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 CHLOROACETALDEHYDE: METHOD 2015, Issue 1, dated 15 August 1994 - Page 4 of 4 REFERENCES: [1] Backup Data Report No. S11 for Chloroacetaldehyde, prepared under NIOSH Contract No. 21076-0123. [2] NIOSH Manual of Analytical Methods, 2nd. ed., V. 5, S11, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979). [3] Williams, R.G., Determination of Chloroacetaldehyde in Air by Differential Pulse Polarography, Anal. Chem., 54(12), 2121-2 (1982). [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 #17-033-00337-8 from Superintendent of Documents, Washington, D.C. 20402.

METHOD REVISED BY: James E. Arnold, NIOSH/DPSE; S11 originally developed under NIOSH Contract 210-76-0123.

APPENDIX: STANDARDIZATION OF CALIBRATION STOCK SOLUTION. Pipet 10-mL aliquots of the stock solution into two separate 250-mL Erlenmeyer flasks. Add 10 mL 2.5% hydrazine sulfate to one of the flasks and allow to stand 10 minutes with occasional swirling. The other flask serves as a blank and determines any free halide ion already present. Add 10 mL 0.100 N silver nitrate solution, 5 mL nitric acid solution, and 2 mL ferric ammonium sulfate solution to each flask. Swirl and add 2 mL nitrobenzene. The nitrobenzene forms an oily coating on the particles of precipitated silver chloride and prevents their undesired reaction with the thiocyanate ion. Titrate contents of each flask with 0.1 N ammonium thiocyanate to a faint orange-brown color that is permanent on shaking. The endpoint color is due to the formation of the Fe(SCN) 6-3 ion. Compute the volumes, V S, of standard silver solution in excess of that used by the chloride in each flask.

where: VT = volume, mL, of standard thiocyanate solution titrated NT = normality of NH 4SCN solution NS = normality of AgNO 3 solution Compute the net volume, V N, of silver solution required for the precipitation of the chloride liberated from chloroacetaldehyde.

Calculate the concentration, C, of chloroacetaldehyde in calibration stock solution.

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