Dilute 208 mL of 12 M HCI to 1.0 L
NH4+/NH4 buffer-Add 2.5MHCIto21 mLof5M NH4OH until the pH = 8.3, then dilute to 100 mL
NOTE: Do this cautiously in a fume hood.
8-hydroxyquinoline solution (10 g/L) - Dissolve 5 grams of 8 hydroxyquinoline (99 plus percent
purity) in 12.5 mL HOAc, then dilute to 500 mL
8-hydroxyquinoline sodium acetate reagent-Mix, in order, 10mL1.0M NaOAc, 50m L water, and
10 mL hydroxyquinoline solution.
This reagent must be prepared daily.
12.11.4.2 Preparation of Aluminum Standard Solutions
Aluminum stock solution - Prepare as described in section 12.11.3.1.
Dilute calibration standards - Daily, quantitatively dilute the Al stock solution to prepare a series
of calibration standards over the range 0 to 0.1 mg/L Al. A blank must be prepared. Prior to analy-
sis, the blank, standards (and any QC samples) must be extracted.
Step 1 - Pipet 25.00 mL of a calibration standard (or calibration blank or QC sample) into a clean 50-
mL separatory funnel (or a clean 50-mL disposable centrifuge tube with cap).
Step2- Add 2 to 3 drops phenol red indicator and 5.00 mL8 hydroxyquinoline NaOAc reagent. Swirl to
mix.
Step 3 - Rapidly adjust the pH to 8 by dropwise additions of 5M NH4OH until the solution turns red.
Immediately add 2.0 mL NH4 + / NH3 buffer and 10 mL MIBK. Cap and shake vigorously for 7 to 10
seconds using a rapid, end-to-end motion. Be careful of pressure buildup.
105
-------
Step 4 - Allow the phases to separate (10 to 15 seconds) and isolate the MIBK layer. If an emulsion
forms, separation can be hastened by centrifugation. Keep the MIBK layer tightly capped to prevent
evaporation.
12.11.4.3 Suggested Instrument Conditions (General)
Drying cycle - Ramp 10 seconds, hold 10 seconds
Drying temperature - 100°C
Ashing cycle - Ramp 5 seconds, hold 20 seconds
Ashing temperature - 1500°C
Atomization cycle - Hold 5 seconds (no ramp, max. power heating)
Atomization temperature - 2500°C
Purge gas - Argon at 20 cc/minute
Lamp - Al HCI at 25 mA
Wavelength - 309.3 nm
Graphite tube - Nonpyrolytic
Sample size - 25 >uL
These operating conditions are for a Perkin-Elmer 5000 with a HGA-500 graphite furnace and AS-40
autosampler.
12.11.4.4 Analysis Procedure
Step 1 - Calibrate the instrument as directed by the instrument manufacturer.
Step 2 - Analyze the samples (including required QC samples).
Step 3 - If a sample concentration exceeds the linear range, dilute with MIBK and reanalyze.
Report results as mg/L Al.
NOTE: By using the same volumes for standards as for samples, con centration factors are taken into
account.
12.11.4.5 Precision and Accuracy
In a multiple lab study using 74 lake samples containing 0.005-3 mg/L extractable Al the overall dupli-
cate relative standard deviation was 7.4 percent (note this is the overall within-lab precision).
Accuracy data are not available.
12.11.5 Procedure for Determination of Dissolved Calcium
Samples for determination of dissolved calcium (filtered and preserved in the field) are analyzed by
flame atomic absorption spectroscopy for calcium (U.S. EPA, 1983).
12.11.5.1 Preparation of Reagents
Lanthanum chloride matrix modifier solution (LaCI3) - Dissolve 29 g La2O2, slowly and in small
portions, in 250 mL concentrated HCI (Caution: Reaction is violent) and dilute to 500 mL with
water.
12.11.5.2 Preparation of Calcium Standard Solutions
Calcium stock solution (500 mg/L Ca) - Suspend 1.250 g CaCO3 (analytical reagent grade, dried
at 180°C for 1 hour before weighing) in water and dissolve cautiously with a minimum of dilute
HCI. Dilute to 1,000 mL with water.
106
-------
Dilute calibration standards - Daily, quantitatively prepare a series of dilute Ca standards from
the calcium stock solution to span the desired concentration range.
12.11.5.3 Suggested Instrumental Conditions (General)
Lamp - Ca, hollow cathode
Wavelength - 422.7
NOTE: The 239.9 nm line may also be used. This line has a relative sensitivity of 120.
« Fuel - acetylene
Oxidant - air
Flame - reducing
12.11.5.4 Analysis Procedure
Step 1 - To each 10.0 mL volume of dilute calibration standard, blank, and sample add 1.00 ml LaCI3
solution (e.g., add 2.0 mL LaCI3 solution to 20.0 mL sample).
Step 2 - Calibrate the instrument as directed by the manufacturer.
Step 3 - Analyze the samples.
Step 4 - Dilute and reanalyze any samples with a concentration exceeding the calibrated range.
Report results as mg/L Ca.
NOTE 1: Phosphate, sulfate and aluminum interfere but are masked by the addition of lanthanum.
Because low calcium values result if the pH of the sample is above 7, both standards and samples are
prepared in dilute acid solution. Concentrations of magnesium greater than 1,000 mg/L also cause
low calcium values. Concentrations of up to 500 mg/L each of sodium, potassium, and nitrate cause
no interference.
NOTE 2: Anionic chemical interferences can be expected if lanthanum is not used in samples and
standards.
NOTE 3: The nitrous oxide-acetylene flame will provide two to five times greater sensitivity and free-
dom from chemical interferences, lonization interferences should be controlled by adding a large
amount of alkali to the sample and standards. The analysis appears to be free from chemical sup-
pressions in the nitrous oxide-acetylene flame.
12.11.5.5 Precision and Accuracy
In a single laboratory (EMSL-Cincinnati), using distilled water spiked at concentrations of 9.0 and 36
mg Ca/L, the standard deviations were ± 0.3 and ± 0.6, respectively. Recoveries at both these levels
were 99 percent.
12.11.6 Procedure for Determination of Dissolved Iron
The samples for determination of dissolved ion (filtered and preserved in the field) are analyzed by
flame atomic absorption spectroscopy (U.S. EPA, 1983).
12.11.6.1 Preparation of Iron Standard Solutions
Fe stock solution (1,000 mg/L Fe) - Carefully weigh 1.000 g pure iron wire (analytical reagent
grade) and dissolve in 5 mL concentrated HNO3, warming if necessary. When iron is completely
dissolved, bring volume of solution to 1 L with water.
Dilute calibration standards - Daily, quantitatively prepare a series of calibration standards
spanning the desired concentration range. Match the acid content of the standards to that of the
samples (ca. 0.1 percent (v/v) HNO3).
107
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12.11.6.2 Suggested Instrumental Conditions (General)
Lamp - Fe, hollow cathode ° Wavelength - 2.48.3 nm
NOTE: The following lines may also be used: 248.8 nm, relative sensitivity 2; 271.9 nm, relative sensi-
tivity 4; 302.1 nm, relative sensitivity 5; 252.7 nm, relative sensitivity 6; 372.0 nm, relative sensitivity 10.
Fuel - acetylene
Oxidant - air
Flame - oxidizing
12.11.6.3 Analysis Procedure
Step 1 - Calibrate the instrument as directed by the instrument manufacturer.
Step 2 - Analyze the samples.
Step 3 - Dilute and reanalyze any samples with concentrations exceed ing the calibrated range.
Report results in mg/L Fe. 12.11.6.4 Precision and Accuracy - An interlaboratory study on trace metal
analyses by atomic absorption was conducted by the Quality Assurance and Laboratory Evaluation
Branch of EMSL-Cincinnati. Six synthetic concentrates containing varying levels of aluminum, cad-
mium, chromium, copper, iron, manganese, lead, and zinc were added to natural water samples. The
statistical results for iron were as follows:
Number
of Labs
77
78
71
70
55
55
True
Value
426
469
84
106
11
17
Mean
Value
( Mg/L)
432
474
86
104
21
21
Standard
Deviation
(Mg/L)
70
97
26
31
27
20
Accuracy
as
% Bias
1.5
1.2
2.1
-2.1
93
22
12.11.7 Procedure for Determination of Dissolved Magnesium
The samples for determination of dissolved magnesium (filtered and preserved in the field) are ana-
lyzed by flame atomic absorption spectroscopy for magnesium.
12.11.7.1 Preparation of Reagents
Lanthanum chloride solution (LaCI3) - Dissolve 29 g La2O3, slowly and in small portions, in 250
mL concentrated HCI (Caution: Reaction is violent), and dilute to 500 mL with water.
12.11.7.2 Preparation of Magnesium Standard Solutions
Stock solution (500 mg/L Mg) - Dissolve 0.829 g magnesium oxide, MgO (analytical reagent
grade), in 10 mL of HNO3 and dilute to 1 L with water.
Dilute calibration standards - Daily, quantitatively prepare from the Mg stock solution a series of
Mg standards that spans the desired concentration range.
