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 DIMETHYL SULFATE: METHOD 2524, Issue 2, dated 15 August 1994 - Page 4 of 4 EVALUATION OF METHOD: For the evaluation, a Tracor Model 310 Hall electrolytic conductivity detector was used [1]. It was operated with a furnace temperature of 950 °C, oxygen at 20 mL/min as the reactant gas, and filtered, deionized water at 1 mL/min as the conductivity solvent. The capacity of Porapak P for the collection of dimethyl sulfate was estimated from a log retention volume vs. reciprocal absolute temperature plot of data obtained by chromatographing 30-µg quantities of dimethyl sulfate on a 100-mg sorbent bed. Based on these data, the estimated volumetric capacity decreases from 39 L at 25 °C to 16 L at 35 °C. In a test of humidity and storage effects, six tubes were spiked with 0.6 µg dimethyl sulfate. After passing 12 L of humid air (80% RH) through each, they were stored for seven days. Upon analysis, these samples showed no significant loss of dimethyl sulfate. This method was compared with an independent method based on collection of dimethyl sulfate on Tenax-GC, derivatization of p-nitrophenol with the collected dimethyl sulfate, and HPLC (UV detection) of the resulting p-nitroanisole. For three sets of six dynamically-generated samples, the concentrations and precisions (relative standard deviations) found using this method were 1.8 (0.061), 4.35 (0.074), and 24.5 (0.070) µg/L. The corresponding results found by the independent method for simultaneously-generated samples were 3.18 (0.153), 7.18 (0.090), and 20.4 (0.086) µg/L. Because of the inconsistency of the results and possible inaccuracy in the independent method, the accuracy of this method remains to be determined.

REFERENCES: [1] Lunsford, R. A., and P. M. Fey. Backup Data Report for P&CAM 301 (NIOSH, unpublished, December 29, 1978). [2] NIOSH Manual of Analytical Methods, 2nd ed., Vol. 5, P&CAM 301, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979). [3] The Merck Index, 11th Ed., Merck & Co., Inc., Rahway, NJ (1989). [4] NIOSH/OSHA Occupational Health Guidelines for Chemical Hazards, U.S. Department of Health and Human Services, Publ. (NIOSH) 81-123 (1981), available as GPO Stock #017-033-00337-8 from Superintendent of Documents, Washington, DC 20402.

METHOD WRITTEN BY: R. Alan Lunsford, Ph.D., NIOSH/DPSE.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94