EPA-600/4-77-034A
July 1977
Environmental Monitoring Series
DETERMINATION OF TRACE METALS
IN EFFLUENTS BY DIFFERENTIAL PULSE
ANODIC STRIPPING VOLTAMETRY
Environmental Monitoring and Support Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology, Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3, Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved methods
and instrumentation for the identification and quantification of environmental
pollutants at the lowest conceivably significant concentrations. It also includes
studies to determine the ambient concentrations of pollutants in the environment
and/or the variance of pollutants as a function of time or meteorological factors.
This document is available to the public through the National Technical Informa-
tion Service. Springfield, Virginia 22161,
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EPA-600/4-77-034
July 1977
DETERMINATION OF TRACE METALS IN EFFLUENTS
BY DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMETRY
by
James T. Kinard
Benedict College
Columbia, South Carolina 29204
Grant No. R803490-01-0
Project Officer
Morris E. Gales, Jr.
Environmental Monitoring and Support Laboratory
Cincinnati, Ohio 45268
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and
Support Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents neces-
sarily reflect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of trade names or commercial pro-
ducts constitute endorsement or recommendation for use.
ii
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FOREWORD
Environmental measurements are required to determine the quality of
ambient waters and the character of waste effluents. The Environmental
Monitoring and Support Laboratory-Cincinnati conducts research to:
o Develop and evaluate techniques to measure the presence
and concentration of physical, chemical, and radiological
pollutants in water, wastewater, bottom sediments, and
solid waste,
o Investigate methods for the concentration, recovery, and
identification of viruses, bacteria, and other microbiological
organisms in water; conduct studies to determine the response
of aquatic organisms to water quality.
o Conduct an Agency-wide quality assurance program to assure
standardization and quality control of systems for monitoring
water and wastewater.
There is an ever-increasing interest in the use of instrumental
methods to analyze water and waste samples, whether the resulting data
are to be used for research, surveillance, compliance monitoring, or
enforcement purposes. Accordingly, the Environmental Monitoring and
Support Laboratory has an on-going methods research effort in the
development, evaluation, and modification of instrumental methods.
This particular report pertains to the evaluation of differential pulse
anodic stripping voltametry. The method has potential routine appli-
cation for the analysis of trace metals in surface waters and domestic
and industrial wastes.
Dwight G. Ballinger, Director
Environmental Monitoring & Support Laboratory
Cincinnati
iii
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ABSTRACT
This investigation was designed to appraise the applicability of
differential pulse anodic stripping voltametry to the determination of
trace metals in a wide variety of industrial and domestic effluents.
Fifteen (15) types of effluents of different industrial processings
were employed, providing a rather comprehensive matrix base for asses-
sing the potential for practical utilization of the technique.
The results revealed that the technique is highly sensitive and
that practical application to total metal determination requires care-
ful analytical work and a quality of sample digestion with which present
state-of-the-art digestion procedures cannot comply. However, when the
technique is coupled with a closed-system acid digestion process, zinc,
cadmium, lead, nickel, antimony, bismuth, copper, thallium, tin and in-
dium can be determined individually and simultaneously in groups at
concentrations ranging from the sub-parts-per-billion to the parts-per-
million levels. A procedure for providing low blank buffer and electro-
lyte systems was tested, and the efficiency for the entire process,
including digestion, sample transfer and analysis, was found to range
from 93 to 100%.
Quantitative data for samples of complex matrices were in good
agreement with flame atomic absorption spectrophotometric results for
each element investigated.
From 40 to 50 previously digested samples with 4 to 5 elements per
sample can be analyzed each 8 hour working day (corresponding to 160 to
250 individual determinations) at about one-third the costs for flame
atomic absorption spectrophotometry.
This report was submitted in fulfillment of Grant Number R803490-
01-0 by Benedict College, Columbia, South Carolina, under the sponsor-
ship of the U. S Environmental Protection Agency. Work was completed
as of February 1, 1977.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vii
Acknowledgment viii
I. Introduction 1
II. Conclusions 3
III. Recomnendations 4
IV. Development of Digestion Procedures 5
V. Evaluation of Reagent Purification Procedures 7
VI. Development of Qualitative and Quantitative Methods - 10
VII. Evaluation and Application of Analytical Methods 21
VIII. Comparison of Differential Pulse Anodic Stripping 25
Voltametry and Flame Atomic Absorption Spectro-
photometry for Effluent Analysis
IX. Discussion 31
References
v
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FIGURES
Number
1 Current-potential curves for DPASV in purified
and unpurified sodium acetate . 9
2 Reproducibility of DPASV for simultaneous
stripping of zinc, cadmium, lead and copper
in 0.5 F sodium fluoride 19
3 Peak current versus concentration for the simul-
taneous stripping of Zn, Cd, Pb, Bi and Cu 20
4 Atomic absorption calibration curves for tin, zinc,
and bismuth 26
5. Atomic absorption calibration curves for cadmium and
lead 27
6 Dependency of reduction potential on atomic radius. ... 33
7. Separation of copper and bismuth signals for DPASV
using acetate ion 35
8 Current-potential curves for the simultaneous stripping
of Cd, Pb, Cu and Bi in the presence of ammonia and
carbonate 36
VI
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TABLES
Number Page
1 Trace Metal Contamination in Different Batches
or Recrystallized Sodium Acetate 8
2 Types of Effluents and the Number of Samples
Analyzed Through this Study 22
3 Trace Metals in a Mixture of Industrial Effluents
and Precision Data 23
4 Recovery Data for the Simultaneous Determination
of Zinc, Cadmium and Lead in Industrial Mixture II. . 23
5 Results from Application of DPASV to a Variety of
Effluents 24
6 Comparison of DPASV and Flame AAS Data for Metals
in Effluents 28
7 Comparison of Sensitivities, Detection Limits and
Linearity Range of Trace Metal Determination for
DPASV and Flame AAS 28
8 Comparison of Start-up Costs for DPASV and Flame AAS. . 29
9 Advantages and Disadvantages of DPASV and Flame AAS . . 30
10 Correlation Between Reduction Potentials and Electronic
Configurations of Metal Ions 32
VI1
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The author would like to express his thanks to the personnel of
the Environmental Monitoring and Support Laboratory for their support
of this effort and to Mr. Clyde Bishop and Dr. Willie Ashley for
administrative guidance. He is especially grateful to Mr. Morris Gales,
Jr. for his technical assistance and his engagement in useful scientific
discussions. Thanks also to Nathaniel Harry and Kenneth James for their
research assistance.
viii
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SECTION I
INTRODUCTION
This investigation comprised an appraisal of the applicability of
differential pulse anodic stripping voltametry (DPASV), using the hang-
ing mercury drop electrode, to the identification and determination of
trace metals in a wide variety of industrial and domestic effluents.
