MONOMETHYLHYDRAZINE: METHOD 3510, Issue 1, dated 15 August 1994 - Page 3 of 3
b. c. d. e.
f.
0.1 M hydrochloric acid. Add 7.5 mL of phosphomolybdic acid solution to all standards and blank and bring the volume up to 25 mL with 0.1 M hydrochloric acid. Transfer aliquots of these solutions to large test tubes and heat to 87 °C for 50 min. Place test tubes under running tap water to cool before measurement. Analyze working standards together with samples and reagent blanks (steps 10 through 12) on a spectrophotometer at 730 nm, using a 5-cm cell. Correct standards for reagent blank absorbance. Prepare a calibration graph of absorbance vs. amount (µg) of monomethylhydrazine per sample.
MEASUREMENT: 10. 11. 12.
Set spectrophotometer according to manufacturer's recommendations and to conditions on p. 3510-1 to monitor 730 nm. Fill 5-cm sample cell with sample or standard. Measure absorbance.
CALCULATIONS: 13. 15.
Determine mass, µg, of monomethylhydrazine found in the sample (W) and blank (B) from the calibration graph. Calculate concentration of monomethylhydrazine in the actual air volume, V (L):
EVALUATION OF METHOD: This method was evaluated over the range 0.17 to 0.78 mg/m 3 using 20-L samples [1,2]. Overall sampling and measurement precision, SˆrT, was 0.106. Collection efficiency of the bubblers was determined to be 96.5% at 1.7 mg/m 3 for a 20-L sample. Sample stability during storage was evaluated at 8 µg monomethylhydrazine per sample. Samples showed 104.4% recovery after five days of storage at ambient conditions compared to one-day old samples.
REFERENCES: [1] [2] [3] [4] [5] [6]
Backup Data Report for Monomethylhydrazine, prepared under NIOSH Contract 210-76-0123 (1977). NIOSH Manual of Analytical Methods, 2nd. ed., V. 4, S149, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-175 (1978). NIOSH Manual of Analytical Methods, 2nd. ed., V. 4, P&CAM 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 Criteria for a Recommended Standard....Occupational Exposure to Hydrazines, DHEW (NIOSH) Publ. No. 78-122 (1978). NIOSH/OSHA Occupational 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
