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1,1-DIMETHYLHYDRAZINE: METHOD 3515, Issue 2, dated 15 August 1994 - Page 3 of 3 a.

b. c.

d.

Add appropriate aliquots (10, 20, 30, 40 and 50 µL) of calibration stock solution to 10 mL of 0.1 M hydrochloric acid in 50-mL volumetric flasks. Prepare a reagent blank using only 10 mL of 0.1 M hydrochloric acid. Treat with (steps 7 and 8) phosphomolybdic acid solution. Analyze working standards together with samples and reagent blanks (steps 10 through 12) on a spectrophotometer at 730 nm, using a 1-cm cell. Correct standards for reagent blank absorbance. Prepare a calibration graph of absorbance vs. amount (µg) of 1,1-dimethylhydrazine per 50 mL of sample.

MEASUREMENT: 10. 11. 12.

Set spectrophotometer according to manufacturer's recommendations to monitor 730 nm. Fill 1-cm sample cell with sample or standard. Measure absorbance.

CALCULATIONS: 13. 14.

Determine mass, µg, of analyte found in sample (W) and average reagent blank (B). Calculate concentration (C) of 1,1-dimethylhydrazine in the air volume sampled V (L):

EVALUATION OF METHOD: This method was evaluated over the range 0.5 to 2.3 mg/m 3 using 91-L samples [1]. Sampling and measurement precision, SˆrT was 0.062 for samples collected at the OSHA standard. Bias could not be determined owing to instability of the 1,1-dimethylhydrazine in the generator. Collection efficiency of the bubblers was determined to be 99.1% at 2.2 mg/m 3. Sample stability during storage was evaluated at 100 µg 1,1-dimethylhydrazine per sample. Samples showed 101.3% recovery after five days of storage at ambient conditions.

REFERENCES: [1] [2] [3] [4] [5]

Backup Data Report for 1,1-Dimethylhydrazine, prepared under NIOSH Contract 210-76-0123 (1977). NIOSH Manual of Analytical Methods, 2nd e.d., V. 3, S143, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-175 (1978). NIOSH Manual of Analytical Methods, 2nd e.d., V. 4, 248, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-175 (1978). L.R. Cook, R.E. Glenn and G.E. Podolak, Am. Ind. Hyg. Assoc. J., 40, 69-74 (1979). 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 #17-033-00337-8 from Superintendent of Documents, Washington, D.C. 20402.

METHOD REVISED BY: E.R. Kennedy, Ph.D., NIOSH/DPSE.

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