12.11.7.3 Suggested Instrumental Conditions (General)
Lamp - Mg, hollow cathode
Wavelength - 285.2 nm
NOTE: The line at 202.5 nm may also be used. This line has a relative sensitivity of 25.
108
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Fuel - acetylene
Oxidant - air
Flame- oxidizing
12.11.7.4 Analysis Procedure
Step 1 -To each 10.0 ml_ dilute calibration standard, blank, and sample, add 1.00 ml_ LaCI3 solution
(e.g., add 2.0 mL LaCI3 solution to 20.0 ml_ sample).
Step 2 - Calibrate the instrument as directed by the manufacturer.
Step 3 - Analyze the samples.
Step 4 - Dilute and reanalyze any samples with a concentration exceeding the linear range.
Report results as mg/L Mg.
NOTE 1: The interference caused by aluminum at concentrations greater than 2 mg/L is masked by
addition of lanthanum. Sodium, potassium, and calcium cause no interference at concentrations
less than 400 mg/L.
NOTE 2: To cover the range of magnesium values normally observed in surface waters (0.1 to 20 mg/
L), it is suggested that either the 202.5 nm line be used or the burner head be rotated. A 90° rotation of
the burner head will produce approximately one-eighth the normal sensitivity.
12.11.7.5 Precision and Accuracy
In a single laboratory (EMSL-Cincinnati), using distilled water spiked at concentrations of 2.1 and 8.2
mg/L Mg, the standard deviations were ±0.1 and ±0.2, respectively. Recoveries at both of these
levels were 100 percent.
12.11.8 Procedure for Determination of Dissolved Manganese
The samples for determination of dissolved manganese (filtered and preserved in the field) are ana-
lyzed by flame atomic absorption spectroscopy for manganese (U.S. EPA, 1983).
12.11.8.1 Preparation of Manganese Standard Solutions
Mn stock solution (1,000 mg/L Mn) - Carefully weigh 1.000 g manganese metal (analytical
reagent grade) and dissolve in 10 mL of HNO3. When metal is completely dissolved, dilute solu-
tion to 1 liter with 1 percent (v/v) HCI.
Dilute calibration standards - Daily, quantitatively prepare a series of calibration standards
spanning the desired concentration range. Match the acid content of the standards to that of the
samples (ca. 0.1 percent (v/v) HNO3).
12.11.8.2 Instrumental Conditions (General)
Lamp - Mn, hollow cathode
Wavelength - 279.5 nm
NOTE: The line at 403.1 nm may also be used. This line has a relative sensitivity of 10.
Fuel - acetylene
Oxidant - air
Flame - oxidizing
12.11.8.3 Analysis Procedure
Step 1 - Calibrate the instrument as directed by the manufacturer.
109
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Step 2 - Analyze the samples.
Step 3 - Dilute and reanalyze any samples with a concentration exceeding the calibrated range.
Report results as mg/L Mn.
12.11.8.4 Precision and Accuracy
An interlaboratory study on trace metal analyses by atomic absorption was conducted by the Quality
Assurance and Laboratory Evaluation Branch of EMSL-Cincinnati. Six synthetic concentrates con-
taining varying levels of aluminum, cadmium, chromium, copper, iron, manganese, lead, and zinc
were added to natural water samples. The statistical results for manganese were as follows:
Number
of Labs
82
85
78
79
57
54
True
Value
( Mg/L)
840
700
350
438
24
10
Mean
Value
(Mg/L)
855
680
348
435
58
48
Standard
Deviation
Ug/L)
173
178
131
183
69
69
Accuracy
as
% Bias
1.8
-2.8
-0.5
-0.7
141
382
12.11.9 Procedure for Determination of Dissolved Potassium
The samples for determination of dissolved potassium (filtered and preserved in the field) are ana-
lyzed by flame atomic absorption spectroscopy for potassium (U.S. EPA, 1983). 12.11.9.1 Preparation
of Potassium Standard Solutions
Potassium stock solution (100 mg/L K) - Dissolve 0.1907 g KCI (analytical reagent grade, dried at
110°C) in water and bring volume of solution to 1 L.
Dilute calibration standards - Daily, quantitatively prepare a series of calibration standards
spanning the desired concentration range. Match the acid content of the standards to that of the
samples (ca. 0.1 percent (v/v) HNO3).
12.11.9.2 Suggested Instrumental Conditions (General)
Lamp - K, hollow cathode
Wavelength - 766.5 nm
NOTE: The 404.4-nm line may also be used. This line has a relative sensitivity of 500.
Fuel - acetylene
Oxidant - air
Flame - slightly oxidizing
12.11.9.3 Analysis Procedure
Step 1 - Calibrate the instrument as directed by the manufacturer.
Step 2 - Analyze the samples.
Step 3 - Dilute and reanalyze any sample with a concentration exceeding the calibrated range.
Report results as mg/L K.
NOTE 1: In air-acetylene or other high-temperature flames (>2,800°C), potassium can experience partial
ionization which indirectly affects absorption sensitivity. The presence of other alkali salts in the sample
no
-------
can reduce this ionization and thereby enhance analytical results. The ionization suppressive effect of
sodium is small if the ratio of Na to K is under 10. Any enhancement due to sodium can be stabilized by
adding excess sodium (1,000 n g/mL) to both sample and standard solutions. If more stringent control of
ionization is required, the addition of cesium should be considered. Reagent blanks should be analyzed
to correct for potassium impurities in the buffer stock.
NOTE 2: To cover the range of potassium values normally observed in surface waters (0.1 to 20 mg/L),
it is suggested that the burner head be rotated. A 90° rotation of the burner head provides approxi-
mately one-eighth the normal sensitivity.
12.11.9.4 Precision and Accuracy
In a single laboratory (EMSL-Cincinnati), using distilled water samples spiked at concentrations of
1.6 and 6.3 mg/L K, the standard deviations were ±0.2 and ±0.5, respectively. Recoveries at these
levels were 103 percent and 102 percent, respectively.
12.11.10 Procedure for Determination of Dissolved Sodium
The samples for determination of dissolved sodium (filtered and preserved in the field) are analyzed
by flame atomic absorption spectroscopy for sodium (U.S. EPA, 1983).
12.11.10.1 Preparation of Sodium Standard Solutions
Sodium stock solution (1,000 mg/L Na) - Dissolve 2.542 g NaCI (analytical reagent grade, dried at
140°C) in water and bring the volume of the solution to 1 L.
Dilute calibration standards - Daily, quantitatively prepare a series of calibration standards
spanning the desired concentration range. Match the acid content of the standards to that of the
samples (ca. 0.1 percent (v/v) HNO3).
12.11.10.2 Suggested Instrumental Conditions (General)
Lamp - Na, hollow cathode
Wavelength - 589.6 nm
NOTE: The 330.2 nm resonance line of sodium, which has a relative sensitivity of 185, provides a
convenient way to avoid the need to dilute more concentrated solutions of sodium.
Fuel - acetylene
Oxidant - air
Flame - oxidizing
12.11.10.3 Analysis Procedure
Step 1 - Calibrate the instrument as directed by the manufacturer.
Step 2 - Analyze the samples.
Step 3 - Dilute and reanalyze any samples with a concentration exceed ing the calibrated range.
Report results as mg/L Na.
NOTE: Low-temperature flames increase sensitivity by reducing the extent of ionization of this easily
ionized metal. Ionization may also be controlled by adding potassium (1,000 mg/L) to both standards
and samples.
12.11.10.4 Precision and Accuracy
In a single laboratory (EMSL-Cincinnati), using distilled water samples spiked at levels of 8.2 and 52
mg/L Na, the standard deviations were ± 0.1 and ± 0.8, respectively. Recoveries at these levels were
102 percent and 100 percent.
Ill
-------
12.12 CALCULATIONS
Generally, instruments are calibrated to output sample results directly in concentration units. If they
do not, then a manual calibration curve must be prepared and sample concentrations must be deter-
mined by comparing the sample signal to the calibrated curve. If dilutions were performed, the appro-
priate factor must be applied to sample values. Report results as mg/L for each analyte.
12.13 REFERENCES
American Society for Testing and Materials, 1984. Annual Book of ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia, Pennsyl-
vania.
Barnes, R. B., 1975. The Determination of Specific Forms of Aluminum in Natural Water. Chem.Geol.,
v. 15, pp. 177-191.
Driscoll,C. T., 1984. A Procedure for the Fractionationof Aqueous Aluminum in Dilute Acidic Waters.
Int. J. Environ. Anal. Chem., v. 16, pp. 267-283.
Manning, D. C., W. Slavin,andG. R. Carnick, 1982. Investigation of Aluminum Interferences Using the
Stabilized Temperature Platform Furnace. Spectrochim. Acta, Part B, v. 37b, n, 4, pp. 331-341.
May, H. M., P. A. Helmke, and M. L. Jackson, 1979. Determination of Mononuclear Dissolved Alumi-
num in Near-Neutral Waters. Chem. Geol., v. 24, pp. 259-269.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes, Method 200.0, Atomic Absorption Methods. EPA 600/4-79-020. U.S. EPA, Cincinnati,
Ohio.
