Page:NIOSH Manual of Analytical Methods - 1609.pdf/2

 TETRAHYDROFURAN: METHOD 1609, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS: 1. 2. 3. 4. 5.

EQUIPMENT:

Carbon disulfide, chromatographic quality.* Tetrahydrofuran (THF), reagent grade.* Hydrogen, prepurified, Nitrogen, purified. Air, filtered, compressed.



See SPECIAL PRECAUTIONS.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4mm ID; flame-sealed ends with plastic caps, 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 then 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 1609-1). 4. Vials, glass, 1-mL, PTFE-lined caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Pipet, 0.5-mL, with pipet bulb. 7. Volumetric flasks, 10-mL.

SPECIAL PRECAUTIONS: Tetrahydrofuran and carbon disulfide are toxic and extremely flammable (flash points -17 °C and -30 °C, respectively) [4]. All work should be performed in a well-ventilated 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 of 1 to 9 L. Cap the samplers. Pack securely for shipment.

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 0.5 mL CS 2 to each vial. Attach cap to each vial. Allow to stand 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 8.

9.

Calibrate daily with at least six working standards over the range 0.05 to 13 mg THF per sample. a. Add known amounts of THF to CS 2 in 10-mL volumetric flasks and dilute to the mark with CS 2 to produce concentrations in the range 0.1 to 26 mg THF/mL. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (peak area vs. mg THF). Determine desorption efficiency (DE) at least once for each lot of charcoal used for sampling in the calibration range (step 8). Prepare three tubes at each of five levels plus three media blanks. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94