National Institute for Occupational Safety and Health

“ Calibrate daily with at least six working standards in the range 2.5 to 64 μg per sample. a. Dilute aliquots of p-chlorophenol stock solution with 30% (v/v) acetonitrile in water in volumetric flasks to encompass the range of interest. Prepare fresh daily. b. Analyze working standards with samples and blanks steps. c. Prepare calibration graph (peak area or peak height vs. μg of p-chlorophenol per sample. Determine desorption efficiency (DE) for each lot of silica gel used for sampling in the calibration range. Prepare three tubes at each of five levels. ”

“ DE stock solution, 5 mg/mL. Dissolve 125 mg p-chlorophenol in hexane to make 25 mL solution.
See SPECIAL PRECAUTIONS.
1. Sampler: Pyrex tubes, 7 cm long with a 6-mm OD and a 4-mm ID, flame sealed at both ends. Each tube contains two sections of 20/40 mesh silica gel (a 150-mg sorbing section and a 75-mg backup section separated and held in place with glass wool plugs) . Tubes are commercially available (SAC, Inc. 226-10 or equivalent.) 2. Personal sampling pump, calibrated, capable of operating 8 hours at 0.05 to 0.2 L/min with flexible connecting tubing. 3. ”