PERCHLORATE SCREENING STUDY:
LOW CONCENTRATION METHOD FOR THE DETERMINATION OF
PERCHLORATE IN AQUEOUS SAMPLES USING ION SELECTIVE ELECTRODES
LETTER REPORT OF FINDINGS FOR METHOD DEVELOPMENT STUDIES,
INTERFERENCE STUDIES, AND SPLIT SAMPLE STUDIES,
INCLUDING STANDARD OPERATING PROCEDURE
FINAL
2 OCTOBER 2001
Prepared for:
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION IX
75 HAWTHORNE STREET
SAN FRANCISCO, CALIFORNIA 94105
DEPARTMENT OF THE ARMY
U.S. ARMY ENGINEER DISTRICT, SACRAMENTO
CORPS OF ENGINEERS
1325 J STREET, SACRAMENTO, CALIFORNIA 95814-2922
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
PREFACE
This letter report of findings has been prepared for the U.S. EPA according to the requirements of Contract
No. DACA05-96-D-0003, Task Order 0062, between the United States (U.S.) Army Corps of Engineers -
Sacramento District and Earth Tech, Inc. (Earth Tech). This letter report of findings includes the results of
method development studies (Task 1), interference studies (Tasks 2 and 4), and split sample analyses (Task 5)
for the Low Concentration Method for the Determination of Perchlorate in Aqueous Samples Using Ion
Selective Electrodes. Also included as Attachment 1 is the standard operating procedure (SOP) for the
method (Task 3).
The U.S. Army Corps of Engineers project manager is Mr. Randy Olsen. The U.S. EPA project manager is
Mr. Richard Russell. The Earth Tech program manager for this project is Mr. Ray Sugiura, and the project
manager and senior method development chemist is Mr. Christopher Davis.
Approved:
Christopher Davis
Project Manager
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TABLE OF CONTENTS
Section Page
1.0 Task 1 - Evaluation of Solid State Probe Performance Characteristics 1
1.1 Background 1
1.2 Equipment Comparison 2
1.3 Method Development 3
1.3.1 Low Concentration Sensitivity Studies 3
1.3.1.1 Calibration Curve s 4
1.3.1.2 Method Detection Limit Studies 4
1.3.1.3 Practical Quantitation Limit 5
1.3.1.4 Linear Range 6
1.3.1.5 Quality Assurance/Quality Control 6
1.3.2 Method Variables 8
1.3.2.1 Perchlorate ISE Module Conditioning 8
1.3.2.2 Sample Volume and Stirring 10
1.3.2.3 Temperature Effects 11
1.3.2.4 Ionic Strength Adjustors (ISA) 12
1.3.2.5 Matrix Effects 15
1.3.2.6 pHAdjustment 16
1.3.2.7 Chloride Correction 16
1.3.2.8 Nitrate Correction 18
1.3.2.9 Bromide Correction 19
1.3.3 Split Sample Analyses 19
1.4 Method Development Conclusions 20
1.5 Method Development Recommendations 21
2.0 Task 2 - Investigate Sample Concentration Methods 21
3.0 Task 3 - Preparation of Revised Standard Operating Procedure 21
4.0 Task 4 - Investigation of Interference Using ISE Protocol 22
4.1 Field Sample Matrix Interferences 23
4.2 Carbonate/Bicarbonate Interference Studies 24
4.3 Chloride Interference Studies 26
4.4 Nitrate Interference Studies 28
4.5 Bromide Interference Studies 30
4.6 Fluoride Interference Studies 32
4.7 Phosphate Interference Studies 32
4.8 Possible Organic Chemical Interference 32
4.9 Method of Standard Additions 33
4.10 ISE Conditioning 36
4.11 Interference Study Conclusions 36
4.12 Interference Study Recommendations 37
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TABLE OF CONTENTS
Section Page
5.0 Task 5 - Analyses of Split Samples 38
5.1 Split Sample Results 38
5.1.1 Non-Detected Result Confirmations 39
5.1.2 Detected Result Confirmations 39
5.1.3 Split Sample Result Interpretation 40
5.2 Quality Control Results for ISE Analyses 42
5.2.1 Calibration Verification 42
5.2.2 Matrix Spike Recoveries 42
5.2.3 Field and Laboratory Duplicate Precision 43
5.2.4 Method and Equipment Blanks 43
5.2.5 ISE Module Reconditioning 44
5.3 Split Sample Study Conclusions 44
5.4 Split Sample Study Recommendations 45
Tables
Section 1 Tables 46
Tables 1-1 through 1-9 47
Section 4 Tables 61
Tables 4-1 through 4-23 62
Attachments
Attachments 1&2 141
1 Standard Operating Procedure (Version 1.0):
Low Concentration Method for the Determination of Perchlorate in
Aqueous Samples Using Ion Selective Electrodes 142
2 Example Spread Sheet 166
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Letter Report of Findings: Perchlorate Screening Method Study
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Abstract: Method development was performed for the Low Concentration Methodfor the Determination of
Perchlorate in Aqueous Samples Using Lon Selective Electrodes with a target detection limit (TDL) of 18
micrograms per liter (|ig/L) to meet the California advisory action limit of 0.018 milligrams per liter (mg/L),
equivalent to 18 |ig/L for perchlorate in water. The studies resulted in a method with a reporting limit (RL) set
at 15 |ig/L. supported by a low calibration point of 10 |ig/L. and a method detection limit (MDL) of 3 |ig/L.
using a Sentek 367-75 Solid State Perchlorate Combination ISE with an Orion Model 290A Advanced Portable
ISE/pH/mV/Temperature Meter.
Calibrations were performed with 10 |ig/L. 20 |ig/L. 40 |ig/L. 60 |ig/L. and 100 |ig/L standards. Logarithmic
calibration curves for perchlorate concentration versus millivolts plotted on Excel spreadsheets consistently
achieved coefficients of determination (r2) greater than 0.990 (equivalent to r greater than 0.995) for the final
method. The method accuracy criterion of+20% was met for standards throughout the linear range of 10 to 100
Hg/L.
The use of 200 mL of standards and sample, use of a magnetic stirrer, and analysis at controlled temperature
were found to be essential elements to achieve sensitivity for perchlorate near the 18 |ig/L TDL and California
action limit. The effect of temperature variation was found to be minimized to less than 3.0 |ig/L perchlorate/°C
above 22°C. At lower temperatures, variations of 3.0 |ig/L/°C at 22°C to 10.9 |ig/L/°C at 10°C were reported.
Recalibration must be performed when temperature changes cause QC recoveries to exceed control limits.
Two ionic strength adjuster (ISA) solutions were studied and found acceptable for the low concentration
method. Optimal ISA addition was determined to be 1.0 mL of Sentek Perchlorate ISAB (1.0 M sodium
acetate) per 200 mL sample; or 2.0-5.0 mL of 0.4 M ammonium sulfate per 200 mL of sample (0.4-1.0 mL of
Orion 930711 ISA) per 200 mL sample. Two times higher concentrations of ISA or ISAB may be used for
samples with high background ionic strength with no expected loss of sensitivity.
Significant interferences were encountered for elevated concentrations of some anions. Interference due to
carbonate and bicarbonate was eliminated by the acidification of all standards and samples to pH 4.0 with
sulfuric acid. Correction factors must be applied for concentrations in excess of 0.12 mg/L nitrate-as-nitrogen
(N03-N), 50 mg/L chloride, and 1.2 mg/L bromide. Some anions, notably nitrate, and possibly some organic
chemicals, were found to reduce electrode sensitivity between analyses. Sample matrices with nitrate
concentrations greater than 0.2 mg/L N03-N were found to require implementation of ISE reconditioning
between every sample analysis.
Split sample analyses were performed for 60 samples with definitive confirmation by EPA Method 314.0. Non-
detected ISE results were confirmed as non-detected in 54 of 55 samples, and detected results were confirmed
with varying degrees of accuracy in five samples. Matrix spike analyses indicate the potential for false
negatives at low perchlorate concentrations in samples with high levels of interfering anions, especially nitrate.
The method was found to perform well in matrices with low concentrations of anions, and is expected to be
especially useful for matrices with less than 1000 mg/L chloride or 1.5 mg/L N03-N. Matrices with higher
concentrations of these anions must be evaluated to determine if this method meets project objectives.
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1.0 Task 1 - Evaluation of Solid State Probe Performance Characteristics
This section of the letter report of findings presents the results of method development for the Low
Concentration Method for the Determination of Perchlorate in Aqueous Samples Using Ion Selective
Electrodes (the low concentration method).
1.1 Background
In 1999 Earth Tech developed a screening method for the determination of perchlorate in soils using an Orion
938101 plastic membrane half-cell perchlorate ion specific electrode (ISE) with double junction reference
electrode. The primary use for this method was to determine the concentration of perchlorate in soil samples
by screening level analysis at or near the site of drilling operations to aid the field sampling crew in selecting
samples for definitive-level analysis and in making decisions for further drilling locations. Ten percent of soil
samples analyzed by this method were confirmed by definitive-level analysis. The method was determined to
be effective, and the USEPA expressed an interest in developing a method for the determination of
perchlorate in aqueous samples using solid state ISEs.
The soils method uses an extraction ratio of 10 grams (g) of soil to 100 milliliters (mL) of water, with analysis
in general accordance with manufacturer specifications and USEPA quality assurance (QA) criteria. The 0.2
to 0.7 milligram per liter (mg/L) detection limits (DLs) for waters (equivalent to 200 to 700 micrograms per
liter [jj.g/L]) specified by the manufacturers of perchlorate ISEs allow for DLs of 2.0 to 7.0 milligram per
kilogram (mg/kg) in soils. Allowing for gradual loss of sensitivity, the reporting limit of 15 mg/kg used for
the soils analyses meets the California Preliminary Remediation Goal (PRG) of 39 mg/kg in residential soils
without modifying manufacturer specified analytical procedures.
As the California advisory action limit for perchlorate in waters is 0.018 mg/L (equivalent to 18 (ig/L). the
focus of the current study was to develop methodology for the determination of perchlorate at a target
detection limit (TDL) of 18 (ig/L. which is 12 to 40 times below manufacturer specified detection limits. The
conceptual basis for the low concentration method is a low-level measurement procedure described in the
instruction manual for the Orion 938101 plastic membrane half cell perchlorate ISE. This procedure was
modified and developed in the current study to produce a method with a reporting limit (RL) set at 15 (ig/L,
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supported by a low calibration point of 10 (ig/L, and a method detection limit (MDL) of 3 (ig/L. using solid
state ISEs.
Aqueous perchlorate concentrations for this study were reported in |_ig/L or parts per billion (ppb), as the
range of interest for perchlorate is 10-100 ppb. Anion interferent concentrations were reported in mg/L, or
parts per million (ppm), as concentrations of interferents studied were in the ppm range. Further references to
perchlorate concentrations in this report are in ppb, and references to anion concentrations are in ppm. All
such references are for aqueous solutions.
1.2 Equipment Comparison
Equipment and supplies were procured for the comparison of the Sentek 367-75 solid state perchlorate
combination ISE (the Sentek ISE) to the Orion 938101 plastic membrane half-cell perchlorate ISE with
double junction reference electrode (the Orion ISE). The Sentek ISE is a solid state sensor with built in
reference element that does not require any filling solution or maintenance, and can be stored dry; whereas the
Orion ISE utilizes a reference electrode that requires maintenance of both inner and outer chamber filling
solutions, and must be stored in a special solution, or dismantled, cleaned, and stored dry. Perchlorate ISEs
with similar characteristics are available from other manufacturers, and no requirement or recommendation of
brand or manufacturer is implied.
In method development, the Sentek ISE was found to be sensitive to concentrations below 10 ppb. The Orion
ISE was found to be sensitive to approximately 50-100 ppb (for details, refer to Section 1.3.1). Due to the
lower detection limits, simplicity of the solid state ISE with built-in reference electrode, and ease of storage,
the Sentek ISE was selected for the full method development studies, interference studies, and split sampling
analyses.
Comparison of data acquisition systems for the read-out of millivolt readings was also performed. The Orion
and Sentek ISEs were set up so millivolt readings could be read on both an Orion Model 290A Advanced
Portable ISE/pH/mV/Temperature Meter and a Laval ELIT 8804 Computer Interface (Four Channel Serial
Port RS232 Communication Port Connection and Laval ELIT Extended Software for ISE Interface 8804 for
10,000 Measuring Points). Data acquisition systems for ISEs with similar characteristics are available from
other manufacturers, and no requirement or recommendation of brand or manufacturer is implied.
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Millivolt readings were found to be consistent for each ISE on both instruments; however, the calibration
features of both instruments were found to be difficult to use effectively. In calibration mode with the Orion
290A, it was difficult to determine when millivolt readings had adequately stabilized; and the Laval ELIT
software was unable to integrate an appropriate curve and was tedious to use for saving data points. Both
instruments were able to effectively readout in millivolts and monitor millivolt reading stability.
Millivolt readings from the meter or ELIT software were therefore manually logged into a bench logbook,
then entered into an Excel spreadsheet which allowed graphic representation of the calibration curves with
equation and output of the coefficient of determination (r2), and direct output of concentration from millivolt
readings (see presentation of data in the attached tables). After two weeks of running ISEs on both
instruments, the meter was used alone for further analyses.
1.3 Method Development
1.3.1 Low Concentration Sensitivity Studies
Initially, aqueous perchlorate standards were prepared from reagent grade potassium perchlorate at 10 ppb, 25
ppb, 50 ppb, 100 ppb, and 500 ppb. Calibrations were then attempted using the Orion and Sentek ISEs with
addition of different types and concentrations of ionic strength adjustor (ISA) solutions, including no ISA.
Difficulties were initially encountered with both ISEs, including similar and inverted millivolt readings for
decreasing perchlorate concentrations below 100 ppb. Experimentation with the following parameters
improved the linearity of the millivolt readings significantly. The volume of the standards was changed from
50 mL to 200 mL, the use of a magnetic stirrer was implemented, stronger perchlorate solutions were used for
preconditioning of the perchlorate ISE, and reconditioning was performed on a more frequent basis. These
protocols significantly improved stabilization time, linearity, accuracy, and precision. Standards at 10 ppb, 20
ppb, 40 ppb, 60 ppb, and 100 ppb were used to focus of the calibration range to the concentrations of interest.
In the initial trials with the orion plastic membrane half-cell ISE with double junction reference electrode,
calibrations were unable to indicate an ability to differentiate between standards below 100 ppb, as presented
in Table 1-1. Although several combinations of ISA were tried, the lower limit of sensitivity for the Orion
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ISE was determined to be 100 ppb. Therefore, the Orion ISE was not used for method development due to
unacceptable performance at the TDL.
In the initial trials with the Sentek 367-75 solid state combination ISE, calibrations demonstrated the ability to
differentiate standards from 20 ppb to 100 ppb, as presented in Table 1-1. Subsequent calibration curves for
the Sentek ISE were acceptable and able to include all standards down to 10 ppb, therefore, the Sentek ISE
was chosen for method development. All further references to method development are for the Sentek ISE,
unless otherwise specified.
1.3.1.1 Calibration Curves
After the initial trials, full calibrations including 10 ppb, 20 ppb, 40 ppb, 60 ppb, and 100 ppb standards were
run on a daily basis, with one Sentek ISE set up for readings on the Orion 290A meter, and one Sentek ISE set
up for readings on the Laval ELIT computer interface. Logarithmic calibration curves for perchlorate
concentration versus millivolt readings were prepared on Excel spreadsheets. Initially, coefficients of
determination (r2) were greaterthan 0.980 (equivalent to rgreaterthan 0.990) for all ofthe calibration curves.
However, as method development progressed and the effects of different variables were determined,
calibration curves with r2 greaterthan 0.990 (equivalent to r greater than 0.995) were consistently achieved,
with r2 for most curves exceeding 0.995 (refer to Table 1-2 for examples of calibration curves with r2
approximately equal to 0.98 and 0.99). For the final low concentration method, coefficients of determination
greaterthan 0.990 are considered necessary to demonstrate acceptable linearity.
1.3.1.2 Method Detection Limit Studies
An initial MDL study was performed on January 4,2001 according to requirements specified in 40 CFR Part
136, using 10 consecutive replicate analyses of a 25 ppb standard with 2 mL of 0.4 molar (M) ISA in 200 mL
of standard, and no pH adjustment. The MDL was determined to be 3 ppb, as presented in Table 1-3. The 3
ppb MDL was confirmed in a second MDL study on January 24 through 29,2001, as presented in Table 1-4.
Fifteen non-consecutive analyses were performed on a 20 ppb standard on four different days, using lmL of
Sentek ISAB in 200mL standard and pH adjustment to pH 4.0. The MDL standards were analyzed
intermittently between field sample analyses to provide an MDL for working conditions.
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U.S. Army Corps of Engineers
Periodic tests of method blanks, 5 ppb standards, and 10 ppb perchlorate standards indicated acceptable
differentiation of millivolt readings at 5 -10 ppb for a distilled water matrix. Although the MDLs were 3 ppb,
results for standards less than 5 ppb could not generally be considered differentiable from results for blanks.
1.3.1.3 Practical Quantitation Limit
The practical quantitation limit (PQL), or reporting limit (RL), was set at 15 ppb, which is five times the
MDL, and 20% below the 18 ppb project TDL and California action limit. The quality control (QC) criterion
for accuracy is ±20% for this method (refer to Section 1.3.1.5, below). Results reported as non-detected (ND)
at the PQL or MDL can be considered to indicate the absence of perchlorate at that concentration. If results
are to be reported as detected between the PQL and MDL, such results should be considered estimated as
quantiatively and qualitatively uncertain due to possible matrix effects. However, results below the PQL of
15 ppb should not be reported as detections unless the matrix is demonstrated to be free of positive
interferences.
For samples with chloride concentrations above 50 ppm, perchlorate readings less than 50 ppb require
subtraction of a correction factor due to positive interference according to Table 4.7; and perchlorate readings
greater than 60 ppb require dilution and reanalysis due to potential negative interference, as indicated in Table
4.2C. For samples with nitrate concentrations above 0.12 ppm nitrate-as-nitrogen (N03-N) or bromide
concentrations greater than 1.2 ppm, perchlorate readings require subtraction of a correction factor due to
positive interference according to Tables 4.8 and 4.9, respectively. For a full description of the matrix
interference studies, refer to the Task 4 Letter Report of Findings, Section 4.0; and Sections 1.3.2.7, 1.3.2.8,
and 1.3.2.9, below.
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1.3.1.4 Linear Range
The linear range for the low concentration method is considered to be 10-100 ppb perchlorate. Linearity and
percent recoveries are acceptable from 10 ppb to 100 ppb; however, the calibration curves flatten off above
100 ppb. To determine concentrations of perchlorate above 100 ppb, samples can be diluted such that they are
within the linear range, or if the concentration exceeds 500 ppb, calibration can be performed to include
standards at higher concentrations with stronger ISA concentrations according to ISE manufacturer
recommendations. Due to the potential for positive bias matrix interference, dilution and reanalysis of
samples with perchlorate readings in the upper half of the linear range is recommended.
Perchlorate ISEs are listed by the manufacturers as having a usable range from 200-700 ppb through 99,500
ppm if appropriately calibrated. As the focus of this investigation is the determination of perchlorate at
concentrations below the manufacturer specified range, analysis of high concentration perchlorate samples is
not included in this Letter Report of Findings.
1.3.1.5 Quality Assurance/Quality Control
Quality assurance/quality control (QA/QC) criteria were applied to all analyses to ensure usable quality of the
data during method development and split sample analyses. The sequences and concentrations of QC samples
were varied during method development, but generally followed typical EPA requirements for QC, as
summarized in this section. Complete QA/QC requirements are specified in Section 8.0 of the Standard
Operating Procedure (SOP) for the Low Concentration Method for the Determination of Perchlorate in
Aqueous Samples Using Ion Selective Electrodes presented in the Letter Report of Findings for Task 3,
Section 3.0, Attachment 1.
Initial calibrations were performed using 5 initial calibration standards (ICAL), with the low standard at a
concentration below the PQL. A blank calibration standard is not recommended in ISE manufacturer
protocols and was not included for the low concentration method as linearity to the origin is not expected for
ISE methods. The logarithmic calibration curves were required to meet a correlation coefficient criterion of r2
>0.990 (r >0.995). In addition, millivolt readings for each ICAL standard were converted to perchlorate
concentrations to verify ±20% accuracy throughout the linear range.
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Second source standards were analyzed as laboratory control samples/initial calibration verification check
samples (LCS/ICV) with each analytical run. Continuing calibration verification check samples (CCV) and
method blanks/initial or continuing calibration blanks (MB/ICB or CCB) were analyzed at a frequency
exceeding one per 10 samples. Matrix spikes and duplicate analyses were analyzed during split sample
analyses at a frequency in excess of one per 20 samples to determine matrix specific accuracy and precision.
Corrective actions were implemented when QC sample recoveries exceeded the ±20% method accuracy
criterion.
All standards were made from reagent grade salts dissolved in deionized water and diluted to the
concentrations required with high accuracy/high precision pipettes. In addition to glass pipettes, a variable
volume pipettor with tip ejector was found to be extremely useful for accurate pipetting. ICVs, LCSs, and
CCVs were prepared at varying concentrations, including 20,25,40, and 50 ppb. Check standards at 5 ppb or
10 ppb were also analyzed for some analytical runs.
The following analytical sequence is recommended as a result of method development: ICALs at 10,20,40,
60, and 100 ppb; ICV/LCS at 25 ppb or 50 ppb; MB/ICB; 10 samples or less; CCV at 20 ppb; MB/CCB; 10
samples or less; LCS; CCB; etc. In addition, a check sample at 10 ppb and/or 5 ppb may be considered
appropriate after the ICAL or ICB to demonstrate sensitivity and the ability to differentiate between a low
concentration standard and a blank, depending on project objectives, especially for clean matrices or if results
are to be reported below the PQL.
Although mid-range check standards (50 ppb for the specified linear range) are normally used for EPA
methods, concentrations for check standards for this method at 20-25 ppb may be preferable to demonstrate
accuracy and sensitivity near the 18 ppb TDL and California action limit. The concentration of the ICV/LCS
may be set at 50 ppb to check mid-range accuracy if appropriate for project objectives, but at least one check
standard (the CCV) should be set at 20-25 ppb.
Accuracy should meet a ±20% criterion, precision should meet a 20 relative percent difference (RPD)
criterion, and MBs/ICBs/CCBs should be less than 7.5 ppb or a level appropriate to project objectives,
generally specified as one-half the PQL or project RL.
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In general, the method demonstrated the ability to perform within the specified QC criteria. Method
development indicated that when ISE sensitivity was diminished by the matrix, QC sample recoveries at all
concentrations were affected. Corrective actions included re-conditioning the ISE module with acidified
blanks and 100-2000 ppb perchlorate solutions (refer to Section 1.3.2.1, below), verification and correction of
operating temperature (refer to Section 1.3.2.3, below), or recalibration and reanalysis of affected samples.
The most significant QC failures were due to matrix interferences that caused a positive bias followed by loss
of sensitivity. Analysis of QC samples between every field sample allowed the problematic samples to be
singled out and the matrix interference to be identified as carbonate/bicarbonate. Nitrate was later found to
cause similar interference during interference studies. Adjustment of pH to 4.0 was implemented to eliminate
carbonate/bicarbonate interference, and all samples were successfully reanalyzed (refer to Sections 1.3.2.6,
4.1, and 4.2). Implementation of reconditioning between samples acceptably mitigated the loss of sensitivity
due to nitrate (refer to Sections 1.3.2.1, 1.3.2.8, and 4.4).
1.3.2 Method Variables
Samples and standards were analyzed at different concentrations in different sequences on many different
dates, varying certain parameters such as ISE module conditioning, sample volume, stirring, temperature,
amounts and composition of ISA, pH, and matrix effects. The effects of different variables are discussed in
this section.
1.3.2.1 Perchlorate ISE Module Conditioning
ISE manufacturers recommend preconditioning ISE modules in perchlorate solutions prior to use. Periodic
reconditioning of the ISE is also recommended during the analytical sequence. For maximum effectiveness,
conditioning solutions should be prepared the same as the standards and samples, including ISA and pH
adjustment, as appropriate. Sentek recommends conditioning their perchlorate ISE modules in a perchlorate
solution at a concentration equivalent to the lowest calibration standard for 10 minutes. Orion specifies
preconditioning a new unit in 100 ppm solution for one-to-two hours, and storing the unit in the same solution
between analyses; however, the Orion unit was not used in method development, and no recommendations for
conditioning the Orion ISE are included in this section.
For the Sentek ISE, the manufacturer-specified working range is 200 ppb to 99,500 ppm and the low standard
would be 200-500 ppb; whereas for the low concentration method, the low standard is 10 ppb. During
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method development with the Sentek ISE, conditioning solution concentrations of 10 ppb, 50 ppb, 500 ppb, 2
ppm, and 50 ppm were tried. Conditioning with 10 ppb was found to be ineffective, and 50 ppm was found to
destabilize low-end sensitivity. A 500 ppb solution was found to work well for preconditioning of the ISE
module.
During field sample analyses, stabilization of the millivolt readings generally took longer than for calibration
standards, most likely due to chemical contaminants from the samples blocking perchlorate electrode or
reference electrode conductivity sites in the ISE module. When time required for millivolt readings to
stabilize became excessive, or if low recoveries for check standard recoveries were encountered after analysis
of field samples, reconditioning of the ISE in a 100 ppb perchlorate solution acidified to pH 4 was generally
found to work effectively, decreasing stabilization time and increasing sensitivity and accuracy. In addition,
the acidification of samples and blanks was found to increase sensitivity without adversely affecting
performance.
Some anions, notably nitrate, and possibly some organic chemicals, appeared to be the cause of electrode
sensitivity loss. During method development, sample matrices with nitrate concentrations greater than 0.2
ppm N03-N were found to require implementation of reconditioning between every sample analysis to
maintain sensitivity. As concentrations of nitrate increased, stronger solutions of perchlorate were required to
recondition the ISE in a reasonable amount of time, with 2000 ppb perchlorate solutions found most effective
in maintaining sensitivity and accuracy when analyzing samples with nitrate concentrations above 2.0 ppm
NO3-N.
Therefore, for the low concentration method, preconditioning the Sentek perchlorate ISE with a 500 ppb
perchlorate solution daily prior to analyses, and reconditioning with 100-2000 ppb perchlorate solutions at a
frequency applicable to the matrix being analyzed is specified in the method. Reconditioning frequency may
range from the use of a 100 ppb perchlorate standard once or twice a day or once per analytical sequence of
10 field samples (12 analyses including MB and CCV) for cleaner matrices, to use of a 2000 ppb solution
between every sample for samples with high nitrate or other loss-of-sensitivity interferents.
Reconditioning includes soaking the perchlorate ISE in deionized water acidified to pH 4.0 for one minute to
clean interfering ions from the electrode membrane; followed by immersion in a 100-2000 ppb perchlorate
solution acidified to pH 4 for one to six minutes, depending on time required for millivolt readings to
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stabilize, to regenerate perchlorate sites in the ISE membrane. The ISE should then be allowed to restabilize
in a blank prior to sample analysis.
Use of 500 or 2000 ppb concentration solutions should be progressively implemented when the 100 ppb
solution is found not to regenerate sensitivity within four to six minutes, or after analysis of any sample with
known high concentrations of nitrate. Use of stronger solutions does not adversely affect accuracy, but
requires additional time for the ISE to restabilize in a blank before sample analysis.
Acid blanks and perchlorate conditioning solutions should be adjusted with ISA and sulfuric acid the same as
the standards and samples. All reconditioning protocols applied to field sample analyses must be applied to
analyses of QC samples as well.
Even when reconditioning is not required due to nitrate, routinely storing the ISE briefly in a 20 ppb
perchlorate standard followed by a thorough rinse between each sample was found to help maintain sensitivity
in general. This can lead to faster analysis times because millivolt readings stabilize more quickly, with fewer
reanalyses required due to declining check standard recoveries.
When sensitivity for a specific ISE module is found to decrease with extended use, Sentek recommends using
an abrasive such as fine emery paper to renew the exposed PVC surface of the electrode. See manufacturer
directions for this procedure. If sensitivity cannot be restored, the ISE module must be replaced. Note that
exposure to samples containing organic solvents may permanently degrade the electrode membrane.
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1.3.2.2 Sample Volume and Stirring
The initial studies were conducted using 50 mL of standard and no stirring mechanism. The Orion ISE was
not able to differentiate between 20 to 100 ppb standards under these conditions, and the Sentek ISE was not
able to meet linearity requirements. The use of200 mL and a magnetic stirrer made a significant difference in
the ability of the Sentek ISE to perform at the required concentrations. Therefore, the use of 200 mL of
standards and sample, and the use of a magnetic stirrer are considered to be essential elements for the
determination of perchlorate near the 18 ppb TDL. Note that due to low volumes of sample provided for the
first round of split samples, sample volumes of 120 mL were successfully analyzed; however, the use of 200
mL is recommended.
1.3.2.3 Temperature Effects
During method development, millivolt readings were found to be very slow in stabilizing at temperatures
below 19°C. As temperatures increased above 20°C, readings were found to stabilize much more readily. At
16-20°C, readings for the lowest concentration standards could take 10 minutes to stabilize enough to read. At
20-25°C, the same standards took less than five minutes to stabilize. In addition, the millivolt readings
increase with temperature, lowering the concentration readout for perchlorate. Calibrations and sample
analyses should be performed an approximately constant temperature.
A study of the effect on temperature was conducted on January 29, 2001, as presented in Table 1-5. For a
standard with a true value of 20 ppb perchlorate and a found value of 19.9 ppb at 25.5°C, the following
changes in concentration with respect to temperature were noted. The most significant effects were noted at
lower temperatures. With temperature increases from 10.0°C to 12.5°C, a 27.2 ppb decrease in the reading
for perchlorate was noted (10.9 ppb/°C). From 19°C to 21.5°C the decrease was 7.8 ppb (3.1 ppb/°C) and
from 21.5°C to 24.0°C the decrease was 5.5 ppb (2.2 ppb/°C). At higher temperatures, the effect was less
pronounced. From 27.5°C to 32.5° the decrease was 7.0°C (1.4 ppb/°C). Additional temperature studies for
other concentrations (method blank, 10 ppb, and 50 ppb) are suggested for future study.
As with all ISE methods, accuracy is best if calibration standards and samples are analyzed at the same
temperature. However, as a field screening method this may not always be possible. The effect of
temperature variation will be minimized as long as the temperature exceeds 22°C and is kept constant to
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U.S. Army Corps of Engineers
within a few degrees. If the temperature changes such that QC sample results are not within control limits, a
recalibration must be performed (refer to Task 3 Letter Report of Findings).
As the temperature of all standards and samples must be the same for accurate analysis, all standards or
samples stored in a cooler or refrigerator must be allowed to warm to ambient temperature before analysis.
Due to the stability of perchlorate in aqueous samples at room temperatures, samples and working standards
may remain at room temperature overnight. Samples or standards should not be warmed by exposure to
sunlight or other light sources, as perchlorate concentrations may be affected by ultraviolet light.
1.3.2.4 Ionic Strength Adjustors (ISA)
ISA solutions are made from the same chemicals present in the reference electrodes for each ISE. For ISE
analyses to succeed, all standards and samples must be at approximately the same background ionic strength.
Therefore, ISA is added to all standards and samples.
Two ISAs were used in method development, and both were found to work acceptably. The manufacturer-
recommended standard amount of ISA for the Orion ISE is 2 mL of 2.0 molar (M) ammonium sulfate per 100
mL sample when operating in the normal operating range (0.7 - 98,500 ppm). The Orion low-level
measurement procedure specifies use of 1 mL 0.4 M ISA per 100 mL sample (10% of the standard Orion
ISA). Sentek specifies use of 2 mL of their 1.0M sodium acetate "Perchlorate ISAB" per 100 mL sample
(ISAB refers to the buffering capacity of this ISA) when operating in the normal operating range (0.2 -
98,500 ppm). The Orion ammonium sulfate ISA is referred to hereafter as "ISA," and the Sentek sodium
acetate ISA is referred to hereafter as "ISAB." Approximately half the method development work and half
the sample analyses were performed with each type of ISA.
Initial studies included an attempt to use no ISA. The attempt to use no ISA was not successful, and is
considered inappropriate for determination of perchlorate at the low concentrations required to meet the TDL.
On January 9, 2001 calibrations were performed using 2 mL, 3 mL, 4 mL, 5 mL, and 11 mL of 0.4 M ISA per
200 mL sample to determine the effects of differing ISA concentrations on method parameters, as presented in
Table 1-6. The calibration with the best coefficient of determination and the steepest slope was the 5 mL of
0.4 M ISA per 200 mL sample, approximately equivalent in concentration to 25% of the standard Orion
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amount of ISA. Similar coefficients of determination and slopes resulted from use of the ISAB at 25% of the
manufacturer recommended amount during subsequent method development.
Therefore, 25% of the standard ISAB or 10-25% of standard Orion ISA were determined to be appropriate for
the low concentration method. These levels of ionic strength adjustment maintain linearity down to the
lowest calibration standard, support check standards of 5 ppb, and the resulting conductivities in the standards
appropriately adjust the background ionic strength to functionally equivalent levels for standards and field
samples.
Parallel calibrations using 2 mL and 5 mL of 0.4 M ISA per 200 mL sample were maintained on January 10,
2001; and 5 mL and 10 mL of 0.4 M ISA per 200 mL sample were maintained on January 12, 2001. Field
samples were analyzed with both concentrations of ISA for each of these dates during investigation of matrix
effects related to sample conductivity (refer to Table 1-7). Perchlorate readings for the analyses of QC
samples and field samples from the parallel calibration curves were within 5% (refer to readings highlighted
in bold in Table 1-7), demonstrating that effectively there was no difference in accuracy forthe different ISA
concentrations. After January 12,2001, 1 mL of 1M ISAB per 200 mL sample was used for further method
development studies (25% of manufacturer-recommended strength).
Millivolt readings for the different amounts of ISA were not significantly different for each level of ICAL
standard in the calibrations for each date or forthe different samples and QC samples in Tables 1-6 and 1-7.
Further indication that accuracy and precision are not affected by the different ISA solutions was provided by
the results of the MDL studies. MDL studies using ISA (Table 1-3) and ISAB (Table 1-4) independently
provided MDLs of 3 ppb. The acceptable calibrations and low concentration check standards achieved with
both ISA and ISAB demonstrate that there was no difference in sensitivity for the different ISA/ISAB
concentrations. Thus, different levels of background ionic strength adjustment in samples do not appear to
significantly affect perchlorate readings, as long as minimum adjustment equivalent to 10% of the Orion ISA
or 25% of the Sentek ISAB are used.
As the conductance of a sample matrix is proportional to the common anions present in the matrix,
conductivities of ISA standards (refer to Table 1-8) and samples (refer to Table 1-9) were measured in
microsiemens/cm (uS/cm) or microMhos/cm (uMhos/cm), which are considered equivalent terms, during the
ISA studies and during split sample analyses to determine relative ionic strengths. Studies of the conductivity
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U.S. Army Corps of Engineers
of different concentrations of ISA with no pH adjustment were performed on January 8, 2001 (refer to Table
1-8A). The lowest concentration ISA in this study (2 mL 0.4 M ISA per 200 mL sample) was the
concentration specified in the Orion low-level procedure, equivalent to 10% of the standard Orion ISA. The
highest concentration ISA was approximately equivalent, when corrected for additional volume, to 50% of the
standard Orion ISA. Additional studies of the conductivity of different concentrations of ISA at pH 4, and
ISAB without pH adjustment and at pH 4 were performed onApril23,2001 and May 1,2001 (refer to Tables
1-8B through 1-8D). Conductivity did not significantly change for the ISA solutions with acidification to pH
4, as very little acid was required to effect pH changes (Tables 1-8A and 1-8B). More significant
conductivity changes were effected by acidification for the ISAB solutions with acidification to pH 4 due to
the buffering capacity of ISAB (Tables 1-8C and 1-8D).
The ionic strengths for ISA and ISAB adjusted solutions are approximately the same for the amounts of ISA
used for method development and recommended for the low concentration method. For the ISA, 2 mL of 0.4
M ammonium sulfate per 200 mL of sample produces a 3.96 millimolar (mM) solution with 11.88
milliequivalents per liter (meq/L) of individual ions; whereas for the ISAB, I mL of 1.0 M sodium acetate
produces a 4.98 mM solution with 9.95 meq of individual ions per liter (refer to Tables 1-8E and 1-8F,
highlighted data; and Table 1-8F graph). Note that each formula weight of ammonium sulfate contributes
three ions and sodium acetate contributes two ions. Although the ISA ionic strength adjustment (meq/L) is
slightly higher than the ISA adjustment, the conductivity for the ISA adjusted solution is significantly higher
due to the higher conductivity of the ions in ammonium sulfate than those in sodium acetate (refer to labeled
points on Table 1-8E graph).