Its scope also encompassed the development and evaluation of sample pre-
treatment and reagent purification procedures to be used in conjunction
with a highly sensitive technique. Problems associated with day-to-day
individual determination of zinc, cadmium, lead, copper, bismuth,
thallium, tin, indium, nickel and antimony were developed.
Since flame atomic absorption spectrophotometry (AAS) is the most
widely used technique for routine determination of metals in water and
wastewaters, a phase of this research constituted a comparative study of
AAS and DPASV for analysis of effluents. Advantages and disadvantages
of both techniques were explored, and cost data based on present-day
economics were generated.
This report then, is not just a compilation of data to demonstrate
the technical elegence of DPASV, but is a prescription for its appli-
cation to routine analysis of effluents with complex matrices and ranging
from domestic to that of the metals plating industry.
Experimentation proceeded in several phases. The first phase
involved (a) development of sample digestion procedures; (b) evaluation
of reagent purification procedures; and (c) development of methods for
identification of metals. Phase two constituted: (a) development of
methods for the quantitative determination of metals and (b) application
of these methods to the analysis of effluents. In phase three, a com-
parative study of flame AAS and DPASV was conducted for determining
metals in the same set of effluent samples. Advantages and disadvantages
of both techniques were assessed.
Several questions surfaced prior to the commencement of this study
and, perhaps, are expressive of the scientific curiosity that gave birth
to it. These are: What metals can be identified and determined by DPASV
and at what levels of detection; can a generalized procedure be given for
all possible metals or groups of these metals in all types of effluent
samples; and, what advantages and disadvantages exist for total metal
determination? Each phase of this investigation was designed to, in some
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way, provide an answer to each of the above questions.
The basic principle of anodic stripping voltametry has been well
presented by Barendrecht (1). It is basically a two-step process that
involves a preconcentration phase and a stripping phase. Preconcentra-
tion is achieved by cathodically reducing the metal ion(s) of interest
at a constant potential that is 300 or 400 millivolts more negative than
the polarographic half-wave potential, Ei, of the ion of interest or of
the ion with the most negative Ei value. The solution is usually agitat-
ed or the electrode is rotated during this first phase. Following pre-
concentration a rest period of about 20 to 30 seconds is allowed for
quiescent conditions to develop. Anodic stripping is then initiated by
applying a potential that is a linear function of time. In DPASV, this
excitation function consists of a fixed-height potential pulse occurring
at regular intervals and superimposed on a slowly varying linear potential
ramp.
Characteristics of the current-potential signal such as the peak
current ( ip ) and the half-peak potential ( Ep/2 ) were tested for their
analytical utility in effluents. Theoretically, *p is a linear function
of the cell concentration and Ep/2 i-s characteristic of the metal being
oxidized. Values for these parameters for a metal depend upon the proper-
ties of a particular electrolyte system —such as its pH, ionic strength
and complexing capability —and on the electrode system. The indicator
electrode used throughout this study was a hanging mercury drop electrode
(HMDE).
The experimentally controllable parameters are rate of stirring,
mercury drop size, preconcentration time ( ^d ), preconcentration
potential ( ^ d ), scan rate (V ), the solution volume and the temper-
ature.
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SECTION II
CONCLUSIONS
It is concluded from this study that trace amounts of zinc, cadmium,
lead,bismuth, copper, thallium, tin, indium, antimony and nickel can be
identified and determined in industrial and domestic effluents by DPASV
following digestion in a closed system. This system and technique, with
regard to total metal determination, is highly competitive with AAS in
terms of precision and accuracy, and is superior to AAS in terms of sensi-
tivity, detection limits and costs. Although the process requires sample
pretreatment, it is a non-destructive technique, and qualitative and
quantitative analyses can be carried out on a sample simultaneously for
as many as five elements.
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SECTION III
REOCMffiNDATIQNS
The Investigator recomnends that:
1. DPASV with the closed acid digestion system be employed as an
alternative method to AAS for routine quantitative determination
of total trace metals such as zinc, cadmium, lead, bismuth, copper,
thallium, tin and indium in industrial and domestic effluents;
2. This technique and system be employed as the most feasible method
for the simultaneous identification of these metals at trace and
ultratrace levels in effluents; and
4. The Chelex-100 ion exchange technique be employed as the most
feasible procedure for rapid removal of trace metals from electro-
lyte systems.
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SECTION IV
DEVELOPMENT OF DIGESTION PROCEDURES
A number of digestion procedures involving wet and dry ashing were
explored and found to be inadequate for the sensitive technique of DPASV.
Trace amounts of organic material and potential complexing species were
found to have a pronounced effect on the position ( EL^ ) an^ size ( xp
or q, the number of coulombs) of the current potential'signal for a particu-
lar metal. Continuous boiling of samples in an oxidizing acid system may
have been adequate for destroying the organic material, but led to
considerable metal contamination and loss of volatile metal constituents.
This evidence dictated the need for a non-contaminating, closed
digestion system that could be subjected to high temperatures when charged
with a concentrated oxidizing acid solution.
The Parr Acid Digestion Bomb, Model No. 4745 (Parr Instrument Co.,
Moline, Illinois) appeared to be a prime candidate. It consisted of a
Teflon (Trademark of E. I. Dupont Co., Delaware) cup and cover and a stain-
less steel encasement with a spring-loaded closure and screw cap. This
general purpose bomb withstood temperatures up to 15CPC and pressures up
to 1200 psig. The furnace used to perform digestions was a Lab Heat
Muffle Furnace (Blue M Electric Co., Blue Island, Illinois).