112
-------
SECTION 13
DETERMINATION OF DISSOLVED METALS (Ca, Fe, Mg, and Mn)
BY INDUCTIVELY COUPLED PLASMA EMISSION SPECTROSCOPY
13.1 SCOPE AND APPLICATION
This method is applicable to the determination of dissolved Ca, Fe, Mg, and Mn in natural surface
waters.
Table 13.1 lists the recommended wavelengths and typical estimated instrumental detection limits
using conventional pneumatic nebulization for the specified elements. Actual working detection lim-
its are sample-dependent, and as the sample matrix varies, these concentrations may also vary.
Because of the differences among makes and models of satisfactory instruments, no detailed instru-
mental operating instructions can be provided. Instead, the analyst is referred to the instructions
provided by the manufacturer of the particular instrument.
13.2 SUM MARY OF METHOD
The method describes a technique for the simultaneous or sequential determination of Ca, Fe, Mg,
and Mn in lake samples collected for the NSWS. The method is based on the measurement of atomic
emission by optical spectroscopy. Samples are nebulized to produce an aerosol. The aerosol is trans-
ported by an argon carrier stream to an inductively coupled argon plasma (ICP), which is produced by
a radio frequency (RF) generator. In the plasma (which is at a temperature of 6,000 to 10,000°K), the
analytes in the aerosol are atomized, ionized, and excited. The excited ions and atoms emit light at
their characteristic wavelengths. The spectra from all analytes are dispersed by a grating spectrome-
ter and the intensities of the lines are monitored by photo multiplier tubes. The photocurrents from
the photomultiplier tubes are processed by a computer system. The signal is proportional to the
Element
Calcium
Iron
Magnesium
Manganese
Wavelength (nm)
317.933
259.940
279.079
257.610
Estimated Detection Limit ( g/L)b
10
7
30
2
a The wavelengths listed are recommended because of their sensitivity and overall acceptance. Other wavelengths may
be substituted if they can provide the needed sensitivity and are treated with the same corrective techniques for
spectral interference.
b The estimated instrumental detection limits as shown are taken from Fassel, 1982. They are given as a guide for an
instrumental limit. The actual method detection limits are sample-dependent and may vary as the sample matrix
varies.
Table 13.1, Recommended Wavelengths3 and Estimated Instrumental Detection Limits,
113
-------
analyte concentration and is calibrated by analyzing a series of standards (U.S. EPA, 1983; Fassel,
1982).
A background correction technique is required to compensate for variable background contribution
to the determination of trace elements. Back ground must be measured adjacent to analyte lines
during sample analysis. The position selected for the background intensity measurement, on either
or both sides of the analytical line, will be determined by the complexity of the spectrum adjacent to
the analyte line. The position used must be free of spectral interference and must reflect the same
change in background intensity as occurs at the analyte wavelength measured. Generally, each
instrument has different background handling capabilities. The instrument operating manual should
be consulted for guidance.
The possibility of additional interferences named in section 13.3 should also be recognized, and
appropriate corrections should be made.
13.3 INTERFERENCES
Several types of interference effects may contribute to inaccuracies in the determination of trace
elements. They are summarized in sections 13.3.1 through 13.3.3.
73.3. T Spectra/ Interferences
Spectral interferences can be categorized as (1) overlap of a spectral line from another element; (2)
unresolved overlap of molecular band spectra; (3) background contribution from continuous or
recombination phenomena; and (4) background contribution from stray light from the line emission
of high-concentration elements. The first of these effects can be compensated by utilizing a com-
puter correction of the raw data, requiring the monitoring and measurement of the interfering ele-
ment. The second effect may require selection of an alternate wave length. The third and fourth
effects can usually be compensated by a background correction adjacent to the analyte line. In addi-
tion, users of simultaneous multi-element instrumentation must assume the responsibility of verify-
ing the absence of spectral interference from an element that could occur in a sample but for which
there is no channel in the instrument array. Listed in Table 13.2 are some interference effects for the
recommended wavelengths given in Table 13.1. The interference information is expressed as analyte
concentration equivalents (i.e., false analyte concentrations) arising from 100 mg/L of the interfering
element. The values in the table are only approximate and should be used as a guide for determining
potential interferences. Actual values must be determined for each analytical system when neces-
sary.
Only those interferences listed were investigated. The blank spaces in Table 13.2 indicate that mea-
surable interferences were not observed for the interferent concentrations listed in Table 13.3. Gener-
Analyte
Calcium
Iron
Magnesium
Manganese
(nm) At Ca
317933
259.940
279.079 0.02
257 610 0.005
Interference
Cr
0.08
0.11
0.01
Cu Fe
0.01
0.13
0.002
Wig
0.01
0.002
Mn
0.14
0.12
0.25
Ni Ti V
0.03 0.03
0.07 0.12
Table 13.2 Analyte Concentration Equivalents (mg/L) Arising from Interferences at the 100-mg/L Level.
114
-------
Analytes (mg/L)
Ca 1
Fe 1
Mg 1
Mn 1
Interferences
Al
Ca
Cr
Cu
Fe
wig
Nn
Ni
Ti
V
(mg/L)
1,000
1,000
200
200
1,000
1,000
200
200
200
200
Table 13.3. Interference and Analyte Elemental Concentrations Used for Interference Measurements
in Table 13.2.
ally, interferences were discernible if they produced peaks or background shifts corresponding to 2
to 5 percent of the peaks generated by the analyte concentrations (also listed in Table 13.3).
13.3.2 Physical Interferences
Physical interferences are generally considered to be effects associated with the sample nebuliza-
tion and transport processes. Changes in viscosity and surface tension can cause significant inac-
curacies, especially in samples that contain high dissolved solids or acid con centrations. The use of
a peristaltic pump may lessen these interferences. If these types of interferences are operative, they
must be reduced by dilution of the sample or utilization of standard addition techniques.
High dissolved solids may also cause salt buildup at the tip of the nebulizer. This affects aerosol flow
rate, causing instrumental drift. Wetting the argon prior to nebulization, the use of a tip washer, or
sample dilution have been used to control this problem.
It has been reported that better control of the argon flow rate improves instrument performance. This
is accomplished with the use of mass flow controllers.
73.3.3 Chemical Interferences
Chemical interferences are characterized by molecular compound formation, ionization effects, and
solute vaporization effects. Normally these effects are negligible with the ICP technique. If observed,
they can be minimized by careful selection of operating conditions (i.e., incident power, observation
position, and so forth), by buffering of the sample, by matrix matching, and by standard addition
procedures. These types of interferences can be highly dependent on matrix type and the specific
analyte element.
73.3.4 Interference Tests
Whenever a new or unusual sample matrix is encountered, a series of tests should be performed prior
to reporting concentration data for analyte elements. These tests, as outlined in sections 13.3.4.1
through 13.3.4.4, will ensure that neither positive nor negative interference effects are operative on
any of the analyte elements, thereby distorting the accuracy of the reported values.
775
-------
13.3.4.1 Serial Dilution
If the analyte concentration is sufficiently high (minimally a factor of 10 above the instrumental
detection limit after dilution), an analysis of a dilution should agree within 5 percent of the original
determination (or within some acceptable control limit that has been established for that matrix). If
not, a chemical or physical interference effect should be suspected.
13.3.4.2 Spiked Addition
The recovery of a spiked addition added at a minimum level of 10X the instrumental detection limit
(maximum 100X) to the original determination should be recovered to within 90 to 110 percent or
within the established control limit for that matrix. If not, a matrix effect should be suspected. The
use of a standard addition analysis procedure can usually compensate for this effect.
CAUTION: The standard addition technique does not detect coincident spectral overlap. If overlap is
suspected, use of computerized compensation, an alternate wavelength, or comparison
with an alternate method is recommended.
13.3.4.3 Comparison with Alternate Method of Analysis
When investigating a new sample matrix, a comparison test may be performed with other analytical
techniques, such as atomic absorption spectrometry or other approved methodology.
13.3.4.4 Wavelength Scanning of Analyte Line Region
If the appropriate equipment is available, wavelength scanning can be performed to detect potential
spectral interferences.
13.4 SAFETY
Generally, the calibration standards, sample types, and most reagents pose no hazard to the analyst.
Protective clothing (lab coats and gloves) and safety glasses should be worn when handling concen-
trated acids.
Follow the instrument manufacturer's safety recommendations for the operation of the ICR
The toxicity or carcinogenicity of each reagent used in this method has not been precisely defined.
Each chemical compound should be treated as a potential health hazard. From this viewpoint, expo-
sure to these chemicals must be reduced to the lowest possible level by whatever means available.
The laboratory is responsible for maintaining a current awareness file of OSHA regulations regard-
ing the safe handling of the chemicals specified in this method. A reference file of material data
handling sheets should also be made available to all personnel involved in the chemical analysis.
Additional references to laboratory safety are available and have been identified (NIOSH, 1977;
OSHA, 1976; ACS, 1979) for the information of the analyst.
13.5 APPARATUS AND EQUIPMENT
Inductively Coupled Plasma-Atomic Emission Spectrometer
Computer-controlled ICP emission spectrometer with background correction capability.