Therefore, for the low concentration perchlorate method, either the Sentek ISAB can be used at 25% of
manufacturer-specified strength or the Orion ISA can be used at 10-25% of the standard manufacturer-
specified strength. For the Sentek ISAB, the use of 1 mL of Sentek Perchlorate ISAB (1.0 M sodium acetate)
per 200 mL sample is recommended. For the Orion ISA, the use of 2-5 mL of 0.4 M ammonium sulfate per
200 mL of sample, or 0.4-1.0 mL of Orion 930711 ISA (2.0 M ammonium sulfate) per 200 mL sample is
recommended. Further study is recommended to determine whether higher adjustment by ISA or ISAB may
be appropriate for samples with high background ionic strength, including samples with high levels of nitrate.
All standards and samples should be spiked with proportionally equivalent concentrations of the same ISA.
Different concentrations of ISA or ISAB should not be used interchangeably within a calibration, although
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U.S. Army Corps of Engineers
minor changes in ISA are not expected to significantly affect data quality. Note that concurrent calibrations
can be maintained for any differences in adjustments to samples (such as pH, ISA/ISAB concentration, or
temperature) by making the same adjustments to the standards.
1.3.2.5 Matrix Effects
As method development progressed, split samples from Edwards AFB were analyzed to determine whether
definitive analytical results for perchlorate by ion chromatography (IC) according to EPA Method 314.0
could be reproduced by ISE using the low concentration method (refer to Table 1-9), and to investigate
method performance for a field matrix. These analyses immediately indicated both positive and negative
matrix interferences, so matrix interferences were systematically evaluated, starting with conductivity, then
specific anions (refer to Section 4.0 and Tables 4-1 through 4-6).
Although a direct relationship between false positive readings and conductivity was noted, some samples
caused significant loss of electrode sensitivity as well. From background information on the sampling
locations, the most likely significant interferents were determined to be carbonate/bicarbonate, chloride, and
nitrate. Bromide, fluoride, iodide, phosphate, and other anions such as thiocyanate were also identified as
interferents in the ISE manufacturer specifications. Carbonate/bicarbonate, chloride, bromide, fluoride,
nitrate, and phosphate were investigated in the current study.
Addition of sulfuric acid to adjust all samples and standards to pH 4.0 was found to effectively remove
carbonate/bicarbonate interference (see Section 1.3.2.6, below). Corrections must be applied for chloride,
nitrate, and bromide interference if applicable to the matrix (see Sections 1.3.2.7,1.3.2.8, and 1.3.2.9, below).
If anion concentrations are not available for field samples and are suspected to be causing false positives or
other unacceptable interference, ion-specific ISEs can be used to determine chloride, nitrate, and/or bromide
with the same ISE meter used for the perchlorate determinations. Alternatively, analysis by the method of
standard additions (MSA) may be used to compensate for unknown anion interference (refer to Section 4.9),
especially for perchlorate readings less than 30 ppb. However, further studies ofthe effectiveness of MSA to
compensate for anion interferences are required.
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Additional interference from organic chemicals is also considered possible, and further study is
recommended. For a detailed description of the interference studies, refer to the Task 4 Letter Report of
Findings, Section 4.0.
1.3.2.6 pH Adjustment
The most troublesome patterns of interference in the initial attempts to analyze split samples from Edwards
AFB were false positives followed by low perchlorate readings and low recoveries of QC check standards.
After some experimentation, specific samples were isolated that caused a false positive bias with loss of
sensitivity for the subsequent analyses (for example, see samples P-6, P-7, P-8, P-9, P-14, P-16, and P-19 in
Table 4-10). Suspecting carbonate/bicarbonate as the interferent, tests on sodium bicarbonate spiked
standards at pHs of 8.0 (bicarbonate present), 6.7 (carbonate present), and 4.0 (no carbonate/bicarbonate)
determined that the effect could be eliminated by acidification to pH 4.0 with sulfuric acid (refer to Tables 4-
1,4-2, 4-11, and 4-12).
Subsequent testing of field samples and sodium bicarbonate spiked standards with all calibration standards,
spiked standards, and field samples acidified to pH 4.0 demonstrated the ability of the method to work
effectively at this pH with no loss of sensitivity after analysis of samples high in carbonate/bicarbonate. Due
to the high prevalence of carbonate and/or bicarbonate in environmental samples and potential difficulties in
determining levels of carbonate/bicarbonate in field samples to be analyzed by this method, the acidification
of all standards and samples to pH 4.0 with sulfuric acid has been incorporated into the low concentration
method. In addition, the acidification of standards and samples to pH 4.0 results in steeper, more linear
calibration curves, and appears to aid in the maintenance of sensitivity of the perchlorate ISE modules.
For a detailed discussion of the carbonate/bicarbonate interference studies, refer to the Letter report of
Finding for Task 4, Sections 4.1 and 4.2.
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U.S. Army Corps of Engineers
1.3.2.7 Chloride Correction
A correlation was noted between historical levels of chloride at sample locations, with apparent false positives
reported for perchlorate in samples with 100-500 ppm chloride by this method. These false positives were
reduced to non-detected levels when chloride and other interference correction factors were applied (refer to
Task 5 Letter Report of Findings).
A chloride interference study was performed on January 18 and 22, 2001 to determine the relationship
between chloride and bias for perchlorate readings. At pH 4.0, positive bias of 0-12 ppb perchlorate was
noted for chloride concentrations of 0-500 ppm in standards with less than 30 ppb perchlorate. For standards
with perchlorate above 30 ppb, the bias becomes less significant, then becomes negative at higher
concentrations. At pH 7.0, bias is insignificant at low concentrations and negative at higher concentrations.
Tables presenting chloride bias at pH 4.0 and pH 7.0 are presented in Tables 4-2A, 4-2B, and 4-2C.
The ISE manufacturer recommended protocol for the removal of chloride and several other ions listed as
interferents is addition of silver sulfate to all standards and samples. The addition of silver sulfate would be
costly, would result in additional waste disposal problems, would create solids in the solutions which would
be difficult to remove and when stirred for analysis could potentially interfere, and would generally impose
unacceptable difficulties on the use of this method as a field screening method.
Since the interferences due to chloride are relatively small, Table 4-7 was developed to correct perchlorate
readings for chloride interference. In general, chloride interference is expected to cause significant accuracy
problems only when perchlorate readings are between the RL (suggested to be 15 ppb) and 45 ppb (at pH
4.0), in which case chloride could contribute significantly to positive bias. The data indicate that for readings
above this level, chloride interference is negligible or may cause negative interference. For perchlorate
readings above 40 ppb, sample dilutions can be used to determine if interference is affecting results in such a
way as to affect project objectives.
If chloride concentrations are not available for field samples and chloride levels are suspected to be causing
false positives or positive bias, a chloride ISE can be used to determine chloride using the same ISE meter to
be used for the perchlorate determinations. Alternatively, analysis by MSA may be used to compensate for
unknown anion interference, especially for perchlorate readings less than 30 ppb, although further studies of
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the effectiveness of MSA to compensate for anion interferences are required (refer to Section 4.9).
Definitive-level analyses should be performed whenever project objectives may be affected by indeterminate
bias.
For a detailed discussion of the chloride interference studies, refer to the Letter report of Finding for Task 4,
Section 4.3.
1.3.2.8 Nitrate Correction
An initial nitrate interference study was performed on February 18, 2001 to determine the relationship
between nitrate and bias for perchlorate readings. Additional nitrate interference studies were performed
April 30 and May 1, 2001 to verify the findings of the initial study and extend the range of concentrations
studied. At pH 4.0, positive bias of 2.75 ppb to greater than 70 ppb perchlorate was noted for concentrations
of 0.11 ppm to 10 ppm N03-N in standards with no perchlorate. (Note that nitrate is most commonly
measured and reported in mg/L nitrate-as-nitrogen [ppm N03-N]. The same results when reported as nitrate
are 4.43 times the results reported as nitrogen.) The data indicate positive interference at all concentrations of
nitrate in all concentration standards of perchlorate, with potential interference of two or more times the RL at
high levels of nitrate (refer to Tables 4-3A and 4-3B).
There is no suggested method for removal of nitrate interference in ISE product literature. Therefore, the
application of correction factors to perchlorate readings according to Table 4-8 should be applied when N03-
N levels exceed 0.12 ppm. In addition, N03-N concentrations greater than 0.2 ppm cause loss of sensitivity to
the electrode, requiring reconditioning of the ISE module in an acidified blank and an acidified 100-2000 ppb
perchlorate solution between every analysis to maintain adequate sensitivity to meet ±20% accuracy criteria
during analytical runs in which such levels of nitrate are expected or encountered in field samples.
For matrices with levels less than 0.12 ppm N03-N, positive interference for perchlorate readings will not
significantly exceed the ±20% accuracy criterion for this method, and correction of perchlorate readings may
not be necessary. If nitrate concentrations are not available for field samples and nitrate levels are suspected
to be causing false positives or other unacceptable interference, a nitrate ISE can be used to determine nitrate
with the same ISE meter used for the perchlorate determinations. Alternatively, analysis by MSA may be
used to compensate for unknown anion interference, especially for perchlorate readings less than 30 ppb,
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although further studies of the effectiveness of MSA to compensate for anion interferences are required (refer
to Section 4.9). Definitive-level analyses should be performed whenever project objectives may be affected
by indeterminate bias.
For a detailed discussion of the nitrate interference studies, refer to the Letter report of Finding for Task 4,
Section 4.4.
1.3.2.9 Bromide Correction
A bromide interference study was performed on March 1,2001 to determine the relationship between nitrate
and bias for perchlorate readings. At pH 4.0, positive bias of 0-8 ppb perchlorate was noted for bromide
concentrations of 0-5 ppm. The data indicate positive interference at all concentrations of bromide in all
concentration standards of perchlorate, with potential interference less than 10 ppb unless bromide exceeds 5
ppm (refer to Table 4-4).
The suggested method for removal of bromide is the addition of 1.0 gram of silver sulfate per 200 mL sample
to all standards and samples, which would generally impose unacceptable difficulties on the use of this
method (refer to Section 1.3.2.7, above). For concentrations of bromide normally expected in environmental
samples, bromide interference is not expected to significantly affect perchlorate results by this method. The
application of correction factors to perchlorate readings according to Table 4-9 has been included for use if
bromide concentrations greater than 1.2 ppm are determined to be present in samples.
For most matrices, bromide levels will be less than 1.2 ppm, and positive interference for perchlorate readings
will not exceed the ±20% accuracy criterion for this method. If bromide concentrations are not available for
field samples and bromide levels are suspected to be causing false positives or other unacceptable
interference, a bromide ISE can be used to determine bromide with the same ISE meter used for the
perchlorate determinations. Alternatively, analysis by MSA may be used to compensate for unknown anion
interference, especially for perchlorate readings less than 30 ppb, although further studies of the effectiveness
of MSA to compensate for anion interferences are required (refer to Section 4.9). Definitive-level perchlorate
analyses should be performed whenever project objectives may be affected by indeterminate bias.
For a detailed discussion of the bromide interference studies, refer to the Letter report of Finding for Task 4,
Section 4.5.
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1.3.3 Split Sample Analyses
To help establish method accuracy and precision for environmental field samples, split samples from Edwards
AFB were analyzed during method development. Definitive analyses were performed by E.S. Babcock &
Sons, of Riverside, California according to EPA Method 314.0 (or CADOHS Modified EPA Method 300.0
for perchlorate). The known results of the definitive analyses for the first round of split sampling were used
to investigate the effects of variations in the method to identify and mitigate matrix interferences and achieve
results consistent with the definitive analyses. These split sampling results are included in Table 1-9. Results
of all split sample analyses are discussed in detail in the Letter Report of Findings for Task 5, Section 5.0.
1.4 Method Development Conclusions
Method development studies for the Low Concentration Method for the Determination of Perchlorate in
Aqueous Samples Using Ion Selective Electrodes indicate that the solid state perchlorate ISE with built-in
reference electrode can be effectively used to determine if perchlorate is present in water at or above the
project TDL and California action limit of 18 ug/L (ppb), and can be used to determine perchlorate in
aqueous samples at concentrations from 15-100 ppb.
Perchlorate readings measured by the method at less than the 15 ppb RL can reliably be considered to be non-
detected within 20% of the reported concentration (the method utilizes a ±20% accuracy criterion).
Perchlorate readings above 15 ppb may be biased high due to anion interference. Such samples require
knowledge or determination of the levels of chloride and N03-N, and correction of perchlorate readings
according to Tables 4-7 and 4-8. Therefore, perchlorate readings between 15-30 ppb for samples with
chloride concentrations of 30-500 ppm may be corrected to less than 15 ppb perchlorate. If N03-N exceeds
0.2 ppm, reconditioning of the electrode between every sample is necessary. Perchlorate readings greater than
15 ppb for samples with N03-N concentrations exceeding 0.12 ppm may be corrected to less than 15 ppb
perchlorate. In matrices for which bromide exceeds 1.2 ppm, additional corrections may be required
according to Table 4-9.
In cases where significant corrections lower results to below project action limits, the data user may decide
that definitive-level analyses are required to confirm the presence or absence of perchlorate, or to confirm bias
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due to chloride, nitrate, or other interferents. For samples with unknown levels of interfering anions, analysis
by MSA may have the potential to compensate for unknown anion interference, especially for perchlorate
readings less than 30 ppb.
1.5 Method Development Recommendations
Further studies are recommended to reconfirm the accuracy of the chloride, nitrate, and bromide correction
factors, and to study the effects of other potential interferents and mixtures of interfering anions. Possible
methods to mitigate nitrate interference, including use of different type or concentrations of ISA should be
explored to make the method more versatile. Further studies to determine and maximize the effectiveness of
MSA are required.
2.0 Task 2 - Investigate Sample Concentration Methods
Task 2 specifies the investigation of the robustness and effectiveness of sample concentration methods for
perchlorate in water analyses including sub-boiling point heating, heating to boiling point, and room
temperature evaporation. Task 4 specifies the investigation of potential interferences for the low-level ISE
screening method. Method development determined that in distilled water, the method detection limit (MDL)
of 3 ug/L (parts per billion - ppb) allows for a reporting limit (RL) of 15 ppb, which meets the proj ect target
detection limit (TDL) and California action limit of 18 ppb with a 20% leeway for analytical accuracy.
However, when the method was applied to sample matrices for groundwater split samples from Edwards
AFB, problems with multiple interferences became apparent. Preconcentration of samples was therefore
deemed counterproductive, as the detection limits are low enough and additional concentration of samples
increases the matrix interference. Therefore, Task 2 was combined with Task 4 so additional work could be
performed to resolve the matrix interferences in the split samples, and to determine what steps could be
included in the method to effectively remove the interferences. For a complete discussion of the investigation
of matrix interferences, please refer to Section 4.0.
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3.0 Task 3 - Preparation of Revised Standard Operating Procedure
This section presents the Standard Operating Procedure (SOP) for the Low Concentration Method for the
Determination of Perchlorate in Aqueous Samples Using Ion Selective Electrodes, d3.
A Preliminary Draft SOP for the Low Concentration Method for the Determination of Perchlorate in Aqueous
Samples Using Ion Selective Electrodes was prepared prior to the analysis of split samples for this project.
The revised SOP is presented as the result of method development (refer to Letter Report of Findings for Task
1, Section 1.0), including method-specific information determined from matrix interference studies (refer to
Letter Report of Findings for Task 4, Section 4.0), and the first round of split sample analyses (refer to Letter
Report of Findings for Task 5, Section 5.0). The SOP is presented as Attachment 1.
4.0 Task 4 - Investigation of Interference Using ISE Protocol
This section of the letter report of findings presents the results of matrix interference studies for the Low
Concentration Method for the Determination of Perchlorate in Aqueous Samples Using Ion Selective
Electrodes, as required for combined Tasks 2 and 4. Task 2 was combined with Task 4 so additional work
could be performed to resolve complex matrix interferences after it was determined that the preconcentration
of samples specified in Task 2 would result in increased matrix interference (refer to Section 2.0).
Task 4 specifies the investigation of potential interferences for the ions specified as interferents in the product
literature for the perchlorate ISEs, and the recommendation of items for further study based on the findings. In
addition to the investigation of six anions for matrix interference, the known results of definitive analyses for
groundwater split samples from Edwards AFB were used to determine and resolve field sample matrix
interferences.
Specific interferences due to carbonate/bicarbonate, bromide, chloride, fluoride, nitrate, and phosphate were
identified and quantitated (refer to Tables 4.1 through 4.6). Although listed as primary interferents in the
perchlorate ISE instrument documentation, thiocyanate and iodide were not investigated as these anions are
not commonly identified in samples at Edwards AFB, where the study was based.
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Carbonate and bicarbonate interferences were identified and removed by acidification of samples and
standards to pH 4.0 with sulfuric acid. Chloride at the 50-500 ppm concentrations in the split samples was
found to be an interferent requiring corrections to perchlorate readings according to Table 4.7. Nitrate was
found to interfere significantly at concentrations greater than 0.12 ppm nitrate-as-nitrogen (N03-N). For
samples with greater than 0.12 ppm N03-N, corrections to perchlorate readings according to Table 4.8 are
required, and reconditioning of the ISE module between every sample is required when matrices with N03-N
concentrations greater than 0.2 ppm are encountered. Bromide was found to interfere at concentrations
greater than 1.2 ppm, which is higher than is typically found in environmental samples. For bromide, if
sample concentrations exceed 1.2 ppm, corrections to perchlorate readings according to Table 4.9 are
required. Fluoride and phosphate were found not to interfere in perchlorate quantitation. Dilution and
reanalysis may be appropriate to confirm applied correction factors. Interference greater than 20% of the
concentration in a perchlorate standard, or 20% of the 15 ppb RL for perchlorate standards less than the RL,
was considered to be significant for the purposes of these studies.
The use of the method of standard additions (MSA) was found to have potential to compensate for unknown
anion interference for samples with unknown levels of interfering anions, especially for perchlorate readings
less than 30 ppb.
4.1 Field Sample Matrix Interferences
As method development progressed, split samples from Edwards AFB were analyzed by the low
concentration ISE method to determine whether definitive analytical results for perchlorate by ion
chromatography (IC) according to EPA Method 314.0 could be reproduced by ISE using the low
concentration method. The ISE analyses immediately indicated both positive and negative matrix
interferences with a strong correlation of false positives to conductivity, so potential matrix interferences were
systematically evaluated by a review of historical results for the wells, where available (refer to Table 1.9).
The strongest correlations were between false positive perchlorate readings and carbonate/bicarbonate and
chloride levels. In addition, significant loss of electrode sensitivity after analysis of some samples with false
positive readings was noted. Several sequences of analyses allowed identification of possible samples
causing loss of sensitivity, including samples P-7 and P-16, which had over 200 ppm alkalinity as CaC03,
and indicated the most likely cause to be carbonate/bicarbonate in the samples. Perchlorate readings for
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samples analyzed subsequent to sample P-7 were very low in spite of expected false positives due to known
concentrations of positive interferents, and were associated with 69% and 34% recoveries of check standards
after analysis of sample P-7 in data for two analytical runs on January 11,2001. Sample P-16 demonstrated
the same effect, causing a 46% recovery of the check standard on January 15, 2001 (see Table 4-10).
Adjustment of pH to 4.0 with sulfuric acid, which converts bicarbonate and carbonate to carbon dioxide,
reduced the false positives significantly (for example, refer to Table 1-9, sample P-16) and removed the
negative interference caused by loss of sensitivity, as demonstrated by acceptable recoveries of check samples
during acidified reanalyses of samples previously associated with low recoveries in non-acidified analytical
runs (see Table 4-10). Correction of chloride interference according to Table 4-7, with additional minor
corrections for low concentrations of nitrate and bromide according to Tables 4-8 and 4-9, then produced
excellent agreement between split sample results, with the exception of samples P-l and P-l 1, which required
significant corrections due to high levels of nitrate.
The results highlighted in bold in Table 1-9 for samples P-6 through P-9, P-16, and P-l9 demonstrate the
corrective effects of acidification and chloride, nitrate, and bromide correction factor subtraction; and the
results for samples P-l and P-l 1 (and samples P-102, P-103, and P-104, resampled for sample P-11)
demonstrate additional significant corrections for high levels of nitrate.
Additional interferences due to other anions were not apparent in the split samples. Interference due to
fluoride and phosphate were investigated with no effective interference demonstrated. Specific anion
interference studies are discussed in the following sections.
Samples with high known concentrations of organic contaminants were not analyzed due to the potential for
deterioration of the ISE module. In general, samples with high concentrations of organics are not
recommended for analysis by ISE as organic solvents are known to deteriorate the ISE membranes.
4.2 Carbonate/Bicarbonate Interference Studies
Carbonate and bicarbonate are listed in ISE product literature as being primary interferents for perchlorate
analysis by ISE. Acidification of samples using sulfuric acid is the suggested method for removal of the
interference. Bicarbonate exists only in samples at pH greater than 8.3. Below pH 8.3, bicarbonate is
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U.S. Army Corps of Engineers
converted to carbonate. Below pH 4.5, total conversion of carbonate to carbon dioxide is expected. As
significant levels (greater than 100 ppm total alkalinity as calcium carbonate) of carbonate and/or bicarbonate
are commonly found in environmental samples at Edwards AFB and other groundwater sample matrices, and
as these ions were identified as causing interference for the low concentration perchlorate method,
interference studies of these anions were performed during method development.
Bicarbonate spiking solutions were prepared from reagent grade sodium bicarbonate. On January 22, 2001,
analysis of a 10 ppb perchlorate standard spiked with 50 ppm bicarbonate produced a perchlorate reading of
19.6 ppb, confirming suspected positive interference for bicarbonate. Subsequent analysis of this spiked
standard acidified with sulfuric acid to pH 6.75 (bicarbonate converted to carbonate) and pH 4.0 (all
carbonate removed by conversion to carbon dioxide) produced significantly increased millivolt readings
indicative of sequential removal of positive bias for perchlorate (refer to Table 4-11). These millivolt
readings for the acidified standards could not be specifically quantitated using the non-acidified calibration, as
the millivolt readings for each level of perchlorate differ between acidified and non-acidified calibrations.
Analyses of a blank, 50 ppm, 100 ppm, and 300 ppm sodium bicarbonate solutions were then performed
without pH adjustment. The 50 ppm bicarbonate solution produced a positive reading for perchlorate of 25.1
ppb. The 100 ppm and 300 ppm bicarbonate solutions produced readings for perchlorate of 31.3 ppb and 38.3
ppb, respectively, indicating increasing positive bias with increasing bicarbonate concentration (refer to
Table 4-1A). However, due to loss of ISE sensitivity after analysis of each bicarbonate standard, as
demonstrated by the 60% recovery of the subsequent check standard, the positive interference at these
concentrations is expected to actually be higher. Again, acidification of the 300 ppm bicarbonate solution to
pH 4.0 increased the millivolt readings significantly to levels that indicate complete removal of the
interference.
To demonstrate the effectiveness of acidification of samples to pH 4.0 in removing carbonate/bicarbonate
interference (both immediate positive bias and subsequent negative bias due to loss of sensitivity), on January
23,2001 a calibration was performed using standards acidified to pH 4.0 with sulfuric acid (refer to Table 4-
12). Initially, blanks with 50 ppm, 100 ppm, and 300 ppm of sodium bicarbonate were analyzed at pH 6.8 to
demonstrate relative positive bias for the carbonate ion (specific bias could not be demonstrated as the
millivolt readings for the non-acidified standards could not be quantitated using the acidified calibration).
Blanks, 10 ppb, 20 ppb, and 50 ppb perchlorate standards with 50 ppm, 100 ppm, and 300 ppm of sodium
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U.S. Army Corps of Engineers
bicarbonate were then analyzed at pH 4.0. All of the perchlorate readings were within the ±20% accuracy
criterion, demonstrating effective removal of all interferences due to bicarbonate or carbonate, with no
residual loss of sensitivity (refer to Table 4-1B).
Note that during analysis of the carbonate samples (pH 6.8), recoveries of the 20 ppb perchlorate check
samples gradually decreased, and during analyses of the samples acidified to pH 4.0, the recoveries gradually
increased (refer to Table 4-12). From this trend it was inferred that conditioning of the ISE module with
acidified blanks helps counteract the loss of sensitivity caused by the carbonate/bicarbonate ions. This
conditioning was later applied to nitrate interference, and has been incorporated as part of the recommended
procedures in the method when loss-of-sensitivity interferences are expected or encountered.
To ensure complete removal of all carbonate and bicarbonate, the acidification of all samples and standards to
pH 4.0 has been incorporated into the low concentration method. This acidification appears to increase
linearity of calibrations as well as sensitivity, as demonstrated by consistent coefficients of determination
greater than 0.9975.
4.3 Chloride Interference Studies
Chloride is listed in ISE product literature as being a minor interferent for perchlorate analysis by ISE. As
significant levels of chloride (greater than 50 ppm) are commonly found in environmental samples at Edwards
AFB and other groundwater sample matrices, and as an obvious correlation was apparent between chloride
and false positives for perchlorate in the first round of split sample analyses, interference studies were
performed for chloride during method development.
Chloride spiking solutions were prepared from reagent grade sodium chloride. On January 18,2001, 10 ppb,
20 ppb, and 50 ppb perchlorate standards spiked with various combinations of 50 ppm, 100 ppm, 300 ppm,
400 ppm, and 500 ppm chloride were analyzed with no pH adjustment (refer to Table 4-13). On January 22,
2001, blanks spiked with 50 ppm, 100 ppm, 300 ppm, and 500 ppm chloride were analyzed with no pH
adjustment (referto Table 4-11). Minor positive interference was noted forthe blank and 10 ppb perchlorate
standards, and more pronounced negative interference was noted forthe 20 and 50 ppb perchlorate standards,
with greater interferences at higher chloride concentrations (refer to Table 4-2A).
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On January 18 and 25, 2001, blanks, 20 ppb, 40 ppb, and 70 ppb perchlorate standards spiked with 50 ppm,
100 ppm, 300 ppm, and 500 ppm chloride were analyzed with pH adjustment to 4.0 (refer to Tables 4-14 and
4-15). Positive interference was noted for the blank, 20 ppb, and 40 ppb perchlorate standards, and negative
interference was noted for the 70 ppb perchlorate standard (refer to Table 4-2B).
Additional analyses of a 50 ppb perchlorate standard spiked with 50 ppm, 60 ppm, 200 ppm, 1000 ppm, and
2000 ppm chloride; as well as 200 ppm, 1000 ppm, and 2000 ppm of chloride in blank, 20 ppb and 70 ppb
perchlorate standards were performed on April 24, 2001 to verify the point of inflection between positive and
negative bias, and extend the range of chloride concentrations studied (refer to Table 4-16). The additional
analyses confirmed levels of bias found previously for the 50-500 ppm chloride standards, and defined bias in
the 500-2000 ppm chloride range. The point of inflection between positive and negative bias was confirmed
to be at or marginally above 50 ppb perchlorate (refer to Table 4-2C).
The potential for significant interference of 3.0 ppb false positive (20% of the 15 ppb RL) in samples with
perchlorate concentrations less than 30 ppb commences at 50 ppm chloride, and rises to 12.5 ppb false
positive at 500 ppm chloride. For samples with perchlorate concentrations between 30 ppb and 50 ppb,
significant interference commences at 100 ppm chloride, and rises to 7.7 ppb false positive at 500 ppm
chloride. The data indicate that for samples with perchlorate concentrations above 50 ppb, chloride
interference becomes negligible then causes negative bias (refer to Table 4-2C). For samples with perchlorate
readings above 50 ppb, sample dilutions should be performed to determine if interference is affecting results
in such a way as to affect project objectives.
The suggested method for removal of chloride is the addition of 1.0 gram of silver sulfate per 200 mL sample
to all standards and samples. The addition of silver sulfate would be costly, would result in additional waste
disposal problems, would create solids in the solutions which would be difficult to remove and when stirred
for analysis could potentially interfere, and would generally impose unacceptable difficulties on the use of
this method. Therefore, the application of correction factors to perchlorate readings according to Table 4-7
has been implemented for the low concentration method. For samples with perchlorate readings above 30
ppb, dilution and reanalysis should be performed to help resolve the proportion of bias due to interference or
actual perchlorate in the samples. This table is applicable to readings using adjustment of pH to 4.0, since pH
adjustment is considered part of the low concentration method.
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U.S. Army Corps of Engineers
If chloride concentrations are not available for field samples and chloride levels are suspected to be causing
false positives or other unacceptable interference, a chloride ISE can be used to determine chloride with the
same ISE meter used for the perchlorate determinations. Alternatively, for samples with unknown levels of
chloride, analysis by MSA may be possible to compensate for unknown anion interference, especially for
perchlorate readings less than 30 ppb, although further studies of the effectiveness of MSA to compensate for
anion interferences are required. The use of MSA for samples with high levels of chloride may not be
effective (refer to Section 4.9). Definitive-level perchlorate analyses should be performed whenever project
objectives may be affected by indeterminate bias.
4.4 Nitrate Interference Studies
Nitrate is listed in ISE product literature as being an interferent for perchlorate analysis by ISE. Levels of
nitrate greater than 1.5 ppm N03-N are not generally found in environmental samples at Edwards AFB and in
many surface and groundwater sample matrices, however, an historical nitrate level of 12.6 ppm was reported
for sample P-l, which had a false positive reading for perchlorate of 70.6 ppb, indicating a possible
correlation between nitrate and false positives for perchlorate. Therefore, interference studies were performed
for nitrate.
Nitrate spiking solutions were prepared from reagent grade sodium nitrate and from a certified 100 ppm ion
chromatography calibration standard. On February 28,2001, blanks, 10 ppb, 20 ppb, and 50 ppb perchlorate
standards spiked with 0.11 ppm, 0.23 ppm, and 0.45 ppm nitrate-as-nitrogen (N03-N), equivalent to 0.5 ppm,
1.0 ppm, and 2.0 ppm nitrate reported as nitrate, were analyzed with pH adjustment to 4.0. In addition, a
blank spiked with 1.13 ppm and 2.26 ppm N03-N (5 ppm and 10 ppm nitrate) were analyzed to quantitate
potential false positives for higher levels ofnitrate (refer to Table 4-17). Positive interference was noted for
all concentrations of nitrate in all levels of perchlorate standards (refer to Table 4-3A). Note that nitrate is
most commonly measured and reported in mg/L (ppm) as nitrate-as-nitrogen (N03-N). The same results
when reported as nitrate are 4.43 times the results reported as nitrogen. All subsequent references will be to
nitrate reported as nitrogen, N03-N.
Additional nitrate interference studies were performed on April 3 0 and May 1,2001, to verify the findings of
the initial study and extend the range of concentrations studied (refer to Table 4-3B). Nitrate spiking
solutions were prepared from a certified 100 ppm nitrate (N03-N) standard prepared from potassium nitrate.
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Blanks and 20 ppb perchlorate standards spiked with 0.05 ppm, 0.1 ppm, 0.2 ppm, 0.5 ppm, 1.0 ppm, 2.0
ppm, 5.0 ppm, and 10 ppm N03-N were analyzed with pH adjustment to 4.0 (refer to Tables 4-18A and 4-
18B).
The potential for significant interference of 3.0 ppb false positive (20% of the 15 ppb RL) or greater than 20%
of perchlorate concentration commences at 0.12 ppm NO3-N, and the potential for a false positive reading
greater than the 15 ppb RL commences at approximately 0.5 ppm N03-N. In the initial study, for 0.45 ppm
NO3-N in a blank, a positive reading for perchlorate of 14.1 ppb, which is below the 15 ppb RL, was reported;
and in the extended study, for 1.0 ppm N03-N in a blank, a 19.0 ppb perchlorate reading was reported,
marginally exceeding the 18 ppb TDL and California action limit.
Note that the curves for nitrate interference were steeper in the initial study than in the follow-up extended
study at all concentrations of perchlorate and nitrate (refer to Table 4-3B). Interference values for low
concentrations of nitrate were within the ±20% accuracy criteria for the method in standards with up to 0.5
ppm NO3-N for both studies. However, the initial study curve for the blank spiked with nitrate diverges
significantly above 0.5 ppm NO3-N. This divergence is caused by the two high points on this curve, which
appear to exceed the predicted curve from the low points and the other initial study perchlorate standard
curves. The divergences may be due to nitrate solution precision, electrode condition, temperature, or other
factors affecting sensitivity, especially since perchlorate readings become significantly more sensitive to
changes in millivolt readings with increasing perchlorate concentration. However, all of the curves are
generally parallel, and the data indicate positive interference at all concentrations of nitrate in all
concentration standards of perchlorate, with potential interference of two to five times the RL in samples with
2-10 ppm NO3-N (refer to Table 4-3B). Due to the consistency of the interference curves for the blank and 20
ppb perchlorate standard in the extended study, these curves were used to generate the correction factors
presented in Table 4-8.
There is no suggested method for removal of nitrate interference in ISE product literature. Therefore, the
application of correction factors to perchlorate readings according to Table 4-8 has been implemented for the
low concentration method. In addition, nitrate at concentrations greater than 0.2 ppm NO3-N causes loss of
sensitivity to the electrode between every analysis to maintain adequate sensitivity to meet ±20% accuracy
criteria. Reconditioning of the ISE module in an acidified blank followed by an acidified 100-2000 ppb
perchlorate solution should be implemented during analytical runs in which such levels of nitrate are expected
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or encountered in field samples. The effectiveness of such reconditioning was demonstrated by the acceptable
recoveries for check standards analyzed between each nitrate-spiked standard during the February 28,2001
nitrate interference studies (refer to Table 4-17).
For matrices with nitrate levels less than 0.12 ppm, positive interference for perchlorate readings will not
exceed the ±20% accuracy criterion for this method and reconditioning of the electrode will not be necessary.
If nitrate concentrations are not available for field samples and nitrate levels are suspected to be causing false
positives or other unacceptable interference, a nitrate ISE can be used to determine nitrate with the same ISE
meter used for the perchlorate determinations. Alternatively, for samples with unknown levels of nitrate,
analysis by MSA may be possible to compensate for unknown anion interference, especially for perchlorate
readings less than 30 ppb, although further studies of the effectiveness of MSA to compensate for anion
interferences are required. The use of MSA for samples with high levels of nitrate may not be effective (refer
to Section 4.9). Definitive-level perchlorate analyses should be performed whenever project objectives may
be affected by indeterminate bias.
Nitrate was found to be the strongest interferent studied, and use of the low concentration method on matrices
with high concentrations of nitrate, especially if significant concentrations of other known interferents are
present or suspected, may not be appropriate without significant dilutions and raised detection limits.
4.5 Bromide Interference Studies
Bromide is listed in ISE product literature as being a potential interferent for perchlorate analysis by ISE;
therefore, interference studies were performed for bromide. Levels of bromide producing significant
perchlorate interference (greater than 1.2 ppm bromide) are not commonly found in environmental samples at
Edwards AFB or in most surface and groundwater sample matrices, so bromide interference is not expected to
affect the usability of the low concentration method.
Bromide spiking solutions were prepared from reagent grade potassium bromide. On March 2,2001, blanks,
10 ppb, 20 ppb, and 50 ppb perchlorate standards spiked with 0.5 ppm, 1.0 ppm, 2.0 ppm, and 5.0 ppm
bromide were analyzed with pH adjustment to 4.0 (refer to Table 4-19). Positive interference was noted for
all concentrations of bromide in all levels of perchlorate standards (refer to Table 4-4). Significant positive
interference (greater than 20% of the perchlorate concentration, or 20% of the 15 ppb RL for perchlorate
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U.S. Army Corps of Engineers
standards less than the RL) was noted for concentrations greater than 1.2 ppm bromide. For 2.0 ppm bromide
in a blank, a reading of 7.5 ppb was noted (versus 4.6 for a blank), and for 5 ppm bromide in a blank, a
positive reading for perchlorate of 10.5 ppb, which is below the 15 ppb RL, was noted. For 2.0 ppm bromide
in a 10 ppb perchlorate standard, a reading of 14.1 ppb was noted, and for 5.0 ppm bromide in a 10 ppb
perchlorate standard, a reading of 17.8 ppb was noted, which is below the 18 ppb TDL and California action
limit. Thus, the potential for a false positive perchlorate reading greater than 18 ppb due to bromide
interference is minimal.
The suggested method for removal of bromide is the addition of 1.0 gram of silver sulfate per 200 mL sample
to all standards and samples, which would generally impose unacceptable difficulties on the use of this
method (refer to Section 4.3, above). For concentrations of bromide normally expected in environmental
samples, bromide interference is not expected to significantly affect perchlorate results by this method.
However, the application of correction factors to perchlorate readings according to Table 4-9 has been
included for use if bromide concentrations greater than 1.2 ppm are determined to be present in samples.
For most matrices, bromide levels will be less than 1.2 ppm, and positive interference for perchlorate readings
will not exceed the ±20% accuracy criterion for this method. If bromide concentrations are not available for
field samples and bromide levels are suspected to be causing false positives or other unacceptable
interference, a bromide ISE can be used to determine bromide with the same ISE meter used for the
perchlorate determinations. Alternatively, for samples with unknown levels of bromide, analysis by MSA
may be possible to compensate for unknown anion interference, especially for perchlorate readings less than
30 ppb, although further studies of the effectiveness of MSA to compensate for anion interferences are
required (refer to Section 4.9). Definitive-level perchlorate analyses should be performed whenever project
objectives may be affected by indeterminate bias.