Procedures that were developed for the digestion of industrial and
domestic effluents using the Parr Acid Digestion Bomb are given below.
(1) Weigh to the nearest 0.1 mg a previously leached and rinsed
Teflon cup. (This step may be omitted if the sample does not
contain a high percentage of particulates and the concentra-
tion can be more appropriately expressed as weight of analyte/
volume of effluent);
(2) Pipet from 0.020 to 10.0 ml of the thoroughly mixed sample into
the Teflon cup (The sample size will depend upon the expected
level of analyte in the sample);
(3) Weigh Teflon cup with sample to the nearest 0.1 mg (This step
may be omitted if step #1 is omitted);
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4. Add 0.5 to 3 ml of high purity nitric acid to the Teflon cup
(if the total volume of liquid in the Teflon cup is less than
3 ml add enough distilled-demineralized water to bring the final
volume to approximately 3 ml);
5. Place Teflon cup in the encasement and tighten screw cap by hand;
6. Place bomb in a furnace that has been preheated to 160OC;
7. Allow time for thermal equilibrium to be attained and adjust the
temperature to 160°C;
8. Heat from 1 to 8 hours or more (depending upon the complexity
of the sample matrix) at 160+5°C;
9. Allow bomb to cool and transfer sample to a volumetric flask
(10, 25, or 50 ml capacity). Dilute to the mark with the ap-
propriate buffer system for determining the analyte of interest
(see SECTION VI - DEVELOPMENT OF QUALITATIVE AND QUANTITATIVE
METHODS).
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SECTION V
EVALUATION OF REAGENT PURIFICATION PROCEDURES
The technique of DPASV has the capability of detecting a number of
metals at the nanogram/ml and sub-nanogram/ml levels. To exploit this
capability required the use of electrolytes and buffer systans of high
purity and quality. Reagent grade chemicals contained high levels of
impurities (see curve B of figure 1) and were not suitable for methods
using DPASV for analytical measurements. High purity versions of most
of these reagents were not available through the market and/or were
highly expensive. For salts, repeated reerystallization was attempted
but was found to be laborious and, in most cases, inadequate (see Table
1).
Electrolytic purification was found to be adequate but required the
use of a potentiostat and a purification period of 24 hours per liter of
electrolyte.
A procedure employing the sodium form of Chelex 100 (BIO • RAD
Laboratories, Richmond, California) was evaluated and found to be suita-
ble. The material is an ion exchange resin that has the capability of
removing copper, lead, zinc and other heavy metals from aqueous solutions.
Curve A in Figure 1 reveals its effectiveness in removing contaminants
from a 1M sodium acetate solution after just one pass through a column.
Two passes gave a blank solution with virtually no detectable amounts of
metal contaminants.
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TABLE 1. TRACE METAL CONTAMINATION IN DIFFERENT
BATCHES OF RECRYSTALLIZED SODIUM ACETATE
Metal concentration (ng/ml)*
Batch no.
1
2
3
4
Zinc
148
166
76.0
17.9
Cadmium
5.69
3.12
2.39
2.30
Lead
96.5
43.2
46.8
49.6
Copper
36.4
37.8
61.3
66.8
* Concentration values are for 2 F sodium acetate solutions prepared
from different batches of recrystallized sodium acetate.
The following procedures for preparing, using and regenerating the
column gave good results in our laboratory.
1. Prepare approximately 20 ml of a saturated solution of disodium
or tetrasodium ethylenediaminetetraacetate.
2. Warm on a hot plate and added enough Chelex 100 (Na - form, 100
to 200 mesh).
3. Develop column (A 50 ml buret with a plug of glass wool near the
outlet will be adequate).
4. Wash extensively with distilled - deminerialized water (about 10
bed volumes).
5. Adjust the pH of the solution of interest to a value above 7.
6. Pass solution through column twice. A flow rate of about 4 ml
Imin/cm2 is adequate. To regenerate the column pass through 2
bed volumns of high purity IF HNCg, 6 bed volumes of distilled-
demineralized water, 2 bed volumes of IF NaOH, and 6 bed volumes
of water.
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ae.
oc,
D
U
IF solution after 1 pass
through Chlex—100
IF untreated solution
Bi
Zn Curve B
I
-i.i
-0.1
-0.9 -0.7 -0.5 -0.3
POTENTIAL VERSUS SCE, volts
Figure 1. Current potential curves for DPASV in purified and unpurified
sodium acetate.
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SECTION VI
DEVELOPMENT OF QUALITATIVE AND QUANTITATIVE METHODS
The anodic stripping data were generated by use of a Model 174
Polarographic Analyzer (Princeton Applied Research Corporation, Princeton,
New Jersey) that was connected to a Model 2000 Omnigraphic X - Y Recorder
(Houston Instruments, Houston, Texas). This instrument was operated in
the differential pulse mode and the current output was always in the
microampere range.
The electrochemical cell consisted of a glass bottom and a self-
mounting plastic top that was purchased from Princeton Applied Research
Corporation. The reference electrode was a saturated calomel electrode
(SCE) with a salt bridge attached. A disc of porous Vycor (Corning Glass)
silicated glass, attached at the end of the isolated electrode tube and
held in place by a Teflon (Dupont) sheath, served as the salt bridge tube
between the isolated electrode and the solution in the electrolysis cell.
This cavity was filled with the same electrolyte system that was used for
the test solution. A spiral of platinum wire served as the isolated
electrode. The sparge tube consisted of a two-way Teflon stopcock, a
glass tube and a tapered Teflon tip (Princeton Applied Research Corpo-
ration) .
The sparge tube was connected to a train assembly that consisted of
a wash bottle containing a concentrated disodium ethylenediaminetetra-
acetate solution, a wash bottle containing a vanadous chloride solution
and a tank of high purity nitrogen gas. Vanadous chloride solution served
as an oxygen scrubber while the disodium EDTA served to remove trace metals
from the gas stream.
Ultrex grade nitric acid (J. T. Baker Company, Phillipsburg, New
Jersey), high purity metals and demineralized - distilled water were used
to prepare the standard solutions. All solutions were stored in poly-
ethylene containers. The containers were leached with 6 M nitric acid
and rinsed thoroughly with demineralized-distilled water before using.
