United States
Environmental Protection
Agency
Environmental Monitoring and
Support Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S4-85/072 Dec. 1985
v>ERA Project Summary
Determination of
Dithiocarbamate Pesticides in
Wastewaters
T. M. Engel, J. S. Warner, T. A.Pressley, and W. M. Cooke
A method was modified and validated
for the determination of dithiocarba-
mate pesticides in wastewaters. The
developed method consists of sample
pH adjustment to pH 12; removal of
indigenous carbon disulfide (682) by
purging in a vortex evaporator; acidi-
fication of the sample to hydrolyze
dithiocarbamate pesticides to form CSi
extraction of the CS2 from the sample
into hexane; and determination of the
CSa by gas chromatography using a Hall
detector in the sulfur mode.
The hydrolysis and CSs extraction
procedures used in this method were
developed during research conducted
under EPA Contract No. 68-03-2956.
The purpose of these studies conducted
under EPA Contract No. 68-03-1760
was to develop a simple, effective
method to remove indigenous CS2from
a water sample prior to dithiocarbamate
determination, and to validate the total
analysis method. Minimal dithiocarba-
mate stability studies were also con-
ducted to aid in determining optimal pH
ranges for sample storage and prepara-
tion.
The final method was validated using
13 dithiocarbamate pesticides. The
method detection limit (MDL) and an
analytical curve were determined for
each dithiocarbamate in reagent water.
The method was then applied to a
wastewater obtained from a manufac-
turer of a dithiocarbamate in order to
determine the precision and accuracy of
the method.
This Project Summary was developed
by EPA's Environmental Monitoring and
Support Laboratory. Cincinnati, OH. to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The group of dithiocarbamates used for
method development and validation pur-
poses was comprised of 17 compounds:
amobam, Busan 40, Busan 85, EXD,
ferbam, KN-methyl, mancozeb, maneb,
metham, nabam, nabonate, Niacide, poly-
ram, sodium dimethyldithiocarbamate
(NaDMDTC), thiram, zineb, and ziram.
The method was found to be unsuitable
for the determination of polymeric dithio-
carbamates such as maneb, mancozeb,
and polyram. The remaining 13 dithio-
carbamates were used for method valida-
tion, the method is based on the determina-
tion of CS2 which is evolved from the
dithiocarbamate moiety upon acid hydro-
lysis. The method is not specific for
dithiocarbamates.
In general, dithiocarbamates are mod-
erately stable in water under very basic
conditions. A CS2 generation method
followed by determination of the CSZ by
GC-Hall analysis was the selected ap-
proach. The CS2 is generated from the
dithiocarbamate upon treatment with a
stannous chloride (SnCI2)/hydrochloric
acid (HCI) mixture. The SnCI2 is present to
reduce any thiuram disulfide to the
dithiocarbamate and to inhibit oxidation
of the dithiocarbamate prior to its de-
composition. The generated CS2 is ex-
tracted from the water into hexane during
the decomposition process and deter-
mined by GC using a Hall detector in the
sulfur mode. This procedure has proven
to be more sensitive and easier than
previously developed colorimetric detec-
tion methods. A cleanup method was
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developed to remove any €82 originally
present in the wastewater. This cleanup
method involves purging of the C$2 from
the sample using a vortex evaporator.
Cleanup
A cleanup method was necessary to
remove indigenous CS2 from the water
sample prior to hydrolysis of dithiocarba-
mates. If this is not done, artifically high
levels of dithiocarbamates would be
determined in the samples. A hexane
extraction step at basic pH was originally
developed for the purpose under EPA
Contract No. 68-03-2956. This method
was found to be effective, but proved to be
tedious and time-consuming when pro-
cessing many water samples. Two alter-
native cleanup methods were identified
based on the fact that CS2 is easily purged
from water: removal of CSz from water
using a vortex evaporator and removal of
C$2 from water by purging with nitrogen.
Use of a vortex evaporator to remove
the CSz from the aqueous media was
slightly more efficient than purging with
nitrogen, presumably because dispersion
of the nitrogen gas from the 19-gauge
needle through the sample was not
sufficient for effective CSz removal.