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4.6 Fluoride Interference Studies
Fluoride is listed in ISE product literature as being a potential interferent for perchlorate analysis by ISE;
therefore, interference studies were performed for fluoride. Fluoride was determined not to produce
interference for the low concentration method.
Fluoride spiking solutions were prepared from reagent grade sodium fluoride. On April 23,2001, blanks, 10
ppb, 20 ppb, and 50 ppb perchlorate standards spiked with 0.5 ppm, 1.0 ppm, 2.0 ppm, and 5.0 ppm bromide
were analyzed with pH adjustment to 4.0 (refer to Table 4-20). No positive or negative interference was
noted (refer to Table 4-5). Phosphate levels normally found in environmental samples are not expected to
affect the usability of the low concentration method.
4.7 Phosphate Interference Studies
Phosphate is listed in ISE product literature as being a potential interferent for perchlorate analysis by ISE;
therefore, interference studies were performed for phosphate. Phosphate was determined not to produce
interference for the low concentration method.
Phosphate spiking solutions were prepared from a certified 1000 ppm ion chromatography calibration
standard. On February 19, 2001, blanks, 10 ppb, 20 ppb, and 50 ppb perchlorate standards spiked with 5.0
ppm, 10 ppm, and 20 ppm phosphate were analyzed with pH adjustment to 4.0 (refer to Table 4-21). No
positive or negative interference was noted (refer to Table 4-6). Phosphate levels normally found in
environmental samples are not expected to affect the usability of the low concentration method.
4.8 Possible Organic Chemical Interference
Additional interference from organic chemicals is also considered possible. In the analyses of sample P-l 1
(well 422-MW01) and recollected samples P-102, P-103, and P-104 from well 422-MW01, which have high
historical levels of organic contaminants, application of high correction factors due to high levels of nitrate
and chloride resulted in corrected results with negative values for perchlorate. This over-correction may be
the result of less interference for combined nitrate and chloride than the sums of the individual interferences.
However, the possibility of response suppression due to organic compounds must be considered.
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Additional studies of complex matrices with combinations of anions, and studies of the effects of organic
compounds on response suppression are recommended.
Other split samples with high known concentrations of organic contaminants were not analyzed due to the
potential for deterioration of the ISE module, including high concentrations ofNDMA (refer to Table 1-9). In
general, samples with high concentrations of organics are not recommended for analysis by ISE as organic
solvents are known to deteriorate ISE membranes.
4.9 Method of Standard Additions
The method of standard additions (MSA) incorporates the sequential addition of three increments of a
standard solution (spikes) to sample aliquots of the same size. Measurements are made on the original and
after each addition. The slope, x-intercept and y-intercept are determined by least-squares analysis. The
analyte concentration is determined by the absolute value of the x-intercept. Regression may be performed
mathematically on a programmable calculator or on a computer; or the results for the three spiked additions of
perchlorate may be graphed and the resulting line or curve extended through the y-axis until it intersects the
x-axis. Ideally, the spike volume is low relative to the sample volume (approximately 10% of the volume).
Standard addition may counteract matrix effects, especially if such effects are constant or linear.
Due to the low concentrations achieved by the low concentration method, significant interference from known
and unknown interferents may result in the need to apply multiple correction factors for samples with
complex matrices. In particular, high levels of nitrate may require the application of correction factors several
times the method RL. In addition, specific anion concentrations necessary for the application of the
appropriate correction factors may not be available. When detected perchlorate readings are expected or
suspected of being due in part, or in entirety, due to anion interference, and correction factors to be applied
are unknown, the use of MSA may be useful in mitigating matrix effects.
The MSA procedure is generally able to effectively compensate for interference and produce accurate results
for many methods. However, initial cursory efforts to assess the use of MSA for the low concentration
method indicates that due to complex curves in the interferences for different anions, MSA may not be
effective for accurate correction of significant interferences due to high nitrate and chloride. MSA may,
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however, be useful in determining whether perchlorate readings not significantly greater than the RL or TDL
are due to interference when anion concentrations are not available.
MSA was not included in the scope of work for method development for this project. However, MSA was
performed on a 20 ppb perchlorate standard spiked with 2 ppm N03-N on May 1, 2001, by addition of
sequential 10 ppb spikes (refer to Table 4-22A). The result of 36.5 ppb perchlorate by MSA was marginally
lower than the 40.8 ppb reading without correction. Subtraction of the 22.5 ppb correction factor according to
Table 4-8 provides a far more accurate final result.
To determine if MSA might be useful at other levels of interference, data from interference studies performed
during method development that include sequences of analyses with levels of perchlorate approximating MSA
sequences were examined. These data were plotted and assessed for effectiveness of regression analysis by
MSA to provide more accurate results than those determined from direct readings.
MSA regression analysis results for blanks, 0.11 ppm, 0.23 ppm, and 0.45 ppmN03-N standards with 10 ppb,
20 ppb, and 50 ppb perchlorate additions are presented in Table 4-22B. The MSA results indicate acceptable
performance in mitigating interference due to low concentrations of nitrate. For example, the 9 ppb
perchlorate result for a blank with 0.45 ppm N03-N is lower than the 14.2 ppb perchlorate reading for this
blank. However, all of the initial perchlorate readings were below the RL and TDL, and additional data for
sequences equivalent to multiple additions at higher levels of nitrate, or for perchlorate with true values
greater than the RL or TDL, were not available.
Although less accurate than multiple additions, double or single additions can be performed to determine
analytical results by regression, so available data for higher concentrations of nitrate (2-10 ppm N03-N) were
plotted as single additions to assess the slopes for potential effectiveness in mitigating more significant
interference (referto Table 4-22C). The slopes and intercepts ofthe graphs indicate poor ability ofMSAto
resolve more significant nitrate interference. Thus, the use of MSA appears to have good potential only for
samples with less than 1 ppm N03-N.
Assessment of similar data sets for chloride interference indicate acceptable ability of MSA to resolve
chloride interference at low concentrations, with poor ability to resolve more significant levels of interference
(refer to Table 4-23A). This appears to be exacerbated by the non-linear nature of the chloride interference
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(refer to Table 4-23B). However, the available data include additions of 20, 40, and 70 ppb perchlorate
instead of 10, 20, and 30 ppb, so to assess the potential for smaller additions of perchlorate to improve
performance, data were plotted eliminating the high point on each curve, thus more closely approximating the
slopes of 10 ppb perchlorate additions (refer to Table 4-23C). These data indicate improved potential for
acceptable resolution by MSA, but again, all of the initial perchlorate readings were quite low (all were below
the TDL), and no data were available for higher initial readings.
To simulate higher initial readings, the data were plotted eliminating the low point on each curve,
approximating the slopes of 10 ppb perchlorate additions to samples with 20 ppb perchlorate true values (refer
to Table 4-23D). The projected perchlorate results by MSA become higher than the initial direct perchlorate
readings as the higher readings for more significant levels of chloride and perchlorate are associated with
sections of the interference curves with flatter slopes. The 17.1-29.6 ppb initial perchlorate readings for the
respective 20 ppb perchlorate standards with 0-500 ppm chloride are far more accurate than the projected 28-
76 ppb perchlorate respective results for these standards. This again indicates poor MSA performance for
significant interference.
Thus, initial cursory assessment of the ability of MSA to resolve anion interference indicates the potential for
MSA to determine whether initial perchlorate readings between 15 ppb and 30 ppb are due to positive
interference, but not to be effective in resolving significant interferences associated with readings higher than
30 ppb perchlorate. This may be useful for matrices with unknown amounts of chloride and nitrate when
chloride is less than 500 ppm and nitrate is less than 1 ppm N03-N, which is expected to include most
matrices. For samples with initial perchlorate readings greater than 30 ppb, dilutions may allow useful
resolution by MSA.
As only a cursory study of MSA has been included in method development to date and no in-depth study of
MSA was performed, a complete study of MSA, including complex interferences due to combinations of
nitrate and chloride, is recommended. In addition, because of the complex interference curves and the
logarithmic nature of the calibrations, additional study of alternative regression methods is recommended to
determine if better results can be achieved.
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
4.10 ISE Conditioning
Due to the nature of the perchlorate ISE, recharging perchlorate sites in the perchlorate ISE membrane is a
routine requirement to maintain sensitivity. The perchlorate ISE requires special preconditioning priorto first
use, then daily before calibration. Some anions, notably nitrate, and possibly some organic chemicals, were
found to cause loss of sensitivity between analyses. During method development, sample matrices with
nitrate concentrations greater than 0.2 ppm N03-N were found to require implementation of reconditioning
between every sample. When long periods of time became necessary for millivolt readings to stabilize, or if
low recoveries for check standard recoveries were encountered after analysis of field samples, reconditioning
of the ISE was found to be effective in maintaining sensitivity and accuracy.
Extended exposure of perchlorate ISEs to field sample matrices will gradually diminish ISE sensitivity.
When sensitivity for a specific ISE module is found to decline with extended use, Sentek recommends using
an abrasive such as fine emery paper to renew the exposed PVC surface of the electrode. See manufacturer
directions for this procedure. Note that exposure to samples containing organic solvents may permanently
degrade the electrode membrane. Refer to Section 1.3.2.1 for details.
4.11 Interference Study Conclusions
Interference studies for the Low Concentration Method for the Determination of Perchlorate in Aqueous
Samples Using Ion Selective Electrodes indicate that the solid state perchlorate ISE with built-in reference
electrode can be used effectively to determine if perchlorate is present in waters at or above the project TDL
and California action limit of 18 ug/L (ppb) in aqueous samples with low concentrations of interfering anions.
Use of the method for samples with high levels of interfering anions, especially nitrate, may not be
appropriate.
The method is especially useful for matrices with less than 1000 mg/L chloride and 1.5 mg/L nitrate as
nitrogen (N03-N). Correction factors must be applied for concentrations in excess of 50 mg/L chloride, 0.12
mg/L N03-N, or 1.2 mg/L bromide, for which significant positive interference (greater than 20% of
perchlorate concentration, or 20% of the 15 (ig/L RL for perchlorate results less than the RL) was
demonstrated. If nitrate exceeds 0.2 ppm NO3-N, reconditioning of the electrode between every sample is
necessary. Samples with uncorrected perchlorate readings less than action limits can be considered to
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
effectively indicate lack of perchlorate if subsequent QC sample recoveries are within specified accuracy
criteria. Interference due to carbonate and bicarbonate is eliminated by the acidification of all standards and
samples to pH 4.0 (± 0.1) with sulfuric acid.
Samples with nitrate concentrations of 1.1 to 5.5 mg/L N03 -N cause positive bias of 15 -45 |_ig/L perchlorate
(one-to-three times the RL). The user may need to determine the maximum level of nitrate correction
acceptable for project objectives if samples include high-nitrate matrices.
Analysis by the method of standard additions (MSA) was found to have the potential to compensate for anion
interference, especially for perchlorate readings less than 30 j^ig/L. Further studies of the effectiveness of
MSA to compensate for anion interferences are required.
Due to the potential for positive bias due to matrix interference, ten percent of samples analyzed by this
method should generally be confirmed by definitive-level analysis, especially to confirm when application of
anion-specific correction factors lower perchlorate readings to below project action limits.
4.12 Interference Study Recommendations
Further studies are recommended to reconfirm the accuracy of the chloride, nitrate, and bromide correction
factors, and to study the effects of mixtures of interfering anions. Interference studies for iodide, other anions,
and organic compounds are also recommended. Possible methods to mitigate nitrate interference, including
use of different type or concentrations of ISA should be explored to make the method more versatile. Further
studies to determine and maximize the effectiveness of MSA are required.
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
5.0 Task 5 - Analyses of Split Samples
This section presents the data report for the analyses of split samples according to USEPA Method 314.0 for
definitive level analyses, and the Low Concentration Methodfor the Determination of Perchlorate in Aqueous
Samples Using Ion Selective Electrodes for the ISE analyses.
Twenty-nine samples were collected at Edwards AFB for split sample analysis during the first semi-annual
groundwater (SAGW) sampling event used for this study in December 2000, of which four samples were not
analyzed due to known high concentrations of organic contaminants and one sample was not successfully
analyzed as the sample was expended in method development. Thirty-five samples were collected for split
sample analysis during a second SAGW sampling event in July and August 2001 and successfully analyzed.
In addition, five duplicate samples were analyzed by ISE in the first SAGW event, and seven duplicate
samples were analyzed by ISE in the second SAGW event.
Results for a total of 72 ISE analyses were available for split sample comparison to the definitive level results
(refer to Table 5-1). Additional samples useful for split sample analyses by the low concentration ISE method
were not available during regularly scheduled sampling events at Edwards AFB during the period of
performance for this project. Split samples were not collected for ten percent of the samples for EPA
perchlorate analysis as specified in the statement of work for this project, per instructions by EPA.
5.1 Split Sample Results
Definitive level analyses were performed by E.S. Babcock & Sons (Babcock), of Riverside, California
according to EPA Method 314.0 (or CADOHS Modified EPA Method 300.0 for perchlorate). ISE analyses
were performed according to the Low Concentration Methodfor the Determination of Perchlorate in Aqueous
Samples Using Ion Selective Electrodes (the low concentration ISE method) developed during this project, per
the Standard Operating Procedure (SOP) presented as Attachment lof Section 3.0, above, by Earth Tech
chemists in San Jose, California.
Perchlorate ISE readings were corrected for anion interference according to Tables 1 -3 of the SOP (Tables 4-7
through 4-9 of this report) using historical data, where available, as specified in the method. When historical
anion data were not available, anion analyses were performed by Babcock, unless the uncorrected perchlorate
reading was already less than the RL, in which case anion correction was considered unnecessary. Sample
location information, historical anion concentrations and correction factors, raw ISE readings and anion-
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
corrected perchlorate ISE results, and definitive perchlorate results are presented in Table 5-1. Analytical
results, including calibrations, field and QC sample ISE readings, and raw perchlorate concentrations for all
ISE analytical runs for split samples, are presented in Tables 5-2 and 5-3.
5.1.1 Non-Detected Result Confirmations
Of the 72 split sample analyses, ISE results for 66 analyses were reported as non-detected at the reporting
limit (RL) of 0.015 mg/L (15 (ig/L, or 15 parts per billion [ppb]). All of these ISE results were confirmed as
non-detected at 4 ppb or 16 ppb by the definitive level analyses (refer to Table 5-1); with the exception of one
sample, its duplicate, and three additional samples subsequently collected at the well (samples P-l 1, P-l ID,
P102, P-103, and P-104) for which the definitive result was reported at 6 ppb; and one sample (sample S-4)
with a reported definitive result of 18 ppb, which is at the ±20% accuracy limit specified for this method
(refer to Section 1.3.1.3, above) and within the <30RPD field precision criterion specified in Section 8.3.5 of
the SOP (refer to Table 5-4). Thus, 100% of the non-detected ISE results were confirmed as non-detected
within 20% of the ISE RL by definitive level split sample analysis.
Note that the anion-corrected ISE result of 10.1 ppb for sample S-4 was the only result reported as non-
detected that was greater than the 10 ppb low-concentration standard for this method. In addition, sample P-1
for the well at this site-location (ED-189-MW03) was not analyzed by ISE during the first SAGW event due
to high historical concentrations of organic contaminants (chloromethane at 1200 ppb, other compounds to
140 ppb). Organic contaminants are considered potentially damaging to the ISE membrane, and may be
responsible for low bias in perchlorate ISE results. Although this was not investigated during method
development due to the potential damage to the instruments and difficulties associated with handling such
samples, several samples with high historical concentrations of organic contaminants were successfully
analyzed at the end of this project, with some unusual interferences noted (refer to Section 5.2.1).
5.1.2 Detected Result Confirmations
Split sample precision is measured for detected results by the relative percent difference (RPD) between the
low concentration ISE and definitive method results. Confirmation of detected results is considered excellent
when split sample results meet the less-than 30 RPD criterion specified in Section 8.3.6 of the low
concentration ISE method SOP.
Detected results were reported by both ISE and definitive analyses for the samples from the wells at two site-
locations during both SAGW events, and at one well sampled only during the second SAGW event (refer to
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
Tables 5-1 and 5-4). Anion corrections were not applied to any of the ISE results for these samples due to
sample dilutions.
At well ED-188-MW01, the ISE result of 126.5 ppb was confirmed by the definitive level result of 140 ppb
for the second SAGW event, for an RPD of 10.1. This location was not sampled during the first SAGW
event.
At well ED-196-MW01, the ISE result of 24,423 ppb was confirmed by definitive level result of 20,000 ppb
for the first SAGW event, for an RPD of 19.9. For the second SAGW event, the 13,270 ppb ISE result was
confirmed by field duplicate definitive level results of 36,000 ppb and 27,000 ppb, for RPDs of.92.3 and 68.2
for the split sample analyses (and an RPD of 28.6 for the definitive level field duplicate sample results).
At well ED-286-MW01, the 4336 ppb ISE result for the first SAGW event was confirmed by a definitive
level result of 5900 ppb, for an RPD of 30.5. For the second SAGW event, the field duplicate ISE results of
612 ppb and 731 ppb were confirmed by field duplicate definitive level results of 920 ppb and 1100 ppb.
RPDs of 22.9, 40.2, 40.3, and 57.0 can be calculated for the four possible combinations of split sample
results, with RPDs of 17.7 and 17.8 for the ISE and definitive field duplicate results, respectively.
The precision for the detected split sample results noted above (refer to Table 5-4) indicates excellent
confirmation of ISE detected results by the definitive method for approximately half of the samples, with
lower precision for the remaining sample pairs, and confirmation of all ISE detections by definitive analysis.
Changes in results at some wells may be attributable to changes in groundwater concentrations with time, or
to differences in sampling techniques or screening levels used for the samples.
The results indicate acceptable overall ability of the ISE method to quantitate perchlorate at concentrations
greater than 100 ppb, even at high dilutions.
5.1.3 Split Sample Result Interpretation
In general, split sample results for this project indicate acceptable reproducibility of perchlorate results by the
low concentration ISE and definitive methods for the samples analyzed for this project. However, the
samples available for this study were notably lacking in detectable concentrations near the target detection
limit (TDL) and California action limit of 18 (ig/L (18 ppb). Most of the samples were reported as non-
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
detected at the ISE RL of 15 ppb and the definitive method RL of 4 ppb or 16 ppb (for samples diluted 4
times due to interference), or detected above 100 ppb.
The low concentration ISE method is demonstrated by the split sample analyses to be effective at determining
whether perchlorate is not present at or above the 18 ppb TDL, especially when perchlorate readings are less
than the TDL before anion correction factors are applied. Only one false negative was reported for anion-
corrected ISE results, and the definitive result for that sample was at the 18 ppb TDL. The 37 ISE readings
less than the 15 ppb RL before anion-correction indicate the potential for the method to successfully assess
the lack of perchlorate in matrices free of significant anion interferences. For example, the method
successfully determined lack of perchlorate in all of the samples from USGS locations (samples P-18 through
P-25 and S-18 through S-25) for which no anion information was available.
However, low matrix spike recoveries indicate the possibility that low concentrations of perchlorate in
environmental matrices may produce false negatives by this method (refer to Section 5-2.2, below).
Therefore, for samples with uncorrected perchlorate ISE readings greater than 18 ppb with final results
reported as non-detected at 15 ppb after anion correction, additional steps should be taken to determine the
potential for matrix interference. This includes matrix spike analyses of the samples in question and
definitive confirmation analyses, especially if the corrected readings exceed 10 ppb. For samples with
uncorrected perchlorate readings above 50 ppb, sample dilutions may be appropriate to determine if
interference is affecting results in such a way as to affect project objectives.
Application of the anion correction factors overcompensates for positive interference in some samples,
resulting in corrected readings with negative values (refer to Table 5-1). Of the 29 non-detected anion-
corrected perchlorate results with original readings greater than 18 ppb, 11 final anion-corrected readings
were less than zero. All of these samples had high historical levels of multiple interfering anions, especially
nitrate. This overcompensation may be due to the use of historical concentrations of anions instead of current
concentrations (which were not generally available), or it may be due to the subtraction of individual
correction factors for each interfering anion, whereas interference for multiple anions may be less than the
sum of the interference for each anion studied separately. Additional study of the effects and ways to
compensate for the presence of multiple interfering anions is recommended.
In addition to effective determination of lack of perchlorate at the 18 ppb TDL in low nitrate matrices, the low
concentration ISE method was demonstrated by the split sample analyses to be effective at determining
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
perchlorate concentrations significantly above 18 ppb, especially for concentrations above 100 ppb, for which
minimal dilutions of five times can be used to eliminate interference.
5.2 Quality Control Results for ISE Analyses
Overall, the low concentration ISE method demonstrates the ability to perform within the QC limits specified
in the SOP for laboratory accuracy and precision. Results for matrix precision were acceptable; however
significant variations in matrix-specific accuracy indicate the sensitivity of the method to matrix interferences.
5.2.1 Calibration Verification
Initial and continuing calibration verifications (ICVs and CCVs) and laboratory control samples (LCS) were
analyzed before, during, and after sample analyses, as specified in the low concentration ISE method SOP.
Recoveries were generally maintained within the ±20% accuracy criterion for the method (referto Tables 5-2
and 5-3). When verifications exceeded the specified criteria, reconditioning or recalibration and reanalysis of
affected samples was generally performed.
Low recoveries tended to occur with continuing use during long analytical runs, especially during the analysis
of samples with more complex matrices, including samples with high concentrations of nitrate or organic
compounds. This effect is most likely due to perchlorate site-blocking in the ISE membrane (referto Section
1.3.2.1, above), which was mitigated by the implementation of ISE module reconditioning, as specified in
Section 10.2 of the low concentration ISE method SOP.
5.2.2 Matrix Spike Recoveries
Matrix spike analyses were performed at an approximate frequency of one-per 20 field samples for the ISE
analyses. Results generally indicate appropriate increases in perchlorate readings for samples with low levels
of anion and organic interferents (samples P-5 and P-7), whereas for samples with high levels of nitrate
(sample P-l 1), matrix spike recoveries were inconsistent (referto Table 5-5). The anion corrected results for
these samples do not indicate detectable recoveries of spikes after anion-correction, except when anion
concentrations are extremely low, such as in sample P-5 for well ED-196-MW01.
For the MS analyses of samples S-2 (diluted five-fold) and S-29 from wells ED-188-MW01 and ED-286-
MW03, respectively, unusual interferences were noted. Matrix spike recoveries varied from over 1000%
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
recovery to non-detection at different times for the same spiked samples. The samples were respiked and
reanalyzed from different spiking solutions with similar results (refer to Table 5-3C). In addition, the pH for
samples S-2 and S-2MS from ED-188-MW01 increased back to pH 8 after initial acidification, indicating
complex matrix effects possibly related to chemical reaction balances between organic compounds and
carbonate/bicarbonate species in this sample. Sample S-2 is known to contain Freon 113 at 21 ppb, whereas
sample S-29 does not contain known concentrations of volatile organic compounds (VOCs). Concentrations
of interfering anions or non-VOC organic compounds are unknown for both samples. Additional study of
these matrices is recommended.
The MS analyses confirm the usability of the low concentration ISE method for samples with low levels of
interfering anions and organic compounds, while reinforcing the understanding that the method may not be
appropriate for complex matrices due to interference at the extreme sensitivity required to accurately
determine perchlorate at the 18 ppb TDL.
5.2.3 Field and Laboratory Duplicate Precision
Field and laboratory precision for the low concentration ISE method was acceptable for all analyses. Field
duplicate samples prepared from separate sample containers collected in the field, and for laboratory replicate
reanalyses of samples prepared from the same sample container indicate excellent precision for the low
concentration ISE method. All field and laboratory duplicate and replicate analyses were within the <20 RPD
criterion for laboratory precision and the <30 RPD criterion for field precision specified in Sections 8.3.4 and
8.3.5, respectively, of the low concentration ISE method SOP (refer to Table 5-6).
5.2.4 Method and Equipment Blanks
Equipment blanks were analyzed by the low concentration ISE method for both SAGW events (refer to
samples P-13 and S-3 in Table 5-1), and method blanks were analyzed before, during, and after sample
analyses as initial and continuing calibration blanks (ICBs and CCBs). All raw perchlorate readings for
blanks were less than one-half the 15 ppb RL, and were generally below 5 ppb.
Method and equipment blank results indicate that false positives due to carry-over contamination are not
likely for the low concentration ISE method.
5.2.5 ISE Module Reconditioning
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
The use of ISE conditioning, as described in Section 10.2 of the low concentration ISE method SOP was
found to be an effective aid to maintaining precision and accuracy. For samples with low concentrations of
nitrate and organic contamination, only preconditioning was required. For samples with high concentrations
of nitrate and for samples with organic contamination, successful analyses were performed using more
rigorous reconditioning of the perchlorate module in 500 ppb perchlorate solutions and acidified blanks
between every field and QC sample analysis.
5.3 Split Sample Study Conclusions
Analyses performed according to the Low Concentration Method for the Determination of Perchlorate in
Aqueous Samples Using Ion Selective Electrodes according to the SOP presented in Attachment 1 of Section
3.0, above, are in general agreement with definitive analyses performed by a fixed based laboratory using
EPA Method 314.0.
Uncorrected perchlorate readings measured by the low concentration ISE method at less than the 15 ppb RL
can reliably be considered to indicate non-detection within 20% of the reported concentration. For
perchlorate readings above 15 ppb, correction according to Tables 1-3 ofthe SOP (Tables 4-7,4-8, and 4-9 of
this document) for positive interference due to interfering anions appears to be an effective method for
accurately compensating for such interference in samples with low-to-moderate concentrations of anions.
However, in samples with complex matrices, including samples with chloride above 500 ppm, bromide above
3.0 ppm, and especially nitrate-as-nitrogen (N03-N) above 1.0 ppm, or combinations thereof, anion-correction
loses accuracy, and overcompensation may result in false negatives for such matrices. In addition, the
presence of organic contaminants may cause interference.
The use of reconditioning routines reduces some forms of matrix interference. Matrix spike analyses may be
used to resolve the potential for false negatives in specific samples or matrices. Otherwise, to mitigate such
effects in samples with complex matrices, dilutions of five-times or more is recommended, effectively raising
the useful detection limit to 50-75 ppb perchlorate. In cases where significant corrections to uncorrected
readings lower final results to below project action limits, the data user may decide that definitive-level
analyses are required to confirm the presence or absence of perchlorate, or to confirm bias due to chloride,
nitrate, or other interferents.
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
The low concentration ISE method appears to be useful for determining the presence of perchlorate at
concentrations above 100 ppb. Such results are best quantitated at dilutions of five-times or more, which
effectively reduces potential interference, although accuracy may vary with matrix and dilution technique.
For samples with perchlorate concentrations above 700 ppb, the low concentration method was found to be
acceptable, but is not required, as such concentrations are within the manufacturer-specified detection range
for perchlorate ISEs, and the standard ISE techniques described in ISE product literature become applicable.
In general, the low concentration ISE method can be effectively used to determine the presence or absence of
perchlorate at the 18 ppb TDL and California action limit in samples with low concentrations of the
interfering anions chloride, nitrate, and, to a lesser extent, bromide. Samples with high concentrations of
these anions require more specific knowledge of anion concentrations, should be analyzed with more frequent
matrix spike analyses, may require additional dilutions, and should be confirmed by definitive analysis at a
higher frequency. Samples with confirmed presence of organic contaminants may be subject to additional
interferences and may damage the ISE membrane.
5.4 Split Sample Study Recommendations
Further studies are recommended to determine more accurate compensation for samples with mixtures of
interfering anions. Additional methods to mitigate nitrate interference should be explored to make the method
more versatile. More study of samples with confirmed presence of organic contaminants is also
recommended, although ISE membrane deterioration may occur.
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U.S. Army Corps of Engineers
SECTION 1 Tables
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U.S. Army Corps of Engineers
TABLES 1-1 THROUGH 1-9
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Final, October 2001
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Table 1-1 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Analyst: Earth Tech, Inc. Date: January 2, 2001
Computer Interface: LAVAL ELIT 8804
Instrument: Instrument:
Orion 938101 Plastic Membrane Half-Cell Perchlorate ISE Sentek 367-75 Solid State Perchlorate Combination ISE with
with Double Junction Reference Electrode Built-in Reference Electrode
Sentek Probe with 0.5 tnL of 0.4M ISA in 50 mL
Using Computer Interface and ELIT Software
Orion Probe with 0.5 mL of 0.4M ISA in 50 mL
Using Computer Interface and ELIT software
250.0
350.
y = 3.5478Ln(x) + 209.82
R2= 0.5821
340.
y = -14.39Ln(x) + 366.28
R2= 0.944
240.0 -
330.
230.0 -
226.1
21.5
.2 320.
~ 224.2
3_14'6 310.0
220.0 -
310.
210.0 -
300.
.297.6
290.
200.0
100
120
100
120
Perchlorate Cone in ppb
Perchlorate Cone in ppb
Sample
Volume
Millivolts
Reading
Concentration in
PPb
Sample
Volume
Millivolts
Reading
Concentration in
PPb
Sample/Calibration ID
Sample/Calibration ID
20
200 mL
218.9
Not Calculated
20
200 mL
321.5
22.4
40
200 mL
224.7
Not Calculated
40
200 mL
314.6
36.3
60
200 mL
226.1
Not Calculated
60
200 mL
310.0
50.1
100
200 mL
224.2
Not Calculated
100
200 mL
297.6
Calibration Date
1/2/2001
Calibration Date
1/2/2001
-------
Table 1-2 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc. Date: January 3, 2001
Laval ELIT 8804 Computer Interface Orion 290A Advanced Portable Meter
Sentek Probe with 2mL of 0.4M ISA in 200 mL
Using Computer Interface and ELIT software
01/D3/01
350.0 -
340.0 -
330.0 -
«
% 320.0 -
a
| 310.0 -
300.0 -
290.0 -
2S0.0 -
0 20 40 60 80 100 120
Perchlorate Cone in ppb
Sentek Probe with 2mL of 0.4M ISA in 200mL
Using Orion 290A+ Meter
~1/03/01
350.0 -
340.0 -
330.0 -
»
% 320.0 -
| 310.0 -
300.0 -
290.0 -
280.0 -
0 20 40 60 80 100 120
Perchlorate Cone in ppb
y = -18.038Ln(x) + 383.09
R:= 0.9812
Sample/Calibration ID
Sample
Volume
Millivolts Reading
Concentration
in ppb
Sample/Calibration ID
Sample
Volume
Millivolts Reading
Concentration
in ppb
10
200 mL
344.4
10.7
10
200 mL
341.8
9.9
20
200 mL
332.6
19.7
20
200 mL
326.6
22.9
40
200 mL
322.0
34.0
40
200 mL
319.8
33.4
60
200 mL
310.2
62.7
60
200 mL
310.0
57.5
100
200 mL
299.9
107.0
100
200 mL
298.2
110.6
Calibration Date & Time
01/04/01 2:25pm
Calibration Date & Time
01/04/01 2:25pm
-------
Table 1-3 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
ISA: 2 ml_ of 0.4M Ammonium Sulfate ISA in 200 ml_ of Standard, No pH Adjustment
Analyst: Earth Tech, Inc. Date: January 4, 2001
Laval ELIT 8804 Computer Interface Orion 290A Advanced Portable Meter
Sentek Probe with 2mL of 0.4M ISA in 200 mL
Using Computer Interface and ELIT software
01/04/01
350.00 -
340.00 -
330.00 -
»
% 320.00 -
a
| 310.00 -
300.00 -
290.00 -
2S0.00 -
0 20 40 60 80 100 120
Perchlorate Cone in ppb
y = -20.874Ln(x) + 391.75
R2= 0.9942
Sentek Probe with 2mL of 0.4M ISA in 200mL
Using Orion 290A+ Meter
01/04/01
420.00
410.00
¦
y = -19.867Ln(x) + 449.24
400.00
¦
^390.10
O
380.00
-
^¦*^ 377.10
i
370.00
-
--^4369/10
360.00
-
* 356.00
350.00
-
340.00
0 20 40 60 80 100 120
Perchlorate Cone in ppb
Sample/Calibration ID
Sample
Volume
Millivolts
Reading
Concentration in
ppb
Sample/Calibration ID
Sample
Volume
Millivolts
Reading
Concentration
in ppb
10
200 mL
342.33
10.67
10
200 mL
402.50
10.51
20
200 mL
330.32
18.97
20
200 mL
390.10
19.62
40
200 mL
315.55
38.49
40
200 mL
377.10
37.76
60
200 mL
307.53
56.53
60
200 mL
369.10
56.48
100
200 mL
293.85
108.86
100
200 mL
356.00
109.20
-------
Calibration Date & Time
01/04/01 2:25pm
Calibration Date & Time
01/04/01 2:25pm
Sample
Millivolts
Concentration in
Sample
Millivolts
Concentration
Sample ID
Volume
Reading
ppb
Sample ID
Volume
Reading
in ppb
LCS/ICV
200 mL
308.39
54.60
LCS/ICV
200 mL
370.23
53.35
MB/ICB
200 mL
388.12
1.19
MB/ICB
200 mL
439.37
1.64
MDL1
200 mL
328.05
21.26
MDL1
200 mL
387.78
22.06
MDL2
200 mL
326.55
22.84
MDL2
200 mL
386.99
22.95
MDL3
200 mL
327.02
22.33
MDL3
200 mL
387.23
22.67
MDL4
200 mL
328.54
20.76
MDL4
200 mL
389.06
20.68
MDL5
200 mL
326.65
22.73
MDL5
200 mL
388.76
20.99
MDL6
200 mL
328.09
21.21
MDL6
200 mL
389.12
20.62
MDL7
200 mL
327.74
21.57
MDL7
200 mL
388.54
21.23
MDL8
200 mL
326.94
22.42
MDL8
200 mL
388.26
21.53
MDL9
200 mL
328.53
20.77
MDL9
200 mL
388.99
20.75
MDL10
200 mL
327.75
21.56
MDL10
200 mL
388.51
21.26
ccv
200 mL
328.52
20.78
CCV
200 mL
388.76
20.99
CCB
200 mL
392.13
0.98
CCB
200 mL
444.37
1.28
Data highlighted in bold used for MDL calculations
Perchlorate MDL Study: Sentek ISE with 1 mL of 0.4M ISA in 200ml_, No pH Adjustment
Mean 21.47
Std Dev. 0.829
T-Value 2.821
Calculated MDL* 2.3
Reported MDL 3
%RSD 0.0386
MDL Qualifier notes Valid MDL Data
Mean
21.75
Std Dev.
0.780
T-Value
2.821
Calculated MDL*
2.2
Reported MDL
3
%RSD
0.0359
MDL Qualifier notes
Valid MDL Data
* According to 40 CFR Part 136, Appendix B
-------
Table 1-4 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective
Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
ISA: 1 ml_ of 0.1M Sodium Acetate ISA in 200 ml_ of Standard, pH Adjustment to 4.0 with Sulfuric Acid
Analyst: Earth Tech, Inc. Dates: January 24-29, 2001
Perchlorate MDL Study: Sentek ISE with 1 mL of 0.1 M ISAB in 200ml_ Using Orion 290A+ Meter, pH 4.0
Sample ID
Date Analyzed
Result (ppb)
Mean
20.13
MDL-1
01/24/01
18.80
Std Dev.
0.918
MDL-2
01/24/01
18.47
T-Value
2.624
MDL-3
01/25/01
20.42
Calculated MDL*
2.4
MDL-4
01/25/01
20.66
Reported MDL
3
MDL-5
01/25/01
19.73
% RSD
0.0456
MDL-6
01/25/01
19.28
MDL Qualifier notes
Valid MDL Data
MDL-7
01/26/01
21.23
* According to 40 CFR Part 136, Appendix B
MDL-8
01/26/01
20.00
MDL-9
01/26/01
20.94
MDL-10
01/26/01
21.04
MDL-11
01/26/01
20.56
MDL-12
01/29/01
20.57
MDL-13
01/29/01
18.97
MDL-14
01/29/01
21.37
MDL-15
01/29/01
19.90
-------
Table 1-5 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc. Date: January 29, 2001
Standard Used: 20 ppb with 1 ml_ ISAB in 200 ml_, pH 4.0
Temperature
Millivolts
Concentration (ppb)
Temperature (cont.)
Millivolts (cont.)
Concentration (ppb) (cont.)
