Page:NIOSH Manual of Analytical Methods - 2546.pdf/2

 CRESOL (all isomers) and PHENOL: METHOD 2546, Issue 1, dated 15 August 1994 - Page 2 of 4 EQUIPMENT:

REAGENTS: 1. 2. 3.

4.

5. 6. 7.

Methanol, chromatographic quality. n-Hexane. Cresol (all isomers).* Dissolve 2 g o-cresol (solid), 3 g p-cresol (solid) in 4 g (4.13 mL) of m-cresol and mix. Calibration stock solution, 10.4 mg/mL. Dilute 104 mg cresol isomer mixture (1.0 mL at 20 °C) to 10 mL with n-hexane. Hydrogen, prepurified. Nitrogen, purified. Air, filtered.

See SPECIAL PRECAUTIONS.

1. Sampler: glass tube, 11 cm long, 6-mm OD, 4- mm ID;two sections of 20/40 mesh XAD-7 separated by a 2-mm portion of silanized glass wool (front = 100 mg, back = 50 mg). 2. Personal sampling pump, 0.01 to 0.1 L/min, with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and column (page 2001-1). 4. Vials, glass, 2-mL, PTFE-lined crimp caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Pipet, 1.0-mL, with pipet bulb. 7. Volumetric flasks, 10-mL. 8. Ultrasonic bath.

SPECIAL PRECAUTIONS: Cresol and phenol cause severe burns [5]. They are toxic if absorbed through skin, inhaled or ingested. All work with them should be performed in a hood.

SAMPLING: 1. 2. 3. 4.

Calibrate each personal sampling pump with a representative sampler in line. Break the ends of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.01 and 0.1 L/min for a total sample size of 5 to 24 L. Cap the samplers with plastic (not rubber) caps and pack securely for shipment.

SAMPLE PREPARATION: 5. 6. 7.

Place the front sorbent section (together with the front glass wool plug) and back sorbent sections of the sampler tube in separate vials. Discard the other plugs. Add 2.0 mL methanol to each vial. Attach crimp cap to each vial. Ultrasonicate 30 min.

CALIBRATION AND QUALITY CONTROL: 8.

9.

Calibrate daily with at least six working standards over the range 1 to 800 µg cresol and phenol per sample. a. Add known amounts of calibration stock solution to methanol in 10-mL volumetric flasks and dilute to the mark. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (total peak area vs. µg analyte). Determine desorption efficiency (DE) at least once per year for each lot of sorbent used for sampling in the calibration range. Prepare three tubes at each of five concentrations plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount of calibration stock solution directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. µg analyte recovered. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94