Dithiocarbamate Stability
Studies
Some of the dithiocarbamate pesticides
were not stable in pH 9 buffer, especially
compounds with the following structures:
-S-CS-N-CHs
X
X = CT, H
One of the dithiocarbamate pesticides
with this structure, Busan 40, was found
to be particularly unstable in pH 9 buffer.
This instability became more pronounced
as the Busan 40 concentration in the
buffer was lowered.
Method Detection Limit
MDLs were determined by the proce-
dure recommended by EPA/EMSL which
defines MDLs in terms of a test that the
data show values greater than zero at the
99 percent confidence level. MDLs were
calculated from data obtained from the
analysis of seven replicate buffer samples
spiked at the 10 i/g/L level with the
appropriate dithiocarbamate pesticide.
Analytical Curves
Reagent water was spiked in duplicate
with the individual dithiocarbamate pesti-
cides at the 10, 50, 100, 500, and 1000
levels. Recoveries of these dithio-
carbamates were determined using the
dithiocarbamate analysis method and
analytical curves were generated by
plotting the amount of dithiocarbamate
spiked into the samples versus the calcu-
lated amount recovered from the samples.
Recoveries for these nonpolymeric dithio-
carbamates were generally greater than
85 percent with the exceptions of EXD,
nabam, and nabonate.
Method Validation in
Wastewater
A wastewater sample was obtained
from a manufacturer of a dithiocarba-
mate pesticide and diluted 1000:1 with
Columbus secondary POTW effluent prior
to use in validation studies. Seven ali-
quot s of this diluted wastewater were
then analyzed to determine background
dithiocarbamate levels. The diluted waste-
water was then spiked at the 50 and 500
fjg/L levels with the individual dithiocar-
bamate pesticides and analyzed. Seven
replicate extractions were performed at
each concentration level. Recoveries of
dithiocarbamates, corrected for back-
ground dithiocarbamate levels, were then
calculated.
The diluted dithiocarbamate waste-
water contained low levels of dithiocar-
bamate, 4.5 to 6.2 //g/L, depending upon
the molecular weight of the dithiocar-
bamate analyzed. Method validation data
for the dithiocarbamate pesticides in
wastewater are given in Table 1. Recov-
eries for these nonpolymeric dithiocar-
bamates were generally greater than 82
percent with the exceptions of EXD,
nabam, and nabonate.
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Table 1. Results
Compound
Amobam
Busan 40
Busan 85
EXD
Ferbam
KN-Methyl
Metham
Nabam
Nabonate
NaDMDTC
Thiram
Zmeb
Ziram
of Method Validation
Background
Level,
ug L
46
46
66
66
5.9
59
45
45
52
52
54
54
6.2
62
48
48
61
6.1
54
54
45
45
5.2
5.2
57
5.7
Study for Dithiocarbamate Pesticides in Wastewater
Amount Average
Spiked, Amount Standard
ug/L Recovered, ug/L Deviation
50
500
50
500
50
500
50
500
50
500
50
500
50
500
50
500
50
500
50
500
50
500
50
500
50
500
45
470
54
510
56
510
36
380
47
540
45
440
53
420
31
320
33
280
53
540
44
410
44
430
50
480
35
41
39
31
30
10
27
91
22
99
27
11
28
25
20
42
38
33
1.3
23
1.3
14
1.5
41
5.9
89
Percent
Relative
Standard
Deviation
78
87
72
6 1
55
20
75
24
48
18
61
25
5.2
5.9
66
13
11
12
2.5
42
29
34
3.4
9.4
12
19
A verage
Percent
Recovery
90
93
no
100
110
100
71
76
94
110
90
89
110
84
62
65
66
56
110
110
89
82
87
86
100
95
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T. M. Engel, J. S. Warner, and W. M. Cooke are with Battelle-Columbus
Laboratories, Columbus, OH43201-2693; the EPA author Thomas A. Pressley
(also the EPA Project Officer, see below) is with the EnvironmentalMonnitoring
and Support Laboratory, Cincinnati, OH 45268.
The complete report, entitled "Determination of Dithiocarbamate Pesticides in
Wastewaters," (Order No. PB86-118 726/AS; Cost: $11.95, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Monitoring and Support Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PA
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S4-85/072
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