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
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        EPA
  PERMIT No. G-35
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Penalty for Private Use $300
EPA/600/S4-85/072

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