10.0
292.2
99.3
21.0
317.2
30.1
10.5
293.4
93.8
21.5
318.9
27.8
11.0
295.3
31185.7
22.0
320.1
26.2
11.5
296.5
80.9
22.5
321.0
25.1
12.0
297.6
76.8
23.0
321.8
24.2
12.5
298.9
72.2
23.5
322.5
23.4
13.0
300.6
66.5
24.0
323.5
22.3
13.5
301.7
63.1 * *
24.5
324.3
21.5
14.0
302.7
60.2
25.5
325.9
19.9
14.5
303.6
57.7
27.5
329.6
16.7
15.0
304.6
55.0
30.5
338.9
10.7
15.5
305.9
51.7 *
32.5
340.9
9.7
16.0
306.8
49.5
16.5
307.9
47.0
17.0
308.9
44.8
17.5
310.1
42.3
18.0
310.9
40.7
18.5
311.8
39.0
19.0
312.9
37.0
19.5
314.2
34.8
20.0
315.5
32.7
20.5
316.4
31.3
-------
Change in Perchlorate Concentration
with change in Temperature
140.0
c 120.0
o
£ 100.0
80.0
60.0
40.0
20.0
0.0
c
a)
o
c
o
O
a)
(0
o
a)
a.
5.0
y = 276.48e
¦0.1069X
FT = 0.9964
292.2 mV
True Value = 20
10.0 15.0 20.0
Temperature (degrees Celsius)
25.0
-------
Table 1-6 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc. Date: January 9, 2001
Laval ELIT 8804 Computer Interface Orion 290A Advanced Portable Meter
Sentek Probe with 2mL of 0.4M ISA in 200 rnL
Using Computer Interface and ELIT software
340 -
330 -
320 -
»
J 310-
n
300 -
290 -
280 -
0 20 40 60 80 100 120
Perchlorate Cone in ppb
y = -19.386Ln(x) + 379.19
R1 = 0.9751
Sentek Probe with 2mL of 0.4M ISA in 200mL
Using Orion 290A+ Meter
420 -
410 -
400 -
M 390 -
£
| 380 "
S 370 -
360 -
350 -
340 -
0 20 40 60 80 100 120
Perchlorate Cone in ppb
y = -19.548Ln(x) + 442.53
R2 = 0.9782
Sample ID/ Calibration
Sample
Volume
Millivolts
Reading
Concentration in
ppb
Sample ID/
Calibration
Sample
Volume
Millivolts
Reading
Concentration in
PPb
10
200 mL
331.45
11.7
10
200 mL
394.6
11.6
20
200 mL
323.98
17.3
20
200 mL
386.7
17.4
40
200 mL
310.31
34.9
40
200 mL
373
35.1
60
200 mL
300.02
59.4
60
200 mL
362.4
60.3
100
200 mL
287.3
114.4
100
200 mL
350.2
112.5
Calibration Date & Time
1/9/2000
5:15pm
Calibration Date & Time
1/9/2000
5:15pm
Temperature
16
°C
Temperature
16
°C
-------
Table 1-7 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc. Date: January 10, 2001
Laval ELIT 8804 Computer Interface Orion 290A Advanced Portable Meter
350.0
340.0 -
330.0
320.0 H
310.0
300.0 H
290.0
230.0
Sentek Prohe with 2mL of 0.4M ISA in 200 tnL
Using Computer Interface and ELIT software
^40.4
y = -18.048Ln(x) + 384.27
R: = 0.9848
332.5
319.3
¦4^107
+ 299.3
20 40 60 80
Perchlorate Cone in ppb
100
120
Sentek Probe with 2mL of 0.4M ISA in 200mL
Using Orion 290A+ Meter
420.0 -|
410.0 -
400.0 -
w
390.0 -
£
380.0 -
£
370.0 -
360.0 -
350.0 -
340.0 -
,410.9
401.3
y = -1 8.722Ln(x) + 455.89
R2= 0.9889
388.7
.379.6
367.!
20 40 60 80
Perchlorate Cone in ppb
100
120
Sample/Calibration ID
Sample
Volume
Millivolts
Reading
Concentration in
ppb
Sample/Calibration ID
Sample
Volume
Millivolts
Reading
Concentration in
PPb
10
200 mL
340.4
11.3
10
200 mL
410.9
11.1
20
200 mL
332.5
17.6
20
200 mL
401.3
18.5
40
200 mL
319.3
36.7
40
200 mL
388.7
36.2
60
200 mL
310.7
58.8
60
200 mL
379.6
58.8
100
200 mL
299.3
111.1
100
200 mL
367.8
110.5
Calibration Date & Time
1/10/2001
2:32pm
Calibration Date & Time
1/10/2001
2:32pm
Temperature
21
°c
Temperature
21
°c
Slope
18.048 || Intercept
384.27
Slope
18.722 || Intercept
455.89
-------
Sample
Millivolts
Concentration in
Sample
Millivolts
Concentration in
Sample ID
Volume
Reading
PPb
Sample ID
Volume
Reading
PPb
LCS/ICV
200 mL
315.4
45.5
LCS/ICV
200 mL
384.1
46.3
MB/ICB
200 mL
357.8
4.3
MB/ICB
200 mL
425.4
5.1
5 ppb
200 mL
353.9
5.4
5 ppb
200 mL
420.8
6.5
MDL 1 (20 ppb)
200 mL
332.8
17.3
MDL 1 (20 ppb)
200 mL
400.8
19.0
P-1
200 mL
307.9
68.8
P-1
200 mL
376.2
70.6
MDL2
200 mL
332.1
18.0
MDL2
200 mL
400.7
19.1
P-6
200 mL
322.1
31.3
P-6
200 mL
395.0
25.9
P-21
200 mL
326.4
24.7
P-21
200 mL
393.7
27.7
P-10 (1:200)
200 mL
339.9
11.7
P-10 (1:200)
200 mL
408.8
12.4
P-10 (1:200)+20ppb ms
200 mL
328.3
22.2
P-10 (1:200)+20ppb ms
200 mL
397.5
22.6
MDL 3 (20 ppb)
200 mL
336.2
14.4
MDL 3 (20 ppb)
200 mL
403.9
16.1
100ppb
200 mL
298.26
117.4
100ppb
200 mL
365.9
122.3
Highlighted data are referenced in Section 1.3.2.4 of the report.
-------
Table 1-8 Conductivity Levels for Ionic Strength Adjustor Solutions for Low-Level Perchlorate Analysis
mL 0.4M ISA per
200 mL Sample,
No pH Adjustment
Conductivity in liS/cm
1
493
2
980
3
1423
4
1849
5
2250
6
2650
7
3030
8
3400
9
3760
10
4120
11
4460
12
4800
15
5870
20
7450
Table 1-8A: Conductivity/ISA Relationships
No pH Adjustment 01/08/01
10000 -r
_ 8000
£
-y eooo
O
= !
3 5
4000
2000
0
y=519.422x
Rs = 0.999
,0/SM
0 5 10 15 20 25
Volume in mL of 0.4M ISA (Ammonium Sulfate) in 200 mL of water
mL ISA per 200 mL
Sample, Sulfuric
Acid to pH 4.0
Conductivity in nS/cm
1
529
1.5
759
2
974
2.5
1193
3
1398
4
1795
5
2180
8
3260
10
3940
15
5700
20
7460
Table 1-8B: Conductivity/ISA Relationships
pH Adjusted to 4 with Sulfuric Acid 05/01/01
10000 -
>, ^ 8000 -
f E
= 6000 -
3 £
^ £ 4000 -
O =L
0 w 2000 -
0 -
0 5 10 15 20 25
Volume (mL) of 0.4M ISA (Ammonium Sulfate) in 200 mL of water
y = 530.727xoa77
Rs= 1.000
-------
Conductivity Levels for Ionic Streng
mL 1.0M ISAB per
200 mL Sample,
No pH Adjustment
Conductivity in uS/cm
0.5
84
1
164
1.5
242
2
319
2.5
394
3
469
4
615
5
756
6
894
8
1163
10
1420
15
2020
20
2590
mL ISAB per 200
mL Sample,
Sulfuric Acid to pH
4.0
Conductivity in nS/cm
1
280
1.5
371
2
471
2.5
574
3
683
4
844
5
1023
8
1496
10
1800
15
2580
20
3360
h Adjustor Solutions for Low-Level Perchlorate Analysis
Table 1-8C: Conductivity/I SAB Relationships
No pH Adjustment 04,23,01
¦o
c
D
10000
8000
E
_o
6000
D
J=
E
4000
=L
2000
0
y = 165.86x'
R2 = 1.00
,0.93
0 5 10 15 20 25
Volume (mL) of 1.0M ISAB (Sodium Acetate) in 200 mL of water
10000 -r
£
?
8000 -
S
_u
o
6000 -
~
£
¦o
r
E
4000 -
o
U
2000 -
0 -
Table 1-8D: Conductivity/ISA Relationships
pH Adjusted to 4 with Sulfuric Acid 05/01/01
y = 269.242X
R2 = 0.999
0 5 10 15 20 25
Volume (mL) of 1.0M ISAB (Sodium Acetate) in 200 mL of water
-------
Table 1-9
Definitive
Result RL
(PPb)
Field ID
ID
Conductivity
(uMhos/cm)
Other Known Interferents** Anions
and TOC in (ppm); Organic compounds in ppb
4
ED-NM-MW01A-W11
P-13
1.47
EB
4
ED-NM-MW03A-W07
P-15
417
F = 0.82, P04 = 3.1, N03-N = 0.4, TOC = 0.47
4
ED-NM-MW02A-W11
P-14
430
F = 1, P04 = 1.2
4
ED-USGS-W1AE4-W05
P-21
432
Not Available
4
ED-USGS-W1AE2-W06
P-20
433
Not Available
4
ED-NM-MW06-W06
P-18
435
TOC = 0.5
4
ED-USGS-W1C4-W09
P-25
482
Not Available
4
ED-USGS-W1C2-W08
P-23
728
Not Available
4
ED-199-MW01 -W14
P-8
796
4
ED-NM-MW04B-W13
P-16
805
Br = 0.4, F = 0.9, P04 = 5.4, TOC = 0.29
4
ED-USGS-W1C3-W08
P-24
823
Not Available
4
ED-USGS-W1C1-W07
P-22
955
Not Available
4
ED-NM-MW01A-W10
P-12
1012
B r= 0.36, F = 0.98, P04 = 15, TOC = 1.2, N03-N = 0.1
16
ED-NM-MW05-W14
P-17
1031
Contains high levels of organic contaminants
400
ED-286-MW01-W08
P-10
1201
Br <1, F <1
4
ED-285-MW02-W06
P-9
1337
N03-N = 0.18, Br = 0.76, F <1
16
ED-196-MW06-W15
P-7
1345
Br = 1.4, F = 0.64, N03-N = 1.4, P04 <0.1
4
ED-NM-MW07-W11
P-19
1363
Br = 1.4, N03-N = 0.14, P04 = 0.13, TOC = 12.4
4000
ED-196-MW01-W09
P-5
1426
Br = 1.2, F = 0.8, P04, N03-N < 0.2
4
ED-196-MW03-W11
P-6
1671
Br =1.1, F = 0.7, P04 = 0.14, N03-N = 0.17;
toluene=44 ppb
16
ED-189-MW03-W08
P-4
1813
Contains high levels of organic contaminants
16
ED-189-MW02-W13
P-3
1948
Contains high levels of organic contaminants
16
ED-189-MW01-W25
P-2
2100
Contains high levels of organic contaminants
16
ED-189-MW01-W24
P-1
2100
N03-N = 12.6, Br = 1.0, F = 0.8; high levels of organic
contaminants
4
ED-422-MW01-W07
P-11
2190
Br = 1.3, F<1, N03-N = 6.3, CI = 500
Contains high levels of organic contaminants:
11 DCA@1.1, FC113@ 9.4,
cis12DCE@8.4,TCE@11,TIC@16 (ppb)
ED-422-MW01-W07-RE1
P-102
NA
ED-422-MW01-W07-RE2
P-103
NA
4
ED-422-MW01-W07-RE3
P-104
NA
"Known intrferents determined from historical data for specified wells from previous sampling events. Not all methods and analytes
were performed at each location.
EB=Equipment Bank
Br=Bromide
Cl=Chloride
F=Fluoride
N03=Nitrate as nitrogen
P04=Phosphate
TOC=Total Organic Carbon
ppb=parts per billion (|ig/L)
ppm=parts per million (mg/L)
1 lDCA=l,l-Dichloroethane
cis 12DCE= c/5-l,2-Dichloroethene
FC113=Freon 113
TCE=Trichloroethene
TIC=Tentatively Identified Compound
-------
Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
SECTION 4 TABLES
L:\WORK\42674\WP\07XLETTER OF FINDINGS TASK 1-5.DOC
61
Final, October 2001
-------
Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
TABLES 4-1 THROUGH 4-23
L:\WORK\42674\WP\07XLETTER OF FINDINGS TASK 1-5.DOC
62
Final, October 2001
-------
Table 4-1 A: Effect of Carbonate/Bicarbonate
Interference on Perchlorate ISE Readings:
50/100/300 ppm Bicarbonate (pH=8.0/8.4/8.7)
• * ja
CL.
•a c
re ,=
4> —
* O
o» ^
1- ®
J®
O C
Z £
^ S
0. U
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
|i
—
r—— ="""
_ —
_ A .... ...
:A
'
1
SO
100
160
200
260
300
360
Sodium Bicarbonate Concentration In ppm
(Note; 60% Recovery of Subsequent CCV]
* PefcMoraEc- Concentration - Oppb
ISE = Ion Selective Electrode
ppb = parts per biliion (jjg/L)
ppm = parts per million (mg/L) CCV = Continuing Calibration Verification
-------
Table 4-1B: Effect of Carbonate/Bicarbonate
on Perchlorate I5E Readings:
Interference Removed by Acidification to pH = 4.0
70.0
60.0
D) a
£ S 60.0
c
a
<33 /-
Q£ 40.0
OJ 'O
13 E
fe E 30-0
¦= nt
% £
o 20 0
£L O
10.0
0.0
0 50 100 150 200 250 300 350
Sodium Bicarbonate Concentration in ppm
' B
¦
1
1 i r i
* PorclVorate Concentration - 0 ppb
Pftirhiorare Concentration - in ppri
* Ponchtaratc Concentration - 20 ppb
— Perchlorare ConcfinTatian - 50 ppb
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
60.0
Table 4-2A: Effect of Chloride Interference on
Perchlorate 1SE Readings:
0-500 ppm Chloride; Approximate pH = 7.0
60.0
"a
,E a.
"u c
-------
c
o
flj a
IS 2
^ I1
H |
Oj. O
£L O
Table 4-2B: Effect of Chloride Interference on
Perchlorate ISE Readings: 0-500 ppm Chloride; pH = 4.0
eo.o
70 .o -
n 60.0 --
U5
£ a
*D
at
cr
60.0
40.0 -
30.0 -
20.0 -
10.0
0.0 -
z
100 200 300 400
Chloride Concentration in ppm
500
—i
600
-Perchlorals Concentratrari = 0 ppb
Pi-ichldiali! t.'«ini:iMilriil«in 411 ppil:
- Perchlorale («30 ppm) Correction Fador for Chloride
-Perchlorate Concentration = 2fl ppb
PiMtihlnriili! Ciini:i!ntriiliun /II pfih
Perchlorate (30-50 ppm) Correction Facsor for Chloride
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
LI .O
® a
,E a.
oc
I
o
L.
CL
<0
h
o
£
o
O
Table 4-2C: Effect of Choride Interference on
Perchlorate ISE Readings, Extended Study:
0-2000 ppm Chloride; pH =4.0
GO.O i
TO O -
eo o -
¦- &0 0
40.0
30.0
£0.0 tH
10.D
0 0
-¦*-
r4i~-
"I
C
*"
500 1000 1500
Chloride Concentration in ppm
2000
Perchlorase Cenc-aiHraSien = 0 ppb
• Pftrrhlnr.n"^ Giw.nn1r.itinn — 4Tl pph
Piiri:hlnr;iCij (<"31 [ifiirif Civrnrliiin h;ji:I nr hir Chliinrli:
O Purchlury'.t* Cum. unlr^ioM IJ ppb isludy
Perchlorate Comcenilration - ppb Extended Study
-m— Psrchlorate CanterttraEian = 20 ppb
t Pfirr.hlnrnf^ Cnrir.cnlrntinri - 7fi pph
Kiiriihliiriili' r.-Sl Wi j urn) Ciiin-;:linn h n 1m lur [llilmiiii:
G Piirthlurutu* Uurtvurflrutiwi JU ppii fc tU.'ndt.'iJ -ilutfy
-g— r3f chlorate Conceniraticf) - 7D jap-a E a;teridgd Stuffy
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
•h
Q.
V
(j
C
o
o
Table 4-3A: Effect of Nitrate Interference on
Perch lorate ISE Readings: 0-0.45 ppm N03-N; pH = 4,0
70.0
•• n
,E a
S -
a)
EC
s
2
o
60.0 —
50.0
40.0
c
o
1 %
2 £ 30.0 4-
20.0 4-r~-r
10.0
0.0
—
0.1 0.2 0.3 0.4
Nitrate Concentration in ppm N03-N
0.5
Par: htoratft Conceniration - 0 pfih
—Parchlorate Conc^rwation - 10 ppb
—•— Parehtarate Concaniratifin - ?\) ppb
- Parchlorafa Concentration - 50 ppb
— Psrchloratft Correction Factor for Nifrats
-*- Perforate Concentration - 0 p®b CvterKted Stud/
o Porchlorato Conccmration - 20 ppb Extended Study
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
® Q.
,E CL
He
£ g
01 =
"S
2 ±=
o c
— i>
* g
0} o
CL L>
Table 4-3B: Effect of Nitrate Interference on
Perchlorate ISE Readings, Extended Study:
0-10 ppm N03-N; pH = 4.0
~~i i i i i r i i i i i i i f i r
a
JL.JL.-
, I
X-1.-1
us -r"
A-
Tt
t
4-4
0 0.5 1 15 2 2 5 3 3.5 4 4 5 5 5 5 6 5.5 7 7 5 9 © 5 S 9 .5 10
Nitrate as Nitrogen (N03-N) Concentration in ppm
• PerchforsTo Concentrator! - Qppb
• Perchioratc Concentration - 10 ppb
¦ Perchloraie Concentration - 3C ppb
• P'orchfenrsto Concentration - 50 ppb
PercNSorstc Correction Factor for Nitrate
a PerchHorate Concentration - 0 ppb Extended Study
-a-1 'eichkirtile Concentration = 20 ppb hxltmdeii Studi1
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
Table 4-4: Effect of Bromide Interference on Perchlorate
ISE Readings: 0-5 ppm Bromide; pH =4.0
C ^
= a.
c
r^i ~
43 c
^ I
4a _
2 is
0 c
— ^
1 =
£ o
a o
70.0
60.0
50.0
40.0
30.0
20 0
10.0
0.0
— *
2 3 4
Bromide Concentration in ppm
PwctilGfHte Concentralion = 0 ppb
¦ Pcrchlwsto concontrau on - 10 ppb
Percfilwtfie Coriceritraiiori = 20 ppb
—— Perchlorate- Concentration - 50 ppb
- Pert til waffle Correction factor for bromi d»3
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
-• n
u> Q.
E CL
"O c
(0 .=
c
a §
a, =
3 2
H
— nt
" §
a o
Table 4-5: Effect of Fluoride Interference on Perch lorate
ISE Readings: 0-5 ppm Fluoride; pH =4.0
60.0
50.0
40,0
30.0
20.0
10.0
0.0
2 3 4
Fluoride Concentration In ppm
~~T
5
—¥— PwcTiioigfa Concentration -
0
ppO
¦ PerchloisTe Concentration -
10
ppb
* Pcrchlorato Concentration -
¦20
ppb
— Perchlwale Coriceritrfcjlfcri =
50
ppi>
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
60,0
50 0
.= Cl
¦o = 4o,o
(S n
tt O
- "p 30.0
TK w
E is
D C
2 £
- =
q! u
30 0
10 0
Table 4-6: Effect of Phosphate Interference on
Perchlorate ISE Readings: 0-20 ppm Phosphate; pH = 4
o.o
6 10 16 20 26
Concentration of Phosphate in ppm
—Pwchlorara Concentration
- 0
ppb
F *tf chlorate ConcfinliHlion:
10
PPk
-±- F "en chlorate Corner ill all on
= 20
\>pb
* Perchlorate Coo: enttati on
-50
PtO
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
Table 4-7 Correction Factors: Subtract from Initial Perchlorate Reading
For Perchlorate Reading <30 ug/L (ppb)
Chloride Concentration in mg/L
Correction Factor to Perchlorate in
(PPm)
ug/L (ppb)
0
0.0
10
0.6
20
1.3
30
2.0
40
2.6
50
3.2
60
3.7
70
4.1
80
4.6
90
5.0
100
5.4
125
6.2
150
6.8
175
7.4
200
8.0
225
8.6
250
9.1
275
9.6
300
10.0
325
10.4
350
10.7
375
11.0
400
11.3
425
11.6
450
11.9
475
12.2
500
12.5
600
13.7
700
14.9
800
16.1
900
17.3
1000
18.5
1500
22.9
2000
27.2
to Chloride Interference
For Perchlorate Reading 30-45 ug/L (ppb)*
Chloride Concentration in mg/L
Correction Factor to Perchlorate in
(PPm)
ug/L (ppb)
0
0.0
10
0.4
20
0.8
30
1.2
40
1.6
50
1.9
60
2.2
70
2.4
80
2.6
90
2.8
100
3.0
125
3.4
150
3.7
175
4.1
200
4.4
225
4.8
250
5.1
275
5.5
300
5.8
325
6.1
350
6.4
375
6.7
400
6.9
425
7.1
450
7.3
475
7.5
500
7.7
600
8.5
700
9.3
800
10.1
900
10.9
1000
11.7
1500
15.4
2000
19.0
* For perchlorate results greater than 50 ppb, chloride interference is negligible or negative. Dilution and reanalysis os recommended.
-------
Table 4-8 Correction Factors: Subtract from Initial Perchlorate Reading Due to Nitrate Interference
For Nitrate-as-Nitrogen Concentration 0.05 - 4.4 ppm For Nitrate-as-Nitrogen Concentration 4.6-15 ppm
Nitrate as Nitrate
(NQ3) in mg/L (ppm)
Nitrate as Nitrogen
(NQ3-N) in mg/L (ppm)
Correction Factor to
Perchlorate in ug/L (ppb)
0.22
0.05
0.44
0.1
2.5
0.89
0.2
4.5
1.33
0.3
6.0
1.77
0.4
7.5
2.22
0.5
9.0
2.66
0.6
10.4
3.10
0.7
11.6
3.54
0.8
12.6
3.99
0.9
13.6
4.43
14.5
4.87
15.3
5.32
16.0
5.76
16.9
6.20
1.4
17.7
6.65
18.5
7.09
19.3
7.53
20.1
7.97
20.9
8.42
21.7
8.86
2.0
22.5
9.75
2.2
24.0
10.63
2.4
25.5
11.52
2.6
27.0
12.40
2.8
28.4
13.29
3.0
29.8
14.18
3.2
31.2
15.06
3.4
32.5
15.95
3.6
33.8
16.83
3.8
35.1
17.72
4.0
36.4
18.61
4.2
37.7
19.49
4.4
38.9
Nitrate as Nitrate
(NQ3) in mg/L (ppm)
Nitrate as Nitrogen
(NQ3-N) in mg/L (ppm)
Correction Factor to
Perchlorate in ug/L (ppb)
20.38
4.6
40.1
21.26
4.8
41.3
22.15
5.0
42.5
23.04
5.2
43.7
23.92
5.4
44.8
24.81
5.6
45.9
25.69
5.8
47.0
26.58
6.0
48.0
27.47
6.2
49.0
28.35
6.4
50.0
29.24
6.6
51.0
30.12
6.8
51.9
31.01
7.0
52.8
31.90
7.2
53.7
32.78
7.4
54.6
33.67
7.6
55.5
34.55
7.8
56.4
35.44
8.0
57.3
36.33
8.2
58.2
37.21
8.4
59.1
38.10
8.6
60.0
38.98
8.8
60.9
39.87
9.0
61.8
40.76
9.2
62.7
41.64
9.4
63.6
42.53
9.6
64.4
43.41
9.8
65.2
44.30
10.0
66.0
48.73
11.0
66.8
53.16
12.0
67.6
57.59
13.0
68.4
62.02
14.0
69.2
66.45
15.0
70.0
-------
Table 4-9 Correction Factors: Subtract from Initial Perchlorate Reading Due to Bromide Interference
For Bromide Concentration 0.2 - 5.0 mg/L (ppm)
Bromide Concentration in mg/L (ppm)
Correction Factor to Perchlorate in ug/L (ppb)
0
0
0.2
0.6
0.4
1.2
0.5
1.5
0.6
1.75
0.8
2.2
1.0
2.6
1.2
2.9
1.4
3.2
1.6
3.5
1.8
3.75
2.0
4.0
2.2
4.25
2.4
4.5
2.6
4.7
2.8
4.9
3.0
5.1
3.2
5.3
3.4
5.5
3.6
5.7
3.8
5.9
4.0
6.1
4.2
6.3
4.4
6.5
4.6
6.7
4.8
6.9
5.0
7.1
-------
Table 4-10
milli- Cone, (ppb) Date Sample ISA/ISAB ICAL ISA/ISAB Assoc. Check pH of Calibration /
Sample ID pH mL Sample volts Reading Analyzed per 200 mL per 200 mL Standard %R Comments
P-1
Not Adi
200 mL
376.20
70.6
1/10/2001
2mL of 0.4M ISA
2mL of 0.4M ISA
20 ppb 95%R
pH Not Adjusted
P-1
4.02
200 mL
281.00
79.7
3/02/2001
2mL of 0.4M ISA
2mL of 0.4M ISA
100 ppb 117%R
pH 4.0
P-2
Not analyzed; Contains
high levels of organics
P-3
Not analyzed; Contains
high levels of organics
P-4
Not analyzed; Contains
high levels of organics
P-5 (400x dilution)
3.99
200 mL
302.40
61.1
1/29/2001
ImLofSentek ISAB
1mL of Sentek ISAB
20 ppb 100% R
pH 4.0 24423 ppb
P-5 (400x dil) + 20ppb
3.98
200 mL
297.10
78.6
1/29/2001
1mL of Sentek ISAB
1mL of Sentek ISAB
20 ppb 100%R
pH 4.0 MS 87.8%R
P-6
P-6
P-6
Not Adj
Not Adj
Not Adi
140 mL
140 mL
140 mL
395.00
389.50
398.50
25.9
20.9
12.5
1/10/2001
1/11/2001
1/11/2001 RE
2mL of 0.4M ISA
2mL of 0.4M ISA
2mL of 0.4M ISA
2mL of 0.4M ISA
2mL of 0.4M ISA
2mL of 0.4M ISA
20 ppb 80%R
100 ppb 68.7%R
40 ppb 34%R
pH Not Adjusted
pH Not Adjusted
pH Not Adjusted
P-6
3.95
140 mL
330.20
14.0
1/25/2001
2mL of 0.4M ISA
ImLofSentek ISAB
20 ppb 96%R
pH 4.0
P-7
Not Adi*
135mL
378.50
34.1
1/11/2001
2mL of 0.4M ISA
2mL of 0.4M ISA
100 ppb 68.7%R
pH Not Adjusted
P-7
Not Adi*
135mL
382.80
26.3
1/11/2001 RE
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R
pH Not Adjusted
P-7
3.99
140 mL
323.10
23.4
1/26/2001
2mL of 0.4M ISA
ImLofSentek ISAB
20 ppb 100%R
pH 4.0
P-7 (dil fac=2) + 20 ppb
3.98
200 mL
316.60
31.6
1/26/2001
2mL of 0.4M ISA
1mL of Sentek ISAB
2- ppb 110% R
pH 4.0 MS 75.8%R
P-7 dilution factor = 2
3.99
100 mL
330.80
16.4
1/26/2001
2mL of 0.4M ISA
1mL of Sentek ISAB
20 ppb 100%R
pH 4.0
'Likely caused loss
of sensitivity
P-8
Not Adi
140 mL
407.30
8.2
36902.00
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R
pH Not Adjusted
pH Not Adjusted
pH Not Adjusted
pH 4.0
P-8
Not Adi
140 mL
385.30
33.6
1/12/2001
5mL of 0.4M ISA
5mL of 0.4M ISA
50 ppb 89%R
P-8
Not Adi
140 mL
385.30
33.0
1/12/2001
10mL of 0.4M ISA
10mL of 0.4M ISA
50 ppb 87%R
P-8
3.99
140 mL
321.90
19.3
1/25/2001
10mL of 0.4M ISA
ImLofSentek ISAB
20 ppb 99%R
P-9
Not Adi
180 mL
326.49
8.5
1/15/2001
ImLofSentek ISAB
ImLofSentek ISAB
50 ppb 70%R
pH Not Adjusted
-------
P-9
8.27
180 mL
309.00
31.2
1/17/2001
1mL of Sentek ISAB
1mL of Sentek ISAB
pH Not Adjusted
P-9
4.42
180 mL
362.00
7.0
1/17/2001
ImLofSentek ISAB
1mL of Sentek ISAB
50 ppb 80% R
pH 4.0
P-9
3.97
180 mL
343.90
14.6
1/24/2001
1mL of Sentek ISAB
1mL of Sentek ISAB
20 ppb 94% R
pH 4.0
P-10 (1:200)
Not Adi
200 mL
408.80
12.4
1/10/2001
2mL of 0.4M ISA
2mL of 0.4M ISA
20 ppb 80%R
pH Not Adjusted
P-10 (1:200)+20ppb ms
Not Adi
200 mL
397.50
22.6
1/10/2001
2mL of 0.4M ISA
2mL of 0.4M ISA
20 ppb 80%R
pH Not Adjusted
P-10 (200x dilution)
3.96
200 mL
324.10
21.7
1/29/2001
2mL of 0.4M ISA
1mL of Sentek ISAB
20 ppb 100%R
pH 4.0 4336 ppb
MS = Matrix Spike
P-11
P-11
_____
resampled)
4.02
3.91
3.98
140 mL
200 mL
200 mL
301.50
285.80
278.80
63.7
45.3
60.1
1/29/2001
2/23/2001
2/23/2001
ImLofSentek ISAB
ImLofSentek ISAB
ImLofSentek ISAB
1mL of Sentek ISAB
1mL of Sentek ISAB
1mL of Sentek ISAB
20 ppb 95% R
20 ppb 83% R
20 ppb 94% R
pH 4.0
pH 4.0
pH 4.0
P-103 (P-11
resampled)
4.01
200 mL
287.60
42.2
2/23/2001
ImLofSentek ISAB
1mL of Sentek ISAB
100 ppb 87%R
pH 4.0
P-104 (P-11
resampled)
4.04
200 mL
288.50
40.7
2/23/2001
ImLofSentek ISAB
1mL of Sentek ISAB
20 ppb 83% R
pH 4.0
P-102 + 20 ppb
4.02
200 mL
275.90
67.6
2/23/2001
ImLofSentek ISAB
1mL of Sentek ISAB
20 ppb 94% R
pH 4.0 MS 111 %R
P-102 + 20 ppb
4.03
200 mL
281.10
54.8
2/23/2001
ImLofSentek ISAB
1mL of Sentek ISAB
20 ppb 94% R
pH 4.0 MS 47.4%R
P-12
Not Adi
140 mL
394.10
15.4
36902.00
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R
pH Not Adjusted
P-12
3.97
140 mL
332.10
15.4
1/26/2001
2mL of 0.4M ISA
1mL of Sentek ISAB
2- ppb 110% R
pH 4.0
P-13 (EB)
140 mL
442.30
1.6
36902.00
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R
pH Not Adjusted
P-13 (EB)
3.95
140 mL
361.40
4.0
1/26/2001
2mL of 0.4M ISA
1mL of Sentek ISAB
20 ppb 103%R
pH 4.0
P-14
Not Adi
140 mL
415.20
5.6
36902.00
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R
pH Not Adjusted
P-14
Not Adi
140 mL
386.90
31.0
1/12/2001
5mL of 0.4M ISA
5mL of 0.4M ISA
50 ppb 89%R
pH Not Adjusted
P-14
Not Adi
140 mL
386.90
30.5
1/12/2001
10mL of 0.4M ISA
10mL of 0.4M ISA
50 ppb 87%R
pH Not Adjusted
P-14
3.97
140 mL
337.20
10.7
1/25/2001
10mL of 0.4M ISA
1mL of Sentek ISAB
20 ppb 99%R
pH 4.0
P-15
Not Adi
140 mL
418.90
4.7
36902.00
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R
pH Not Adjusted
P-15
3.98
140 mL
344.10
8.9
1/26/2001
2mL of 0.4M ISA
1mL of Sentek ISAB
20 ppb 103%R
pH 4.0
P-16
Not Adi
200 mL
303.00
47.0
1/15/2001
ImLofSentek ISAB
1mL of Sentek ISAB
50 ppb 46% R
pH Not Adjusted
-------
P-16 |6.50 1200 mL
322.90 I29.0 1.17.2001 |l mL of Sentek ISAB |l mL of Sentek ISAB |50 ppb 80%R?
pH 4.0
P-16/H2S04 pH 6
P-16 H2S04
6.00 200 mL 341.40 17.9 :1/15/2001 :1 mL of Sentek ISAB :1 mL of Sentek ISAB :50 ppb 78%R
4.00 |200 mL .341.70 14.6 h/17/2001 h mL of Sentek ISAB |l mL of Sentek ISAB |50 ppb 80%R?
pH 4.0
pH 4.0
P-16 H2S04
4.40 i200 mL
341.10 Il5.0 1.17.2001
1mL of Sentek ISAB
1 mL of Sentek ISAB
50 ppb 80%R?
pH 4.0
P-16
3.96 200 mL
337.80 h 8.0
1/24/2001
1mL of Sentek ISAB
1mL of Sentek ISAB
20 ppb 92% R
pH 4.0
P-17
Not analyzed; Contains!
high levels of organics !
]
P-18 iNotAdi
140 mL
418.50
4.8
36902.00
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R (pH Not Adjusted
P-18
3.96
140 mL
345.60
8.3
1/26/2001
2mL of 0.4M ISA il mL of Sentek ISAB
20 ppb 103%R (pH 4.0
MS = Matrix Spike
P-19
Not Adj h 40 mL 1409.10
7.5 136902.00
2mL of 0.4M ISA
2mL of 0.4M ISA
40 ppb 34%R
Not Adi
P-19
Not Adj 1140 mL [384.60 [34.8 [l/12/2001 |5mL of 0.4M ISA
NotAdj 140 mL 384.60 34.1 1.12.2001 h OmL of 0.4M ISA
5mL of 0.4M ISA
50 ppb 89%R
Not Adi
P-19
10mL of 0.4M ISA
50 ppb 87%R
Not Adi
P-19
4.03
140 mL 328.10 |l 5.2
1/25/2001 llOmL of 0.4M ISA
1mL of Sentek ISAB
20 ppb 107%R
pH 4.0
P-20 INotAdi
135mL 399.60 ll1.8
1/11/2001 RE l2mL of 0.4M ISA [2mLof0.4M ISA
40 ppb 34%R [Not Adi
P-20 13.95
140 mL |345.20 [8.4
!