Each blank was prepared by adding to a volumetric flask (10, 25 or
50 ml) the same amount of HNO3 as used for digestion, a volume of de-
mineralized-distilled water equal to that of the digested sample and
diluting to the mark with the appropriate electrolyte system.
10
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QUALITATIVE APPROACH
The blank was transferred to the electrolysis cell and was purged
for 5 minutes with nitrogen. The nitrogen stream was then diverted over
the solution by turning the stopcock to the appropriate position on the
sparge tube. A deposition potential was selected and the mercury drop
was adjusted to give a size that corresponded to 2 divisions/drop on the
micrometer head of the HMDE. Stirring was initiated. The instrument was
switched to "Cell" concurrently to activating a timing device. Thirty
(30) seconds were allowed to pass after stirring was terminated, and strip-
ping was initiated at 10 mv/s. Preconcentration and stripping were re-
peated to check for reproducibility. An aliquot of a standard solution
of a metal ion (if *-d of 30 seconds to 3 minutes were used and a blank
volume of 25 ml was in the cell, 20 - 50 of 10 - 20 ppb of standard) was
added to the cell and the solution was purged again. Stirring precon-
centration, and stripping were conducted under the same conditions, and
the spiked curve was obtained. Other metals were added sequentially and
DPASV was conducted to assess their ddetectability in the blank and in the
presence of potentially interfering analytes.
QUANTITATIVE APPROACH
Once an assessment was made to identify the metals that were detect-
able in a particular electrolyte system, the pH and ionic strength of that
system were varied separately to ascertain conditions for optimizing the
current-potential signal. A modified blank was prepared and the linearity
between ip and C, was investigated for each metal. Considerable time was
saved by preparing a combined standard (composed of all of the detectable
metals). Preconcentration and stripping were performed following each
addition of standard.
The following are methods that were developed through this study.
11
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ANALYTICAL METHOD NO. 1
SIMULTANEOUS IDENTIFICATION AND DETERMINATION
OF ZINC, CADMIUM, LEAD, BISMUTH, AND COPPER IN EFFLUENTS
Analytes: Zn, Cd, Pb, Bi, and Cu
Matrix: Industrial
or Domestic Effluent
Electrolyte System:
Ed= -1.4 V
Range:
Zn
Cd
Pb
Bi
Cu
Precision:
(% rela-
tive stan-
dard devi-
ation)
Accuracy:
0.5
0.08
0.10
0.32
0.50
Zn
Cd
Pb
Acetate buffer, PH=5.5-5.8
115 ng/ml
120 ng/ml
200 ng/ml
210 ng/ml
118 ng/ml
+ 2.7
+ 2.2
+ 2.4
Zn and Cd
Pb
Bi and Cu
Cu
Bi
2.6
2.3
100 +_ 6%
100 + 4%
100 + 8%
1. Procedure
1.1 Leach all glassware in 6M HNO3 for 5 hours and rinse thoroughly
with demineralized - distilled water.
1.2 Transfer digested sample from Teflon cup to a 25 ml volumetric
flask. Add the appropriate amount of sodium acetate to acid
solution to form a buffer of pH = 5.5 to 5.8. If the acid
concentration is high in the digested sample, increase the con-
centration of sodium acetate or evaporate the solution slowly to
drive off most of the acid and take up digestate in sodium
acetate. Adjust pH to 5.5 - 5.8.
1.3 Transfer the solution to the cell and purge for 5 minutes.
1.4 Set the Ed to ~
solution.
V. Divert the stream of nitrogen over the
12
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2.
1.5 Stir solution and preconcentrate for 30 seconds to 5 minutes.
1.6 Turn off stirrer and allow 30 seconds for quiescent conditions
to develop.
1.7 Initiate scan at 10 mv/s and scan to the desired potential of
termination.
1.8 Repeat steps 1.4 - 1.7.
1.9 Spike with from 10 - 100 of combined standard. Try to use a
spike size that will give signals that are about twice the size
of the original signals. (Step 1.9 is not necessary if a cali-
bration curve is used) .
1.10 Purge and repeat steps 1.4 - 1.7.
Calculation
C = ii v Cs/ (i2 v + (i2 - %) V)
Where
Cc = original cell concentration
Cs = concentration of standard solution
used for spiking
il = peak height in original cell solution
±2 = spiked peak height
v = volume of standard solution added as spike
V = original sample volume
3 . Interferences
In interferes with Cd and Tl interferes with Pb. Long preconcentration
times and high concentration of analytes may cause a Cu - Zn intermetallic
to form. This intermetallic strips at the same potential as that of Cu and
enhances the Cu signal while lowering the Zn signal. It may be eliminated
by using a shorter preconcentration time or diluting the sample solution.
13
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ANALYTICAL MEfflCD NO. 2
SIMULTANEOUS IDENTIFICATION AND DETERMINATION
OF ZINC, INDIUM, THALLIUM, BISMUTH AND COPPER IN EFFLUENTS
Analytes: Zn, In, Tl, Bi, and Cu Matrix: Industrial
or Domestic Effluent
Electrolyte System: Acetate buffer, pH=5.5-5.8
Ed=-1.4V
Range: Zn, Bi and Cu (same as Method 1)
In 0.3 ng/ml 150 ng/ml
Tl 0.10 ng/ml — 200 ng/ml
Precision: Zn, Bi and Cu (same as Method 1)
(% Relative
Standard Deviation) In + 3.0 Tl + 2.6
Accuracy: 96 +_ 6%
1. Procedure
(Same as Method 1)
2. Calculations
(Same as Method 1)
3. Interferences
Cd interferes with In and Pb interferes with Tl.
(See Method 1)
ANALYTICAL METHOD NO. 3
DETERMINATION OF LEAD AND THALLIUM IN EFFLUENTS
Analytes: Pb and Tl Matrix: Industrial
or Domestic Effluent
Electrolyte System: Acetate buffer, pH 5.5 - 5.8.
for total Pb plus Tl.
Add 0.33 g of EDTA salt
for Tl determination in the presence of Pb.
