PHOSPHORUS: METHOD 7905, Issue 2, dated 15 August 1994 - Page 3 of 4
9.
10.
range 0.01 to 5 µg/mL. b. Analyze with samples and blanks (steps 11 and 12) c. Prepare calibration graph (peak area vs. µg phosphorus). Determine desorption efficiency (DE) at least once for each batch of Tenax-GC 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 directly onto front sorbent section with a microliter syringe. c. Cap the tub. Allow to stand overnight. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. µg phosphorus 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 7905-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE: If peak area is above the range of the working standards, dilute with xylene, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area.
CALCULATIONS: 13.
14.
Determine the mass, µg (corrected for DE) of phosphorus 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 concentrations, C, of phosphorus in the air volume sampled, V (L):
EVALUATION OF METHOD: Method S334 was issued on November 25, 1977 [2], and validated with generated atmospheres using a solution (11 mg/mL) of phosphorus in tetralin in a calibrated syringe drive, verified by independent collection in xylene [1]. Average recovery was 106% with Sˆr = 7.4% (18 samples) in the range 0.056 to 0.24 mg/m 3 for 12-L samples. In an experiment in which 25-L samples of an atmosphere containing 0.35 mg/m 3 phosphorus vapor were analyzed, the same phosphorus concentration was found in xylenefilled impingers with or without cellulose ester membrane prefilters. Breakthrough (effluent = 5% of test concentration) did not occur after sampling for 240 min at 0.2 L/min from an atmosphere containing 0.311 mg/m 3 at 85% RH. Desorption efficiency for 18 samples in the range 0.6 to 2.4 µg per sample average 95% with Sˆr = 2.6%. The overall precision, SˆrT, including pump error was 0.090.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
