National Institute for Occupational Safety and Health

“ Filter the solution through a moistened PVC filter in a Buchner funnel to remove interferences from suspended dust. Collect the filtrate in a clean centrifuge tube. Rinse the bottle, which contained the filter, with 2 to 3 mL 0.5 N H2SO 4 and pour into the funnel. Rinse the funnel and filter with 5 to 8 mL 0.5 N H2SO 4. e. Add 0.5 mL diphenylcarbazide solution to each centrifuge tube. Bring the total volume in each centrifuge tube to 25 mL with 0.5 N H2SO 4. Shake to mix and allow color to develop (at least 2 min but no longer than 40 min. [6] ) . ”

“ Do not boil the solution or heat longer than 45 min. Do not allow the solution to evaporate to dryness because hexavalent chromium may be lost owing to reaction with the PVC filter. An indication that hexavalent chromium has been lost in this manner is a brown-colored PVC filter. b. Cool the solution and transfer it quantitatively with distilled water rinses to a 25-mL volumetric flask, keeping the total volume about 20 mL. NOTE: If the solution is cloudy, filter it through a PVC filter in a vacuum filtration apparatus using distilled water rinses. ”

“ U.S. Department of Health, Education, and Welfare, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 76-129. [5] NIOSH/OSHA Occupational Health Guidelines for Chemical Hazards. Occupational Health Guidelines for Chromic Acid and Chromates. ”