14
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Ed = -0.8 V
Range: Pb 0.10 200 ng/ml
PI 0.10 200 ng/ml
Precision: Pb +_ 2.4
(% Relative
Standard Deviation) Tl + 2.6
Accuracy: 95+6%
1. Procedure
Follow procedure in Method 1 to determine the sum of Pb and Tl
in acetate buffer. Add EDTA salt and repeat the procedure to
determine the amount of Tl present.
2. Calculations
Subtract the concentration of Tl from the sum of the concen-
tration of Tl and Pb.
3. Interferences
There are no known interferences.
ANALYTICAL METHOD NO., 4
IDENTIFICATION AND DETERMINATION OF INDIUM IN EFFLUENTS
Analyte: In Matrix: Industrial
or Domestic Effluent
Electrolyte System: 0.1 MNI^CNS - 0.015 M C6 H3 (OH)3 (pyrogallic acid)
Ed = -0.8
Range: 0.05 ng/ml 170 ng/ml
Precision: +2.7
(% Relative
Standard Deviation)
15
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1. Procedure
(Same general procedure for DPASV)
2. Interferences
(There are no known interferences.
ANALYTICAL METHCD NO. 5
DETERMINATION OF TIN IN EFFLUENTS
Analyte: Sn Matrix: Industrial
or Domestic Effluent
Electrolyte System: 5N HC1
% =-0.8 V
Range: 0.5 160 ng/ml
Precision: +_ 3.8
(% Relative
Standard Deviation)
Accuracy: Undetermined (Low level blank was difficult to obtain)
1. Procedure
Digest sample according to the Parr bomb digestion procedure.
Carefully evaporate sample to near dryness, without heating
too rapidly. Take up the digestate in 5N HC1.
2. Calculations
(Same as Method No. 1)
3. Interferences
Pb interferes with the determination of Sn.
ANALYTICAL METHCD NO. 6
DETERMINATION OF ANTIMONY IN EFFLUENTS
Analyte: Sb Matrix: Industrial
or Domestic Effluent
Electrolyte System: 1M H Cl
16
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Ed =-0.8 V
Range: 1 200/ug/ml
Precision: +_ 4.2
(% Relative
Standard Deviation)
Accuracy: Undetermined (Low level blank was difficult to obtain)
1. Procedure
Same as Method No. 5 except the digestion is to be taken up in
INHC1
2. Calculations
(Same as Method 1)
3. Interferences
No apparent interferences
ANALYTICAL METHOD NO. 7
DETERMINATION OF NICKEL IN EFFLUENTS
Analyte: Ni Matrix: Industrial
or Domestic Effluent
Electrolyte System: airmonia-tartrate
Ed =-1.0 V
Range: 0.8 150ng/ml
Precision: +_ 4.0
(% Relative
Standard Deviation)
Accuracy: 91 +_ 6%
1. Procedure
Same as Method No. 5 except the digestate is taken up in -^,
arrmonia - .5M tartrate.
2. Calculations
Same as Method No. 1
17
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DETECTION LIMITS AND PRECISION
The operational definition of detection limit used by the investi-
gator was the minimum detectable amount of analyte that produces a
signal significantly different from zero.
A large number (n>10) of blanks were analyzed and the standard
deviation for each element present was calculated. The detection limit
in each case was calculated as
D.L. >
ns
Where ns and n^ were the number of determinations performed on the sample
and blank, respectively. The parameter t was taken from the t - Distri-
bution table (2), its value depended upon the degrees of freedom
ng + n^ - 2 at the 95$> probability level.
Precision data were acquired by analyzing a large number (n 10) of
samples of the same effluent and determining the % relative standard
deviation. Since the method of standard additions were used to acquire
quantitative data the reproducibility was the same as the precision.
Typical reproducibility data are shown in Figure 2.
DEPENDENCY OF PEAK CURRENT ON CONCENTRATION
Calibration curves are prepared from peak-current versus concentra-
tion data. Figure 3 gives a set of typical calibration curves. These
were determined while simultaneously stripping Zn, Cd, Pb, Cu and Bi in
acetate buffer. The method of standard additions gave results that were
not significantly different from results acquired by use of the calibra-
tion curves. Of course, use of the standard additions method required
that there is a linear relationship between ip and C. In the application
of these methods the calibration data were treated by the method of least
squares .
18
-------
1.0 -0.8 -0.6 -0.4 -0.2
POTENTIAL VERSUS SCE, volts
Figure 2. Reproducibility of DPASV for simultaneous stripping of
cadmium, lead, and copper in 0.5F sodium fluoride.
zinc,
-------
Cu
Bi
Cd Zn Pb
£ 200500 100
k.
D
Q.
E
2 160 400 80
120300 60 -
OL
OL
Z>
u
< 80 200 40 -
40 100 20 -
20 40 60 80 100 Pb
40 80 120 160 200 Zn and Bi
10 20 30 40 50 Cu and Cd
CONCENTRATION, nanograms/ml
Figure 3. Peak current versus concentration for the simultaneous
stripping of Zn, Cd, Pb, Bi and Cu. (Acetate buffer of
PH 5.481, td=3Q S, Ed= -1.400V, M.S.= 3)
-------
SECTION VII
EVALUATION AND APPLICATION OF ANALYTICAL METHODS
The methods have been applied to the identification and determination
of trace metals in a variety of effluents. The various types and the
number of samples studied in this laboratory are listed in Table 2. This
represents a broad spectrum of effluent matrices that were tested, and the
conclusions presented in the first part of this report are derived from a
comprehensive matrix data base.
A mixture constituting various amounts of practically all types of
effluents listed in Table 2 was developed and analyzed. The results along
with precision data are given in Table 3.
A second mixture composed of effluents and tap water was developed
and analyzed. The results along with the recovery data are shown in
Table 4. This recovery reflects the total efficienty for the digestion
procedure, sample transfer, and analytical measurement. Since it was
acquired by the use of a real sample of perhaps the most complex matrix
available it is a good representation of the applicability of the entire
procedure for DPASV, provided careful analytical work is conducted.
Table 5 contains a listing of some results that were obtained for
some of the different effluent types. The Egg Processing and Steel Mill
sample required the greatest amount of time for digestion (10 hours).