13.6 REAGENTS AND CONSUMABLE MATERIALS
Acids used in the preparation of standards and for sample processing must be ultra-high purity
grade or equivalent (e.g., Baker Ultrex grade or SeaStar Ultrapure grade).
a. Hydrochloric Acid, concentrated (sp gr 1.19)
b. Hydrochloric Acid (50 percent v/v)--Add 500 ml_ concentrated HCI to 400 ml water and dilute
to 1 L.
116
-------
c. Nitric Acid, concentrated (sp gr 1.41)
d. Nitric Acid (50 percent v/v)-Add 500 mL concentrated HNO3 to 400 mL water and dilute to 1 L.
Water-Water must meet the specifications for Type I Reagent Water given in ASTM D 1193
(ASTM, 1984).
Standard Stock Solutions-Solutions may be purchased or prepared from ultra-high purity grade
chemicals or metals. All salts must be dried for 1 hour at 105°C unless otherwise specified.
CAUTION: Many metal salts are extremely toxic and may be fatal if swallowed. Wash hands
thoroughly after handling.
a. Calcium Stock Standard Solution (100 mg/L)--Suspend 0.2498 g CaCO3 (dried at 180°C for 1
hour before weighing) in water and dissolve cautiously with a minimum amount of 50 percent
HNO3. Add 10.0 ml concentrated HNO3 and dilute to 1,000 mL with water.
b. Iron Stock Standard Solution (100 mg/L)-Dissolve 0.1430 g Fe2O3 in a warm mixture of 20 mL
50 percent HCI and 2 mL concentrated HNO3. Cool, add an additional 5 mL concentrated
HNO3, and dilute to 1,000 mL with water.
c. Magnesium Stock Standard Solution (100 mg/L)-Dissolve 0.1658 g MgO in a minimum
amount of 50 percent HNO3. Add 10.0 mL concentrated HNO3 and dilute to 1,000 mL with
water.
d. Manganese Stock Standard Solution (100 mg/L)-Dissolve 0.1000 g of manganese metal in an
acid mixture consisting of 10 mL concentrated HCI and 1 mL concentrated HNO3, and dilute
to 1,000 mL with water.
13.7 SAMPLE HANDLING, PRESERVATION, AND STORAGE
For the determination of trace elements, contamination and loss are of prime concern. Dust in the
laboratory environment, impurities in reagents, and impurities on laboratory apparatus which the
sample contacts are all sources of potential contamination. Sample containers can introduce either
positive or negative errors in the measurement of trace elements by (a) contributing contaminants
through leaching or surface desorption and (b) by depleting concentrations through adsorption.
Thus the collection and treatment of the sample prior to analysis requires particular attention.
Labware should be thoroughly washed as described in Appendix A.
Samples are collected and processed in the field. A portion (aliquot 3) of each sample is filtered and
acidified (0.1-mL increments) with nitric acid until the pH < 2. The processed samples are then sent
to the lab and are analyzed (as is) for dissolved metal (Ca, Fe, Ma, Mn) content.
13.8 CALIBRATION AND STANDARDIZATION
Prepare a calibration blank and a series of dilute calibration standards from the stock solutions
spanning the expected sample concentration range. Match the acid content of the standards to that
of the samples (written on the sample label, ca. 0.2 percent). A multi-element standard may be pre-
pared.
The calibration procedure varies with the various ICPES instruments. Calibrate the ICPES for each
analyte following the instrument operating conditions.
13.9 QUALITY CONTROL
The required QC procedures are described in Section 3.4.
117
-------
13.10 PROCEDURE
Step 1. Set up instrument as recommended by the manufacturer or as experience dictates. The
instrument must be allowed to become thermally stable before beginning (10 to 30 minutes).
Step 2. Profile and calibrate instrument according to instrument manufacturer's recommended pro-
cedures. Flush the system with the calibration blank between each standard. (The use of the average
intensity of multiple exposures for both standardization and sample analysis has been found to
reduce random error.)
Step 3. Begin sample analysis, flushing the system with the calibration blank solution between each
sample. Remember to analyze required QC samples.
Step 4. Dilute and reanalyze any samples with a concentration exceeding the calibration range.
13.11 CALCULATIONS
Generally, instruments are calibrated to output sample results directly in concentration units. If not,
then a manual calibration curve must be prepared and sample concentrations determined by com-
paring the sample signal to the calibrated curve. If dilutions were performed, the appropriate factor
must be applied to sample values. Report results as mg/L for each analyte.
13.12 PRECISION AND ACCURACY
In an EPA round-robin phase 1 study, seven laboratories applied the ICP technique to acid-distilled
water matrices that had been dosed with various metal concentrates. Table 13.4 lists the true value,
the mean reported value, and the mean %RSD (U.S. EPA, 1983).
13.13 REFERENCES
American Chemical Society, 1979. Safety in Academic Laboratories, 3rd ed. Committee on Chemical
Safety, ACS, Washington, D.C.
American Society for Testing and Materials, 1984. Annual Bookof ASTM Standards, Vol. 11.01, Stand-
ard Specification for Reagent Water, D 1193-77 (reapproved 1983). ASTM, Philadelphia, Penn-
sylvania.
Department of Health, Education, and Welfare, 1977. Carcinogens Working with Carcinogens. No.
77-206. DREW, Public Health Service, Center for Disease Control, National Institute for Occu-
pational Safety and Health, Cincinnati, Ohio.
Element
Mn
Fe
1 Not
Ca
True
Value
N/L)
350
600
all elements
and Mg were
Sample 1
Mean
Reported
Value
N/L)
345
594
Mean
%RSO
2.7
3.0
True
Value
f/ug/L)
15
20
Sample 2
Mean
Reported
Value Mean
{ug/L) %RSD
15 6.7
19 15
True
Value
(nfl/L)
100
180
Sample 3
Mean
Reported
Value
fog/U
99
178
Mean
%RSD
3.3
6.0
were analyzed by all laboratories.
not determined.
Table 13.4. ICP Precision and Accuracy Data1.
118
-------
Fassel, V. A., 1982. Analytical Spectroscopy with Inductively Coupled Plasmas - Present Status and
Future Prospects. In: Recent Advances in Analytical Spectroscopy. Pergamon Press, Oxford
and New York.
Occupational Safety and Health Administration, 1976. OSHA Safety and Health Standards, General
Industry. OSHA 2206 (29 CFR 1910). OSHA.
U.S. Environmental Protection Agency, 1979. Inductively Coupled Plasma Atomic Emission Spec-
troscopy - Prominent Lines. EPA-600/4-79-017. U.S. EPA, Cincinnati, Ohio.
U.S. Environmental Protection Agency, 1983 (revised). Methods for Chemical Analysis of Water and
Wastes, Method 200.7, Inductively Coupled Plasma-Atomic Emission Spectrometric Method
for the Trace Element Analysis of Water and Wastes. EPA-600/4-79-020. U.S. EPA, Cincinnati,
Ohio.
779
-------
APPENDIX A
CLEANING OF PLASTICWARE
A laboratory supplies clean plastic sample containers (cubitainers, Nalgene bottles, centrifuge
tubes) to the field stations. The containers are composed of amber, high-density linear polyethylene,
and are of the wide-mouth design. Each lake sample requires one 4-L cubitainer, one 500-mL capacity
bottle, two 250-mL capacity bottles, three 125-mL capacity bottles, one 50-mL graduated centrifuge
tube with cap, and one 10-mL centrifuge tube with cap. Samples that are split require additional
containers, as indicated in Table 2.4. The equipment list, Table 2.1, contains names of suitable brands
of each container.
Plasticware, depending on its use, is cleaned by either an acid leaching procedure or water leaching
procedure:
CLEANING PROCEDURE 1 (ACID LEACHING)
All plasticware (with the exceptions in the next paragraph) is rinsed three times with deionized water,
three times with 3N HNO3 (prepared from Baker InstraAnalyzed HNO3 or equivalent), and six times with deion-
ized water. It is then filled with deionized water and allowed to stand for 48 hours. Next, it is emptied, dried in a
laminar-flow hood delivering Class 100 air (when dry containers are necessary), and placed in clean plastic bags
(bottles are capped first).
CLEANING PROCEDURE 2 (Dl WATER LEACHING)
Plasticware to be used for pH, acidity, alkalinity, and anion determinations is rinsed three times with
deionized water, filled with deionized water, allowed to stand for48 hours., then emptied and sealed in
clean plastic bags.
NOTE: The deionized water used in cleaning the plasticware must meet or exceed specifications for
ASTM Type I reagent grade water.
After the initial cleaning (by procedure 1 or procedure 2), 5 percent of the containers are checked to
ensure that rinsing has been adequate. The check is made by first adding 500 mL (or maximum amount)
deionized water to a clean container, sealing the container with a cap or parafilm, and slowly rotating it so
that the water touches all surfaces. The specific conductance of the water is then measured. It must be
less than 1 M S/cm. If any of the containers fail the check, all of the containers are rerinsed and 5 percent
are retested.
A-l
-------
APPENDIX B
BLANK DATA FORMS
The National Surface Water Survey forms shown in this appendix are facsimiles of the forms used in
the laboratory.