1/26/2001 |2mL of 0.4M ISA
1mL of Sentek ISAB
20 ppb 103%R ipH 4.0
P-21 Not Adj
200 mL
393.70 27.7 1.10.2001 2mLof0.4M ISA 2mLof0.4M ISA
388.30 |26.8 h/10/2001 RE )5mL of 0.4M ISA |5mL of 0.4M ISA
20 ppb 80%R iNot Adj
P-21 INotAdi )200 mL
60 ppb 97%R [Not Adj
P-21 (1:2) I Not Adj I200 mL
398.00 h 5.5 h/10/2001 RE bmL of 0.4M ISA [5mL of 0.4M ISA [60 ppb 97%R iNotAdj
P-21 (1:4)
Not Adj [200 mL
409.90
7.9 h/10/2001 RE [5mL of 0.4M ISA l5mL of 0.4M ISA [60 ppb 97%R
Not Adi
P-21 (1:5)
Not Adi
200 mL
416.60
5.4 1/10/2001 RE
5mL of 0.4M ISA
5mL of 0.4M ISA
60 ppb 97%R
Not Adi
P-21
Not Reanalyzed at pH
4; No more sample for
reanalysis after original
sample used for serial
dilution
P-22
3.99
140 mL
348.50
6.8 1.29.2001
1mL of Sentek ISAB
1mL of Sentek ISAB
20 ppb 100%R
pH 4.0
P-23
Not Adi
200 mL
328.66
7.3 1.15.2001
1mL of Sentek ISAB
1mL of Sentek ISAB
50 ppb 70%R
Not Adi
-------
P-23
4.01
200 mL
354.20
10.1
1/24/2001
ImLofSentek ISAB
1mL of Sentek ISAB
20 ppb 94% R
pH 4.0
P-24
3.99
140 mL
338.50
10.9
1/29/2001
ImLofSentek ISAB
1mL of Sentek ISAB
20 ppb 107%R
pH 4.0
P-25
3.99
140 mL
351.80
5.8
1/29/2001
ImLofSentek ISAB
1mL of Sentek ISAB
20 ppb 100%R
pH 4.0
tap water
Not Adi
200 mL
305.10
40.3
1/15/2001
1mL of Sentek ISAB
1mL of Sentek ISAB
Not Adi
tap water
pH 4.0
200 mL .364.70
6.8
1/15/2001
1mL of Sentek ISAB
1mL of Sentek ISAB
pH 4.0
Assoc. = associated m = molar ppb = parts per billion (|jg/L)
dil fac =dilution factor mL = milliliter %R = percent recovery
EB = equipment blank ms = matrix spike RE = reanalysis
ISA and ISAB = ionic strength adjustor solutions not adj = not adjusted
-------
Table 4-11 Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion
Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination
ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 22, 2001
330 -
320 -
(ft
3 310 -
>
| 300 -
290 -
280 -
0 20 40 60 80 100 120
Perchlorate Cone in ppb
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter
^24.8
V = -14.884Ln(x) + 35947
\^3154
R2 = 0.9964
^4040
U997
' 290.2
Sample/Calibration ID
pH
Sample
Volume
Millivolts
Reading
Concentration in ppb
10
6.7
200 mL
324.8
10.3
20
6.69
200 mL
315.4
19.3
40
6.68
200 mL
304.0
41.5
60
6.7
200 mL
299.7
55.5
100
6.67
200 mL
290.2
105.0
Calibration Date
1/22/2001
Time
12:00pm
Temperature
21
°C
-------
Slope
14.884
| Intercept
359.5
Sample/Calibration ID
PH
Sample
Volume
Millivolts
Reading
Concentration in ppb
LCS/ICV
i 6.72
o
o
CM
mL
302.7
45.3
MB/ICB
: 6.74
O
O
CM
mL
335.7
4.9
blank + Oppm CI
j 6.73
O
O
CM
mL
335.8
4.9
blank + 50ppm CI
; 6.72
O
O
CM
mL
332.6
6.1
blank + 100ppm CI
669
O
O
CM
mL
332.9
6.0
blank + 300ppm CI
; 6.67
O
O
CM
mL
328.8
7.9
blank + 500ppm CI
i 6.65
O
O
CM
mL
326.8
9.0
ccv
6.7
O
O
CM
mL
305.6
37.3
ccb
6.53
O
O
CM
mL
337.7
4.3
10ppb std +0ppm HC03
: 6.85
O
O
CM
mL
325.3
9.9
10ppb std +50ppm HC03
8.05
O
O
CM
mL
315.2
19.6
10ppb std +50ppm HC03*
; 6.74*
O
O
CM
mL
338.8
4.0*
10ppb std +50ppm HC03*
: 4.02*
O
O
CM
mL
382.5
0.2*
60 ppb standard
; 6.67
O
O
CM
mL
299.0
58.1
blank
6.92
O
O
CM
mL
336.7
4.6
blank + 50ppm HC03
j 8.02
O
O
CM
mL
3115
25.1
blank + 100ppm HC03
( 8.38
O
O
CM
mL
308.2
31.3
blank + 300ppm HC03
8.68
O
O
CM
mL
305.2
38.3
blank + 300ppm HC03*
: 3.93*
O
O
CM
mL
442.1
0.0*
60 ppb standard
: 6.65
200
mL
306.2
35.8
Data in bold used for graphs in Tables 4-1 and 4-2
* pH adjusted with sulfuric acid. As the calibration curve uses standards not pH adjusted with acid, the perchlorate concentrations
reported for pH adjusted samples indicate relative changes in perchlorate readings but are quantitatively inaccurate as the
referenced calibration curve is not applicable to these samples.
-------
Table 4-12
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 23, 2001
o
>
360
350 -
340 -
330 -
320
310 -
300 -
290 -
280
0
Sentek Probe with 1 mL of Sentek ISAB in 200 mL
Using Orion 290A+ Meter
\350.2
y = -24.145Ln(x) + 406.51
^^335.3
R2 = 0.9977
~ 295.3
20
40
60
30
100
120
Perchlorate Cone in ppb
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.03
200 mL
350.2
10.3
20
4.00
200 mL
335.8
18.7
40
4.02
200 mL
316.8
41.1
60
3.95
200 mL
306.9
61.9
100
4.03
200 mL
295.8
98.0
Calibration Date
1/23/2001
Time
2:30
Temperature
22
°C
Slope
24.145
|| Intercept
406.51
-------
Sample/Calibration ID
PH
Sample
Volume
Millivolts
Reading
Concentration in ppb (pH 4.0 CAL Curve)
LCS/ICV
3.98
o
o
CM
ml_
311.1
52.0
MB/ICB
3.98
O
O
CM
mL
369.9
4.6
Blank
6.84
O
O
CM
mL
348.7
11.0**
20 ppb std
6.83
O
O
CM
mL
325.9
28.2**
Blank + 50ppm bicarb*
6.78*
O
O
CM
mL
343 6
13.5**
20 ppb std
6.82
O
O
CM
mL
328 7
25.1**
Blank + 100ppm bicarb*
6.80*
O
O
CM
mL
334.8
19.5**
20 ppb std
6-79
O
O
CM
mL
S29-3
24.5**
Blank + 300ppm bicarb*
6.82*
O
O
CM
mL
335.3
19.1**
20 ppb std
6.78
O
O
CM
mL
330.6
23.2**
20 ppb std
4.04
O
O
CM
mL
3386
16.7
Blank
4.03
O
O
CM
mL
367.6
5.0
Blank + 50ppm bicarb
3.97
O
O
CM
mL
367.1
5.0
20 ppb std
4.02
O
O
CM
mL
338.4
16.8
Blank + 100ppm bicarb
3.98
O
O
CM
mL
3672
5.1
20 ppb std
4.02
O
O
CM
mL
337.9
17.1
Blank + 300ppm bicarb
4.03
O
O
CM
mL
3663
5.3
20 ppb std
4.00
O
O
CM
mL
337.2
17.6
50 ppb std
3.97
O
O
CM
mL
310.6
53.1
50 ppb std +50ppm bicarb
3.97
O
O
CM
mL
310.8
52.7
50 ppb std +100ppm bicarb
4.02
O
O
CM
mL
310.4
53.5
50 ppb std +300ppm bicarb
4.02
O
O
CM
mL
310.3
53.8
20 ppb std
400
O
O
CM
mL
336 9
17.9
20 ppb std +50ppm bicarb
3.96
20°
mL
335.9
18.6
20 ppb std +100ppm bicarb
3.97
o
o
CM
mL
3362
18.4
20 ppb std +300ppm bicarb
3.99
O
O
CM
mL
335.4
19.0
10 ppb std
4.01
O
O
CM
mL
349.2
10.7
10 ppb std +50ppm bicarb
4.03
O
O
CM
mL
349.1
10.8
10 ppb std +100ppm bicarb
4.01
O
O
CM
mL
348.6
11.0
10 ppb std +300ppm bicarb
3.99
O
O
CM
mL
348.1
11.2
CCV (60 ppb)
4.02
O
O
CM
mL
308.4
58.2
CCB
4.03
O
O
CM
mL
372.4
4.1
* Adjusted
Concentration in ppb
(Non-Acidified pH
Curve)
g 4***
18.5*** (92.5%R)
0 >| ***
16.2*** (81,0%R)
12 2***
15.8*** (79.0%R)
>j 2 Q***
14.9*** (74.5 %R)
* pH adjusted to approximately pH 6.7 using sulfuric
acid so bicarbonate is converted to carbonate.
** As the calibration curve uses standards adjusted to
pH 4.0 with acid, the perchlorate concentrations
reported for samples pH adjusted to 6.8 or for non-pH
adjusted check standards indicate relative changes in
perchlorate readings but are quantitatively inaccurate.
*** Modified results were quantitated with calibration
data from 1/11/01 to simulate calibration at pH 6.75
and demonstrate relative effect of carbonate
interference. Note loss of sensitivity in check
standards due to carbonate interference.
Data in bold used for graphs in Table 4-1
-------
Table 4-13
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: None
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 18, 2001
Sentek Probe with 1mL of Sentek ISAB in 200mL
340.0 -
330.0 -
320.0 -
| 310.0 -
| 300.0 -
i 290.0 -
280.0 -
270.0 -
260.0 -
0 20 40 60 80 100 120
Perchlorate Cone in ppb
Using Orion 290A+ Meter - No pH Adjustment
^29.5
y = -20.856Ln(x) + 378.43
\^316.9
R2 = 0.9982
^ 302.1
» 281.7
t 1 1 1 r
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
6.80
200 mL
329.5
10.4
20
6.81
200 mL
316.9
19.1
40
6.80
200 mL
302.1
38.9
60
6.80
200 mL
293.1
59.8
100
6.82
200 mL
281.7
103.3
Calibration Date
1/18/2001
Time
12:30pm
Temperature
20.5
UC
Slope
20.856
|| Intercept
378.43
-------
Sample/Calibration ID
PH
Sample
Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
6.79
200
mL
297.2
49.1
MB/ICB
6.74
200
mL
342.2
5.7
20 ppb std
6.72
200
mL
316.8
19.2
20 ppb std + 50ppm CI
6.69
200
mL
318.1
18.0
20 ppb std + 100ppm CI
6.68
200
mL
318.9
17.4
20 ppb std + 300ppm CI
6.65
200
mL
319.5
16.9
10 ppb std
6.65
200
mL
328.0
11.2
10 ppb std + 50ppm CI
6.63
200
mL
328.4
11.0
10 ppb std + 100ppm CI
6.61
200
mL
328.6
10.9
10 ppb std + 300ppm CI
6.6
200
mL
325.5
12.7
10 ppb std + 400ppm CI
658
200
mL
325.1
12.9
10 ppb std + 500ppm CI
6.58
200
mL
324.1
13.5
50 ppb std
6.74
200
mL
297.0
49.6
50ppb std + 50ppm CI
6.7
200
mL
297.9
47.5
50ppb std + 100ppm CI
6.68
200
mL
298.7
45.7
50ppb std + 300ppm CI
6.64
200
mL
301.1
40.8
50ppb std + 400ppm CI
6.63
200
mL
301.7
39.6
CCV (10Oppb)
6.88
200
mL
283.7
93.9
CCB
6.64
200
mL
356.8
2.8
Data in bold used for graphs in Table 4-2
-------
Table 4-14
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 18, 2001
Sentek Probe with 1 mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter - pH 4
380 -t
360 -
£
340 -
o
>
320 -
S
300 -
230 -
260 -
\365.1
y = -31.628Ln(x) +439.8
^¦*346.5
R2 = 0.9959
3254
" 292.5
20 40 60 80
Perchlorate Cone in ppb
100
120
Sample/Calibration ID
PH
Sample
Volume
Millivolts Reading
Concentration in ppb
10
3.98
200 mL
365.1
10.6
20
3.99
200 mL
346.5
19.1
40
3.98
200 mL
325.4
37.2
60
3.96
200 mL
310.1
60.4
100
3.97
200 mL
292.5
105.3
Calibration Date
1/18/2001
Time
2:45pm
Temperature
20.5°C
Slope
31.628
Intercept
439.8
-------
Sample/Calibration ID
PH
Sample
Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
3.98
o
o
CM
mL
315.3
51.3
MB/ICB
3.97
O
O
CM
mL
385.4
5.6
20 ppb std
3."
O
O
CM
mL
350.0
17.1
20ppb std + 50ppm CI
3.97"
O
O
CM
mL
344.9
20.1
20ppb std + 100ppm CI
3.95
O
O
CM
mL
341.9
22.1
20ppb std + 300ppm CI
3.93
O
O
CM
mL
335.9
26.7
20ppb std + 500ppm CI
3.91
O
O
CM
mL
332.7
29.6
40 ppb std
398
O
O
CM
mL
321.9
41.6
40ppb std + 50ppm CI
3.96
O
O
CM
mL
320.1
44.0
40ppb std + 100ppm CI
3.94
O
O
CM
mL
319.7
44.6
40ppb std + 300ppm CI
3.93
O
O
CM
mL
319.4
45.0
40ppb std + 500ppm CI
3.91
O
O
CM
mL
318.8
45.9
70ppb std
3.97
O
O
CM
mL
306.5
67.7
70ppb std + 50ppm CI
3.95
O
O
CM
mL
306.5
67.7
70ppb std + 100ppm CI
3.93
O
O
CM
mL
306.7
67.2
70ppb std + 300ppm CI
3.91
O
O
CM
mL
309.0
62.5
70ppb std + 500ppm CI
3.89
O
O
CM
mL
310.2
60.2
ccv
3.91
O
O
CM
mL
348.5
17.9
CCB
3.99
O
O
CM
mL
387.3
5.3
Data in bold used for graphs in Table 4-2
-------
Table 4-15
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 25, 2001
350
340
330
320
310
300
290
280
270
Sentek Probe with 1 mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH=4
\338.5
y = -25.939Ln(x) + 398.65
\^214
R2 = 0.9985
^30Z5
293.8
"—» 278.3
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.01
200 mL
338.5
10.2
20
3.98
200 mL
321.4
19.7
40
4.02
200 mL
302.5
40.7
60
4.00
200 mL
293.8
57.0
100
4.03
200 mL
278.3
103.5
Calibration Date
1/25/2001
Time
11:20am
Temperature
21
°C
Slope
25.939
|| Intercept
398.65
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts
Reading
Concentration in ppb
LCS/ICV
3.98
200 mL
292.8
59.2
MB/ICB
3.96
200 mL
357.3
4.9
20 ppb std
3."
200 mL
320.4
20.4
P-19
4.03
140 mL
328.1
15.2
20 ppb std
4.00
100 mL
319.1
21.5
80 ppb
3.98
200 mL
284.7
80.9
80 ppb
3.98
100 mL
283.6
84.4
Blank
3.97
200 mL
357.5
4.9
Blank + 50ppm CI
3.95
200 mL
344.1
8.2
Blank + 100ppm CI
3.93
200 mL
338.1
10.3
Blank + 300ppm CI
3.91
200 mL
327.4
15.6
Blank + 500ppm CI
3.91
200 mL
324.8
17.2
CCV (20 ppb std)
3.98
200 mL
320.1
20.7
CCB
3.99
200 mL
362.5
4.0
P-8
3."
140 mL
321.9
19.3
P-14
3.97
140 mL
337.2
10.7
20 ppb std
3.95
200 mL
321.3
19.7
P-6
3.95
140 mL
330.2
14.0
20 ppb std
3.97
200 mL
321.9
19.3
ccv (60 ppb std)
3.98
200 mL
292.5
59.9
ccb
4.01
200 mL
358.2
4.8
Data in bold used for graphs in Table 4-2
-------
Table 4-16
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 25, 2001
Sentek Probe with 1 mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH=4
315 -
305 -
« 295 -
| 285 -
= 275 -
S 265 -
255 -
245 -
0 20 40 60 80 100 120
Perchlorate Concentration in ppb
y = -22.157Ln(x) + 359.36
R2 = 0.9991
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.01
200 mL
308.7
9.8
20
3.98
200 mL
292.8
20.2
40
4.02
200 mL
277.5
40.2
60
4.00
200 mL
267.8
62.3
100
4.03
200 mL
258.1
96.6
Calibration Date
4/24/2001
Time
11:55am
Temperature
25.5
°C
Slope
22.157
Intercept
359.36
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts
Reading
Concentration in ppb
LCS/ICV
200 mL
274.4
46.3
Blank
200 mL
328.6
4.0
50 ppb std
200 mL
2743
46.5
50 ppb std + 50ppm chloride
200 mL
273.0
49.3
50 ppb std + 60ppm chloride
200 mL
2728
49.7
20 ppb std
200 mL
295.4
17.9
Blank
200 mL
333.1
3.3
Blank + 200 ppm chloride
200 mL
303.1
12.7
Blank + 1000 ppm chloride
200 mL
289.5
23.4
Blank + 2000 ppm chloride
200 mL
283.1
31.2
40 ppb std
200 mL
279.2
37.3
20 ppb std
200 mL
293.2
19.8
20 ppb + 200 ppm chloride
200 mL
288.9
24.0
20 ppb + 1000 ppm chloride
200 mL
279.4
36.9
20 ppb + 2000 ppm chloride
200 mL
275.2
44.6
70 ppb std
200 mL
265.9
67.9
70 ppb + 200 ppm chloride
200 mL
266.8
65.2
70 ppb + 1000 ppm chloride
200 mL
269.0
59.0
70 ppb + 2000 ppm chloride
200 mL
269.2
58.5
50 ppb std
200 mL
273.1
49.1
50 ppb + 200 ppm chloride
200 mL
272.6
50.2
50 ppb + 1000 ppm chloride
200 mL
272.1
51.3
50 ppb + 2000 ppm chloride
200 mL
271.6
52.5
20 ppb
200 mL
293.5
19.5
Blank
200 mL
332.6
3.3
Data in bold used for graphs in Table 4-2
-------
Table 4-17
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: February 28, 2001
340.0 -1
330.0 -
320.0 -
w
310.0 -
_>
300.0 -
n
290.0 -
280.0 -
270.0 -
260.0 J
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH=4
\331.7
y = -22.482Ln(x) + 384.17
^^317.9
R2 = 0.9984
' ¦* 280.8
^^30T6
^2912
20
40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts
Reading
Concentration in ppb
10
3.95
200 mL
331.7
10.3
20
3.96
200 mL
317.9
19.1
40
3.98
200 mL
301.6
39.4
60
3.96
200 mL
291.2
62.5
100
4.01
200 mL
280.8
99.3
Calibration Date:
2/28/01
2/28/2001
Time
11:00am
Temperature
23.5
°C
Slope:
22.482
22.482
|| Intercept
384.17
-------
Sample/Calibration ID
PH
Sample
Volume
Millivolts
Reading
Concentration in ppb
LCS/ICV
3.95
200 mL
296.2
50.0
Blank
3.99
200 mL
352.9
4.0
Blank + 0.5 ppm nitrate (0.11 ppm N03-N)
3.99
200 mL
338.1
7.8
20 ppb std
3.98
200 mL
318.4
18.6
Blank + 1 ppm nitrate (0.23 ppm N03-N)
3.98
200 mL
331.1
10.6
20 ppb std
3.97
200 mL
317.9
19.1
Blank + 2ppm nitrate (0.45 ppm N03-N)
3.98
200 mL
324.5
14.2
20 ppb std
3.97
200 mL
317.4
19.5
Blank + 5ppm nitrate (1.13 ppm N03-N)
3.99
200 mL
311.3
25.6
20 ppb std
3.97
200 mL
317.1
19.8
Blank + 10ppm nitrate 2.26 ppm N03-N)
3.99
200 mL
302.2
38.3
10 ppb std
4.02
200 mL
330.1
11.1
10 ppb std + 0.5 ppm nitrate (0.11 ppm N03-N)
4.01
200 mL
322.1
15.8
20 ppb std
3.97
200 mL
316.4
20.4
10 ppb std + 1 ppm nitrate (0.23 ppm N03-N)
4.01
200 mL
318.1
18.9
20 ppb std
3.98
200 mL
316.1
20.7
10 ppb std + 2 ppm nitrate (0.45 ppm N03-N)
4.01
200 mL
314.5
22.2
50 ppb std
401
200 mL
294.9
53.0
50 ppb std + 0.5 ppm nitrate (0.11 ppm N03-N)
4.01
200 mL
292.8
58.2
50 ppb std +1 ppm nitrate (0.23 ppm N03-N)
4.01
200 mL
291.5
61.7
50 ppb std + 2 ppm nitrate (0.45 ppm N03-N)
4.01
200 mL
290.2
65.4
20 ppb std
3.98
200 mL
316.5
20.3
20 ppb std + 0.5 ppm nitrate (0.11 ppm N03-N)
3.98
200 mL
312.5
24.2
20 ppb std + 1ppm nitrate (0.23 ppm N03-N)
3.98
200 mL
309.9
27.2
20 ppb std + 2 ppm nitrate (0.45 ppm N03-N)
3.98
200 mL
307.4
30.4
ccv (20 ppb std)
3.97
200 mL
316.1
20.7
ccb
3.99
200 mL
353.6
3.9
Note: ISE probe reconditioned between every analysis with acidified 100 ppb perchlorate standard.
To convert nitrate to nitrate as nitrogen (N03-N), divide by 4.43 Data in bold used for graphs in Table 4-3
-------
Table 4-18A
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: April 30, 2001
o
>
310.0
300.0
290.0
280.0
270.0
260.0
250.0
240.0
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH=4
\301.9
y = -22.127Ln(x) + 353.27
\^288.1
R2 = 0.9979
^2714
^2615
252.1
~l T
20 40 60 80 100
Perchlorate Concentration in ppb
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.95
200 mL
301.9
10.2
20
3.96
200 mL
288.1
19.0
40
3.98
200 mL
271.4
40.4
60
3.96
200 mL
261.5
63.3
100
4.01
200 mL
252.1
96.8
Calibration Date
4/30/2001
Time
12:00pm
Temperature
23.5
UC
Slope
22.127
Intercept
353.27
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts
Reading
Concentration in ppb
LCS/ICV
4
200 mL
268.1
47.0
Blank
4
200 mL
320.0
4.5
Blank + 0.05 ppm Nitrate as N
4
200 mL
313.3
6.1
Blank + 0.1 ppm Nitrate as N
4
200 mL
309.5
7.2
Blank + 0.2 ppm Nitrate as N
4
200 mL
304.1
9.2
Blank + 0.5 ppm Nitrate as N
4
200 mL
295.0
13.9
Blank +1.0 ppm Nitrate as N
4
200 mL
288.1
19.0
Blank + 2 ppm Nitrate as N
4
200 mL
280.0
27.4
Blank + 5 ppm Nitrate as N
4
200 mL
267.8
47.6
Blank + 10 ppm Nitrate as N
4
200 mL
258.7
71.8
ccv (20 ppb)
4
200 mL
288.2
18.9
ccb
4 _
200 mL
321.2
4.3
20ppb
4
200 mL
288.1
19.0
20 ppb + 5 ppm Nitrate as N
4
200 mL
262.5
60.5
20 ppb +10 ppm Nitrate as N
4
200 mL
255.4
83.4
ccv (20 ppb)
4
200 mL
288.5
18.7
ccb
4
200 mL
319.5
4.6
Data in bold used for graphs in Table 4-3
Note: ISE probe reconditioned between every analysis with acidified 100 ppb perchlorate standard.
To convert nitrate as nitrogen (N03-N) to nitrate as nitrate, multiply by 4.43
-------
Table 4-18B
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: May 1, 2001
o
>
310.0
300.0
290.0
280.0
270.0
260.0
250.0
240.0
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH=4
\303.2
y = -20.353Ln(x) + 350.98
R2 = 0.9971
\^90.8
^ 277.2
.^266^9
~ 256.8
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.95
200 mL
303.2
10.5
20
3.96
200 mL
290.8
19.2
40
3.98
200 mL
277.2
37.5
60
3.96
200 mL
266.9
62.2
100
4.01
200 mL
256.8
102.2
Calibration Date
5/1/2001
Time
1:15pm
Temperature
25.5
°C
Slope
20.353
Intercept
350.98
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts
Reading
Concentration in ppb
LCS/ICV
200 mL
272.5
47.3
Blank
200 mL
321.2
4.3
20 ppb std
200 mL
291.1
19.0
20 ppb + 0.05ppm N03 as N
200 mL
289.7
20.3
20 ppb + 0.1 ppm N03 as N
200 mL
288.7
21.3
20 ppb + 0.2 ppm N03 as N
200 mL
287.0
23.2
20 ppb + 0.5 ppm N03 as N
200 mL
283.5
27.5
20 ppb + 1 ppm N03 as N
200 mL
279.5
33.5
100 ppb check std
200 mL
256.7
102.7
ccb
200 mL
320.5
4.5
20 ppb std
200 mL
291.5
18.6
20 ppb std + 2 ppm N03 as N*
200 mL
275.5
40.8
*+ 10 ppb CI04
200 mL
271.3
50.1
* + 20 ppb CI04
200 mL
267.9
59.3
* + 30 ppb CI04
200 mL
264.1
71.4
ccv (20 ppb)
200 mL
292.2
18.0
ccb
200 mL
322.5
4.1
Data in bold used for graphs in Table 4-3
Note: ISE probe reconditioned between every analysis with acidified 100 ppb perchlorate standard.
To convert nitrate as nitrogen (N03-N) to nitrate as nitrate, multiply by 4.43
* Determination by the method of standard additions (MSA); See Table 4-22
-------
Table 4-19
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable)
Date: March 2, 2001
Sentek Probe with 1ml_ of Sentek ISAB in 200ml_
Using Orion 290A+ Meter at pH 4
o
>
350
0 1
340
o
i
330
o -
320
o
i
310
o -
300
o
i
290
o -
280
o
i
270
o -
260
0 -1
t 337.7
y = -26.903Ln(x) + 398.78
>s^17.5
R2 = 0.9988
^208.5
^288^8
~ 275.6
~i 1 r
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.96
200 mL
337.7
9.7
20
4.01
200 mL
317.5
20.5
40
4.01
200 mL
298.5
41.6
60
4.02
200 mL
288.8
59.6
100
3.98
200 mL
275.6
97.4
Calibration Date
3/2/2001
Time
12:00pm
Temperature
23.5°C
Slope
26.903
Intercept
398.8
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
3.96
200 mL
293.2
50.6
Blank
3.97
200 mL
357.7
4.6
Blank + 0.5 ppm Bromide
3.97
200 mL
351.1
5.9
Blank + 1 ppm Bromide
3.97
200 mL
348.2
6.6
Blank + 2 ppm Bromide
3.97
200 mL
344.5
7.5
Blank + 5 ppm Bromide
3.97
200 mL
335.2
10.6
20 ppb
4.01
200 mL
319.5
19.0
10 ppb std
3.96
200 mL
337.8
9.6
10 ppb std+ 0.5 ppm bromide
3.96
200 mL
334.1
11.1
10 ppb std+ 1 ppm bromide
3.96
200 mL
331.1
12.4
10 ppb std+ 2 ppm bromide
3.96
200 mL
327.6
14.1
10 ppb std+ 5 ppm bromide
3.96
200 mL
321.3
17.8
20 ppb
4.01
200 mL
318.6
19.7
20 ppb std+ 0.5 ppm bromide
4.01
200 mL
315.8
21.9
20 ppb std+ 1 ppm bromide
4.01
200 mL
313.7
23.6
20 ppb std+ 2 ppm bromide
4.01
200 mL
311.6
25.5
20 ppb std+ 5 ppm bromide
4.01
200 mL
308.1
29.1
50 ppb
3.95
200 mL
292.0
52.9
50 ppb std+ 0.5 ppm bromide
3.95
200 mL
291.5
53.9
50 ppb std+ 1 ppm bromide
3.95
200 mL
291.1
54.7
50 ppb std+ 2 ppm bromide
3.95
200 mL
290.6
55.8
50 ppb std+ 5 ppm bromide
3.95
200 mL
289.7
57.7
20 ppb
3.98
200 mL
318.5
19.8
Blank
4.01
200 mL
354.2
5.2
P-1
4.02
200 mL
281.0
79.7
100 ppb std
4.01
200 mL
270.6
117.3
ccb
4.01
200 mL
355.1
5.1
Data in bold used for graph in Table 4-
4
-------
Table 4-20
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: April 23, 2001
o
>
315.0
305.0 -
295.0 -
285.0
275.0
265.0 H
255.0
245.0
0
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH 4
t 309.1
y = -24.31 Ln(x) + 364.33
X^91.4
R2 = 0.9978
*^273.2
.^264.4
" ^ 253.6
"I 1 T
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.96
200 mL
309.1
9.3
20
4.01
200 mL
291.4
19.5
40
4.01
200 mL
273.2
41.7
60
4.02
200 mL
264.4
60.3
100
3.98
200 mL
253.6
94.8
Calibration Date
4/23/2001
Time
12:45pm
Temperature
24.5°C
Slope
24.31
|| Intercept
364.3
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
200
mL
269.1
49.6
Blank
200
mL
330.3
3.8
Blank + 0.1 ppm Fluoride
200
mL
330.1
3.9
Blank + 0.5 ppm Fluoride
200
mL
330.5
3.8
Blank + 1 ppm Fluoride
200
mL
331.5
3.6
Blank + 2 ppm Fluoride
200
mL
330.5
3.8
Blank + 5 ppm Fluoride
200
mL
329.8
3.9
20 ppb
200
mL
290.4
20.3
10 ppb std
200
mL
309.1
9.3
10 ppb std+ 0.5 ppm Fluoride
200
mL
308.9
9.4
10 ppb std+ 1 ppm Fluoride
200
mL
308.7
9.5
10 ppb std+ 2 ppm Fluoride
200
mL
308.5
9.5
10 ppb std+ 5 ppm Fluoride
200
mL
308.0
9.7
20 ppb
200
mL
292.4
18.7
20 ppb std+ 0.5 ppm Fluoride
200
mL
292.3
18.8
20 ppb std+ 1 ppm Fluoride
200
mL
292.2
18.9
20 ppb std+ 2 ppm Fluoride
200
mL
292.1
18.9
20 ppb std+ 5 ppm Fluoride
200
mL
291.9
19.1
50 ppb
200
mL
268.0
51.9
50 ppb std+ 0.5 ppm Fluoride
200
mL
267.9
52.1
50 ppb std+ 1 ppm Fluoride
200
mL
267.9
52.1
50 ppb std+ 2 ppm Fluoride
200
mL
268.0
51.9
50 ppb std+ 5 ppm Fluoride
200
mL
267.8
52.3
20 ppb
200
mL
289.5
21.1
Blank
200
mL
330.5
3.8
Data in bold used for graph in Table 4-5
-------
Table 4-21
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: February 19, 2001
Sentek Probe with 1mL of Sentek ISAB in 200mL
330.0 -
320.0 -
310.0 -
in
| 300.0 -
= 290.0 -
280.0 -
270.0 -
260.0 -
0 20 40 60 80 100 120
Perchlorate Concentration in ppb
Using Orion 290A+ Meter at pH 4
<318.1
y = -22.151Ln(x) + 368.9
>k^02.3
R2 = 0.9998
^ 287.3
.^277.8
267.2
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.96
200 mL
318.1
9.9
20
4.01
200 mL
302.3
20.2
40
4.01
200 mL
287.3
39.8
60
4.02
200 mL
277.8
61.1
100
3.98
200 mL
267.2
98.6
Calibration Date
2/19/2001
Time
11:30pm
Temperature
22
UC
Slope
22.151
|| Intercept
368.9
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
4.02
200
mL
282.7
49.0
MB/ICB
3.97
200
mL
335.2
4.6
10 ppb
4.01
200
mL
318.1
9.9
10 ppb + 1ppm Phosphate
4.02
200
mL
318.1
9.9
10 ppb + 5ppm Phosphate
4.01
200
mL
318.0
10.0
10 ppb +10ppm Phosphate
4.01
200
mL
318.0
10.0
10 ppb +20ppm Phosphate
4.01
200
mL
317.9
10.0
Blank
3.98
200
mL
336.8
4.3
Blank +1ppm phosphate
3.99
200
mL
336.9
4.2
Blank +5ppm phosphate
3.99
200
mL
337.2
4.2
Blank +10ppm phosphate
3.99
200
mL
337.5
4.1
Blank +20ppm phosphate
3.99
200
mL
337.6
4.1
Blank +50ppm phosphate
4.0°
200
mL
337.1
4.2
20 ppb
4.02
200
mL
305.0
17.9
20ppb +1ppm phosphate
4.02
200
mL
304.9
18.0
20ppb +5ppm phosphate
4.02
200
mL
304.5
18.3
20ppb +10ppm phosphate
4.01
200
mL
304.3
18.5
20ppb +20ppm phosphate
4.02
200
mL
304.1
18.6
50 ppb
3.97
200
mL
281.8
51.0
50ppb+1ppm phosphate
3.97
200
mL
281.6
51.5
50ppb +5ppm phosphate
3.97
200
mL
281.5
51.7
50ppb +10ppm phosphate
3.97
200
mL
281.5
51.7
50ppb +20ppm phosphate
3.98
200
mL
281.4
51.9
20 ppb std
4.01
200
mL
306.9
16.4
ccb
4
200
mL
335.3
4.6
Data in bold used for graph in Table 4-6
-------
Table 4-22A: Perchlorate Determination by MSA:
Linear Fit
70.00
y=1.0641x+38.996
R*-Q.S932
60.00
? O 40.00
2 =
ra I"1
30.00
" 20.00
L. c
v o
D. O
10 00
0.00
-40
-30
-20
-10
0
10
20
30
40
Perchlorate Standard Addition In ppb
(Read perchlorate concentration at negative x Intercept)
True Value = 20 ppb perchlorsie with 2.0 pprn NOD-N
Perchlorate Reading = 8 ppb
rnitnd Value = flfi ppti pprnhlnratip
Data From Table 4-18B
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
GO. 00
1.088k * 6.91 J
nr njflnr.r.
|kiiu« V
Table 4-228: Perchlorate Determination by MSA:
Low Nitrate Interference, Linear Fit
70.00
y- 1,0001 a * 10JGQ1
H:" " ll.Wtfc1
f- 1.11/fiH* i 4.
-------
5 a50
fZ e
a C40
£ =
2 gao
O c
¦ V
U "20
<3? O
°- O10
Table 4-23A: Perchlorate Determination by MSA:
Chloride Interference
20/40/70 ppb Perchlorate Additions - Linear Fit
70.0
60.0
0
0
0
0
.0
0.0
y
•JH92I * 11,111
if" - un
y D.7K9* -1411
Rl" P.WT3
r-H.ltl1fil.D1k>
IT" ¦ MSJ4
*
n.swsic ¦ i.i&fci
n; - umi
y-Udfllr l.>1M
fiJ - 6.«»T
'''
[ 15.&
"J
V"
-30
-20
GO
-10 D 10 20 30 40 50
perchlorate standard Addition in ppu
(Read perchlorate concentration at negative x intercept)
70
8D
—~— 1 rue Value - D ppb Pent, SOU jjpsn CI
Tnjfc Vnlufi - fl pph F'wt, 1dl |ipm CI
—i— 1 ruL» Vuluu U ppb Pfcit, U ppfn CI
¦ Pujift Rr-atfnn O pph fir-rc. Tn ppm CI
¦ Mvic H(.*j$»iu U ppb pvrc. MJ ppm CI
UrMar (True value = Q ppb F'src 0 ppm CO
liin'iir i'Tiiji' Villiji* II jipli PurC, lllJ |:nm i.l)
im-eat (Tfus Value = 0 ppb Perc, SCO pj>m Clj
¦ Value « 0 ppb l s0re, 3UU ppm CI
Teiafi Value- ^ 0 ppb Piftne, Gfl ppm CI
• Pure Ht'udmg U ppb pure, §QQ p'pm CI
PrsrC Ftoadinq 0 ppb pnrt, 100 ppm Gl
¦ Pure Beading U ppb pure, U pprn CI
Lnear fTrne Value = 0 ppb Hare, 50 ppm Ch
1 irmji [Jru(f ViiliHi |] ppb Pun:, dOD pprn O]
Data From Table 4-14
ISE = Ion Selective Electrode
ppb = parts per billion (|jg/L)
ppm = parts per million (mg/L)
-------
cn -9
c
„ a
Q C
* S
u —
2 £
2 c
.c
E £
BD.D
70.D
6D.D
60.0
40.0
30.0
20.0
10 0
0 0
JO
Table 4-23B: Perchlorate Determination by MSA:
Background Chloride Interference
0/20/40/70 ppb Perchlorate
^¦ry
2—
y
r' -
r' /
I
f-"~~ """
J*
—
-2D
-10
70
0 10 20 30 40 SO 60
Pei chlorate Standard Addition in ppb
{Read perchlorate concentration at negative x intercept)
— Tins Vslus = fl pph Purr., fifl! ppm l".J —Trim Vain ft = O pph Pftrr., .inn ppm CI
Tfue Value = 0 ppb Pere, 10] ppm CI Trae Value = 0 ppb Perc. 50 p.prn CI
fun! Villi in II pplt Pun:, 0 pjim CI
aa
Data From Table 4-14
ISE = Ion Selective Electrode
ppb = parts per biiiion (|jg/L)
ppm = parts per million (mg/L)
-------
en -9
if
& =
nj
* g
B o
E 2
5h "
2 C
.C ^
t O
i- c
at o
C. (J
50.0
46.0
40.0
36.0
30.0
26.0
20.0
16.0
10.0
6.0
0.0
-20
Table 4-23C: Perchlorate Determination by MSA:
Chloride Interference
20/40 ppb Perchlorate Additions
-10
/A
y^y^
y
yy/
y
1S6
t y
y yy
y ./ y
V
///
/ B-2.
s/
''
y ¦
y//
40
0 10 20 30
Perchlorate Standard Addition in ppb
(Read perchlorate concentration at negative x Intercept)
50
—True Value = 0 ppb Perc, 330 ppm CI [17 2 pe-'C reading)
¦ True Value = 0 ppb Pert, 300 ppm C'l (1D.G pcti pert reading)
Tmo V.ili in — fl pph Prrr., l(Tl ppm CI (1fl H fipli jimt marling)
1 rsn- Viiliii! II jifiii Hurt, fill pjini CI B 1' ppli pint: Nidinq'
—— liwYtfyv U vpI> ^vrt. U vwn CI «.? owe wt ivfiling'
Data From Table 4-14
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
Table 4-23D: Perchlorate Determination by MSA:
Chloride Interference
40/70 ppb Perchlorate Additions
GOO
70,0
-S eo o
50.0
4i ~ 40.0
30.0
20 0
<¦ i/.i
100
0.0
-SO -70 -60 -60 -40 -30 -20 -10 0 10 20 30 40 50 60
Perchlorate Standard Addition in ppb
(Read perchlorate concentration at negative x intercept)
—Itue Value = Jj ppb I 'efc, tOJ ppm CI ra ti ppb perc reading
—•—True Value = 20 ppb Pe'c, 300 ppm CI @6 7 ppb perc readmqi
True Value = 20 ppb F'eft, 100 ppm CI g2 1 ppb pBrc reading)
True- Value = 20 ppb P«c, 50 ppm CI CO 1 ppb perc radingi
—*—Tnjc Value - 20 oob Pen: 0 nam CI H ¦¦ 1 ppb ocrc re.idin.ji
Data From Table 4-14
ISE = Ion Selective Electrode
ppb = parts per billion (pg/L)
ppm = parts per million (mg/L)
-------
Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
SECTION 5 TABLES
L:\WORK\42674\WP\07\LETTER OF FINDINGS TASK 1-5.DOC
111
Final, October 2001
-------
Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
TABLES 5-1 THROUGH 5-6
L:\WORK\42674\WP\07\LETTER OF FINDINGS TASK 1-5.DOC
112
Final, October 2001
-------
Table 5-1A - Sample Site/Locations with Historical Interferent Anion Concentrations and Correction Factors
Site-Location ID
Historical
Alkalinity
as C03
(PPm)
Historical
Chloride
Level (ppm)
Chloride
Correction
Factor, Table
4-7
Historical
Nitrate
(N03-N) Level
(ppm)
Nitrate (N03-N)
Correction
Factor, Table 4-8
Historical
Bromide
Level (ppm)
Bromide
Correction
Factor, Table
4-9
Other Known Anions (ppm);
TOC (ppm); and Organic
Compounds(ppb)
ED-188-MW01
NA
NA
N/A
NA
N/A
NA
N/A
Contains high levels of organic contaminants
ED-189-MW01
205
331
8.1
12.6
68.1
1.0
2.6
F = 0.8; High levels of organic contaminants
E D-189-MW01 -D U P
205
331
8.1
12.6
68.1
1.0
2.6
...
