Page:NIOSH Manual of Analytical Methods - 5009.pdf/2

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BENZOYL PEROXIDE: METHOD 5009, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS: 1. 2. 3. 4. 5.

EQUIPMENT:

Benzoyl peroxide, 99% pure.* Ethyl ether, purified, without stabilizer.* Methanol, distilled in glass. Water, deionized and distilled. Calibration stock solution, 10 mg/mL. Dissolve 250 mg benzoyl peroxide in ethyl ether and dilute to 25 mL. Stable at least one week at 4 °C.

See SPECIAL PRECAUTIONS.

1. Sampler: cellulose ester membrane filter, 0.8-µm pore size, 37-mm diameter, with backup pad in cassette filter holder. 2. Personal sampling pump, 1 to 3 L/min, with flexible connecting tubing. 3. Refrigerated, bagged ("Blue Ice," or equivalent). 4. Vials, 20-mL, PTFE-lined caps. 5. High performance liquid chromatograph, 254-nm UV detector, sample injection valve with a 20-µL external sample loop, syringe filter, integrator and column (page 5009-1). 6. Tweezers. 7. Microliter syringes, 10- and 100-µL. 8. Volumetric flasks, 10- and 25-mL, assorted sizes. 9. Pipet, 10-mL, with pipet bulb.

SPECIAL PRECAUTIONS: Benzoyl peroxide is a flammable solid and may explode when heated; it will attack some plastics, rubber, and coatings [4]. Ethyl ether is highly flammable and forms explosive peroxides on exposure to air.

SAMPLING: 1. 2.

Calibrate each personal sampling pump with a representative sampler in line. Sample at an accurately known flow rate between 1 and 3 L/min for a total sample size of 40 to 400 L. Do not exceed 2 mg particulate loading on the filter. Ship samples in an insulated container with bagged refrigerant.

3.

SAMPLE PREPARATION: 4. 5. 6.

Immediately upon receipt at laboratory, refrigerate the samples. As soon as possible after receipt, transfer each filter to a clean vial with tweezers. Pipet 10 mL ethyl ether into each vial; screw on cap. Swirl to mix.

CALIBRATION AND QUALITY CONTROL: 7. a. b. c. 8. a. b. c. 9.

Calibrate daily with at least six working standards covering the range 0.01 to 1.7 mg per sample. Add calibration stock solution with a microliter syringe to ethyl ether in a 10-mL volumetric flask and dilute to the mark. Analyze together with samples, blanks and control samples (steps 10 through 12). Prepare calibration graph of peak area vs. mass (mg) of benzoyl peroxide per sample. Determine recovery of benzoyl peroxide from filters at least once for each lot of samplers in the calibration range (step 7). Prepare three filters at each of five levels plus media blanks. Add aliquot of calibration stock solution with a microliter syringe directly onto a media blank filter in a vial. Prepare and analyze together with working standards (steps 5, 6 and 10 through 12). Prepare a graph of recovery vs. mg benzoyl peroxide recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94