B-l
-------
NATIONAL SURFACE WATER SURVEY
FORM 11
SUMMARY OF SAMPLE RESULTS
LAB NAME BATCH 10
SAM-
PL E
ID:
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
LAB MANAGER'S SIGNATURE
ALIQUOT ID
1
Ca
mg/L
Mg
mg/L
K
mg/L
Na
mg/L
Mn
mg/L
Fe
mg/L
2
Extr.
. Al
mg/L
3
Cl
mg/L
S042~
mg/L
NOi-
mg/L
Si02
mg/L
ISE
Total r
mg/L
CO
NOTE: Approved Data Qualifiers and instructions for their use are listed In Table 3.10.
NSWS Form 11 - Summary of Sample Results.
-------
LAD NAME
NATIONAL SURFACE WATER SURVEY
FORM 11
SUMMARY OF SAMPLE RESULTS
BATCH ID LAB MANAGER'S SIGNATURE
SAM-
PLE
ID:
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
ALIQUOT ID
4
DOC
mg/L
NH/
mg/L
5
Measured
Eq.
PH
Alk
In1t. pH
key
Inlt. pH
Acy
yeq/L
Alk
lieq/L
*
COND.
pS/cm
Eq.
DIG
mg/L
Ink.
DIG
mg/L
6
Total
P
mg/L
7
Total
Al
mg/L
NOTE: Approved Data Qualifiers and Instructions for their use are listed in Table 3.10.
/VSl/l/S Form 11 - Summary of Sample Results (Continued)
-------
NATIONAL SURFACE WATER SURVEY
Form 13
Lab Name
ALKALINITY AND ACIDITY RESULTS
Batch 10
Sample ID
Lab Manager's Signature
RESULTS
CAlk] =
DATA
CA -
Ca
INITIAL SAMPLE VOLUME
yeq/L
eq/L
eq/L
Analyst
DATE STANDARDIZED
DATE STANUAROIZED
raL
BLANK ALKALINITY
ACID TITRATION
BASE TITRATION
VOLUME HC1
(ml)
0.00
0.00 (with KCl)
MEASURED
pH'
i
CALCULATED
PH
VOLUME NaOH
(inL)
0.00
0.00 (with KCl )
MEASURED
pH1
1
CALCULATEU j
prt
1
NSWS Form 13 - Alkalinity and Acidity Results.
B-4
-------
NATIONAL SURFACE WATER SURVEY
Form 14* '
QC DATA FOR ALKALINITY
AND ACIDITY ANALYSES
LAB NAME
BATCH ID
LAS MANAGER'S SIGNATURE
SAMPLE
ID
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
ZB
29
30
Alk
ueq/L
C0£-Acy
ueq/L
CALCULATED Alk
RESULT
DIFFERENCED
SXb
'Form not required in data package but reconmended for internal QC requirements.
a Difference = Calculated Allc-Measured Alk
b%X « DIC (in umoles/L)-([Alk] + [C02-Acy])
DIC
X 100
NSWS Form 14 - QC Data for Alkalinity and Acidity Analyses.
B-5
-------
NATIONAL SURFACE HATER SURVEY
Form 15*
CD
LAB HAKE
CONDUCTIVITY
BATCH ID
LAB MANAGER'S SIGNATURE
Sample
in
01" '
02
' 03"
04
OT
06 '
' 07
oa
09"
10
II
12 '
13
14
15
16
.. ^ ... .
"lH "
19
' 20
Zl
22
23 '
24
25
26 '
27
2fl
29 "
30
SPECIFIC CONDUCTANCE
( MS/cm)
Calculated
Measured
%D**
CALCULATE!) CONDUCTANCE FOR EACH ION pS/cm
HCOJ
Ca+2
co3-'
Cl-
Mg*2
N03-
K+
Na*
so4-^
NH4+
H+
OH"
- 3.5X1CP 1.92x10
Specific Conductance Factors of Ions
[(»S/cm at 2S*q per mg/L] 0.71S
2.60 2. 62 2.14 3.82 1.15 1.84 2.13 1.54
(per (per
4.13 mole/I) mole/I 1
* Form not required In data package but recommended for Internal QC requirements
Calculated Cond.-Measured Cond.
** % Conductance Difference
Measured Conductance
x 100
NSWS Form 15 - Conductivity.
-------
LAB NAME
NATIONAL SURFACE WATER SURVEY
Form 16*
ANION-CATION BALANCE CALCULATION
BATCH ID LAB MANAGERS SIGNATURE
Sample
ID
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Zb
26
27
28
29
30
Factor
mg/L t
i Ion
Difference **
to Convert
o yeq/L
Ca+2
49.9
CT
28.2
Ions -
Kg*'
82.3
(ueq/
NO^"
16.1
-)
K+
25.6
Na+
43.5
S04-2
20.8
F~
52.6
NH4+
55.4
ALK
H+**+
* Form not required in data package but recommended for internal QC requirements
Alk + I Anions - I Cations (except H+)
** % Ion Difference =
CH+] = (io-pH) x io6
I Anions + I Cation + Alk + 2[H+]
x 100
NSWS Form 16 - Anion-Cation Balance Calculation.
B-7
-------
NATIONAL SURFACE WATER SURVEY
Form 17 Page 1 of 1
1C RESOLUTION TEST
LAB NAME
BATCH ID
LAB MANAGER'S SIGNATURE
1C Resolution Test
1C Make and Model:_
Date:
Concentration: S042~ wg/mL, N03 yg/mL
Column Back Pressure (at max. of stroke): psi
Flow Rate: mL/min
Column Model: Date of Purchase:
Column Manufacturer:
Column Serial No:
Is precolumn in system Yes No
(a) cm (b) cm
Percentage Resolution: 100 x (1-a/b)
The resolution must be greater than 60%
Test Chromatogram:
/VSI/I/S Form 17 - 1C Resolution Test,
B-8
-------
LAB NAME
NATIONAL SURFACE WATER SURVEY
Form 18
QUALITY ASSURANCE
(DETECTION LIMITS)
BATCH ID
LAB MANAGER'S SIGNATURE
Parameter
Contract Required
Units Detection Limit
Instrumental
Detection Date Determined
Limit {DO MMM YY)
Ca mg/L
Mg mg/L
K mg/L
Na mg/L
Mn mg/L
Fe mg/L
Total Extractable
AT mg/L
CT mg/L
S0|- mg/L
N03- mg/L
S102 mg/L
Total F- mg/L
NH4+ mg/L
DOC mg/L
Specific
Conductance yS/cm
DIC mg/L
Total P mg/L
Total Al mg/L
0.01
0.01
0.01
0.01
0.01
0.01
0.005
0.01
0.05
0.005
0.05
0.005
0.01
0.1
*
0.05
0.002
0.005
Report the 7, which must not exceed 0.9 uS/cm, of six (6) nonconsecutive blanks.
NSWS Form 18 - Quality Assurance (Detection Limits)
B-9
-------
NATIONAL SURFACE WATER SURVE*
FORM 19
Page 1 of 2
CO
LAB NAME
BATCH ID
SAMPLE HOLDING TIME SUMMARY
LAB MANAGER'S SIGNATURE
DATE* SAMPLED
DATE RECEIVED
Parameter
Holding
Time
Holding Time
Plus
Date Sampled
Sample ID:
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Ca
28
Mq
28
K
28
Na
28
Mn
28
Fe
28
Total
Extr. Al
7
Cl
28
SO
28
NO
7
SiO?
28
ISE
Total F~
28
Date* Analyzed**
,
*Report these dates as Julian dates (i.e., March 26, 1984 = 4086).
**if parameter was reanalyzed due to QA problems, report the last date analyzed.
NSWS Form 19 - Sample Holding Time Summary.
-------
NATIONAL SURFACE WATER SURVEY
FORM 19
Page 2 of 2
SAMPLE HOLDING TIME SUMMARY
LAB NAME
BATCH ID
LAB MANAGER'S SIGNATURE
DATE* SAMPLED
DATE RECEIVED
Parameter
Holding
Time
Holding Time
Plus
Date Sampled
Sample ID:
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
~2T
24
25
26
27
28
29
30
DOC
14
NH^
28
Eq. PH
7
Acidity
14
Alkalinity
14
Specific
Conductance
14
Eq. OIC
14
Init. DIC
14
Total P
28
Total Al
28
Date* Analyzed**
Report these dates .as Julian dates (i.e., March 26, 1984 « 4086).