ED-189-MW02
NA
490
NA
2.9
NA
1.8
3.8
Contains high levels of organic contaminants
ED-189-MW03
NA
325
10.4
0.29
5.8
1.0
2.6
Contains high levels of organic contaminants
ED-196-MW01
223
380
N/A
0.18
4.1
1.2
2.9
F = 0.8, P04
ED-196-MW03
NA
330
10.4
0.17
4.0
1.1
2.7
F = 0.7, P04 = 0.14; toluene=44 ppb
ED-196-MW06
206
425
11.6
1.4
17.7
1.4
3.2
F = 0.64, P04 <0.1
ED-196-MW06
206
425
11.6
1.4
17.7
1.4
3.2
F = 0.64, P04 <0.1
ED-199-MW01
NA
245
9.0
0.06
1.5
0.7
2.0
None Detected
ED-199-MW01
NA
245
9.0
0.06
1.5
0.7
2.0
None Detected
ED-274-MW01
NA
32
2.1
0.25
5.3
0.3
0.9
F=0.8
ED-274-MW02
NA
31
2.2
0.10
2.5
0.3
0.9
F=0.9
ED-274-MW03
NA
26
1.7
0.24
5.1
0.3
0.9
F=0.8
ED-285-MW01
EB
NA
0
NA
0
NA
0
EB
ED-285-MW02
218
255
9.1
0.18
4.3
0.8
2.2
F <1
E D-285-MW02-D U P
218
255
9.1
0.18
4.3
0.8
2.2
...
ED-286-MW01
232
300
N/A
0.29
N/A
0.7
2.0
F <1
E D-286-MW01 -D U P
232
300
N/A
0.29
N/A
0.7
2.0
...
ED-286-MW03
NA
NA
NA
NA
NA
NA
NA
Contains low levels of organic contaminants
ED-286-MW03 (RE)
NA
NA
NA
NA
NA
NA
NA
...
ED-286-MW03 (RE)
NA
NA
NA
NA
NA
NA
NA
...
ED-286-MW03 (RE)
NA
NA
NA
NA
NA
NA
NA
...
ED-286-MW03-DUP
NA
NA
NA
NA
NA
NA
NA
...
ED-422-MW01
NA
500
7.7
6.3
49.5
1.3
3.1
Contains high levels of organic contaminants
ED-422-MW01
NA
500
7.7
6.3
49.5
1.3
3.1
...
ED-422-MW01-RE1
NA
500
7.7
6.3
49.5
1.3
3.1
...
ED-422-MW01-RE2
NA
500
7.7
6.3
49.5
1.3
3.1
...
-------
ED-422-MW01-RE3
NA
500
7.7
6.3
49.5
1.3
3.1
...
ED-NM-MW01A
295
110
3.1
0.1
2.5
0.4
1.2
F = 0.98, P04 = 15, TOC = 1.2
ED-NM-MW01A1
EB
0
0.0
0
0.0
0.0
0.0
EB
ED-NM-MW01C
157
721
9.5
1.9
21.7
2.1
4.1
F = 0.99, N02 = 0.33, P04 = 4.7, TOC = 0.57,
11 SVOC TICs<20ppb, Tol = 1.3ppb
ED-NM-MW01 B
311
117
5.9
0.06
1.5
0.5
1.5
F = 1, P04 = 1.2, TOC = 0.2, 1 SVOC
TICs@29ppb
ED-NM-MW02A
173
10
0.6
0.3
6.0
ND
0.0
F = 1, P04 = 1.2, TOC = 0.24, 1 SVOC
TICs<29ppb
ED-NM-MW02B
161
451
11.9
0.05
1.5
1.3
3.1
P04 = 0.45, TOC = 0.4, 1 SVOC TIC@16ppb
ED-NM-MW02C
130
130
5.5
0.11
2.7
0.6
1.7
F = 1.3, P04 = 0.3, TOC = 0.6
ED-NM-MW03A
169
30
2.0
0.4
7.5
ND
0.0
F = 0.82, P04 = 3.1, TOC = 0.47
ED-NM-MW03B
190
242
11.8
0.16
3.7
0.8
2.2
P04 = 0.3.4, TOC = 0.9, PERC = 77 (5/2000)
ED-NM-MW03C
115/40.9
485/1160
18.6
0.14
3.3
3.4
5.5
F = 0.7, P04 = 5.3, TOC = 0.8, 1 SVOC
TIC@7ppb
ED-NM-MW04A
254/176
25
1.7
0.41
7.6
ND
0
F = 1, P04 = 5.3/1, TOC = 0.5, MTBE@2.4ppb
ED-NM-MW04B
210
120
6.2
0.44
8.1
0.4
1.2
F = 0.9, P04 = 5.4/0.74, TOC = 0.3; 1 SVOC
TIC@57ppb
ED-NM-MW04B-DUP
210
120
6.2
0.44
8.1
0.4
1.2
—
ED-NM-MW04C
88
1000
18.5
0.15
3.5
3.5
5.6
F = 3, P04 = 0.24, TOC = 1.0, 18 SVOC
TIC<37ppb
ED-NM-MW05-W14
222
146
6.8
0.06
1.5
0.5
1.5
P04 = 0.13; Contains high levels of organic
contaminants: Ethanol@35000, Tol@1.1, VOC
TIC@21, 6 SVOC TIC<770/13 SVOC TIC<240
ED-NM-MW06-W06
167
25
1.7
0.16
3.7
0.2
0.6
P04 = 0.07, TOC = 0.5, 1 SVOC TIC@45ppb
ED-NM-MW07-W11
101
350
10.7
0.14
3.3
1.4
3.2
P04 = 0.13, TOC = 12.4, NDMA @3ppt
ED-USGS-W1AE2
NA
NA
NA
NA
NA
NA
NA
Not Available
ED-USGS-W1AE4
NA
NA
NA
NA
NA
NA
NA
No Anions Available, all organics ND
ED-USGS-W1C1
NA
NA
NA
NA
NA
NA
NA
No Anions Available, all organics ND
ED-USGS-W1C2
NA
NA
NA
NA
NA
NA
NA
Not Available
ED-USGS-W1C3
NA
NA
NA
NA
NA
NA
NA
Not Available
ED-USGS-W1C4
NA
NA
NA
NA
NA
NA
NA
Not Available
-------
Table 5-1B - First Semi-Annual Groundwater (SAGW) Event (December 2000) Samples,
Perchlorate ISE Readings and Results, and Definitive Level Results by EPA Method 314.0
First SAGW Event (December 2000)
Split Sample ID
First SAGW
(12/00) ISE ID
Uncorrected
Perchlorate ISE
Reading (ppb), pH
4.0
Anion Corrected
Perchlorate ISE
Reading (ppb), pH
4.0
Final Reported
Perchlorate ISE
Result (ppb), pH 4.0
Perchlorate
Definitive Result by
EPA 314.0 (ppb)
Definitive Result
RL (ppb)
Not Collected This Event
NC
...
...
...
...
...
ED-189-MW01-W24/-W16
P-1
79.7
0.9
ND (<15)
ND (<16)
16
ED-189-MW01-W25/-W17
P-2
Not Analyzed
Not Analyzed
Not Analyzed
ND (<16)
16
E D-189-MW02-W13/-W09
P-3
Not Analyzed
Not Analyzed
Not Analyzed
ND (<16)
16
E D-189-MW03-W08/-W07
P-4
Not Analyzed
Not Analyzed
Not Analyzed
19
16
ED-196-MW01 -W09/-W05,-W06
P-5
24423
NA (diluted 400X)
24423
20000, 25000
4000
ED-196-MW03-W11 /-W09
P-6
14.0
-3.1
ND (<15)
ND (<4)
4
ED-196-MW06-W15/-W11
P-7
23.4
-9.1
ND (<15)
ND (<16)
16
Not Collected This Event
NC
NC
NC
NC
NC
NC
ED-199-MW01 -W14/-W13
P-8
19.3
6.8
ND (<15)
ND (<4)
4
Not Collected This Event
NC
...
...
—
—
...
Not Collected This Event
NC
...
...
—
—
...
Not Collected This Event
NC
...
...
...
...
...
Not Collected This Event
NC
...
...
...
...
...
Not Collected This Event
NC
...
...
...
...
...
E D-285-MW02-W06/-W05
P-9
14.6
-1.0
ND (<15)
ND (<4)
4
E D-285-M W02-W06-DU P/-W05
P-9-DUP (pH 4.4)
7.0
-8.6
ND (<15)
ND (<4)
4
ED-286-MW01-W08/-W03
P-10
4336
N/A (diluted 200X)
4336
5900
P-10
...
NC
...
...
...
...
...
Not Collected This Event
NC
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
...
ED-422-MW01-W07/-W06
P-11
63.7
3.4
ND (<15)
6
4
E D-422-MW01-W07-D U P/-W06
P-11-DUP
45.3
-15.0
ND (<15)
6
4
ED-422-MW01-W08/-W06
P-102
60.1
-0.2
ND (<15)
6
4
-------
ED-422-MW01-W09/-W06
P-103
42.2
-18.1
ND (<15)
6
4
ED-422-MW01 -W10/-W06
P-104
40.7
-19.6
ND (<15)
6
4
ED-NM-MW01A-W10/-W09
P-12
15.5
8.7
ND (<15)
ND (<4)
4
ED-NM-MW01A-W11(EB)
P-13
4.0
4.0
ND (<15)
ND (<4)
4
Not Collected This Event
NC
—
...
—
—
...
Not Collected This Event
NC
—
...
—
—
...
ED-NM-MW02A-W11/-W09
P-14
10.7
4.1
ND (<15)
ND (<4)
4
Not Collected This Event
NC
...
...
—
—
...
Not Collected This Event
NC
...
...
—
—
...
E D-N M-M W03A-W07/-W06
P-15
9.0
-0.5
ND (<15)
ND (<4)
4
Not Collected This Event
NC
...
...
—
—
...
Not Collected This Event
NC
...
...
—
—
...
Not Collected This Event
NC
...
...
...
...
...
ED-NM-MW04B-W13/-W11
P-16
15.0
-0.5
ND (<15)
ND (<4)
4
ED-NM-MW04B-W13/-W08
P-16-DUP
18.0
2.5
ND (<15)
ND (<4)
4
Not Collected This Event
NC
...
...
—
—
...
ED-NM-MW05-W14/-W11
P-17
Not Analyzed
Not Analyzed
Not Analyzed
ND (<16)
16
E D-N M-M W06-W06/-W05
P-18
8.3
Anions NA
ND (<15)
ND (<4)
4
E D-N M-M W07-W11 /-W10
P-19
15.2
-2.0
ND (<15)
ND (<4)
4
ED-USGS-W1AE2-W06/-W03
P-20
8.5
Anions NA
ND (<15)
ND (<4)
4
ED-USGS-W1AE4-W05/-W04
P-21
Sample Expended
Not Analyzed
Not Analyzed
ND (<4)
4
ED-USGS-W1C1-W07/-W05
P-22
6.8
Anions NA
ND (<15)
ND (<4)
4
ED-USGS-W1C2-W08/-W06
P-23
10.1
Anions NA
ND (<15)
ND (<4)
4
ED-USGS-W1C3-W08/-W07
P-24
10.9
Anions NA
ND (<15)
ND (<4)
4
ED-USGS-W1C4-W09/-W05
P-25
5.8
Anions NA
ND (<15)
ND (<4)
4
-------
Table 5-1C - Second Semi-Annual Groundwater (SAGW) Event (July-August 2001) Samples,
Perchlorate ISE Readings and Results, and Definitive Level Results by EPA Method 314.0
Second SAGW Event
(July-August 2001)
Split Sample ID
Second SAGW
(7-8/00)
ISE ID
Uncorrected
Perchlorate ISE
Reading (ppb),
pH 4.0
Anion Corrected
Perchlorate ISE
Reading (ppb),
pH 4.0
Final Reported
Perchlorate ISE
Result (ppb), pH 4.0
Perchlorate Definitve
Result by EPA 314.0
(ppb)
Definitive
Result RL
(ppb)
E D-188-MW01 -W11 /-W10
S-2
126.5
N/A
126.5
140
4
ED-189-MW01-W36/-W31 ,W32
S-1
66.4
-12.4
ND (<15)
ND, ND (<4)
4
—
NC
...
...
—
—
...
ED-189-MW02-WNC/-W24,-W26,-W30
Split NC
...
...
—
11 and ND, ND (<4)
4
E D-189-MW03-W11 /-W10
S-4
28.9
10.1
ND (<15)
18
4
ED-196-MW01 -W14/-W12,-W13
S-5
13270.0
13270.0
13270.0
36000, 27000
8000
E D-196-MW03-W13/-W12
S-6
25.9
8.8
ND (<15)
ND (<16)
16
E D-196-MW06-W24/-W23
S-7
28.8
-3.7
ND (<15)
ND (<16)
16
ED-196-MW06-W24-DUP/-W23
S-7D
30.5
-2.0
ND (<15)
ND (<16)
16
ED-199-MW01 -W16/-W15
S-8
16.1
3.6
ND (<15)
ND (<16)
16
ED-199-MW01 -W16-DUP/-W15
S-8D
13.9
1.4
ND (<15)
ND (<16)
16
ED-274-MW01 -W12/-W13
S-26
2.6
-5.7
ND (<15)
ND (<16)
16
ED-274-MW02-W13/-W14
S-27
13.7
8.1
ND (<15)
ND (<16)
16
E D-274-MW03-W06/-W07
S-28
17.6
9.9
ND (<15)
ND (<16)
16
ED-285-MW01 -W(EB)
S-3
1.6
1.6
ND (<15)
N/A
...
ED-285-MW02-W16/-W15
S-9
14.1
-1.5
ND (<15)
ND (<4)
4
Not Collected This Event
NC
...
...
—
—
...
E D-286-MW01 -W16/-W14
S-10
612
N/A
612
1100
80
ED-286-MW01-W16-DUP/-W15
S-10D
731
N/A
731
920
80
ED-286-MW03-W16/-W14, -W15
S-29
9.7
Anions NA
ND (<15)
ND (<16)
16
ED-286-MW03-W16-RE1 /-W14,-W15
S-29RE1
8.5
Anions NA
ND (<15)
ND (<16)
16
ED-286-MW03-W16-RE2/-W14,-W15
S-29RE2
9.4
Anions NA
ND (<15)
ND (<16)
16
ED-286-MW03-W16-RE3/-W14,-W15
S-29RE3
8.6
Anions NA
ND (<15)
ND (<16)
16
ED-286-MW03-W16-DUP/-W14,-W15
S-29D
10.8
Anions NA
ND (<15)
ND (<16)
16
ED-422-MW01-W09/-W17
S-11
64.2
3.9
ND (<15)
ND (<16)
16
Not Collected This Event
NC
...
...
—
—
...
-------
ED-422-MW01 -W10/-W17
S-102
66.5
6.2
ND (<15)
ND (<16)
16
ED-422-MW01 -W11 /-W17
S-103
65.8
5.5
ND (<15)
ND (<16)
16
ED-422-MW01 -W18/-W17
S-104
67.5
7.2
ND (<15)
ND (<16)
16
ED-NM-MW01A-W15/-W16
S-12
13.1
6.3
ND (<15)
ND (<16)
16
Not Collected This Event
NC
—
...
—
—
...
ED-NM-MW01C-W09/-W10
S-13
34.5
-0.8
ND (<15)
ND (<16)
16
ED-NM-MW01 B-W06/-W07
S-30
7
-1.9
ND (<15)
ND (<16)
16
ED-NM-MW02A-W14/-W15
S-14
8.7
2.1
ND (<15)
ND (<4)
4
ED-NM-MW02B-W08/-W09
S-31
18.1
1.6
ND (<15)
ND (<16)
16
ED-NM-MW02C-W06/-W07
S-32
10.8
0.9
ND (<15)
ND (<16)
16
ED-NM-MW03A-W10/-W11
S-15
7.2
-2.3
ND (<15)
ND (<4)
4
ED-NM-MW03B-W09/-W10
S-33
13.6
-4.1
ND (<15)
ND (<4)
4
ED-NM-MW03C-W08/-W09
S-34
24.9
-2.5
ND (<15)
ND (<16)
16
E D-N M-M W04A-W08/-W09
S-35
10.1
0.8
ND (<15)
ND (<4)
4
ED-NM-MW04B-W16/-W17
S-16
11.8
-3.7
ND (<15)
ND (<4)
4
Not Collected This Event
NC
—
...
—
—
...
ED-NM-MW04C-W07/-W08
S-20
25.1
-2.5
ND (<15)
ND (<16)
16
ED-NM-MW05-W17/-W20, -W21
S-17
19.3
9.5
ND (<15)
ND, ND (<16)
16
E D-N M-M W06-W07/-W08
S-18
7.8
Anions NA
ND (<15)
ND (<4)
4
E D-N M-M W07-W13/-W14
S-19
16.0
-1.2
ND (<15)
ND (<16)
16
Not Collected This Event
NC
—
...
—
—
...
ED-USGS-W1AE4-W08/-W09
S-21
12.3
Anions NA
ND (<15)
ND (<16)
16
ED-USGS-W1C1-W09/-W10
S-22
12.1
Anions NA
ND (<15)
ND (<16)
16
ED-USGS-W1C2-W10/-W11
S-23
12.5
Anions NA
ND (<15)
ND (<16)
16
ED-USGS-W1C3-W10/-W11 ,-W17
S-24
10.1
Anions NA
ND (<15)
ND, ND (<16)
16
ED-USGS-W1C4-W11/-W12
S-25
7.4
Anions NA
ND (<15)
ND (<16)
16
-------
Table 52-A
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 24, 2001
Sentek Probe with 1mL of Sentek ISAB in 200mL
3RD -
350 -
340 -
330 -
Cfl
| 320 -
| 310 -
300 -
290 -
280 -
270 -
0 20 40 60 80 100 120
Perchlorate Concentration in ppb
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.03
200 mL
353.9
10.3
20
3.97
200 mL
336.1
19.1
40
4.01
200 mL
314.5
40.8
60
3.98
200 mL
303.7
59.6
100
4.01
200 mL
288.7
100.7
Calibration Date
1/24/2001
Time
2:15pm
Temperature
22 °C
Slope
28.533
Intercept
420.31
Using Orion 290A+ Meter at pH 4
*353.9
V = -28.533Ln(x) + 420.31
>^336.1
R2 = 0.9991
¦>314.5
303.7
" * 288.7
t 1 1 1 r
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
3.98
200 mL
307.3
52.5
MB/ICB
3.98
200 mL
369.3
6.0
20 ppb std with 5mL ISA
3.99
200 mL
337.4
18.3
100 ppb std
3.99
200 mL
289.6
97.6
25 ppb std
4.01
200 mL
327.7
25.7
P-9
3.97
180 mL
343.9
14.6
25 ppb std
3.98
200 mL
327.8
25.6
P-23
4.01
200 mL
354.2
10.1
20 ppb std
3.98
200 mL
336.6
18.8
P-16
3.96
200 mL
337.8
18.0
20 ppb std
3.98
200 mL
337.1
18.5
blank
4.01
200 mL
372.5
5.3
CCV (60 ppb)
3.99
200 mL
304.2
58.5
CCB
3.99
200 mL
374.1
5.1
-------
Table 5-2B
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 25, 2001
360 -
350 -
340 -
330 -
V)
| 320 -
| 310 -
300 -
290 -
280 -
270 -
0 20 40 60 80 100 120
Perchlorate Concentration in ppb
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.01
200 mL
338.5
10.2
20
3.98
200 mL
321.4
19.7
40
4.02
200 mL
302.5
40.7
60
4.00
200 mL
293.8
57.0
100
4.03
200 mL
278.3
103.5
Calibration Date
1/25/2001
Time
11:20am
Temperature
21
°c
Slope
25.939
|| Intercept
398.65
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH 4
\338.5
y = -25.939Ln(x) + 398.65
>^321.4
R2 = 0.9985
^ 302.5
293.8
* * 278.3
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
3.98
200 mL
292.8
59.2
MB/ICB
3.96
200 mL
357.3
4.9
20 ppb std
3.99
200 mL
320.4
20.4
P-19
403
140 mL
328.1
15.2
20 ppb std
4.00
100 mL
319.1
21.5
80 ppb
3.98
200 mL
284.7
80.9
80 ppb
3.98
100 mL
283.6
84.4
Blank
3.97
200 mL
357.5
4.9
Blank +50ppm CI
3.95
200 mL
344.1
8.2
Blank +100ppm CI
3.93
200 mL
338.1
10.3
Blank +300ppm CI
3.91
200 mL
327.4
15.6
Blank +500ppm CI
3.91
200 mL
324.8
17.2
CCV (20 ppb std)
3.98
200 mL
320.1
20.7
CCB
3.99
200 mL
362.5
4.0
P-8
3.99
140 mL
321.9
19.3
P-14
3.97
140 mL
337.2
10.7
20 ppb std
3.95
200 mL
321.3
19.7
P-6
3.95
140 mL
330.2
14.0
20 ppb std
3.97
200 mL
321.9
19.3
ccv (60 ppb std)
3.98
200 mL
292.5
59.9
CCB
4.01
200 mL
358.2
4.8
-------
Table 5-2C
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 26, 2001
360
350
340
£ 330
320
310
300
290
280
270
o
>
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH 4
\341.6
y = -21.702Ln(x) + 391.51
R2 = 0.998
,^312.5
303.3
* 290.7
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.01
200 mL
341.6
10.0
20
3.99
200 mL
325.6
20.8
40
3.97
200 mL
312.5
38.1
60
3.98
200 mL
303.3
58.2
100
4.01
200 mL
290.7
104.1
Calibration Date
1/26/2001
Time
12:30pm
Temperature
21
°c
Slope
21.702
Intercept
391.51
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
4.01
200 mL
306.4
50.5
MB/ICB
3.97
200 mL
361.2
4.0
20 ppb std
3.97
200 mL
325.2
21.2
P-7
3.99
140 mL
323.1
23.4
P-7 dilution factor = 2
3.99
100 mL
330.8
16.4
20 ppb
3.97
180 mL
326.5
20.0
Blank
3.97
200 mL
362.9
3.7
20 ppb std
3.97
200 mL
325.5
20.9
P-7 (dil fac=2) + 20 ppb
3.98
200 mL
316.6
31.6
P-12
3.97
140 mL
332.1
15.4
20 ppb std
3.98
200 mL
325.4
21.0
Blank
3.98
140 mL
344.1
8.9
P-13
3.95
140 mL
361.4
4.0
P-18
3.96
140 mL
345.6
8.3
P-20
3.95
140 mL
345.2
8.4
ccv (20 ppb std)
3.97
200 mL
325.9
20.6
ccb
200 mL
361.9
3.9
-------
Table 5-2D
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: January 29, 2001
360
350
340
^ 330
320
310
300
290
280
270
o
>
Sentek Probe with 1mL of Sentek ISAB in 200ml_
Using Orion 290A+ Meter at pH 4
•\339.6
y = -20.959Ln(x) + 388.58
R2 = 0.9989
^<£26.6
^31T8
,302_5
' 291.7
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.99
200 mL
339.6
10.3
20
4.01
200 mL
326.6
19.2
40
3.98
200 mL
311.8
39.0
60
4.00
200 mL
302.5
60.8
100
3.99
200 mL
291.7
101.7
Calibration Date
1/29/2001
Time
11:40am
Temperature
21
°c
Slope
20.959
|| Intercept
388.58
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
3.98
200 mL
313.7
35.6
MB/ICB
3.99
200 mL
354.2
5.2
20 ppb std
4.01
200 mL
325.2
20.6
100 ppb std
4.02
200 mL
291.6
102.2
P-11
4.02
140 mL
301.5
63.7
20 ppb std
3.96
200 mL
326.9
19.0
P-24
3.99
140 mL
338.5
10.9
20 ppb std
3.97
200 mL
324.4
21.4
P-25
3.99
140 mL
351.8
5.8
P-22
3.99
140 mL
348.5
6.8
P-10 (200x dilution)
3.96
200 mL
324.1
21.7
P-5 (400x dilution)
3.99
200 mL
302.4
61.1
P-5 (400x dilution) + 20ppb
3.98
200 mL
297.1
78.6
ccv (20 ppb std)
3.98
200 mL
325.9
19.9
ccb
3.97
200 mL
370.4
2.4
-------
Table 5-2E
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: February 23, 2001
330 ¦
320 -
310 -
| 300 -
= 200 -
230 ¦
?70 -
200 -
n 20 go no ioo i?o
Pi:ii:hliii,-tli: Turin;uli
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
3.99
200 mL
284.8
47.2
MB/ICB
3.98
200 mL
348.5
3.6
P-102
3.98
200 mL
278.8
60.1
20 ppb std
4.01
200 mL
3076
18.8
P-102
4.01
200 mL
279.1
59.4
P-102+ 20ppb
4.02
200 mL
275.9
67.6
20 ppb std
4.01
200 mL
307.5
18.9
P-103
4.01
200 mL
287.6
42.2
100 ppb
4.00
200 mL
269.7
86.8
P-104
4.04
200 mL
288.5
40.7
P-102 + 20 ppb
4.03
200 mL
281.1
54.8
P-11 (old, w. scum)
3.91
200 mL
285.8
45.3
ccv (20 ppb std)
4.01
200 mL
310.8
16.5
ccb
3.99
200 mL
349.4
3.5
-------
Table 5-2F
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: March 2, 2001
360
350
340
« 330
320
310
300
290
280
270
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH 4
o
>
^337.7
y = -26.903Ln(x) + 398.78
^*^17.5
--^298J5
_^288.8
R2 = 0.9988
~ 275.6
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.96
200 mL
337.7
9.7
20
4.01
200 mL
317.5
20.5
40
4.01
200 mL
298.5
41.6
60
4.02
200 mL
288.8
59.6
100
3.98
200 mL
275.6
97.4
Calibration Date
3/2/2001
Time
12:00pm
Temperature
23.5
°C
Slope
26.903
|| Intercept
398.78
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV
3.96
200 mL
293.2
50.6
Blank
3.97
200 mL
357.7
4.6
Blank + 0.5 ppm Bromide
3.97
200 mL
351.1
5.9
Blank + 1 ppm Bromide
3.97
200 mL
348.2
6.6
Blank + 2 ppm Bromide
3.97
200 mL
344.5
7.5
Blank + 5 ppm Bromide
3.97
200 mL
335.2
10.6
20 ppb
4.01
200 mL
319.5
19.0
10 ppb std
3.96
200 mL
337.8
9.6
10 ppb std+ 0.5 ppm bromide
3.96
200 mL
334.1
11.1
10 ppb std+ 1 ppm bromide
3.96
200 mL
331.1
12.4
10 ppb std+ 2 ppm bromide
3.96
200 mL
327.6
14.1
10 ppb std+ 5 ppm bromide
3.96
200 mL
321.3
17.8
20 ppb
4.01
200 mL
318.6
19.7
20 ppb std+ 0.5 ppm bromide
4.01
200 mL
315.8
21.9
20 ppb std+ 1 ppm bromide
4.01
200 mL
313.7
23.6
20 ppb std+ 2 ppm bromide
4.01
200 mL
311.6
25.5
20 ppb std+ 5 ppm bromide
4.01
200 mL
308.1
29.1
50 ppb
3.95
200 mL
292
52.9
20 ppb std+ 0.5 ppm bromide
3.95
200 mL
291.5
53.9
20 ppb std+ 1 ppm bromide
3.95
200 mL
291.1
54.7
20 ppb std+ 2 ppm bromide
3.95
200 mL
290.6
55.8
20 ppb std+ 5 ppm bromide
3.95
200 mL
289.7
57.7
20 ppb
3.98
200 mL
318.5
19.8
Blank
4.01
200 mL
354.2
5.2
P-1
4.02
200 mL
281
79.7
100 ppb std
4.01
200 mL
270.6
117.3
cob
4.01
200 mL
355.1
5.1
-------
Table 5-3A
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: ORION 290A (Portable) Date: September 6, 2001
270 -
250 -
W
o 230 -
>
| 210 -
190 -
170 -
0 20 40 60 80 100 120
Perchlorate Concentration in ppb
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
3.95
200 mL
252.3
9.45
20
4.04
200 mL
233.9
22.77
40
3.94
200 mL
223.2
37.98
60
3.93
200 mL
214.9
56.46
100
4.02
200 mL
202.1
104.08
Calibration Date
9/6/2001
Time
13:05
Temperature
21.8 -24.6 °C
Slope
20.927
Intercept
299.3
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH 4
y = -20.927Ln(x) + 299.31
052.3
R2 = 0.9916
^2222
214.9
" » 202.1
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV (25/50 ppb std)
3.96
200 mL
216.2
53.1
Blank
4.01
200 mL
291.6
1.4
10 ppb std
3.96
200 mL
251.7
9.7
S-3
3.96
200 mL
2900
1.6
S-3 MS
3.97
200 mL
243.2
14.6
S-4 High Org. Severe interference
3.95
200 mL
79.9
35758.4
LCS (50 ppb std)
3.96
200 mL
221.7
40.8
temp up to 24.6
LCS (50 ppb std)
3.96
200 mL
221.2
41.8
S-6
3.95
200 mL
231.2
25.9
CCV (50 ppb sensitivity check)
3.92
200 mL
216.1
53.3
S-9
3.87
200 mL
243.9
14.1
S-10
4.07
200 mL
159.5
797.0
S-10 D
4.03
200 mL
156.2
933.1
S-10 (1x10)
3.93
200 mL
213.2
61.2
S-10 D (1x10)
4.02
200 mL
209.5
73.1
CCV (50 ppb)
3.94
200 mL
213.9
59.2
Blank
4.05
200 mL
270.3
4.0
S-12
3.94
200 mL
245.4
13.1
S -14
3.98
200 mL
254.1
8.7
S 15
3.95
200 mL
257.9
7.2
S 16
3.93
200 mL
247.7
11.8
S 18
4.06
200 mL
256.4
7.8
S 19
4.06
200 mL
241.3
16.0
CCV (50 ppb)
3.93
200 mL
216.1
53.3
Blank
4.06
200 mL
268.9
4.3
-------
Table 5-3B
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: Computer Interface - LAVAL ELIT 8804 Date: September 10, 2001
360.0 n
350.0 -
340.0 -
W
330.0 -
o
320.0 -
310.0 -
300.0 -
290.0 -
280.0 -
270.0 J
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH 4
\342.2
^v^24.2
^ 308.0
,^295_8
y = -25.553Ln(x) + 401.08
R2 = 0.9991
" ~ 283.3
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.0
200 mL
342.2
10.0
20
4.0
200 mL
324.2
20.3
40
4.0
200 mL
308.0
38.2
60
3.9
200 mL
295.8
61.6
100
4.1
200 mL
283.3
100.4
Calibration Date
9/10/2001
Time
13:10
Temperature
23.7-24.5 °C
Slope
25.553
Intercept
401.1
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV (50 ppb)
4.0
200 mL
303.4
45.7
Blank
4.0
200 mL
375.6
2.7
10 ppb std
4.1
200 mL
340.4
10.8
S-27
4.0
200 mL
334.2
13.7
S-8
4.0
200 mL
330.1
16.1
S-29
4.0
200 mL
343.1
9.7
S-29 D
4.0
200 mL
340.2
10.8
S-8 D
4.0
200 mL
333.8
13.9
CCV (40 ppb)
4.0
200 mL
307.3
39.3
Blank
4.0
200 mL
369.7
3.4
S-20
4.0
200 mL
318.8
25.1
S-30
4.0
200 mL
351.4
7.0
S-32
4.0
200 mL
340.4
10.8
S-7
4.0
200 mL
315.3
28.8
S-7 D
4.0
200 mL
313.7
30.5
LCS (50 ppb)
4.0
200 mL
301.0
50.1
Blank
4.1
200 mL
368.9
3.5
S-22
4.0
200 mL
337.4
12.1
S-23
4.0
200 mL
336.6
12.5
S-21
4.0
200 mL
337.0
12.3
S-24
4.0
200 mL
342.1
10.1
CCV (20 ppb)
4.0
200 mL
320.1
23.8
Blank
4.0
200 mL
359.9
5.0
S-2
4.0
200 mL
276.3
132.1
S-25
4.0
200 mL
350.0
7.4
S-35
4.0
200 mL
342.1
10.1
S-26
4.0
200 mL
178.6
6045.1
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
S-13
4.0
200 mL
310.6
34.5
LCS (50 ppb)
4.0
200 mL
297.3
58.0
Blank
4.0
200 mL
355.1
6.0
S-34
4.0
200 mL
3189
24.9
S-33
...40
200 mL
334.4
13.6
S-31
4.0
200 mL
327.1
18.1
S-28
4.0
200 mL
327.8
17.6
S-102
4.0
200 mL
293.8
66.5
S-103
4.0
200 mL
294.1
65.8
S-104
4.0
200 mL
293.4
67.5
S-11
4.0
200 mL
294.7
64.2
CCV (20 ppb)
4.0
200 mL
321.1
22.9
Blank
4.0
200 mL
362.1
4.6
S-1
4.0
200 mL
297.2
58.4
S-4
4.0
200 mL
315.2
28.9
S-17
4.0
200 mL
325.4
19.3
S-1 D
4.1
200 mL
293.9
66.4
LCS (50 ppb)
4.0
200 mL
297.0
58.8
Blank
4.1
200 mL
360.1
5.0
-------
Table 5-3C
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: Sentek 367-75 Solid State Perchlorate Combination ISE
Analyst: Earth Tech, Inc.
