National Institute for Occupational Safety and Health

“ Calibrate daily with at least six working standards. a. Add 10 mL of acidic permanganate solution and 1 mL of ferrous reagent to a 125-mL separatory funnel. b. Add 2 to 400 μL of the standard phosphate solution to cover the range 0.1 to 10 μg of PH 3. Add 8 to 9 mL of water to make the total volume of the solution (permanganate solution, ferrous solution, phosphate solution and water) equal to 20 mL. Prepare at least six calibration standards and a blank containing no phosphate. c. Add 7.5 mL of molybdate reagent and 25 mL of toluene-isobutanol solvent to the funnel. ”

“ Caution should be exercised when preparing the sampling media because mercuric cyanide is toxic. Work only in a hood.
SAMPLING: 1. 2.
3. 4.
Calibrate each personal sampling pump with a representative sampler in line. Immediately before sampling, break the ends of the silica gel tubes to provide an opening of at least one half the internal diameter of the tube. Attach the silica gel tube to the sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.01 and 0.2 L/min for a total sample size of 1 to 16 L. Seal tubes with plastic (not rubber) caps. ”

“ Turn on the spectrophotometer and allow sufficient time for warmup. Adjust the wavelength to 625 nm and set the zero and 100% transmittance scale using 5-cm cells filled with distilled water. Check these settings prior to making any measurement to check on instrument drift. NOTE: Steps 16 through 18 must be performed within one minute. 16. Add 0.5 mL (25 drops) of stannous chloride reagent and dilute to volume using alcoholic sulfuric acid solution. Mix thoroughly. 17. Transfer the sample into a 5-cm cell and stopper immediately. ”