TETRAETHYL LEAD (as Pb): METHOD 2533, 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 concentrations 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 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 tetraethyl lead (as Pb) 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 2533-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE 1: Under these conditions, t r = 4.5 min for tetraethyl lead; dodecane elutes later. NOTE 2: If peak area is above the linear range of the working standards, dilute an aliquot of the desorbed liquid with pentane, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area.
CALCULATIONS: 13.
14.
Determine the mass, µg (corrected for DE) of tetraethyl lead (as Pb) 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 tetraethyl lead (as Pb) in the air volume sampled, V (L):
EVALUATION OF METHOD: Method S383 was issued on March 18, 1977 [2], and validated with generated atmospheres in the range 0.045 to 0.2 mg/m 3 for eighteen 120-L samples [1,4]. Partial breakthrough (effluent = 2.5% of test concentration) occurred after sampling for 240 min at 1.0 L/min from an atmosphere containing 0.156 mg/m 3 tetraethyl lead (as Pb) at 90% RH. Desorption efficiency for eighteen spiked samples in the range 4.3 to 17 µg tetraethyl lead (as Pb) averaged 1.05 with S r = 0.04.
REFERENCES: [1]
[2] [3]
A.D. Little, Inc. Backup Data Report S383 prepared under NIOSH Contract 210-76-0123 (unpublished, 1976), available as "Ten NIOSH Analytical Methods, Set 3," Order No. PB-275834 from NTIS, Springfield, VA 22161. NIOSH Manual of Analytical Methods, 2nd ed., Vol. 4, S383, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-175 (1978). NIOSH/OSHA Occupational Health Guidelines for Chemical Hazards, U.S. Department of Health and Human Services, Publ. (NIOSH) 81-123 (1981), available as Stock #PB83-154609 from NTIS, Springfield, VA 22161. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