**If parameter was reanalyzed due to QA problems, report the last date analyzed.
NSWS Form 19 - Sample Holding Time Summary (Continued)
-------
CO
LAB NAME
NATIONAL SURFACE MATER SURVEY
FORM 20
BLANKS AND QCCS
BATCH ID ' LAB MANAGER'S SIGNATURE
Pa
rameter
Calibration
Blank
Reagent Blank
DL
QCCS
Low t
True
Iheoreticai
Measured
ices
> Value
Low QCCS Upper
Control Limit
Low QCCS Lower
Control Limit
IniU
Conti
Cont
Cont
Cont
font
Fina
High
Tru
High
Con
High
Con
Inlt
Cont
Fina
_al
nuing
.nmng
nuing
nuing
nuing
QCCS
i Value
QCCS Upper
trol Unit
QCCS Lower
trol Limit
ial
-------
NATIONAL SURFACE WATER SURVEY
FORM 20
BLANKS AND QCCS
LAB NAME
BATCH ID
LAB MANAGER'S SIGNATURE
Parameter
Calibration
Blank
Reagent Blank
DL theoretical
QCCS measured
Low QCCS
True Value
Low QCCS Upper
Control Limit
Low QCCS Lower
Control Limit
Initial
Continuing
Continuing
Continuing
Continuing
Continuing
Final
High QCCS
True Value
High QCCS Upper
Control Limit
High QCCS Lower
Control Limit
Initial
Continuing
Final
4
DOC
mg/L
N
N
N
NH/
mg/L
N
N
N
ALIQUOT ID
Measured
Eq
pH
N
N
N
N
Alk
PH
N
N
N
N
Acy
PH
N
N
N
N
S
Cond.
pS/cm
N
N
N
tq.
DIC
mg/L
N
N
N
Init.
DIC
mg/L
N
N
N
6
Total
P
mg/L
N
7
Total
Al
mg/L
Note: Approved Data Qualifiers and Instruction for their use are listed In Table 3.10
NSWS Form 20 - Blanks and QCCS (Continued)
-------
NATIONAL SURFACE WATER SURVEY
FORM 21
MATRIX SPIKES
Parameter
MS First
(orig.)
Sample ID
Sample Result
Spike Result
Spike Added
Percent
Recovery
MS Second
Sample ID
Sample Result
Spike Result
Spike Added
Percent
Recovery
MS Third
Sample ID
Sample Result
Spike Result
Spike Added
Percent
Recovery
ALIQUOT ID
1
Ca
mg/L
Mg
mg/L
K
mg/L
Ha
mg/L
Mn
mg/L
Fe
mg/L
3
Cl
mg/L
SV~
mg/L
N03
mg/L
S102
mg/t
tSE
Total F
mg/L
4
DOC
mg/L
NH/
mg/L
6
Total
P
mg/L
r 7
Total
Al
mg/L
CO
Note: Matrix spikes not required for allquots 2 and 5.
NSWS Form 21 - Matrix Spikes.
-------
CD
LAB NAME
NATIONAL SUFACE WATER SURVEY
Form 22
DUPLICATES
BATCH ID
LAB MANAGER'S SIGNATURE
Parameter
Duplicate
Sample ID
Sample Result
Duplicate
Result
% RSD
Second Dupl 1cate
Sample ID
Sample Result
Dupl Icate
Result
J RSD
Third Duplicate
Sample ID
Sample Result
Dupl Icate
Result
% RSD
ALIQUOT ID
1
Ca
mg/L
Mg
mg/L
K
mg/L
Na
mg/L
Hn
mg/L
Fe
mg/L
2
Total
Extr.Al
mg/L
3
cr
mg/L
»«z-
mg/L
NO,
mg/L
SlOo
mg/L
ISE
Total F-
mg/L
Note: Approved Data Qualifiers and Instructions for their use are listed In Table 3.10.
NSWS Form 22 - Duplicates.
-------
CO
NATIONAL SURFACE WATER SURVEY
Form 22
Pdye 2 of 2
DUPLICATES
LAB NAME
BATCH ID
LAB MANAGER'S SIGNATURE
Parameter
Dupl icate
Sample ID
Sample Result
Duplicate
Result
X RSD*
Second
Duplicate
Sample ID
Sample Result
Duplicate
Result
J RSD*
Third Duplicate
Sample ID
Sample Result
Duplicate
Result
% RSD*
ALIQUOT ID
4
DOC
mg/L
NH,+
mg/L
Measured
Eq.
PH
Alk
Initial
PH
Acy
Initial
PH
5
C02-
Acy
ueq/L
Alk
ueq/L
Cond.
yS/cm
Eq.
DIG
mg/L
Init.
QIC
mg/L
6
Total
P
mg/L
7
Total
Al
mg/L
Note: Approved Data Qualifiers and instructions for their use are listed In 3.10.
*Report absolute difference rather than RSD for pH determinations.
NSWS Form 22 - Duplicates (Continued)
-------
NATIONAL SURFACE WATER SURVEY
Form 23
STANDARD ADDITIONS
Parameter
MS First
(orlg.)
Sample ID
Single
Response
Spike added
_{Conc.)
Sample
Spike 1
Response
Spike 2
Cone.
Sample
Spike 2
Response
Calc. Sample
Cone, for
Urlg. Sample
(Summarized
on Form 11}
ALIQUOT io
1
Ca
mg/L
Mg
mg/L
K
mg/L
Na
mg/L
Mn
J22ZL-
Fe
mg/L
3
Cl
mg/L
S0.2-
mg/L
N03-
mg/L
S10,
mg/C
ISE
Total F-
mg/L
4
DOC
mg/L
NH/
mg/L
6
Total
P
mg/L
7
Total
Al
mg/L
Note: Approved Data Qualifiers and Instructions for their use are lested In Table 3.10.
NSWS Form 23 - Standard Additions.
-------
Appendix C
Examples of Calculations Required for
Alkalinity and Acidity Determinations
1.0 HCI STANDARDIZATION (TEXT SECTION 4.8.1)
1.00 mL of a 0.01038N Na2CO3 plus 40.00 mL C02-free deionized water is titrated with HCI titrant. The titrant
data are given below:
mLHCI
added
0.00
0.100
0.200
0.300
0.400
0.500
0.600
0.700
PH
10.23
9.83
9.70
9.54
9.28
8.65
7.20
6.71
mLHCI
added
0.800
0.900
1.000
1.100
1.200
1.300
1.400
1.500
pH
6.37
6.03
5.59
4.91
4.48
4.26
4.11
4.00
mLHCI
added
1.700
1.900
2.100
2.300
2.500
pH
3.84
3.72
3.63
3.56
3.49
F1b is calculated for the data sets (V, pH) with pH 4-7 using the equation
rii+ii/ i O I/ I/" \ I/
[n JrX-j T £. l\-( l\2 % *\VV
Fib = (Vs + V)
where
[VSC /
^77) (
Vs = initial sample volume = 41.0 mL
V = Volume of HCI added
C = 1.266 x 10"4 = (N Na2CO3)/(2 X 41)
[H+]= 10"pH
K-, = 4.3 x 10~7
K2 = 5.61 x 10~11
Kw= 1.01 x 10"14
The (V, F1b) values are tabulated below.
F1b(x IP'3) V F1b(x IP'3)
0.700
0.800
0.900
1.000
3.57
2.59
1.60
0.64
1.100
1.200
1.300
1.400
1.500
-0.34
-1.33
-2.28
-3.26
-4.23
C-7
-------
The plot of F1b versus V is shown in Figure C-1. The data lie on a straight line and are analyzed by linear regres-
sion to obtain the coefficients of the line
F1b = a + bV
from regression,
r = 1.0000
a = 0.01038 ± 0.00001
b = -0.009747 ± 0.000012
Then V^ = -a/b = 1.065mL
and
N Na2C03 X VNa2C03 (0.01 038) (1.00)
NHCI = - 2- - 1 - 2- 3- = - i - ii - i - = 0.009743 eq/L
V, 1.065
2.0 NaOH STANDARDIZATION (TEXT SECTION 4.8.2)
2.1 INITIAL NaOH STANDARDIZATION WITH KHP (TEXT SECTION 4.8.2.1)
5.00 mL of 9.793 x 10~4 N KHP plus 20.0 mL CO2 - free deionized water are titrated with approximately 0.01N
NaOH. The titration data and appropriate Gran function values are given in the table below.
Volume NaOH
(ml) pH F3b(x 10'3)
0.000 4.59
0.050 4.78
0.100 4.97 3.90
0.150 5.14 3.39
0.200 5.31 2.86
0.250 5.48 2.34
0.300 5.66 1.82
0.350 5.87 1.29
0.400 6.14 0.79
0.450 6.66 0.26
0.500 8.99 -0.25
0.700 9.95 -2.29
0.900 10.23 -4.40
1.100 10.39
1.300 10.51
The Gran function F3b is calculated for data with pH 5-10. F3b is calculated by
n/ IA
F3b = (VS + V) ^ ^ + V) [H+]2 + [
Vs = Volume NaOH added
V = Initial sample volume = 25.00 mL
C = N KHP/5 = 1.9586 X 10"4
H + ]=10"pH
KT = 1.3 X 10~3
K2 = 3.9 x 10"6
C-2
I
J
-------
4 -
3-
2-
O
t
x 0
JQ
uT -1 -
-2-
-3-
-4-
-5-
I
0.2
0.6
1.0
V
i
1.8
Figure C-1. Plot of Fw Versus V for HCI Standardization.
