Page:NIOSH Manual of Analytical Methods - 1550.pdf/2

 NAPHTHAS: METHOD 1550, Issue 2, dated 15 August 1994 - Page 2 of 5 REAGENTS: 1.

2. 3. 4. 5.

EQUIPMENT:

Eluent: Carbon disulfide*, chromatographic quality, containing 0.1% (v/v) octane, 0.5% (v/v) hexadecane or other suitable internal standard. NOTE 1: Use an internal standard which is not a major constituent of the sample. NOTE 2: Use toluene in place of carbon disulfide for low-boiling analytes [5]. Naphtha bulk sample. Nitrogen or helium, purified. Hydrogen, prepurified. Air, filtered.



See SPECIAL PRECAUTIONS.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4mm ID, flame-sealed ends, containing two sections of activated (600 °C) coconut shell charcoal (front = 100 mg; back = 50 mg) separated by a 2-mm urethane foam plug. A silylated glass wool plug precedes the front section and a 3-mm urethane foam plug follows the back section. Pressure drop across the tube at 1 L/min airflow must be less than 3.4 kPa. Tubes are commercially available. 2. Personal sampling pump, 0.01 to 0.2 L/min, with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and column (page 1550-1). 4. Vials, glass, 2-mL, PTFE-lined crimp caps. 5. Syringe, 10-µL (1-µL syringe for capillary columns) and other convenient sizes for preparing standards, readable to 0.1 µL. 6. Volumetric flasks, 10-mL. 7. Pipet, delivery, 1.0-mL, with pipet bulb.

SPECIAL PRECAUTIONS: Carbon disulfide is toxic and an acute fire and explosion hazard (flash point = -30 °C); work with it only 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 0.2 L/min for a total sample size which contains between 0.5 and 8 mg naphtha. Cap the samplers with plastic (not rubber) caps and pack securely for shipment. Ship a bulk sample (5 to 10 mL) in a separate container from the sorbent tubes.

SAMPLE PREPARATION: 5. 6. 7.

Place the front and back sorbent sections of the sampler tube in separate vials. Discard the glass wool and foam plugs. Add 1.0 mL eluent to each vial. Attach crimp cap to each vial. Allow to stand 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 8.

Calibrate daily with at least six working standards over the range 0.1 to 10 mg naphtha per sample. a. Add known amounts of naphtha bulk sample to eluent in 10-mL volumetric flasks and dilute to the mark. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94