21
-------
TABLE 2. TYPES OF EFFLUENTS AND NUMBER OF SAMPLES
ANALYZED THROUGH THIS STUDY
Effluent
Type
Further description
No. of
Samples Studied
Textile & domestic
Raw sewage
Printing industry
and domestic waste
Meat Packing
Aluminum products
Alumnium products
Paper mill
Paper mill
Egg treatment
Steel mill
Steel mill
Textile
Slaughter house
Metals plating
Metals plating
Soft drink
Synthetic Fibers
Dyeing and Finishing
Chicken Farm
Waste from corrugated box manufac-
turing facility also. Influent to
oxidation pond.
Domestic waste.
60% industrial and 40% domestic.
Raw waste.
Different locations.
Collected from pond-after oil
separation.
Raw. After pH adjustment.
Raw waste.
Effluent from clarifier.
Raw waste.
Raw waste.
Refined.
Raw.
Raw.
Raw.
Refined.
Raw.
Raw.
Raw.
Raw
6
10
5
3
6
3
5
2
3
25
18
10
2
6
2
3
2
1
3
22
-------
TABLE 3 TRACE METALS IN A MIXTURE OF INDUSTRIAL
EFFLUENTS AND PRECISION DATA
CONCENTRATION, ug/ml
Element
Zn
Cd
Pb
Bi
Cu
Sample #1
17.2
20.4
27.4
14.50
12.0
Sample #2
21.9
20.4
27.9
4.61
13.6
Sample #3
21.8
20.6
29.1
4.28
12.4
Sample #4
32.4*
18.3
27.2
4.13
12.7
Standard
Deviation
Mg/mL
+ 2.60
+ 1.33
+ 0.85
± °-18
+ 0.68
* Apparent contamination. Rejected this datum in computing
the standard deviation.
TABLE 4. RECOVERY DATA FOR THE SIMULTANEOUS DETERMINATION
OF ZINC, CADMIUM AND LEAD IN INDUSTRIAL MIXTURE II
Naturally
Occurring
Element C«g/ml)
Zn 25.4
26.1
Cd 4.42
5.76
Pb 8.34
8.95
Added
C«g/ml)
4.44
4.92
4.25
5.24
2.54
4.61
Found
C«g/ml)
33.9
29.5
8.63
11.65
11.4
14.0
Recovery
(%)
113.6
95.1
97.5
106
105
96.8
23
-------
TABLE 5. RESULTS FROM APPLICATION OF DPASV TO A
VARIETY OF EFFLUENTS
Concentration, ng/ml
Effluent
Type
Textile
Printing
Lake Marion
Egg Processing
Steel Mill
Zn
0.90
2.30
30.61
268
848
X103
Cd
11.0
1.5
114
10.3
XLO3
Pb
16.9
7.8
121
93.4
711
X103
Cu
24.1
2.43
193
420
X103
Bi
3.72
11
X103
24
-------
SECTION VIII
COMPARISON OF DIFFERENTIAL PULSE ANCDIC
STRIPPING VOLTAMETRY AND FLAME ATOMIC
ABSORPTION SPECTRCHOTCMETRY FOR EFFLUENT ANALYSIS
Flame atonic absorption spectrophotometric data on metals in
effluents were acquired by using a Model 503 Atomic Absorption Spectro-
photometer (Perkin-Elmer Corporation, Norwalk, Connecticut). For most
samples a triple slot burner head was used and the deuterium arc back-
ground corrector was activated. New single element hollow cathode lamps
of short shelf life were used in all cases except for the determination
of copper. This element was determined while using aCo-Cu-Fe-Mn-
Mo multielement lamp. An air - acetylene flame was employed for all
samples and final readout data were acquired while operating in the concen-
tration mode with integration times of 3 and 10 seconds.
Refrigerated samples were allowed to reach thermal equilibrium with
the laboratory atmosphere prior to analysis. Effluents that were dif-
ficult to aspirate because of a large percentage of particulates were
filtered. No sample pretreatment was conducted with exception of the
addition of nitric acid (approximately 5 ml of HMOs/ liter of effluent)
immediately following sample collection for the purpose of preservation.
Figures 4 and 5 are typical calibration curves obtained by flame AAS. In
most cases linearity complied with the specifications given in reference
(2).
Table 6 contains some of the quantitative data obtained from the
comparative analyses of effluents by DPASV and flame AAS. The DPASV
results were ascertained by employment of the methods developed through
this study. The working solution that resulted after application of the
Parr acid digestion bomb technique and dilution contained levels of metals
that ranged from 10 ng/ml to 400 ng/ml.
25
-------
Zn
5.0
Bi
Sn
50
4.0 40
O
9 3.0 30
LU
2.0 20
1.0 10
!
I
Sn
—-D Zn
—-•*-— Bi
10
1
20 30
2 3
40
4
50 Sn,Bi
5 Zn
CONCENTRATION, micrograms/ml
Figure 4. Atomic absorption calibration curves for tin, zinc,
and bismuth.
-------
NJ
Pb Cd
50 30
10
Pb
/
—o- Cd
—&— Pb
I
Cd
50 Pb
Figure 5. Atomic absorption calibration curves for
cadmium and lead.
5 10 15 20
10 20 30 40
CONCENTRATION,
-------
TABLE 6. COMPARISON OF DPASV AND FLAME AAS
DATA FOR METALS IN EFFLUENTS
Concentration, (ug/ml)
Sample no. and
effluent type
Mixed sample
#12
Steel Mill
#4028
TABLE 7.
Detection
DPASV*
Element Cng/ml)
Zn 0.5
Cd 0.08
Pb 0.10
Bi 0.32
Cu 0.50
Tl 0.10
In 0.30
Element DPASV
Zinc 0.72
Cadmium 20.6
Lead 29.1
Copper 19.2
Bismuth 4.28
Cadmium .07
Lead 6.97
Copper .654
Bismuth 11.6
AAS
0.80
20.9
31.5
17.3
2.51
0.07
5.86
0.57
12.9
Percent
Difference
10
1.4
7.62
9.90
41.4
0
15.9
12.8
10.1
COMPARISON OF SENSITIVITIES, DETECTION LIMITS
AND LINEARITY RANGE OF TRACE METAL DETERMINATION
FOR DPASV AND FLAME AAS
Limit Sensitivity Linearity
Range
AAS DPASV AAS DPASV** AAS
Cng/ml) (ng/ml/nA) (ng/ml/lfebs)(ng/ml)(ng/ml)
2 5
5 1
30 2
50 8
5 4
200 3
50 2
18
25
500
400
90
500
700
1,000
2,000
20,000
2,000
5,000
20,000
50,000
28
-------
The good agreement that exists between the results for most metals
suggests that DPASV competes well with the present widely accepted
technique, AAS, for metal determination. It was observed in most cases
throughout this comparative study that the Parr bomb digestion - DPASV
results were higher than the flame AAS data. The consistency in this
trend together with the accuracy of the DPASV methods suggests that the
Parr bomb digestion technique and the sensitivity of DPASV provide for
the combined total determination of metals in the solution and particulate
phases of an effluent sample.