C-3
-------
Kw= 1.01 x 1Q-14
F3b versus V is plotted in Figure C-2. The data lie on a straight line with the equation F3 = a + bV. The coeffi-
cients are calculated using linear regression., From the regression,
r = 1.0000
a = 0.004931 ± 0.000008
b = -0.01036 ± 0.00002
From this V3 and NNa0H are calculated by
V3 = -a/b = 0.4761 mL
MNaOH = «HP K"F = 0.01028 eq/L
V3
2.2 STANDARDIZATION CHECK (TEXT SECTION 4.8.2.2)
0.500 ml of 0.00921 N NaOH plus 25.0 mL CO2 - free deionized water is titrated with 0.0101 N HCI (standardized
with Na2C03). The titration data and appropriate Gran function values are given in the table below.
Volume HCI
{mL) pH F!< x 10'3)
0.000 10.29
0.100 10.15
0.200 10.03 2.75
0,250 9.91 2.09
0.300 9.78 1.55
0.350 9.60 1.03
0.400 9.34 0.57
0.450 8.39 0.064
0.500 4.76 -0.45
0.550 4.44 -0.94
0.600 4.26 -1.43
0.650 4.12 -1.98
0.700 4.04 -2.39
0.800 3.88
The Gran function F-, is determined for data in the pH range 4-10. F-, is calculated by
= (V + VS)
IH i
Vs = Volume of HCI added
V = Initial sample volume = 25.5 mL
x 10~14
Fj versus V is plotted in Figure C-3. The data are on a straight line with the equation F, = a + bV. The coeffi-
cients, determined by linear regression, are
C-4
-------
CO
I
o
.a
CO
u_
Figure C-2. Plot of F3b Versus V for Initial NaOH Standardization With KHP.
C-5
-------
CO
b
-3-
Figure C-3. Plot of F1 Versus V for Standardization Check-Titration of NaOH With HC1.
C-6
-------
r = 0.9994
a = 0.00465 ± 0.00005
b = -0.001016 ± 0.00011
From these values V3 and NHC| are calculated by
VT = -a/b = 0.4577 mL
N'HC, = - = 0.01006
v,
Comparing this value for N'HC, with the previously determined value of NHC), the absolute RFD is
0.01006 - 0.0101
RPD in NHC, values =
0.5(0.0101 + 0.01006)
x 100 = 0.4%
This RPD is acceptable since it is less than 5%.
2.3 ROUTINE NaOH STANDARDIZATION WITH STANDARDIZED HCI (TEXT SECTION
4.8.2.3)
mLHCI
added pH
mLHCI
added
0.00
0.200
0.400
0.600
0.650
0.700
pH
10.44
10.30
10.13
9.71
9.51
9.19
mLHCI
added
0.750
0.800
0.850
0.900
1.000
1.100
PH
5.35
4.65
4.37
4.22
4.02
3.88
1.200 3.78
1.400 3.62
FT is calculated for each data pair (V, pH) with a pH 4-10 using the equation
where
Vs = Initial sample volume = 25.00 + 1.00 = 26.00 mL
V = Volume of HCI added
[H+]=10"pH
Kw= 1.0 x 10~14
The new data pairs (V, F.,) are tabulated below.
C-7
-------
F1b(x 10'3)
Fib(x IP'3)
0.400
0.600
0.650
0.700
0.750
3.56
1.36
0.86
0.41
-0.12
0.800
0.850
0.900
1.000
1.100
-0.60
-1.14
-1.62
-2.58
-3.57
A plot of FT versus Vis shown in Figure C-4. The data sets corresponding to volumes from V = 0.40 to V = 1.10 lie
on a straight line with the equation
F1 = a + bV
The coefficients are obtained by linear regression. The results are
r = 0.9996
a = 0.007488 ± 0.00008
b = -0.0101 ± 0.0001
From these results,
V3 = -alb = 0.741
N
N
NaOH
HCI
X V
1 _
'NaOH
(0.009830) (0.741)
1.000
= 0.00728
3.0 ELECTRODE CALIBRATION (TEXT SECTION 4.8.3)
This section describes the electrode calibration procedure. The tables below (A and B) tabulate both the titra-
tion data (V and pH), the calculated pH values (pH*), and the coefficients for the line pH = a + b pH*.
Table A. Acid Titration
Vs = 50.50 ml NHCI = 0.00983
Volume HCI
(mL)
0.000
0.025
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
r = 1.00
PH
5.37
5.25
4.97
4.68
4.51
4.38
4.29
4.22
4.15
4.10
a = 0.10 ±0.01
pH*
5.31
5.01
4.71
4.54
4.41
4.31
4.24
4.17
4.11
b = 0.971 ±0.002
Volume HCI
(mL)
0.450
0.500
0.600
0.800
1.000
1.200
1.500
1.700
2.000
PH
4.05
4.00
3.92
3.80
3.71
3.64
3.55
3.50
3.43
PH*
4.06
4.02
3.94
3.81
3.72
3.64
3.55
3.50
3.43
C-8
-------
4 -i
3 -
2 -
1 -
<*)
i
O
-1 -
-2 -
-3 -
-4 -J
0.4
0.6
Figure C-4. Plot of F-, Versus V for Routine NaOH Standardization.
C-9
-------
Table B. Base Tit rat ion
Vs = 50.50
Volume HCI
(mL)
0.000
0.050
0.200
0.300
0.400
0.500
0.600
r = 0.99
ml NHCI =0.00983
PH
6.66
9.03
9.55
9.66
9.75
9.90
10.00
a = 0.08 ±0.27
pH*
9.00
9.60
9.77
9.90
9.99
10.07
b = 0.99 ± 0.03
Volume HCI
(mL)
0.820
0.940
1.080
1.200
1.300
1.400
1.500
PH
10.18
10.25
10.31
10.36
10.40
10.43
10.47
PH*
10.20
10.26
10.32
10.37
10.40
10.43
10.46
The data in Tables A and B are plotted in Figure C-5. Except for two points in the base titration (at V = 0.3 and 0.4),
the data lie on a straight line. (The lines calculated for each titration are essentially coincident as indicated by
their coefficients.) Excluding these two points, the data are fit to the line with the equation pH = a + bpH'.The
coefficients of the line (obtained by linear regression) are
r = 1.0000
a = -0.014 ± 0.0011
b = 0.999 ± 0.002
4.0 BLANK ANALYSIS - ALKALINITY DETERMINATION (TEXT SECTIONS 4.9.2 and
4.11.1)
This section describes the determination of alkalinity in a blank solution. The blank is prepared by adding 0.40
mL of 0.10M NaCI to 40.00 ml deionized water. It is titrated with 0.00983N HCI. The titration data are given below
(both measured and calculated pH* values are included).
Volume HCI
(mL)
0.000
0.080
0.120
0.200
0.300
0.400
pH
5.84
4.69
4.52
4.31
4.14
4.01
0.00194
0.00295
0.00390
Volume HCI
(mL)
0.500
0.600
0.700
1.000
1.200
1.500
pH
3.91
3.84
3.77
3.62
3.55
3.45
F,
0.00503
0.00593
0.00698
0.00993
0.0117
0.0149
The Gran function F1a(F1a = (V + V) [H + ] is calculated for pH* value less than 4.5 and the values included in the
table.
F, versus V is plotted in Figure C-6. The data are linear and fit the line
FT = a + bV using linear regression. The resulting coefficients are
r = 0.9998
a = (-0.70 ± 5.6) x 10
b = 0.00989 ± 0.00007
,-5
C-10
-------
11-1
10-
X
a
Figure C-S. Plot ofpH* Versus pH for Electrode Calibration.
C-ll
-------
14-
12-
10-
CO
b 8-
U.
6
2-
0.2 0.4 0.6 0.8 1.0 1.2 1.4
V
Figure C-6. Plot of F1a Versus V for Alkalinity Determination of Blank.
C-12
-------
From this,
[Alk] =
V, = -a/b = 7.05 X 10"4 mL
'HCI 7 6C!
= 1.7 x 10"7 = 0.17 /ueq/L
L
This value for [Alk] is acceptable.
5.0 SAMPLE ANALYSIS
5.1 TITRATION DATA
A natural lake sample was titrated as described in Section 4.10 of the text. The titration data are given below.
Also included are values for the calculated pH (pH*).
Acid Titration
Vsa = 40.00 mL Vsa,t = 0.40 mL
Ca = 0.00983
va
0.000
0.040
0.080
0.120
0.140
0.160
0.260
0.280
0.380
eq/L
pH
5.10
4.89
4.71
4.56
4.50
4.44
4.24
4.21
4.08
PH*
5.11
4.90
4.72
4.57
4.51
4.44
4.24
4.21
4.08
Va
0.460
0.550
0.650
0.750
0.900
1.100
1.400
1.700
PH
3.99
3.91
3.84
3.77
3.69
3.61
3.50
3.42
pH*
3.99
3.91
3.84
3.77
3.69
3.61
3.50
3.42
Base Titration
Vsa = 40.00 mL Vsau =0.40 mL
Ca = 0.00702
va
0.00
0.015
0.030
0.050
0.080
0.120
0.160
0.200
0.240
0.280
0.320
0.340
0.360
3.380
0.400
eq/L
pH
5.08
5.13
5.26
5.35
5.57
5.78
6.06
6.30
6.65
6.98
7.29
7.46
7.62
7.83
8.03
pH*
5.09
5.14
5.27
5.36 >
5.58
5.79
6.07
6.31
6.66
7.00
7.31
7.48
7.64
7.85
8.05
va
0.425
0.470
0.500
0.540
0.560
0.600
0.660
0.700
0.780
0.900
1.000
1.100
1.405
1.700
2.200
2.500
pH
8.30
8.66
8.85
9.01
9.10
9.21
9.35
9.44
9.57
9.72
9.83
9.92
10.12
10.26
10.43
10.51
PH*
8.32
8.68
8.87
9.03
9.12
9.23
9.37
9.47
9.60
9.75
9.86
9.95
10.15
10.29
10.43
10.54
C-13
-------
5.2 INITIAL ESTIMATE OF V, (TEXT SECTION 4.11.1)
The Gran function F1a is calculated for each data pair from the acid titration with a pH*<4. The values are given
in the table below.
