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 ------- 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. ------- 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 ------- 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 ------- |