The rather poor agreement between the results of the two techniques
for bismuth in mixed sample #12 is apparently due to the fact that level
of this metal is close to its lower detection limit for AAS. The accuracy
of the DPASV method for Bi at the 100 - 200 ng/ml (the range of concen-
tration of Bi in the working solution for which this sample was prepared).
Table 7 lists sensitivity, detection limits, and linearity (upper
limit), data for both techniques. Table 8 lists the items that constitute
start-up costs for each method. It appears that DPASV is superior to AAS
in terms of detection limits, sensitivity, and cost (see Table 9). The
precision for the two techniques is comparable.
TABLE 8. COMPARISON OF START-UP COSTS
FOR DPASV AND FLAME AAS
Estimated Cost
( $ )
Category DPASV AAS
Basis Instrumentation 5,200 16,000
Needed Accessories 1,750 1,490
six lamps and
HMDE Set Up burner head
six capillaries
4 cells and 3
bombs
Reagents 350 450
and supplies
(start-up)
SPECIAL fan and venting 160
$7,300 $18,000
29
-------
TABLE 9. ADVANTAGES AND DISADVANTAGES OF
DPASV AND FLAME AAS
Advantages and Disadvantages
Category
DPASV
ASS
Superior
technique
1. Start-up
costs
2. Annual
Maintenance
3. Technical
skill
required
4. Instrumental
Tune-up
Estimated to be 1/2
about 2/5 the costs
for AAS
Have used instrument
for 3 years at zero
maintenance cost
Highly sensitive
experienced technician
Ininediate use
5. Counter space Very compact
6. Supportive
supplies and
equipment
7. Sample
preparation
8. Precision
9. Accuracy
10. Detection
Limits
Must digest
completely
Depends on purity of
reagents and preconcen-
tration time
$1,000
(routine)
Must tune-up
for optimum
performance
Requires about
4 times the
space for DPAS
Little or
none
DPASV
DPASV
AAS
11. Sensitivity Very sensitive
DPASV
DPAV
DPASV
DPASV
Comparable
Comparable
DPASV
DPASV
30
-------
SECTION IX
DISCUSSION
DPASV AND CHEMICAL PERIODICITY
IB
IIB
IIIA
IVA
VA
+0.103 V
Cu-
-1.0043 V
Zn
-0.5936 V
Cd
-0.580 V
In
-0.5778 V
Tl
-0.4779 V
Sn
-0.3620 V
Fb
+0.080 V
Bi
A number of interesting correlations have been made between the DPASV
characteristics of these elenents and their chemical periodicities. The
number that is written above each elenent in the above portion of the
periodic Table is the standard reduction potential (3) of the most stable
form of the metal ion in aqueous acid media. For comparative purposes,
these potentials are given.'in reference to the SCE.
Table 10 gives the electronic configuration of each ion along with its
reduction potential.
31
-------
TABLE 10. CORRELATION BETWEEN REDUCTION POTENTIALS AND
ELECTRONIC CONFIGURATIONS OF METAL IONS
Metal ion
Cu+2
Bi+3
Pb+2
Sn +2
Tl +1
In+3
Cd+2
Zn+2
Outer Electronic
Configuration
4s23d23d23d13d13d1
6s25d106p06p°6p0
6s25d106p°6p06p°
5s24d105P05p°5p0
6s25d106p°6p°6p0
5so4d105po5p05po
5s04d105P05p°5P0
4s°3d104p04p°4p0
Reduction
potential
+ 0.103
+ 0.080
- 0.3620
- 0.3779
- 0.5778
- 0.580
- 0.5936
- 1.0043
Since the reduction potential is related to the free energy change
(spontaneity) for the corresponding half-cell reaction it may be looked
upon as a quantity related to the energy necessary to produce the neutral
atom or amalgam. Zn+2 requires the greatest amount of energy to be
reduced, and this apparently is related to the scheme that two electrons
must be placed in the somewhat shielded 4s empty orbital. Similarly,
Cd+2 ion has all 4 d orbitals filled, shielding the 5s empty orbital. But
the reduction potential for Cd+2 is over 400 mv more positive than the
value for Zn+2 ion. The outer orbitals for Cd+2 are for principal levels
4 and 5 while those for Zn+2 are 3 and 4. This may account for the con-
siderable difference in the reduction potentials of the two ions. The
entire order of the reduction potentials of the metal ion can be explained
based on their electronic configuration. Notice the order by which the
ions occur in Table 10 and the order by which they exist in the periodic
chart. When Cu+2 is excluded there appears an interesting correlation
between the reduction potentials of these ions and their periodic place-
ment.
Another interesting correlation was made between the electronic
densities (4) of the neutral atoms and their stripping positions on the
current-potential curves. A typical case is shown in Figure 6.
32
-------
to
•5
Q
1.40-
1.20-
-1.0 -0.8 -0.6 -0.4 -0.2 0.0 +0.2
POTENTIAL VERSUS SCE, volts
Figure 6. Dependency of reduction potential on atomic radius.
-------
Separation of Bi and Cu
The sensitivity of the signal for Tl in acetate buffer is approximately
twice that of the acetate buffer-EDTA solution, 2.42 nA/ng/ml and 1.35
nA/ng/ml, respectively, with the *d = 10 seconds. The detection limits
for Tl are 3.25 ng/ml and 1.58 ng/ml for acetate buffer and acetate
buffer - EDTA solution, respectively with a *d = 10 seconds. The Ep/2
value for Pb + Tl in acetate buffer is -0.505 V versus SCE while a value
of -0.520 V versus SCE exists for Tl in acetate buffer - EDTA solution.