IP'3)* Va F1a(x 10'3)*
0.460
0.550
0.650
0.750
4.18
5.04
5.93
6.99
0.900
1.100
1.400
1.700
-8.43
10.2
13.1
16.0
F1a versus Va is plotted in Figure C-7. A regression of F1a on Va is performed to fit the data to the line F1a =
a + bV. The resulting coefficients are:
r = 0.9999
a = -0.000217 ± 0.000050
b = 0.009548 ± 0.000048
From this, the initial estimate of V-, is calculated by
VT = -a/b = 0.0227 mL
Since V-,>0 and the initial sample pH*<7.6, calculation procedure B (Text Section 4.11.3) is used to determine the
Alk and Acy of the sample.
5.3 INITIAL ESTIMATES OF V2, ALK, ACY, AND C (TEXT SECTION 4.11.3, STEP 1)
From the base titration data, V2 is estimated to be 0.40 mL (the first point with a pH*<8.2). Now that the initial
estimates of V., and V2 have been obtained, estimates of Alk, Acy, and C can be calculated.
ViCa
Alk = = 5.6 x 10'5 eq/L
Acy = = 7.02 x 10'5 eq/L
Vsb
C = Alk + Acy = 7.58 x 10'5 eq/L
5.4 REFINED ESTIMATES OF Vt and V2 (TEXT SECTION 4.11.3, STEP 2)
tion 4.11.1.3) is calculated for acid titration data wil
given below.
F1c(x IP'4) Va F1c(x 1(T4)
The Gran function F1c (Equation 1, Section 4.11.1.3) is calculated for acid titration data with volumes across the
current estimate of Vv The values are given below.
0.000
0.040
0.080
0.120
0.140
-6.68
-4.10
-7.05
-10.4
-12.1
0.160
0.260
0.280
0.380
-14.4
-23.2
-24.9
-33.8
F1c versus Va is plotted in Figure C-8. A regression of F1b on Va is performed. The regression results are
C-14
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16-
14-
12-
«? 10-
o
^
_>£
(0
uT {
6-
4-
2-
0.2
0.4
i
0.6
0.8 1.0
Va
I
1.2
1.4
1.6 1.8
Figure C-7. Plot of F1a Versus Va for Initial Determination of V,
C-/5
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Va
-0.04 0 0.04 0.12 0.20 0.28 0.36 0.44
I I i i I 111 » I I
b
UL
-5-
-10-
-15-
-20-
-25-
-30-
-35
Figure C-8. Plot of F1c Versus Va for VT Determination,
C-16
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r = 0.999
a = -0.00006 ± 0.00003 ' .
b = -0.00864 ± 0.00016
A new estimate of V1 is
V1 = -a/b = -0.007 mL
Next the Gran function F2c (Equation 2, Text Section 4.11.1.3) is calculated from data sets from the base titration
with volumes across the current estimate of V2. The values are given below.
F2c(x ID'4) V^ F2c(x IP'4)
0.340
0.360
0.380
0.400
0.425
1.99
1.28
.555
-0.031
-.868
0.470
0.500
0.540
0.560
0.600
-2.60
-2.14
-6.03
-7.43
-9.55
F2c versus Vb is plotted in Figure C-9. A regression of F2c on Vb is performed. (Data with Vb>0.5 are not used in the
regression.) The regression results are
r = 0.999
a = 0.00135 ± 0.000024
b = -0.003400 ± 0.000060
A new estimate of V2 is
V2 = -a/b = -0.398 mL
5.5 NEW ESTIMATES OF ALK, ACY, AND C (TEXT SECTION 4.11.3, STEP 3)
From the new estimates of V-, and V2, new estimates of Alk, Acy, and C are calculated.
Vi Ca
Alk* = - = 1.6 x 10'6eq/L j
Acy* = L±_ = 6.98 x 10'5eq/L
Vsb
C* = Alk + Acy = 6.83 x 10"5eq/L
5.6 COMPARISON OF LATEST TWO ESTIMATES OF TOTAL CARBONATE (TEXT
SECTION 4.1 1.3, STEP 4)
C C*
= 0.041 > 0.001
C + C*
Since C and C* do not agree, a new C is calculated from their average
C(new) = (C + C*)/2 = 7.09 x 10~5eq/L
The calculations in Sections 5.4 through 5.6 of this Appendix are repeated until successive iterations yield total
carbonate values which meet the above criteria. The results from each iteration (including those already given)
are given below.
C-17
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Figure C-8. Plot of F1c Versus Vb for V, Determination.
C-18
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Iteration
1
2
3
4
5
6
7
8
9
VT (ml)
0.0227
-0.0060
-0.0067
-0.0071
-0.0072
-0.0074
-0.0074
-0.0074
-0.0074
V2(mL)
0.400
0.398
0.397
0.397
0.396
0.396
0.396
0.396
0.396
Alk
fr/eq/L)
5.6
-1.5
-1.6
-1.7
-1.8
-1.8
-1.8
-1.8
-1.8
Acy
fceq/L)
70.2
69.9
69.7
69.7
69.6
69.5
69.5
69.5
69.5
C
Cueq/L)
75.8
68.4
68.1
67.9
67.8
67.7
67.7
67.7
67.7
C-C*
C + C*
0.051
0.029
0.016
0.009
0.005
0.003
0.001
0.008
NewC
(A/eq/L)
72.1
70.1
69.0
68.4
68.1
67.9
67.8
The final values for Alk and Acy are reported on Form 11.
6.0 QUALITY CONTROL CALCULATIONS
Examples of the QC calculations are described in this section.
6.1 COMPARISON OF CALCULATED ALKALINITY AND MEASURED ALKALINITY (TEXT
SECTION 4.9.5)
For the sample analyzed in Section 5.0 of this Appendix, the following data were obtained.
initial pH = 5.09 air-equilibrated pH = 5.06
DIG = 0.59 mg/L air-equilibrated DIG = 0.36
From these data, the calculated Alk values are computed using the equation
[/ \ m
nif^ i rui + ii^ i o if v I if I
u\\j § in ir\-i-t-£i\-ii\o i "MA/ 4- T I ^ «fi
~120TT ( [H+12 + [H + ]K +K K )+ Thn " X
\ 1 1 2 f J
The results are
[Alk]G1 = -5.6>ueq/L [Alk]C2 = -7.2/ueq/L
Then
|[Alk]G1-[Alk]C2| = 1.6 yueq/L <15 ,ueq/L
Since [Alk]G1 and [Alk]C2 are in agreement, their average value is used for comparison to be the measured value.
[Alk]c.avg = -6.4>xeq/L Alk = -1.8/ueq/L
D = | Alkc - Alk | = 4.6/
-------
From these data, the Acy is computed using the equation
[DIG / [H + ]2 - ^K2 \ r. Kw
-^T ( [H+f + tH + lK^K,)* [H ] --[F
[AIK]cMq/L) I -=±- I ru^'.' T^ 1+ [H + l - -^ I X 106
[Acy]c = 54.7
This value is compared to the measured value
D = [Acy]c-Acy = -14.7 jueq/L < -10 jueq/L
Although borderline, this value of D is indicative of other protolytes in the system which are contributing to the
measured Acy. This might be expected since the sample also contains 3.2 mg/L DOC.
6.3 COMPARISON OF CALCULATED TOTAL CARBONATE AND MEASURED TOTAL
CARBONATE (TEXT SECTION 4.9.7)
For the sample analyzed in Section 5.0 of this Appendix, the following data were obtained.
initial pH = 5.09 Acy = 69.5 /teq/L = 69.5 ^mole/L
DIC = 0.59 mg/L Alk = -1.8 /ueq/L = -1.8 ATnole/L
From the DIG value, the total carbonate is calculated.
Cc = 83.26 x DIG = 49.1 /umoie/L
The calculated value is then compared to the measured value.
D = Cc-(Alk + Acy) = -18.6 jumole/L <-10 /umole/L
Although borderline, this value of D is indicative of other protolytes in the system. This might be expected since
the sample also contains 3.2 mg/L DOC. Notice that the same conclusion was reached in the Acy comparison.
In general, noncarbonate protolytes are significant (i.e., contribute significantly to the total protolyte concentra-
tion), when indicated by one (or both) of the individual comparisons (Alk and Acy comparisons) and the total
carbonate comparison.
C-20
i, U.S. GOVERNMENT PRINTING OFFICE. 19885 48-158 '67135
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