Page:NIOSH Manual of Analytical Methods - 2528.pdf/3

 2-NITROPROPANE: METHOD 2528, Issue 2, dated 15 August 1994 - Page 3 of 4 9.

10.

Determine desorption efficiency (DE) at least once for each lot of sorbent used for sampling in the range of interest. Prepare three tubes at each of five levels plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount (2 to 20 µL) of calibration stock solution, or a serial dilution thereof, 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 with working standards (steps 11 and 12). e. Prepare a graph of DE vs. µg 2-nitropropane recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.

MEASUREMENT: 11.

12.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2528-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE: If peak area is above the linear range of the working standards, dilute an aliquot of the desorbed liquid with ethyl acetate, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area. NOTE: Retention time of 2-nitropropane is ca. 20 min under these conditions.

CALCULATIONS: 13.

14.

Determine the mass, µg (corrected for DE) of 2-nitropropane found in the sample front (W f) and back (W b) sorbent sections, and in the average media blank front (B f) and back (B b) sorbent sections. NOTE: If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of 2-nitropropane in the air volume sampled, V (L):

EVALUATION OF METHOD: Method P&CAM 272 was issued on August 1, 1978. Synthetic atmospheres of the analyte in humidified air were generated dynamically at 25 °C and 745 torr over the range 3.1 to 28.3 mg/m 3 by the vapor pressure saturation/air dilution technique [1]. The concentrations were verified by total hydrocarbon analyzer. A 100-mg bed of acetone-washed sorbent retained 374 µg of analyte before 5% breakthrough occurred at 10.4 L when a challenge atmosphere of 36 mg/m 3 analyte in humid air was sampled at 0.2 L/min. There were no statistically significant differences in the recoveries of 3-L samples collected from synthetic atmospheres containing 4.7 mg/m 3 2-nitropropane in humid air and stored for 1, 7, 14 or 28 days prior to analysis. The 14- and 28-day samples were stored at 0 °C after an initial seven-day storage at ambient temperature. A previous study showed 2-nitropropane to be unstable after collection on activated petroleum-based charcoal [5].

REFERENCES: [1] [2]

Glaser, R. and W. J. Woodfin. A Method for Sampling and Analysis of 2-Nitropropane in Air, Am. Ind. Hyg. Assoc. J., 42: 18-22 (1981). NIOSH Health Hazard Evaluation Report HHE-80-57-781 (1980).

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94