Through a separate study performed in this laboratory, it has been
determined that the diffusion coefficient of Tl+1 is twice that of_Pb+2.
Tl+1 gives virtually the same iD/C value (6.22 X 1011 nA/M) as Pb+z
(6.28 X IQll nA/M) when run separately in acetate buffer. Thus in acetate
buffer, the amount of electricity or total charge (coulombs) involved in
the stripping of a certain concentration of Tl+l should be the same as the
one for Pb+2 under the same experimental conditions. In the determination
of the sum of the concentrations for Tl and Pb (which have the same EL/2
it does not matter which of the two metal ion standards is used for
the spike.
EDTA completely complexes the lead to form a stable species when it
is added to the acetate buffer system. Tl gives a good signal in the
presence of EDTA and can be readily determined in this new medium.
Separation of Bi and Cu
A number of workers have experienced difficulty in determining bismuth in
the presence of copper. Figure 7 shows how acetate is used to separate
the signals for bismuth and copper. Greater consistency in the data was
obtained when the decaying portion of the wave was used to determine ip
for copper.
A different electrolyte system that provides for the simultaneous
determination of Bi and copper is O.IENK^ Cl -
Ammonium chloride and potassium carbonate separately do not lead to
the separation of Cu and Bi. Figure 8 reveals how the combination of the
two effect the needed separation. Curves A and B represent the stripping
for a nonpurged and purged solution - in 0.1FNH4 Cl. Curve C is obtained
after traces of Pb, Cd and Cu have been added. Curve D was run after the
NHj Cl solution was made 0.23 F in KgCOs- The addition of carbonate ion
causes all species to be stripped at more negative potentials. Peaks 1 and
2 in curve C become 1 and 2, respectively, in curve D while 3 splits into
two peaks. Curve E is a repeat run, and the reproducibility is very good.
Lead and copper standards were added before running curve F and we can see
that Cu is component C^ while C2 is Bi, just the reverse order as occurs
in acetate. Notice that the front part of the wave for Bi has decreased
since the addition of Cu. This forces one to read the decaying current
for Bi, which gives good reproducibility, even when the solution is spiked
with copper.
34
-------
z
U4
Q£
oe.
ID
u
in
Ii;I~
Curves A and B - Duplicate curves in solution of 2.5 ml of nitric acid
diluted to 25 ml with 2M sodium acetate.
C, D and E - Repeated runs after addition of 6.8 grams
of sodium acetate.
F - Run after addition of another 6.8 grams of
sodium acetate.
F
I
I
-0.6
0.0
-0.4 .0.2
POTENTIAL VERSUS SCE, volts
Figure 7. Separation of copper and bismuth signals for DPASV using
acetate ion.
-------
OL
3
U
I I
Curve A - Unpurged 0.1 F NH4CI
Curve B - purged 0.1F NH4Cl
Curve C - Spiked with Cd, Pb and Bi
Curve D - Added K7CO3
Curve E - Repeat run
Curve F - Spiked with Pb and Cu.
Cd
-0.8
-0.6 -0.4
POTENTIAL VERSUS SCE, volts
-0.2
Figure 8. Current potential curves for simultaneous stripping
of Cd, Pb, Cu and Bi in the presence of ammonia
and acetate.
36
-------
Summary - The technique of DPASV is highly sensitive and requires
an experienced analyst to apply the associated methods for determining a
number of metals. The investigation has attempted to focus on those
elements that are relatively ubiquitous, difficult to determine by other
methods, are known toxicants or have questionable toxicity, and are likely
to be more prevalent in effluents than other metals. Although through
this investigation elements such as antimony, tin, and nickel have been
explored using a number of electrolyte systems, this report does not pre-
clude the extension of this list of metals to a wider spectrum.
37
-------
1. Barendrecht, E., Review article on "Stripping Voltametry",
Electroanalytical Chemistry, Vol. 2, ed. Bard, J. A., Marcel
Dekker, Inc., New York, New York, p. 53 (1967).
2. Analytical Methods for Atomic; AbsorptIon Spectrophotometry,
Perkin-Elmer Corporation, Norwalk, Connecticut (1973).
3. Latimer, W. M., Oxidation Potentials, 2nd ed., Prentice-Hall,
Inc., New York, New York (1952).
4. Sanderson, R. T., Chemical Periodicity. Reinhold Publishing
Corporation, New York, New York (I960).
38
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/A-77-034
2.
i. RECIPIENT'S ACCESSIOI»NO.
4. TITLE AND SUBTITLE
DETERMINATION OF TRACE METALS IN EFFLUENTS BY
DIFFERENTIAL PULSE ANODIC STRIPPING .VOLTAMETRY
5. REPORT DATE
July 1977 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
James T. Kinard
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Benedict College
Columbia, South Carolina 29204
10. PROGRAM ELEMENT NO.
1HA-322-JBA-027
11. CONTRACT/GRANT NO.
R803490-01-0
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Monitoring and Support Laboratory-Gin.,
Office of Research and Development OH
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/06
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Differential pulse anodic stripping volametry (DPASV) was evaluated to
determine its applicability to industrial and domestic effluents. The results
show that trace amounts of zinc, cadmium, lead, bismuth, copper, thallium,
indium, antimony, tin and nickel can be determined individually and simultaneously.
A procedure for providing low blank buffer and electrolyte systems was tested.
The efficiency for the entire process, including digestion, sample transfer and
analysis, was found to range from 93 to 100%. Pulse anodic stripping voltametry
was found to be superior to atomic absorption in terms of sensitivity, detection
limits and cost.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Volumetric Analysis, Digesters, Cadmium,
Metals, Copper, Bismuth, Antimony, Indium
Water Analysis, Lead (metal), Nickel,
Tin, Thallium, Zinc, Containers
Anodic Stripping
07B
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report}
TTMPT
21. NO. OF PAGES
47
20. SECURTTV~CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
39
*UA 60VBNMO(rPmKTIK60FFIC£! 1977- 7S7-OS6/6470
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