Page:NIOSH Manual of Analytical Methods - 5012.pdf/2

 EPN: METHOD 5012, Issue 2, dated 15 August 1994 - Page 2 of 3 REAGENTS: 1. 2. 3.

4. 5. 6. 7.

EQUIPMENT:

EPN.* Isooctane, chromatoquality.* Calibration stock solution, 15 mg/mL isoctane (prepare fresh daily): NOTE: 4 µL of this solution contains a mass of EPN (0.06 mg) equivalent to a 120-L air sample at OSHA PEL. Nitrogen, purified. Hydrogen, prepurified. Oxygen, purified. Air, filtered, compressed.
 * See SPECIAL PRECAUTIONS.

SPECIAL PRECAUTIONS: EPN is a highly toxic cholinesterase inhibitor with cumulative effects [4,5]. Special care must be taken to avoid inhalation or skin contact.

1. Sampler: glass fiber filter (Gelman Type AE or equivalent), 37-mm, in a two-piece polystyrene cassette supported by a backup pad. 2. Personal sampling pump, 1 to 2 L/min, with flexible connecting tubing. 3. Gas chromatograph, column bypass valve, flame photometric detector, phosphorus filter, integrator and column (page 5012-1). 4. Vials, 20-mL, glass with PTFE-lined caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Volumetric flasks, 10-mL. 7. Pipets, 15-mL, with pipet bulb. 8. Tweezers.

SAMPLING: 1.

Calibrate each personal sampling pump with a representative sampler in line. 2. Sample at an accurately known flow rate in Isooctane is flammable. Prepare all samples in a the range 1 to 2 L/min for a total volume of well-ventilated hood. 15 to 700 L. Do not exceed 2 mg total dust loading on the filter. 3. Within 1 h after sampling, transfer the glass fiber filter with tweezers to a clean 20-mL vial.

SAMPLE PREPARATION: 4.

Pipet 15 mL isooctane into each vial. Cap each vial and swirl the contents for 1 h.

CALIBRATION AND QUALITY CONTROL: 5.

6.

Prepare at least six working standards covering the analytical range of the method, by diluting aliquots of the calibration stock solutions to 15 mL with isooctane. a. Analyze calibration standards in triplicate with the unknowns, blanks and other quality control spiked samples following steps 7 through 9. b. Prepare calibration graph (peak area or peak height vs. µg of EPN). Analyze recovery (R) samples with each sample set, in duplicate. a. Place filter media blanks in clean 20-mL vials. b. Inject analyte calibration stock solution directly onto the filter with a microliter syringe. c. Cap the vial and allow to stand overnight. d. Analyze according to steps 4 and 7 through 9. e. Calculate recovery (µg found on filter divided by µg added to filter).

MEASUREMENT: 7. 8.

Set gas chromatograph to conditions given on page 5012-1, optimizing the air, hydrogen and oxygen according to the GC manufacturer's instructions. Inject 5-µL sample aliquots using solvent flush technique. a. Vent the solvent peak by opening the column bypass valve at the time of injection. Close the column bypass valve after the solvent peak has eluted (ca. 30 sec) and before the NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94