Meter: Computer Interface - LAVAL ELIT 8804 Date: September 12, 2001
350
0 -I
330
0 -
u>
A-'
o
310
0 -
>
i
290
0 -
270
0 -
250
0 -
Sentek Probe with 1mL of Sentek ISAB in 200mL
Using Orion 290A+ Meter at pH 4
\328.1
^^410.4
^2919
^2810
y =-25.621 Ln(x) + 386.88
R2 = 0.999
269.8
~l T
20 40 60 80
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
4.0
200 mL
328.1
9.9
20
4.0
200 mL
310.4
19.8
40
4.1
200 mL
291.9
40.7
60
4.0
200 mL
281.0
62.3
100
4.0
200 mL
269.8
96.4
Calibration Date
9/12/2001
Time
12:09
Temperature
22.2-24.5°C
Slope
25.621
Intercept
386.9
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
LCS/ICV (50 ppb std)
4.0
200 mL
288.0
47.4
Blank
4.0
200 mL
382.4
1.2
S-26 (1:100)
4.0
200m L
373.1
1.7
S-26 (1:10)
4.0
200m L
366.6
2.2
S-26
3.9
200 mL
375.8
1.5
S-29
4.0
200 mL
332.1
8.5
S-29 MS
4.1
200 mL
237.7
337.7
S-2
4.0
200 mL
267.4
106.1
S-2 (1:5)
4.1
200 mL
304.1
25.3
S-2 (1:5) MS
4.1
200 mL
335.8
7.3
LCS (50 ppb)
4.0
200 mL
291.4
41.5
Blank
4.1
200 mL
360.0
2.9
Reconditioned Probe
LCS (50 ppb)
4.0
200 mL
292.5
39.8
S-2 (1:5) MS
4.1
200 mL
236.5
354.0
S-2 (1:5) MS Remade
4.1
200 mL
237.0
347.2
S-2 needed more acid
8.2
200 mL
256.0
165.4
S-2 added more acid
4.1
200 mL
273.2
84.5
S-2 (1:5) MS needed more acid
8.2
200 mL
229.2
470.7
S-2 (1:5) MS added more acid
4.0
200 mL
236.5
354.0
S-2 added more acid+10 min
4.1
200 mL
274.3
81.0
S-2 added more acid+MS-re
4.1
200 mL
270.2
95.0
S-2 added more acid+MS-re+30 min
4.0
200 mL
235.8
363.8
S-29
4.0
200 mL
329.5
9.4
S-29 MS+30 min
4.0
200 mL
339.8
6.3
S-29 MS+MS-re (Remade)
4.0
200 mL
239.0
321.1
S-29 MS+MS-re+15 min
4.1
200 mL
239.3
317.4
-------
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
S-29
4.0
200 mL
331.7
8.6
S-29+MS-re
4.0
200 mL
311.5
19.0
S-26
4°
200 mL
362.0
2.6
LCS (50 ppb)
40
200 mL
293.5
38.3
blank
4.1
200 mL
355.0
3.5
S-29+MS-re
4.0
200 mL
240.6
301.7
20 ppb ccv
4.1
200 mL
315.4
16.3
Blank+MS@4 min
4.1
200 mL
312.6
18.2
Blank+MS@10 min
4.1
200 mL
315.2
16.4
Blank+MS@40 min w recond
4.1
200 mL
315.4
16.3
S-5
4.1
200 mL
168.2
5090.8
S-5 (1:100)
4.1
200 mL
261.6
132.9
S-5 (1:200)
4.1
200 mL
279.4
66.4
Blank+MS (25 PPB)
4.0
200 mL
322.1
12.5
CCV20 PPB
4.1
200 mL
324.0
11.6
blank
4.1
200 mL
353.8
3.6
+MS = 0.1 mL 50 ppm std instead of 10 mL 50 ppb std
S-2 pH = 8.5+
-------
Table 5-4
Field Sample IDs
ISE Sample ID
ISE Result
Definitive
Result
Precision
(RPD)
ED-196-MW01-W09/-W05
P-5
24423
20000
19.9
ED-196-MW01-W09/-W06
P-5
25000
ED-286-MW01-W08/-W03
P-10
4336
5900
30.6
ED-422-MW01-W07/-W06
P-11
ND (<15)
6
Both
<15 ppb ISE
RL
ED-422-MW01-W07-DUP/-W06
P-11-DUP
ND (<15)
6
Both
<15 ppb ISE
RL
ED-422-MW01-W08/-W06
P-102
ND (<15)
6
Both
<15 ppb ISE
RL
ED-422-MW01-W09/-W06
P-103
ND (<15)
6
Both
<15 ppb ISE
RL
ED-422-MW01 -W10/-W06
P-104
ND (<15)
6
Both
<15 ppb ISE
RL
ED-188-MW01-W11/-W10
S-2
126.5
140
10.1
ED-189-MW03-W11/-W10
S-4
(10.1) ND (<15)
18
56.2
ED-196-MW01-W14/-W12
S-5
13270
36000
92.3
ED-196-MW01-W14/-W13
S-5
13270
27000
68.2
ED-286-MW01 -W16/-W15
S-10
612
1100
57.0
ED-286-MW01 -W16/-W14
612
920
40.2
ED-286-MW01 -W16-DUP/-W14
S-10D
731
920
22.9
ED-286-MW01 -W16-DUP/-W15
731
1100
40.3
-------
Table 5-5
Uncorrected
Corrected
Uncorrected
Uncorrected
Field Sample ID
ISE Sample ID
ISE Reading
ISE Result
%R
%R
ED-196-MW01-W09
P-5 (1:200)
61 10
|43.10
ED-196-MW01-W09-MS
P-5 (1:200)-MS
78.60
60.60
j 87.5 %R
87.5%R
only anions, low N03
ED-196-MW06-W15
P-7 ("1:2)
16.40
-16.10
ED-196-MW06-W15-MS
P-7 (1:2)-MS
31.60
-0.90
76.0 %R
;0 %R
only anions, med-low N03
ED-422-M W01 -WO 7
fp-11
63.74
3.44
ED-422-MW01-W07-MS
P-11-MS
67.60 1 ^1
7.30 2
19.3 %R
;0 %R
ED-422-MW01-W07-MSD
P-11-MSD
54.80
-5.50
-64.0 %R
0 %R
ED-422-MW01-W07 RE
P-11 RE
40.70
-19.60
ED-422-MW01-W07-RE-MS
P-11 RE-MS
67.60
7.30
134.5 %R
0 %R
ED-422-MW01-W07-RE-MSD
P-11RE-MSD
54.80
-5.50
-64.0 %R
:0 %R
high nitrate and organics
ED-286-MW03-W16
jS-29
9.70
NA
!NA
ED-286-MW03-W16-RE1
S-29RE1
8.50
NA
:NA
ED-286-MW03-W16-RE2
S-29RE2
9.40
NA
NA
ED-286-MW03-W16-RE3
S-29RE3
8.60
NA
!NA
ED-286-MW03-W16-DUP
S-29D
10.80
NA
NA
ED-286-MW03-W16-MS
S-29-MS
337.00
NA
1309.2 %R
NA
ED-286-MW03-W16-MS RE1
S-29-MS RE1
317.00
NA
1229.2 %R
:NA
ED-286-MW03-W16-MS RE2
S-29-MS RE2
19.00
NA
37.2 %R
NA
ED-286-MW03-W16-MS RE3
S-29-MS RE3
310.00
NA
1201.2 %R
iNA
med nitrate and low organics (VOCs at 0.5-2.5 ppb)
ED-188-MW01-W11
S-2
126.50
NA
ED-188-MW01-W11 (1:5)
S-2 (1:5)
25.30
NA
ED-188-MW01-W11 (1:5)-MS
S-2 (1:5)-MS
7.30
NA
-72.0 %R
NA
ED-188-MW01-W11 (1:5)-MS RE1
S-2 (1:5)-MS RE1
354.00
NA
1314.8 %R
NA
ED-188-MW01-W11 (1:5)-MS RE2
S-2 (1:5)-MS RE2
347.00
NA
1286.8 %R
:NA
unknown nitrate and high organics
(Freon 113 at 22 ppb, TCE at 11 ppb, others 0.5-4 ppb)
ED-285-MW01-W(EB)
S-3
1.60
1.60
ND (<15) N/A
—
ED-285-MW01-W(EB)-MS
14.60
14.60
65.0 %R
:65 %R
-------
Table 5-6
Field Sample ID
ISE Sample ID
Uncorrected
ISE Reading
Corrected Type of Sample:
ISE Result Dup or Rep
RPD
Uncorrected
RPD
Corrected
ED-285-MW02-W06
IP-9
14 6
1-1.0
:Parent Sample
:Field Dup. RPD
:Lab. Dup. RPD
ED-285-MW02-W06-DUP P-9-DUP (pH 4.4) 7 0
-8.6
;Field Dup
0.0 Both ND (<15) 0.0 Both ND (<15)
ED-422-MW01-W07-MS
P-11-MS
67 6
7.3
MS/MSD
MS/MSD RPD
MS/MSD RPD
ED-422-MW01-W07-MSD
P-11-MSD
54 8
-5.5
MS/MSD
20.9
0.0 Both ND (< 15)
ED-286-MW03-W16
S-29
9 7
NA
jParent Sample
ILab Rep. RPDs
:NA
E D-286-M W03-W16-R E1
S-29RE1
8 5
NA
Lab Replicate
0.0 All ND (< 15)
NA
E D-286-M W03-W16-R E2
S-29RE2
9 4
NA
:Lab Replicate
0.0 All ND (< 15)
NA
E D-286-M W03-W16-R E3
S-29RE3
8 6
NA
;Lab Replicate
0.0 All ND (< 15)
NA
E D-286-M W03-W16-DU P
S-29D
10 8
NA
:Field Duplicate
0.0 All ND (<15)
NA
ED-NM-MW04B-W13
P-16
15 0
-0.5
Parent Sample
Field Dup. RPD
Lab. Dup. RPD
ED-NM-MW04B-W13
P-16-DUP
18 0
2.5
iField Duplicate
18.2
0.0 All ND (<15)
ED-188-MW01 -W11
S-2
106.1
N/A
Parent Sample
Ser. Dil. RPD
;N/A
ED-188-MW01 -W11 (1:5)
S-2 (1:5)
25.3
25.3
Ser Dilution
17.5
N/A
ED-286-MW01-W16
S-10
612.0
N/A
Parent Sample
Field Dup. RPD
:N/A
E D-286-MW01 -W16-D U P
S-10D
731.0
N/A
Field Duplicate
17.7
;N/A
ED-286-MW03-W16
S-29
9.7
Anions NA
,Parent Sample
Field/Lab RPDs
:NA
E D-286-M W03-W16-R E1
S-29RE1
8.5
Anions NA
;Lab Replicate
0.0 All ND (<15)
NA
E D-286-M W03-W16-R E2
S-29RE2
9.4
Anions NA
:Lab Replicate
0.0 All ND (<15)
NA
E D-286-M W03-W16-R E3
S-29RE3
8.6
.Anions NA
|Lab Replicate
0.0 All ND (<15)
NA
E D-286-M W03-W16-D U P
S-29D
10.8
Anions NA
Field Duplicate
0.0 All ND (<15)
NA
ED-422-MW01-W09
S-11
64.2
3.9
Parent Sample
Field Dup. RPDs
Field Dup. RPDs
ED-422-MW01 -W10
S-102
66.5
6.2
Field Duplicate
3.5
0.0 All ND (<15)
ED-422-MW01 -W11
S-103
65.8
5.5
iField Duplicate
j2.5
0.0 All ND (<15)
ED-422-MW01 -W18
S-104
67.5
7.2
¦Field Duplicate
5.0
0.0 All ND (<15)
NA = Not Available
N/A = Not Applicable, result reported from dilution
-------
Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
ATTACHMENTS
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141
Final, October 2001
-------
Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
ATTACHMENT 1:
STANDARD OPERATING PROCEDURE (VERSION 1.0):
LOW CONCENTRATION METHOD FOR THE DETERMINATION
OF PERCHLORATE IN AQUEOUS SAMPLES
USING ION SELECTIVE ELECTRODES
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Final, October 2001
-------
Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
STANDARD OPERATING PROCEDURE
Low Concentration Method for the Determination of Perchlorate in Aqueous Samples Using
Ion Selective Electrodes
1.0 Scope and Application
The primary use for this method is to determine 15-100 pg/L concentrations of perchlorate in water samples
at or near field sampling sites. Matrices with high concentrations of specific anions, especially nitrate, may
not be appropriate for the use of this method due to significant positive bias and potential loss of sensitivity
after analysis of samples high in nitrate. Matrices with very high concentrations of interfering anions must be
evaluated to determine if this method meets project objectives.
The method is especially useful for matrices with less than 1000 mg/L chloride and 1.5 mg/L nitrate as
nitrogen (N03-N). Correction factors must be applied for concentrations in excess of 50 mg/L chloride, 0.12
mg/L NO3-N, or 1.2 mg/L bromide. Interference due to carbonate and bicarbonate is eliminated by the
acidification of all standards and samples to pH 4.0 (± 0.1) with sulfuric acid.
The California action limit for perchlorate in water is 0.018 mg/L (equivalent to 18 pg/L); therefore, this
method is intended to meet a target detection limit (TDL) of 18 pg/L, which is 12 to 40 times below the 200
to 700 pg/L manufacturer-specified detection limits for perchlorate ion selective electrodes (ISEs). The
method is expected to support a reporting limit (RL) of 15 pg/L, supported by a low calibration point of 10
pg/L, and a method detection limit (MDL) less than 7.5 pg/L, using solid state ISEs.
Due to the potential for positive bias due to matrix interference, ten percent of samples analyzed by this
method should generally be confirmed by definitive-level analysis, especially to confirm when application of
anion-specific correction factors lower perchlorate readings to below project action limits. Samples with
uncorrected perchlorate readings less than action limits can be considered to effectively indicate lack of
perchlorate if subsequent QC sample recoveries are within specified accuracy criteria.
Due to the potential for significant interferences from specific anions, the matrix must be characterized as to
concentrations of nitrate, chloride, and bromide. Alternatively, analysis by the method of standard additions
(MSA) may be used to compensate for unknown anion interference, especially for perchlorate readings less
than 30 pg/L. Further studies of the effectiveness of MSA to compensate for anion interferences are required.
2.0 Method Summary
Perchlorate is determined by ISE using a specialized solid state ion-specific perchlorate electrode with built in
reference element and a portable ISE meter. A computer interface may be used in place of the ISE meter. All
standards and samples must be at approximately the same background ionic strength, therefore ionic strength
adjustor (ISA) is added to all standards and samples. All standards and samples are acidified to pH 4.0 (+0.1)
with sulfuric acid to remove carbonate/bicarbonate interference. It is recommended that a pH meter be set up
along side the ISE.
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
Analyses are performed on 200 mL aliquots of sample continuously stirred using a magnetic stirring bar
rotating at a slow to moderate rate without causing a vortex. Analyses must be performed at approximately
the same temperature as the calibration. As the sensitivity required to meet the TDL and RL are significantly
below the intended range of the ISE, millivolt readings may take several minutes to stabilize. Millivolt
readings are logged instead of direct perchlorate concentration read-out using ISE meter or computer interface
calibration features. Millivolt readings for calibration standards and samples can be entered onto a
spreadsheet capable of producing a logarithmic calibration curve, or plotted on logarithmic or semilogarithmic
graph paper. Perchlorate readings can then be obtained from the spreadsheet by formula, or manually read
from the graph paper.
Correction factors must be applied to perchlorate readings for interference caused by significant
concentrations of chloride, nitrate, bromide, or fluoride, as appropriate for the matrix. If nitrate is present
above 0.2mg/LNO3-N, reconditioning of the perchlorate ISE using 100-2000 (ig/L perchlorate solutions and
acidified blanks between every sample is required. Otherwise, ISE conditioning is required prior to
calibration and is recommended at regular intervals.
3.0 Sample Handling and Preservation
Samples may be collected in plastic or glass bottles. All bottles must be thoroughly cleaned and rinsed with
reagent water. The recommended sample volume is 500 mL to insure a representative sample, allow for
replicate analysis, and minimize waste disposal. Additional volume should be collected for samples
designated for matrix spike analysis, if required.
No sample preservation is required. Analytical holding time is 28 days. Samples are not required to be
shipped iced or stored cold in a refrigerator; however, samples collected for perchlorate analysis are
recommended to be stored at 4 ± 2°C from the time of collection until prior to analysis, and every effort
should be taken to protect the samples from temperature extremes and exposure to sources of ultraviolet light.
The use of ice packs or a thermally insulated sampling kit, designed to fit sampling bottles securely during
shipment, may be used to protect the samples from high temperatures. Samples must be allowed to reach the
same ambient temperature at which calibration is performed prior to analysis.
Note that EPA studies have shown perchlorate to be stable for more than 28 days(1) but extended holding time
studies (beyond 35 days) were not conducted by EPA. Typically, when analytes are believed to be stable, a
28 day holding time is established as a sufficient time period to permit analysis of samples.
4.0 Interferences
This method requires operation of perchlorate ISEs at sensitivity significantly below intended manufacturer-
specified detection limits, and is therefore subject to potential matrix interferences. Sample matrices should be
evaluated to determine appropriateness of this method with respect to specific project objectives. Several
common anions have been demonstrated to cause significant positive interference (greater than 20% of
perchlorate concentration, or 20% of the 15 (ig/L RL for perchlorate results less than the RL) for this method.
In addition, loss of sensitivity has been demonstrated to occur after analysis of samples high in carbonate,
bicarbonate, or nitrate.
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Final, October 2001
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
Interference due to carbonate and bicarbonate is eliminated by the acidification of all standards and samples to
pH 4.0 (± 0.1) by the addition of 0.2 to 0.5 normal (N) sulfuric acid. Matrices with greater than 0.2 mg/L
N03-N require reconditioning of the perchlorate ISE using acidified blanks and acidified 100-2000 (ig/L
perchlorate solutions between every sample to prevent loss of sensitivity (refer to Section 10.2). Matrices
high in nitrate may not be appropriate for this method. Samples with nitrate concentrations of 1.1 to 5.5 mg/L
NO3-N cause positive bias of 15-45 ug/L perchlorate (one-to-three times the RL). The user may need to
determine the maximum level of nitrate correction acceptable for project objectives if samples include high-
nitrate matrices.
Matrices with concentrations of nitrate less than 0.12 mg/L NO3-N, bromide less than 1.2 mg/L, and chloride
less than 50 mg/L will not be significantly affected by known interferences. Higher concentrations of these
anions require application of correction factors according to Tables 1 through 3. Anion concentrations from
historical or contemporary data may be applied. If such data does not exist, ISEs for these anions may be
used utilizing the same ISE meter or computer interface. Alternatively, analysis by MSA may be used to
compensate for unknown anion interference, especially for perchlorate readings less than 30 (ig/L. However,
further studies of the effectiveness of MSA to compensate for anion interferences are required.
Note that for low-nitrate matrices, the only anion likely to require application of correction factors is chloride,
for which correction factors are relatively small (12 (ig/L perchlorate for 500 mg/L chloride). During method
development studies, concentrations of up to 0.5 mg/L NO3-N, 300 mg/L chloride, or more than 5.0 mg/L
bromide did not produce false positives in spiked blanks. When perchlorate readings associated with
acceptable QC indicate that perchlorate is not present above project action limits, perchlorate can be
confidently considered not to be present at that level, and correction factors need not be addressed, since all of
the interferences are for positive bias.
In general, a minimum of ten percent of samples analyzed by this method should be confirmed by definitive-
level split sample analysis. Whenever project objectives are potentially affected by the application of
correction factors such that perchlorate readings are adjusted to within ±20% of a project action limit (or
±40% using historical anion data), confirmation of the analysis is recommended by definitive-level analysis
according to EPA Method 314.0 or other approved methodology.
This method is not appropriate for samples high in cyanide or thiocyanate. These anions are presented in
perchlorate ISE literature as potential interferents, but interference studies on these anions were not been
performed during method development. Acidification to pH 4.0 of samples with cyanide, and to a lesser
extent thiocyanate, causes generation of cyanide gas, which is poisonous.
5.0 SAFETY
This method does not address all safety issues associated with its use. The laboratory or field team leader is
responsible for maintaining a safe work environment and a current awareness file of OSHA regulations
regarding the safe handling of the chemicals specified in this method. A reference file of material safety data
sheets (MSDSs) should be available to all personnel involved in these analyses.
This method is designed for potential use in the field by trained technicians or experienced laboratory
analysts. Before commencing use of this method, the user must undergo initial training to become familiar
with the equipment and chemicals used in the method. This training will include practice handling the
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Letter Report of Findings: Perchlorate Screening Method Study
U.S. Army Corps of Engineers
chemicals and solutions, performing serial dilutions using pipettes and volumetric glassware, reading all
MSDSs for chemicals used, and reading all instrument manuals and the method standard operating procedure
(SOP).
Safety glasses and protective gloves and clothing must be worn while handling perchlorate salts and solutions,
sulfuric acid, and environmental samples which may contain unknown contaminants.
The toxicity or carcinogenicity of each reagent used in this method has not been fully established. Each
chemical should be regarded as a potential health hazard and exposure should be as low as reasonably
achievable. Cautions are included for known extremely hazardous materials or procedures.
The following chemicals have the potential to be highly toxic or hazardous. The MSDS for each chemical
should be consulted.
Sulfuric acid (Sec. 7.3).
Sodium perchlorate, potassium perchlorate, and magnesium perchlorate (Sec. 7.4).
Although stable under most conditions, perchlorate salts are considered to be explosive and are strong
oxidizers. Handle and store with care. Do not allow perchlorate salts or solutions to contact other materials,
especially reducing agents, organic compounds, reactive metals, or skin or eyes. Wear eye and skin
protection when handling perchlorate salts and solutions. In case of contact with skin, flush with water for 5
minutes or more. In case of contact with eyes, flush with water for 15 minutes or more. Seek medical
attention if burning or irritation persists.
All perchlorate solutions included in this SOP are considered oxidizers and hazardous materials, and must be
properly labeled with concentration identification and right-to-know OXIDIZER 5.1 labels. Carefully follow
all requirements and protocols for mixing, diluting, and storing the chemicals in this method. Follow all
procedures for cleaning containers specified in Section 14.0 (Clean-up Protocols), and for collecting, storing,
and disposing of wastes specified in Section 15.0 (Waste Management).
6.0 Apparatus and Equipment
Ion Specific Electrode (ISE): The method requires use of a perchlorate-specific ISE. During method
development, the Sentek 367-75 Solid State Perchlorate Combination ISE was used and found to perform
satisfactorily; however, equivalent equipment can be used, and no requirement or recommendation of brand or
manufacturer is implied. Note that a double junction reference electrode ISE was found not to meet
sensitivity requirements during method development for this method. Therefore, a solid state combination
ISE is recommended, as it also can be stored dry and no inner or outer chamber reference electrode solutions
are required. Having a back-up perchlorate ISE module is recommended in case of severe deterioration of
sensitivity or failure.
Data Acquisition System: An ISE meter such as the Orion Model 290A Advanced Portable
ISE/pH/mV/ORP/ Temperature Meter is required. A computer interface such as the Laval ELIT 8804
Computer Interface (Four Channel Serial Port RS232 Communication Port Connection and Laval ELIT
Extended Software for ISE Interface 8804 for 10,000 Measuring Points) may be used instead of an ISE meter.
The above referenced equipment was used during method development and found to perform satisfactorily,
however, equivalent equipment can be used, and no requirement or recommendation of brand or manufacturer
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is implied. Due to sensitivity requirements and time required to stabilize, millivolt readings are logged
instead of direct perchlorate concentration read-out using ISE meter or computer interface calibration features.
Entry of the logged data into a spreadsheet program capable of producing a logarithmic calibration curve is
recommended for calibration and perchlorate concentration readout. Alternatively, data may be plotted on
semilogarithmic graph paper.
pH Meter: A pH electrode and meter is required to determine when standards and samples have been
acidified to pH 4.0 (± 0.1).
Additional ISEs: ISEs for chloride, nitrate, and/or bromide may be used to determine concentrations of
interfering anions if appropriate historical or contemporary data is not available. The ISE meter or computer
interface for the perchlorate ISE can be used for data acquisition.
Conductivity Meter: A conductivity meter may provide useful insights into relative levels of anions. This
meter should be capable of measuring conductance over a range of 1 - 10,000 microsiemens/cm (uS/cm) or
microMhos/cm (uMhos/cm), which are considered equivalent terms.
Flexible-Arm Electrode Stand and Holder: A flexible device to hold the perchlorate ISE, pH meter,
thermometer, and any other electrodes to be used simultaneously is recommended. The device should be able
to move the electrodes in and out of the containers holding the standard or sample.
Magnetic Stirrer: A magnetic stirrer is required for this method.
Analytical Balance: If stock standards for calibration standards, second source check standards, or ISA
solutions are to be made from reagent salts, an analytical balance capable of accurately weighing target
analyte salts to ±0.01 g is required. Analytical balances with higher accuracy can be used to reduce the
concentration of primary stock perchlorate solutions. Perchlorate stock solutions and ISA solutions are
commercially available, and may be purchased if available.
Desiccator Cabinet: Dry perchlorate chemicals are recommended to be stored in a desiccator cabinet if
standards are to be made from reagent salts.
Autopipettor: A variable volume 100-1000 |aL autopipettor with disposable tips is highly recommended for
dilution of primary and working standards to make calibration and check standards, and to add ISA to
standards and samples.
Containers and Glassware: All containers for perchlorate solutions must be chemical resistant. Standard
laboratory glassware or chemically resistant plastic-ware such as polymethylpentene or high density
polypropylene (HDPE) should be used for concentrated perchlorate solutions. All containers should be
thoroughly washed and rinsed with distilled or deionized water before use. The following glassware/plastic-
ware are recommended:
Assorted pipettes: 0.1 mL, 0.2 mL, 0.5 mL, 1.0 mL, 2.0 mL, 10 mL (or autopipettor)
Pipetting Aid: Device to aid in pipetting without skin contact, such as the Eppendorf Pipette Helper
100 mL, 200 mL, and/or 1,000 mL volumetric flask(s) with stopper or screw cap (glass or
polymethylpentene) 400 mL beakers (for analysis of 200 mL aliquots). Appropriate wide mouth screw cap
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plastic containers may be used, allowing extended storage of standards and samples after analysis, as long as
the mouth is wide enough for the ISE, pH electrode, thermometer, and magnetic stirrer.
Thermometer(s)
Assorted polymethylpentene and polypropylene storage containers for primary and working standards (250-
400 mL recommended) and waste solutions (1-4 L recommended)
Assorted supplies: Plastic spatulas, stirring rods, plastic dropper for sulfuric acid, plastic squeeze bottles for
rinsing electrodes and glassware, larger plastic bottles for storing wastes, 100 mL graduated cylinder(s),
disposable graduated plastic syringe pipettes (1-12 mL), 6"X6" tare (weighing) paper, chemwipes, etc.
Personal Protective Equipment (PPE): Safety glasses, protective gloves, and clothing must be worn while
handling perchlorate solutions, sulfuric acid, and environmental samples, which may contain unknown
contaminants.
7.0 Reagents, Standards, and Solutions
All standards should be made from reagent grade chemicals or certified solutions. ASTM Type I distilled or
deionized water, free of the anion of interest, should be used in the preparation of all standards and solutions.
Use of a variable volume 100-1000 pL autopipettor with disposable tips is highly recommended for dilution
of primary and working standards to make calibration and check standards, and to add ISA to standards and
samples. If a variable volume autopipettor is not available, use traditional 1.0-10.0 mL high accuracy pipettes
and 100-200 mL volumetric flasks to make the required standards by appropriate serial dilutions.
Perchlorate salts are hygroscopic, they will adsorb water, thus causing gravimetric errors in the concentrations
of the calibration standards. Keep the perchlorate salts in a cool (not refrigerated) desiccator cabinet at all
times, except to briefly weigh out aliquots for preparation of standards. Keep bottles tightly closed and keep
screw threads clean (carefully wipe with dry chemwipe or paper towel if necessary).
7.1 Primary Ionic Strength Adjustor (ISA) Solution
Purchase a commercially available ISA appropriate to the ISE used for the project, or make an ISA working
solution from reagent salts or solutions. In method development, ISA solutions made from 0.1 M sodium
acetate (recommended as the Sentek perchlorate ISA) and from 2.0 M ammonium sulfate (recommended as
the ISA for Orion double junction perchlorate ISEs) were found to perform satisfactorily at 25% of the
manufacturer-recommended concentrations, as follows.
For the Sentek ISA, the use of 1 mL of "Sentek Perchlorate ISAB" (1.0 M sodium acetate) per 200 mL
sample is recommended for the low concentration method (ISAB refers to the buffering capacity of this ISA).
For the Orion ISA, the use of 1.0 mL of Orion 930711 ISA (2.0 M ammonium sulfate) per 200 mL sample is
recommended for the low concentration method. Although both ISAs are acceptable, use of the Sentek ISAB
is recommended when using the Sentek ISE on the basis that sodium acetate is the internal solution for the
built-in reference electrode.
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If the Orion ISA or Sentek ISAB are not available, ISA solution can be made from reagent salts by adding
8.21 g sodium acetate or 26.43 g ammonium sulfate to a 100 mL volumetric flask, and diluting to the mark
with distilled water. Transfer to 120 mL wide mouth polymethylpentene Nalgene bottle with screwcap.
Clearly label bottle ISAB - 1M NaCH3C02 or ISA - 2 M (NH^SC^ and expiration date (date solution made
+5 days). Store in cooler or refrigerator. May be stored and used for 5 days.
All standards and samples must be spiked with proportionally equivalent concentrations of the same ISA.
Different concentrations of ISA or ISAB should not be used interchangeably within a calibration, although
minor changes in ISA are not expected to significantly affect data quality. Note that concurrent calibrations
can be maintained to account for any differences in adjustments to samples (such as pH, ISA/ISAB
concentration, or temperature) by making the same adjustments to the calibration and check standards.
EVERY STANDARD OR SAMPLE TO BE ANALYZED REQUIRES ADDITION OF ISA. If the ISA
is not added, the analysis may be severely biased low and must be rejected. ISA can be transferred using
graduated syringe pipettes or a variable volume autopipettor.
7.2 Perchlorate Standards for Calibration
7.2.1 Primary Perchlorate Standards for Calibration
A stock standard perchlorate solution at 1,000 or 10,000 mg/L (mg/L) prepared from American Chemical
Society (ACS) reagent grade material is required for preparation of calibration standards. Purchase a
commercially available 1000 mg/L perchlorate stock standard solution, usually made from sodium
perchlorate; or prepare a primary stock solution from one of the following ACS reagent grade salts:
Potassium Perchlorate, Analytical Grade (MW 138.55)
1 M = 138.55 g KCIOVL = 99.45 g CIO4VL = 99,450 mg/L (mg/L) C104
139.32 g KCIO4/L = 100.00 g CIO4VL = 100,000 mg/L C104 (1.0055 M)
Sodium Perchlorate, Analytical Grade (MW 122.45)
1 M = 122.45 g KCIO4/L = 99.45 g CIO4VL = 99,450 mg/L (mg/L) C104
123.13 g KCIO4/L = 100.00 g CIO4VL =100,000 mg/L C104" (1.0055 M)
Depending on project accuracy requirements, a 1,000 mg/L primary perchlorate stock solution can be made
using an analytical balance with ±0.01 g accuracy, if a 1,000 mL volume of primary stock solution is
acceptable for waste disposal and storage considerations. A 10,000 mg/L primary stock solution must be
made if using an analytical balance with ±0.01 g accuracy and a 100 mL volume of primary stock standard is
preferred for waste disposal and storage considerations. An analytical balance with ±0.001 g or greater
accuracy can be used to make 100 mL of 1,000 mg/L primary perchlorate stock solution.
Add 1.39 (1.3932) g KCIO4 or 1.23 (1.2313) gNaC104to a 100 mL glass volumetric flask (for 10,000 mg/L
solution) or a 1,000 mL glass volumetric flask (for 1,000 mg/L solution), dilute to mark with distilled water.
Stopper or cap the flask, or transfer to appropriate Teflon FEP Nalgene bottle or equivalent with screwcap and
right-to-know OXIDIZER 5.1 label. Clearly label bottle 1° PERCHLORATE STD / 0.1 M /1,000 or 10,000
mg/L C104- and expiration date (date solution made +180 days). Do not add ISA solution to this primary
standard.
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7.2.2 Intermediate Perchlorate Working Standard for Calibration
The primary stock solution is used to prepare intermediate working standards for use in preparation of daily
calibration standards by serial dilution. Any combination of working standard concentrations and serial
dilutions is acceptable as long as all calculations are carefully checked, but the following sequence is
suggested.
To prepare a 50 mg/L working standard, pipette 5.0 mL of 1,000 mg/L (or 0.5 mL of 10,000 mg/L) 1°
PERCHLORATE STD into a 100 mL glass volumetric flask, dilute to mark with distilled water. Transfer to
an appropriate Teflon FEP Nalgene, polymethylpentene Nalgene, or equivalent bottle with screwcap and
right-to-know OXIDIZER 5.1 label. Clearly label bottle PERCHLORATE WORKING STD / 50 mg/L
C104- and expiration date (date solution made +28 days). Do not add ISA solution to this or any
intermediate working standard.
Store in refrigerator or in a cool dark place. Perchlorate stock standards, stored at room temperature, may be
stable for an extended period of time. Avoid exposure to sunlight or elevated temperatures. Specified
expiration dates should be clearly marked on the label of each prepared stock standard. Properly stored
unused or rarely used primary stock 10,000 (ig/L or 1,000 (ig/L perchlorate standards should not be held for
more than 6 months, or according to vendor recommendation. Depending on project facilities and how often
the standards are opened and used, it is recommended that frequently used primary stock standards be freshly
prepared more often. Intermediate stock 1,000 (ig/L perchlorate standards should not be held for more than
28 days, and lower concentration intermediate stock and dilute working standards should be prepared weekly.
Calibration standards are prepared daily. Verify solutions on an ongoing basis by analysis of second source
standards and periodic review of instrument millivolt readings.
7.2.3 Prepare Calibration Standards Daily
Prepare calibration standards at 10 (ig/L, 20 j^ig/L, 40 (ig/L, 60 (ig/L, and 100 (ig/L on a daily basis by the
dilution of the intermediate perchlorate working standard. If less method sensitivity is required for project
requirements, choose higher concentrations to focus of the calibration range to the concentrations of interest.
If the working range is elevated significantly above the 10-100 (ig/L range specified for this low
concentration method, such that calibration within the manufacturer specified range of 200-700 |_ig/L to
99,500 (ig/L is appropriate, then this method may be used for guidance (for example, for soils), but full
strength ISA (four times the amount specified for the low concentration method) should be used per ISE
manufacturer recommendation, and matrix interference will not be significant.
Any combination of working standard concentrations and serial dilutions is acceptable as long as all
calculations are carefully checked, but the following sequence is suggested. Pipette 1.0 mL, 2.0 mL, 4.0 mL,
6.0 mL, and 10.0 mL of 50 mg/L perchlorate working standard into a 200 mL volumetric flask, and dilute to a
total volume of200 mL with distilled water (if a 100 mL volumetric flask is used, dilute to mark and combine
with another 100 mL volume of water). Transfer to an appropriate container for analysis with a magnetic
stirrer, such as a 400 mL beaker or appropriate wide mouth screw-cap plastic container. Clearly label each
container 10, 20, 40, 60, or 100 mg/L Perchlorate Calibration Standard and preparation/expiration date
(standards must be made daily).
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Add ISA: Add 1.0 mL of 1.0 M sodium acetate or 1.0 mL of 2.0 M ammonium sulfate per 200 mL) to
each calibration standard, as specified in Section 7.1. If the ISA is not added to the calibration
standards, the calibration will be severely affected and all results will be unusable.
7.3 Perchlorate Second Source Standard: Initial Calibration Verification (ICV)/ Laboratory Control
Sample (LCS)
As all calibration standards and samples must be prepared using the same chemicals, the ICV and LCS are
functionally equivalent. The ICV/LCS is a second source standard used to verify the accuracy of the
instrument calibration and monitor ongoing batch QC. Prepare a 1000 (ig/L or 10,000 (ig/L primary
perchlorate stock solution using a material source different from that of the calibration stock for use in
preparing the ICV/LCS.
7.3.1 Primary Perchlorate Standard for ICV/LCS
Purchase a commercially available certified 1,000 mg/L perchlorate stock standard using a vendor different
from the vendor of the calibration standards, being sure the standard is from a different source or lot number;
or prepare an ICV/LCS primary stock standard from one of the above referenced salts not used for calibration
standards, or from the following reagent salt:
Magnesium Perchlorate (anhydrone), Reagent Grade (MW 223.21)
1 M = 223.21 g Mg(C104)2/L
0.5 M = 111.61 g Mg(C104)2/L = 99.45 g C104 /L = 99,450 mg/L (mg/L) C104
112.22 g Mg(C104)2/L = 100.00 g C104/L = 100,000 mg/L C104
Prepare a primary perchlorate ICV/LCS stock solution as specified for calibration standards in Section 7.2.1,
above, or using 1.12 (1.122) g Mg(C104)2. Do not add ISA solution to this primary standard. Clearly
label bottle ID PERCHLORATE ICV/LCS STD /1,000 or 10,000 mg/L C104" and expiration date. This
solution is used as a master solution to prepare an intermediate working standard to be used in preparation of
the daily ICV/LCS standards by serial dilution, as specified for calibration standards in Section 7.2.2, above.
Do not add ISA solution to this or any intermediate working standard. Any combination of working
standard concentrations and serial dilutions is acceptable as long as all calculations are carefully checked.
7.3.2 Prepare ICV/LCS Daily
Prepare one or more LCSsat25 or 50 (ig/L (depending on project QC objectives, see Section 8.2.4, below) on
a daily basis by dilution of the intermediate LCS working standard. 25 or 50 |_ig/L LCSs can be prepared as
specified for calibration standards in Section 7.2.3, above, using 2.5 or 5.0 mL of 50 mg/L intermediate
perchlorate working standard diluted to 200 mL. Clearly label each standard, including expiration date (date
standard made for the LCS). Add ISA to each ICV/LCS, as specified in Section 7.1. Failure to add the
ISA will generally result in severe low bias.
