Page:NIOSH Manual of Analytical Methods - 2504.pdf/2

 TETRAETHYL PYROPHOSPHATE: METHOD 2504, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS: 1.

2. 3. 4.

5. 6. 7. 8.

EQUIPMENT:

TEPP, purified*. NOTE: TEPP is hygroscopic and easily hydrolyzed. Tripropyl phosphate, reagent grade, or other suitable internal standard. Toluene, reagent grade. Eluent: Dilute a weighed amount of tripropyl phosphate to 100 mL with toluene. Concentration of solution must be within the linear range of the FPD. Nitrogen or helium, purified. Hydrogen, prepurified. Air, filtered. Calibration stock solution, 1.18 mg/mL. Dilute 11.8 mg (10 µL) TEPP to 10 mL with eluent. Prepare in duplicate.

See SPECIAL PRECAUTIONS.

1. Sampler: two glass tubes, 10-cm long, 8-mm OD, 6-mm ID, flame-sealed ends, front tube containing a 100-mg section of extracted resin and a back containing a 50-mg section, retained by silylated glass wool plugs in each tube. Pressure drop across the tubes in series at 1 L/min airflow must be less than 3.4 kPa. (Tubes commercially available as SKC, Inc. ST 226-105). 2. Personal sampling pump, 0.01 to 0.2 L/min, with flexible connecting tubing. 3. Gas chromatograph, flame photometric detector, phosphorus filter, integrator and column (page 2504-1). 4. Vials, 2-mL, PTFE-lined caps. 5. Syringe, volumetric, 10- and 100-µL. 6. Flasks, volumetric, 10-mL. 7. Pipettes, volumetric, 1-mL, with pipet bulb. 8. File.

SPECIAL PRECAUTIONS: TEPP is a cholinesterase inhibitor and can be absorbed through the skin. Wear protective gloves and suitable protective clothing when handling the pure material [3].

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. Connect the two sorbent tubes with a short piece of flexible tubing. 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 20 to 48 L. Separate the front and backup tubes. Cap the tubes with plastic (not rubber) caps. This prevents migration of TEPP between sorbent sections. 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 plugs. Add 1.0 mL eluent to each vial. Attach crimp cap to each vial. Allow to stand 60 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 8.

Calibrate daily with at least six working standards over the range 0.1 to 6 µg TEPP per sample. a. Add known amounts of calibration stock solution to eluent 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 (ratio of peak area of analyte to peak area of internal standard vs. µg TEPP). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94