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7.4 Perchlorate Reagent and Solution Storage, Cleanup, and Waste
Although stable under most conditions, perchlorate salts are considered to be explosive and are strong
oxidizers. Handle and store with care. Keep the perchlorate salts in a desiccator cabinet or in a dry, dark
place (avoid heat or refrigeration) at all times, except to briefly weigh out aliquots for preparation of
standards. Keep bottles tightly closed and keep screw threads clean (carefully wipe with dry paper towel if
necessary). Do not mix with other substances. If solid perchlorate salts must be discarded, they must be
properly labeled with concentration identification and OXIDIZER 5.1 labels and disposed of as hazardous
waste according to state and federal guidelines.
Store all perchlorate solutions in a refrigerator or in a cool dark place. Perchlorate solutions are strong
oxidizers. Store according to all applicable requirements. Do not store with reducing agents. All solutions
must be allowed to reach ambient temperature before analysis.
If calibration standards or LCSs are to be prepared in the field, transfer adequate volumes of the working
standards into polymethylpentene, polypropylene, or equivalent bottles with screwcap for transport to the site.
Standards transported to the site must be discarded at the end of the day.
Transfer discarded solutions to a 1 Liter polypropylene wide mouth screw top container (or other appropriate
polypropylene waste collection container) labeled HIGH CONC PERCHLORATE WASTE with right-to-
know OXIDIZER 5.1 label.
Triple rinse glassware with water into 1000 mL polypropylene beaker and transfer rinsate to 1 Liter
polypropylene wide mouth screw top container (or other appropriate polypropylene waste collection
container) labeled LOW CONC PERCHLORATE WASTE with right-to-know OXIDIZER 5.1 label. Wash
triple rinsed plastic or glassware with soap and water in sink, triple rinse with distilled water, drip dry.
Follow all procedures for cleaning containers specified in Section 14.0 (Clean-up Protocols).
Maintain and dispose of all wastes according to applicable state and federal regulations. Follow all
procedures for collecting, storing, and disposing of wastes specified in Section 15.0 (Waste Management).
8.0 Quality Control (QC)
The QC requirements for this method include frequency and acceptability criteria for initial calibrations,
second source check standards (ICV/LCS), continuing calibration verification standards (CCV), method
blanks (MB), continuing calibration blanks (CCB), matrix spike samples (MS), and laboratory duplicate
samples. Field QC, such as field duplicate sample analyses and field blanks may be required if specified to
meet project-specific QC objectives.
This section details the specific requirements for each of these QC parameters.
The primary use for this method is to determine 15-100 (ig/L (parts per billion [jj.g/L]) concentrations of
perchlorate in water samples at or near field sampling sites by trained technicians or experienced laboratory
analysts. As a field screening method, ten percent of samples analyzed by this method should generally be
confirmed by definitive-level analysis at a fixed base laboratory. Therefore, some elements of QC generally
specified for ongoing laboratory analyses, such as a formal initial demonstration of capability with MDL
studies, linear range studies, etc., are not included for the low concentration method.
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The user should maintain records to document the quality of the data generated. All data sheets and quality
control data should be maintained for reference or inspection.
8.1 Initial Demonstration of Proficiency
An initial demonstration of proficiency may be required to characterize instrument performance and
laboratory performance prior to performing analyses by this method. However, for field screening use,
acceptability of the initial calibration curve for each analytical run will meet this requirement, as follows.
8.1.1 Linear Calibration Range (LCR) - The LCR must be determined to meet project objectives. The
method is intended to have a 10-100 j^ig/L LCR; however, the method is expected to perform acceptably and
with less matrix interference at higher concentrations. The calibration curve must use a sufficient number of
standards at appropriate intervals to insure that the resulting curve is linear. To demonstrate linearity for the
low concentration method, the coefficient of determination (r2) must be greater than or equal to 0.990
(equivalent to r >0.995) and/or the concentration calculated for each calibration standard from its millivolt
response using the calibration curve should be within ± 20% of its true value; and ICV/LCSs and CCVs must
meet accuracy criteria of ± 20%.
8.1.2 Method Detection Limit (MDL) Studies - Depending on project objectives and the intended use of the
data, MDL studies may be required. However, for field screening use, demonstration of the ability to
distinguish between a blank and a standard below the project reporting limit (RL) or practical quantitation
limit (PQL) is acceptable. Blanks must be less than one-half the RL or PQL, and the low calibration standard
must meet ±20% accuracy criteria.
During method development, an MDL of 3 (ig/L was determined. Method blanks were generally in the 2-5
(.ig/L range, and the RL was set at 15 |_ig/L to meet the California action limit and target detection limit (TDL)
ofl8 (ig/L. Tosupportthe 15 (ig/L RL, blank results must be less than 7.5 (ig/L and readings for a 10 (ig/L
standard must be 8.0-12.0 |_ig/L.
8.2 Method Performance QC
8.2.1 Method and Calibration Blanks - At least one MB must be prepared with each batch of 20 or fewer
samples. As all calibration standards and samples must be prepared using the same chemicals, the MB and
initial and continuing calibration blanks (ICB and CCBs) are functionally equivalent. An ICB/MB must be
analyzed after the ICV/LCS and before any samples, and a CCB must be analyzed at a minimum of every 10
samples and at the end of the analytical sequence. Reanalysis of the ICB/MB is acceptable as the CCB.
Values that exceed one half the RL/PQL indicate that laboratory or reagent contamination should be
suspected and corrective action must be taken before continuing the analysis, including reanalysis of any
samples with detected results less than five times the result for the blank.
8.2.2 Laboratory Control Sample (LCS) - For each batch of 20 or fewer samples processed, at least one
LCS must be carried through the entire sample preparation and analytical process. As all calibration
standards and samples must be prepared using the same chemicals, the ICV and LCS are functionally
equivalent as second source standards. An ICV/LCS must be analyzed after every calibration and before any
samples, and for each additional batch of 20 or fewer samples.
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8.2.3 Calibration Verification - For all determinations, the second source check standard (ICV/LCS) and
an initial calibration blank (ICB/MB) must be analyzed immediately following daily calibration to verify that
the instrument is functioning within method criteria before samples are analyzed. A continuing calibration
verification standard (CCV) and CCB must be analyzed after every ten samples and at the end of the
analytical run. CCV analyses must verify that the calibration is still within specified criteria. The LCS and
CCV may alternate for extended analytical runs of more than 20 samples.
8.2.4 ICV/LCS and CCV Concentrations - The ICV/LCS and CCV should be prepared at concentrations
appropriate to project objectives. The ICV/LCS must be prepared from a different source than the calibration
standards. The CCV can be from the same source as the calibration standards, and may utilize initial
calibration solutions. For projects with an action limit of 18 (ig/L, ICV/LCS concentrations of 25 (ig/L or 50
(.ig/L are recommended, depending on project objectives, and CCV concentrations of 20 (ig/L are
recommended, with alternating standards at 25 or 50 (ig/L and 20 (ig/L to verify mid-range accuracy and
sensitivity near the action limit.
8.2.5 Analytical Sequence - The following analytical sequence is recommended: ICAL, ICV/LCS,
ICB/MB, 10 samples (including matrix specific QC samples), CCV, CCB, 10 samples, CCV, CCB. If a
second batch of samples is to be analyzed, the last CCV, CCB can be omitted and the sequence continued
with: LCS, CCB/MB, 10 samples (including matrix specific QC samples), CCV, CCB, etc.
Note that millivolt readings for each ICAL standard should be quantitated utilizing the calibration curve, and
all results should be within ± 20% of true values. Analytical data for all QC analyses including calibration
verification and blanks must be kept on file with the sample analysis data.
8.2.6 Acceptance Criteria for Method Performance QC
Acceptance criteria for the ICV/LCS and CCV should be set to meet project-defined requirements. In
general, the accuracy criterion for the low concentration method should be set at ± 20% of the spiked or true
value.
8.2.7 Corrective Action for Method Performance QC - If ICAL standard, ICV/LCS, or CCV recovery is
not acceptable, sample analysis must be discontinued, the problem must be identified and corrective action
must be taken.
Verify that the temperature has not changed by more than 1-2°C since analysis of calibration standards and
that pH has been correctly adjusted. Re-prepare and reanalyze an unacceptable ICV/LCS. For CCVs or LCSs
run after field samples, verify that loss-of-sensitivity interference due to nitrate or carry-over due to high
concentrations of perchlorate or other interferents is not the cause by reconditioning the ISE module with an
acid blank and 100-2000 (ig/L perchlorate solution (refer to Section 10.2). If the problem is identified and
corrected, reanalyze all samples since the last acceptable ICV/LCS or CCV. If necessary, implement ISE
reconditioning between every analysis.
If the problem cannot be identified, check that all calibration standards, CCVs, and second source standards
were correctly prepared. If necessary, reprepare all standards and recalibrate. If the problem persists, refinish
the tip of the ISE with fine emery paper according to manufacturer directions, or replace the ISE module.
Reanalyze all samples since the last acceptable ICV/LCS or CCV in an acceptable analytical run.
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8.3 Matrix-Specific QC
8.3.1 Matrix spike (MS) - Perform matrix spike analysis on at least one sample per batch of 20 or fewer
samples. A higher frequency may be required to demonstrate the ability of the method to accurately work in
matrices requiring application of significant correction factors for interfering anions. Performing MS
analyses on samples with differing concentrations of nitrate may be particularly informative.
The sample aliquot used for MS analysis must be a duplicate of the aliquot used for sample analysis. The
perchlorate concentration in the MS should be chosen to verify accurate determination of perchlorate in the
environmental matrix at concentrations critical to project objectives. For projects with an action limit of 18
(.ig/L, spike concentrations of 20 (ig/L or 25 (ig/L are recommended. Prepare the MS using the same stock
working solution as the calibration standards, as this will remove the bias contributed by an externally
prepared stock and focus on any potential bias introduced by the field sample matrix.
If the concentration of spike is less than 25% of the background concentration of the matrix, the matrix
recovery should not be calculated. With an LCR of 10-100 |_ig/L and an MS of 25 (ig/L, this will only occur
for samples with results exceeding the calibration range. In such cases, choose another sample for MS
analysis with results near the action limit to verify accuracy of results at concentrations critical to project
objectives, or spike a diluted aliquot of the sample for MS analysis at the same dilution used for final
quantitation to verify accuracy of higher results.
Calculate the percent recovery for perchlorate, corrected for the concentration measured in the unspiked
sample before application of all correction factors, according to the following equation:
%R = (Cs - C) x 100 / S
where:
%R = percent recovery
Cs = concentration of sample plus spike
C = sample background concentration
S = concentration of spike added to sample
8.3.2 MS Acceptance Criteria and Corrective Action - Acceptance criteria for the MS should support
project-defined requirements. In general, the acceptability criteria for matrix spike recoveries for this method
should be set at 65-135 %R. If the recoveries for perchlorate matrix spikes fall outside 65-135 %R, verify
that the temperatures for the duplicate analyses did not differ by more than 1-2°C and that pH was correctly
adjusted. In addition verify that loss-of-sensitivity interference due to nitrate or carry-over due to high
concentrations of perchlorate or other interferents is not the cause by reconditioning the ISE module with an
acid blank and 100-2000 (ig/L perchlorate solution (refer to Section 10.2) and reanalyzing the parent sample
and MS.
If the problem is identified and corrected, it may be necessary to reanalyze some or all of the samples in the
batch. If necessary, implement ISE reconditioning between every analysis. If corrective actions do not
alleviate the problem and the performance for all other QC performance criteria is acceptable, the accuracy
problem is judged to be matrix related. The results for perchlorate in all samples with similar concentrations
of interfering anions must be labeled suspect due to matrix interference.
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Due to the sensitivity of the low concentration method to anion interferences, ongoing evaluation of matrix
spike recoveries is required to help determine the accuracy of this method when correction factors must be
applied. Repeated failure to meet specified MS criteria may indicate the low concentration method is
inappropriate for the matrix.
Split sample analyses by EPA Method 314.0 (or equivalent) of all questionable samples may be required to
determine the appropriateness of the low concentration method for the matrix (refer to Section 8.3.6). In such
cases, raising the RL or LCR and re-evaluation of the ability of the low concentration method to meet project
objectives, especially for specific samples with high nitrate concentrations, may be required.
8.3.3 Laboratory Duplicate Sample Analysis - Perform duplicate sample analysis on at least one sample
per batch of 20 or fewer samples. The duplicate analysis should be performed on two separate aliquots taken
from one sample container, prepared and analyzed in the same manner as each other and all other samples in
the batch. Duplicate sample results should be within 20 relative percent difference (RPD). Calculate RPD
according to the following equation:
RPD = (Cj - C2) x 100 / »/2 (Ci + C2)
Where:
RPD = relative percent difference for the sample pair
Ci and C2 = perchlorate concentrations for the two samples
8.3.4 Laboratory Duplicate Sample Acceptance Criteria and Corrective Action - Acceptance criteria
for duplicate sample analyses should support project-defined requirements. In general, the precision criterion
for the low concentration method should be set at <20 RPD. If RPDs fall outside the specified criteria, verify
that the temperatures for the duplicate analyses did not differ by more than 1-2°C and that pH was correctly
adjusted for both samples. In addition verify that loss-of-sensitivity interference due to nitrate or carry-over
due to high concentrations of perchlorate or other interferents is not the cause by reconditioning the ISE
module with an acid blank and 100-2000 (ig/L perchlorate solution (refer to Section 10.2) and reanalyzing the
duplicate samples.
If the problem is identified and corrected, it may be necessary to reanalyze some or all of the samples in the
batch. If necessary, implement ISE reconditioning between every analysis. If corrective actions do not
alleviate the problem and the performance for all other QC performance criteria is acceptable, the precision
problem is judged to be matrix related. The results for perchlorate in all samples with similar concentrations
of interfering anions must be labeled suspect due to matrix interference.
8.3.5 Field Duplicate Sample Analyses - Field duplicate samples may also be analyzed to monitor the
precision of the sampling technique. The recommended criterion for field duplicate samples is <30 RPD. If
RPDs fall outside the specified criteria, follow suggested corrective actions specified for laboratory duplicate
samples, above. If corrective actions do not alleviate the problem and the performance for laboratory
duplicate analyses are acceptable, the precision problem is judged to be field sampling technique or matrix
related.
8.3.6 Split Samples - In general, a minimum of ten percent of samples analyzed by this method should be
confirmed by definitive-level split sample analysis. Split samples should be true duplicate samples collected
from the same sampling container or device at the same location and time, with one sample analyzed for
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perchlorate by this method and the other sent to a laboratory for analysis according to EPA Method 314.0 or
other approved methodology. The recommended criterion for split samples is <30 RPD.
Whenever project objectives are potentially affected by the application of correction factors such that
perchlorate readings are adjusted to within ±20% of a project action limit (or ±40% using historical anion
data), confirmation of the analysis is recommended. If split samples were not collected in the field for the
sample in question, the aliquot used for ISE analysis may be sent for analysis.
9.0 Calibration
Perform calibrations according to the instruction manual for the ISE meter used, and according to the
requirements in this section. Calibration must be performed daily or whenever excessive drift is
demonstrated. Note that changes in temperature may affect readings; therefore, recalibration may be required
if the ambient temperature of samples being analyzed changes. If analyses are to be performed in the field,
the instrument may be calibrated in the morning before deployment into the field, or in the field before sample
analysis. The meter may require recalibration periodically, so all calibration solutions must be transported in
a cooler to the field.
9.1 Define LCR - A five-point calibration is required for the purposes of the low-concentration method
when the LCR is 10-100 (ig/L. The low calibration standard should be at or slightly below the project RL.
Do not include a blank in ISE calibrations. Prepare calibration standards at 10 (ig/L, 20 (ig/L, 40 (ig/L, 60
(ig/L, and 100 (ig/L on a daily basis. If less method sensitivity is required for project requirements, choose
higher concentrations to focus of the calibration range to the concentrations of interest. Preparation of
calibration standards is described in Section 7.2.
9.2 Initial Calibration - Prepare 200 mL of each calibration standard in an appropriate beaker or screw-cap
jar, add 1 mL of "Sentek Perchlorate ISAB" (1.0 M sodium acetate) or 1 mL of Orion 930711 ISA (2.0 M
ammonium sulfate) per 200 mL standard, as specified in Section 7.1. Add 0.2 N sulfuric acid drop-wise to
each standard until pH stabilizes at 4.0 (± 0.1). Record perchlorate ISE millivolt readings for each calibration
standard, analyzing low concentration standards first according to analytical procedures specified in Section
10.1. Millivolt readings are logged into a notebook instead of using ISE meter or computer interface
calibration features due to difficulties in determining when millivolt readings have stabilized at the low
perchlorate concentrations for this method. Also record temperature and pH for each analysis. Instrument
set-up and analysis procedures are specified in Section 10.1.
9.3 Calibration Curve - Prepare a calibration curve for perchlorate concentration versus millivolt readings
on a spreadsheet capable of producing a logarithmic calibration curve. This allows graphic representation of
the calibration curve with equation and output of the coefficient of determination (r2), and direct output of
perchlorate readings from millivolt readings by application of the calibration curve equation in a spreadsheet
formula.
Functionally equivalent curves can be prepared by plotting the perchlorate concentration versus the natural
logarithm of the millivolt reading, producing a semi-logarithmic calibration curve; or by plotting the natural
logarithm of perchlorate concentration versus the natural logarithm of the millivolt readings, producing a
linear calibration curve. Alternatively, the calibration data can be entered into a programmable calculator or
plotted on semilogarithmic or linear graph paper, and perchlorate readings manually read from the calculator
or graph paper.
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9.4 Calibration Curve Acceptability Criteria - Demonstration and documentation of acceptable initial
calibration is required prior to sample analysis. To demonstrate calibration curve acceptability for the low
concentration screening level method, the coefficient of determination (r2) must be greater than or equal to
0.990 (equivalent to r >0.995), and the concentration calculated for each calibration standard from its
millivolt response using the calibration curve must be within ± 20% of its true value, as specified in Section
8.1. If using graph paper, the acceptability of the calibration curve is verified if each calibration standards
meets the ± 20% of true value requirement.
9.5 Calibration Verification - The calibration curve must be verified by analyzing a second source check
standard (ICV/LCS) and ICB/MB prior to sample analysis, and CCVs and CCBs every 10 samples, as
specified in Section 8.2. These calibration check standards must be within 20% of true values, and blanks
should be less than one half the RL, or corrective action must be performed, as specified in Section 8.2.7.
10.0 Procedure
10.1 Instrument Set-up and Sample Analysis
Precondition the perchlorate ISE in a 500 (ig/L perchlorate solution for a minimum of 15 minutes (1 hour for
a new module) prior to use, as specified in Section 10.2. Connect the ISE and other detectors to the
appropriate meters, turn on meters, and prepare for analysis according to appropriate instruction manuals. Set
up the perchlorate ISE along with a thermometer and pH electrode, plus any additional anion ISEs desired,
such that all detectors can be placed in the sample solution without touching each other or the sides of the
container.
Prepare 200 mL of each standard or sample in an appropriate beaker or screw-cap jar by adding 1 mL of
"Sentek Perchlorate ISAB" (1.0 M sodium acetate) or 1.0 mL of Orion 930711 ISA (2.0 M ammonium
sulfate) per 200 mL of standard or sample, as specified in Section 7.1. Use equivalent additions of the same
ISA solution for all calibration standards, QC samples, and samples. If the ISA is not added to all samples
and calibration standards, the analyses will be severely affected and all results will be unusable. If the
LCRis elevated significantly above the 15-100 (ig/L range specified for this low concentration method, such
that calibration within the manufacturer specified range of 200-700 (ig/L to 99,500 (ig/L is appropriate, then
full strength ISA (four times the above referenced ISA solutions per 200 mL sample) should be used per ISE
manufacturer recommendation for all standards and samples.
Calibrate and check the system calibration as described in the appropriate instruction manuals for the ISE
meter according to the requirements in Section 9.0. If required, perform corrective action as described in
Section 8.2.7.
Place sample with magnetic stir bar on a magnetic stirrer set to slow or medium speed such that no or minimal
vortex is present. Place the perchlorate ISE along with a thermometer and pH electrode, plus any additional
anion ISEs desired, into the sample. Detectors should not touch each other or the sides of the container. Be
sure ISA has been added to every sample and standard.
Add 0.2 N sulfuric acid drop-wise to the standard until pH stabilizes at 4.0 (± 0.1). Use of 0.4 N sulfuric acid
may be appropriate for samples with high levels of carbonate/bicarbonate.
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Monitor millivolt readings until the readings stabilize such that upward or downward drift has stopped. This
may take several minutes, especially for low concentrations of perchlorate, or if temperatures are low. Note
that stabilization at an exact millivolt reading may not be possible. If stabilization takes excessive time,
reconditioning of the ISE as specified in Section 10.2 may be required.
Record millivolt readings for the perchlorate ISE, pH, and temperature for each analysis, as well as date and
other relevant information, into a bench data log book for permanent record.
If a sample concentration exceeds the calibration range, the sample must be diluted with reagent water to fall
within the working range, and reanalyzed. Be sure to add ISA proportional to dilution before proceeding
with analysis. Pre-spiking of water used for dilutions with ISA at the same concentration as samples is a
convenient way to maintain ISA proportionality.
Remove sample from magnetic stirrer, thoroughly rinse perchlorate electrode, pH electrode, and thermometer
with deionized water from a squeeze bottle, and shake off excess water (do not blot dry). Remove magnetic
stir bar using a second magnet, rinse, and place in next sample. Place next sample on magnetic stirrer and
proceed with analysis as above.
Storing the ISE briefly in a reconditioning solution followed by a thorough rinse between each sample, has
been found to help maintain sensitivity in general. If nitrate is present in samples above 0.2 mg/L N03-N, or
if loss of sensitivity is otherwise noted, reconditioning of the perchlorate ISE using acidified blanks and 100-
2000 (ig/L perchlorate solutions between every sample is required, as specified in Section 10.2.
Analyze samples according to the following analytical sequence, as specified in Section 8.2.5: ICAL,
ICV/LCS, ICB/MB, 10 samples (including matrix specific QC samples), CCV, CCB, 10 samples, CCV, CCB.
If a second batch of samples is to be analyzed, the last CCV, CCB can be omitted and the sequence continued
with: LCS, CCB/MB, 10 samples (including matrix specific QC samples), CCV, CCB, etc.
10.2 ISE Conditioning
Due to the nature of the perchlorate ISE, regenerating perchlorate sites in the perchlorate ISE membrane is a
routine requirement to maintain sensitivity. The perchlorate ISE requires special preconditioning priorto first
use, then daily before calibration. For the low concentration method, the initial preconditioning should be
performed for a minimum of one hour (overnight is acceptable), and the daily preconditioning should be
performed for 15-20 minutes, in a 500 (ig/L perchlorate solution. The ISE should then be placed in a blank
and allowed to stabilize before commencing calibration.
All perchlorate conditioning solutions and blanks must be adjusted with ISA and sulfuric acid to pH 4.0 the
same as all standards and samples.
When long periods of time become necessary for millivolt readings to stabilize, or if low recoveries for check
standard recoveries are encountered after analysis of field samples, reconditioning of the ISE is required to
maintain sensitivity. Some anions, notably nitrate, and possibly some organic chemicals, have been found to
cause loss of sensitivity between analyses. Sample matrices with nitrate concentrations greater than 0.2 mg/L
N03-N were found to require implementation of reconditioning.
When required, recondition between every analysis by placing the perchlorate ISE in an acidified blank for
one minute to clean, then in a 100-2000 (ig/L perchlorate solution acidified to pH 4 for one to six minutes to
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recondition. The concentration and length of time required should be proportional to the severity of the
problem, depending on nitrate concentration or how long is required for millivolt readings to stabilize.
Follow by immersion in an acidified blank for one to two minutes before sample analysis, again depending on
time required for millivolt readings to stabilize.
Use of 500 or 2000 (ig/L concentration solutions should be progressively implemented when the 100 |_ig/L
solution is found not to regenerate sensitivity within four to six minutes, or after analysis of any sample with
known high concentrations of nitrate. A quick check of sensitivity can be performed by immersing the ISE in
a 20 (ig/L standard to verify that millivolt readings are in the correct range. Use of stronger solutions does not
adversely affect accuracy, but requires additional time for the ISE to restabilize in a blank before sample
analysis.
Even when not required, routinely storing the ISE briefly in a 20 (ig/L perchlorate solution followed by a
thorough rinse between each sample, has been found to help maintain sensitivity in general. This can lead to
faster analysis times because millivolt readings stabilize more quickly, with fewer reanalyses required due to
declining check standard recoveries.
If sensitivity for a specific ISE module is found to decline with extended use, Sentek recommends using an
abrasive such as fine emery paper to renew the exposed PVC surface of the electrode. See manufacturer
directions for this procedure. Note that exposure to samples containing organic solvents may permanently
degrade the electrode membrane.
11.0 Calculations
11.1 Convert Millivolt Readings to Perchlorate Readings - Prepare a calibration curve, as specified in
Section 9.3. If a spreadsheet is used, enter all sample IDs (including calibration standards and QC samples
with true value concentrations, perchlorate ISE millivolt readings, pH, and temperature into adjacent columns.
Also enter date and other relevant information from the data log-book. Graph perchlorate concentration (in
(ig/L) versus millivolt readings for the calibration standards, and show the resulting equation for the
calibration curve.
Enter a formula based on the calibration curve equation into a perchlorate concentration column for each of
the analyses, including the initial calibration standards, referencing the millivolt reading cell to input the value
of the millivolt reading. The spreadsheet can then calculate and display the perchlorate concentration in the
results column. This result is a raw perchlorate result, referred to as the "perchlorate reading" throughout this
method. Refer to Attachment 2 for an example spreadsheet.
Alternatively, the calibration data can be entered into a programmable calculator or plotted on logarithmic or
semilogarithmic graph paper and perchlorate readings manually read from the graph paper, as discussed in
Section 9.3.
For the low concentration method, any perchlorate reading less than the 15 (ig/L RL should be reported as
non-detected at the RL, even when sensitivity has been demonstrated for the 10 j^ig/L low concentration
standard, due to the effects of potential matrix interference.
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The perchlorate readings can be used for reporting of all method QC results, including ICAL, ICV/LCS,
CCV, ICB/MB, and CCB check standards. The perchlorate readings for all environmental samples and
matrix-specific QC samples must be corrected for matrix interference, as specified in Section 11.2, below.
11.2 Apply Correction Factors for Anion Interferent for Final Perchlorate Results - For samples with
concentrations of specific anions known to cause positive interference greater than 20% (or 3 (ig/L for non-
detects) correction factors must be subtracted from positive perchlorate readings to calculate final perchlorate
results (refer to Tables 1, 2, and 3). When perchlorate readings with acceptable associated QC indicate that
perchlorate is not present above project action limits, perchlorate can confidently be considered not to be
present at that level, and correction factors need not be addressed, since all of the interferences are for positive
bias.
Subtract applicable correction factors from the initial perchlorate reading for concentrations in excess of 0.12
mg/L N03-N, 50 mg/L chloride, or 1.2 mg/L bromide. Matrices with lower concentrations of these anions
will not be significantly affected by known interferences. Anion concentrations from historical or
contemporary data may be applied. If such data does not exist, ISEs for these anions may be used with the
same ISE meter or computer interface used for the perchlorate determinations. Alternatively, analysis by
MSA may be used to compensate for unknown anion interference, as specified in Section 11.3, especially for
perchlorate readings less than 30 (ig/L. However, further studies of the effectiveness of MSA to compensate
for anion interferences are required.
If chloride exceeds 50 mg/L (parts per million - mg/L), apply correction factors from Table 1.
If nitrate exceeds 0.12 mg/L N03-N, apply correction factors from Table 2, and reconditioning of the ISE
module between every sample is required.
If bromide exceeds 1.2 mg/L, which is higher than is typically found in environmental samples, apply
correction factors from Table 3.
Note that for many matrices, the only anion likely to require application of correction factors is chloride, for
which correction factors are relatively small (12 (ig/L perchlorate for 500 mg/L chloride), and historic levels
may not significantly change.
11.3 Method of Standard Additions
When a perchlorate reading greater than the RL or PQL is suspected of being due in part or entirely due to
matrix interference, but anion correction factors cannot be applied due to lack of anion data, the use of MSA
may be used to compensate for unknown anion interference, especially for perchlorate readings less than 30
(ig/L. Further studies of the effectiveness of MSA to compensate for anion interferences are required.
MSA incorporates the sequential addition of three increments of a standard solution (spikes) to a sample.
Measurements are made on the original sample and after each addition. The slope, x-intercept and y-intercept
are determined by least-squares analysis. The analyte concentration is determined by the absolute value of the
x-intercept. Regression may be performed mathematically on a programmable calculator or on a computer; or
the results for the three spiked additions of perchlorate may be graphed and the resulting line or curve
extended through the y-axis until it intersects the x-axis. Ideally, the spike volume is low relative to the
sample volume
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(should not exceed 10% of the volume). MSA may counteract matrix effects, especially if such effects are
constant or linear.
To perform MSA on a sample, analyze the sample and three spikes consecutively. After analysis of the parent
sample, spike the sample with 10 (ig/L perchlorate, reanalyze, and record the perchlorate reading. Repeat
with an additional 10 (ig/L spike two more times such that perchlorate readings are recorded for 10 (ig/L, 20
(ig/L, and 30 (ig/L perchlorate spikes.
MSA additions are generally performed with volumes of 10% or less of the original sample volume. If
additions total more than 5%, the proportional addition of ISA to the spiking solution may be appropriate.
Further study of MSA for this method is recommended.
All MSA perchlorate readings must be within the linear calibration range. Due to complex interference
curves for high levels of interference, dilution of the sample prior to MSA is recommended for samples with
initial perchlorate readings greater than 30 (ig/L. Be sure to add ISA proportional to dilution before
proceeding with analysis.
MSA is generally performed with spikes of 50%, 100%, and 150% of initial analyte reading. For the low
concentration method, the use of 10 (ig/L perchlorate spikes is recommended to avoid complex curves and to
meet linearity requirements.
The data for each MSA analysis shall be recorded and clearly identified in the raw data documentation. Plot
or input added perchlorate concentration as the x-variable and perchlorate reading as the y-variable. Do not
enter the values for the initial (unspiked) perchlorate reading. The slope, x-intercept, y-intercept and
correlation coefficient (r) for the least squares fit of the data should be reported from the spreadsheet,
calculator, or computer program.
The perchlorate result for the sample by MSA is the absolute value of the x-intercept as calculated by linear
regression. Non-linear regression techniques may be appropriate due to the complex interference curves for
the low concentration method. Further study is recommended
If the coefficient of determination (r2) is less than 0.990 or the correlation coefficient (r) less than 0.995 for
the regression, the result should be considered quantitatively uncertain. Due to the complex interference
curves involved, linearity for MSA regression may be significantly affected. If the coefficient of
determination (r2) is less than 0.980 or the correlation coefficient (r) less than 0.99 for the regression, the
result should be considered significantly impacted and may not be usable.
Each full MSA counts as two analytical samples towards determining 10% QC frequency (i.e., five full MSAs
can be performed between calibration verifications). For ISE meters capable of operation in MSA mode,
MSA can be used to determine QC samples during that run.
12.0 Record Keeping
Maintain a standards preparation log, sample extraction log, and a sample analysis log. Include record of ISA
addition to each sample and standard. The analysis run log should include time of initial calibration (ICV,
CCV, or LCS). All logs should include the date and initials of the analyst.
Maintain a sample results log or worksheet, which may be integrated with the extraction/analysis logs.
Include calibration standard IDs, QC sample IDs (including true values), field sample IDs, pH, temperature,
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millivolt reading, and initial (uncorrected) perchlorate readings for each analysis. The results log or
worksheet, or a sample results reporting worksheet or form should also include all anion concentrations and
correction factors, and final corrected perchlorate results reported. The source of anion concentrations used
for correction factors should be included in the data.
13.0 Method Performance
Method performance studies for this method have not been completed. For a complete discussion of method
development to date, refer to the Letters of Findings for Tasks 1 and 4, Sections 1.0 and 4.0 ofthe report for
which this SOP is Attachment 1.
14.0 Clean-Up Protocols
Perchlorate salts and perchlorate solutions are considered hazardous materials. Care must be exercised not to
allow perchlorate or perchlorate-containing rinsates to escape to the environment. In addition, acidified
solutions and field samples containing regulated contaminants should be treated as hazardous materials.
All solutions or solids containing perchlorate, including analytical standards, field and QC samples, or
perchlorate salts, must be properly discarded (see Section 15.0, Waste Management, below). Triple rinse
glassware, plasticware, sample sleeves, or other equipment with water, catching all rinsate into an appropriate
polypropylene beaker, and transfer rinsate to 1-4 Liter polypropylene wide mouth screw top container (or
other appropriate polypropylene waste collection container) labeled LOW CONC PERCHLORATE WASTE.
Wash triple rinsed plastic or glassware with soap and water in sink, triple rinse with distilled water, drip dry.
Keep work area clean and free of obstructions to prevent spillage of hazardous solutions. In case of spills,
soak up perchlorate solutions with paper towels or other absorbent material, squeeze out excess into rinsate
collecting container, and dispose of paper towel or absorbent as solid waste. Protective gloves or other
personal protective equipment contaminated with perchlorate should be triple rinsed into a rinsate collecting
container, then disposed of as non-hazardous trash (perchlorate is very soluble, triple rinsing is expected to
remove all traces of perchlorate).
15.0 Waste Management
Perchlorate wastes must be stored in satellite waste storage areas, in appropriate containers (polypropylene)
labeled with perchlorate identification and right-to-know OXIDIZER 5.1 labels, and disposed of as hazardous
waste according to state and federal guidelines.
All perchlorate solutions included in this SOP are strong oxidizers, are considered hazardous materials, and
must be properly labeled with concentration identification and OXIDIZER 5.1 labels. Store expended
standards and samples with high concentration detected results in polypropylene wide mouth screw top
containers container (or other appropriate polypropylene waste collection container) labeled HIGH CONC
PERCHLORATE WASTE with OXIDIZER 5.1 labels. Collect and store rinsates from the washing of
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perchlorate contaminated surfaces and samples with low concentration detected results in polypropylene wide
mouth screw top containers container (or other appropriate polypropylene waste collection container) labeled
LOW CONC PERCHLORATE WASTE with OXIDIZER 5.1 labels.
All discarded solutions and rinsates are considered hazardous waste and must also be properly labeled and
maintained according to state and federal storage and disposal regulations.
The Environmental Protection Agency requires that waste management practices be conducted consistent with
all applicable rules and regulations. Excess reagents, samples and method process wastes should be stored,
characterized and disposed of in an acceptable manner. The Agency urges laboratories to protect the air,
water, and land by minimizing and controlling all releases from hoods and bench operations, by complying
with the letter and spirit of any waste discharge permit and regulations, and by complying with all solid and
hazardous waste regulations, particularly the hazardous waste identification rules and land disposal
restrictions. For further information on waste management consult the "Waste Management Manual for
Laboratory Personnel," available from the American Chemical Society, 1155 16th Street NW, Washington,
DC 20036, (202) 872-4477.
16.0 References
1. Inter-Agency Perchlorate Steering Committee, Analytical Subcommittee Report (1998).
Report on the interlaboratory validation of IC methods for perchlorate.
2. Methods for Chemical Analysis of Water and Wastes, U.S. EPA Manual 600/4-79-020 (U.S. EPA,
1983 with additions)
3. Physical/Chemical Methods, SW-846 3rd edition (U.S. EPA, 1986a), and Updates I, II, IIA, and III
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ATTACHMENT 2:
EXAMPLE SPREADSHEET
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Attachment 2 Spreadsheet
Analytical Method: Low Concentration Method for the Determination of Perchlorate by Ion Selective Electrode
Matrix: Water Units: ug/L (ppb) Extraction/Digestion: Acidification to pH 4 with Sulfuric Acid
Instrument: [NAME] Solid State Perchlorate Combination ISE
Analyst:
Meter: Date:
IMAM EI Probe with 1mL of Senteh ISAB in 20DmL
Using [NAME] Meter at pH 4
315
3C5 -
2fl5 -
Jl
fl
285
275 -
s
26S
255 -
245 \
*309 1
A
^,£712
yr .24.31Ln(y) + 3M.33
R2 - 0.9$78
W*~' ~ 253 e
20 40 W 30
Perchlorate Concentration in ppb
100
120
Sample/Calibration ID
PH
Sample Volume
Millivolts Reading
Concentration in ppb
10
200 mL
309.1
=(EXP(-((D27-364.3)/24.31)))
20
200 mL
291.4
=(EXP(-((D28-364.3)/24.31)))
40
200 mL
273.2
=(EXP(-((D29-364.3)/24.31)))
60
200 mL
264.4
=(EXP(-((D30-364.3)/24.31)))
100
200 mL
253.6
=(EXP(-((D31 -364.3)/24.31)))
Calibration Date
mimm
Time
12:45 pm
Temperature
##.#" c
Slope
24.31
Intercept
364.3
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