Page:NIOSH Manual of Analytical Methods - 1020.pdf/3

 1,1,2-TRICHLORO-1,2,2-TRIFLUOROETHANE: METHOD 1020, Issue 2, dated 15 August 1994 - Page 3 of 4

9.	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 TTE or a standard solution of TTE in CS2 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. mg TTE. 10.	Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control. MEASUREMENT: 11.	Set gas chromatograph according to manufacturer’s recommendations and to conditions given on page 1020-1. 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 CS2, reanalyze, and apply the appropriate dilution factor in calculations. 12.	Measure peak area. CALCULATIONS: 13.	Determine the mass, mg (corrected for DE) of TTE found in the sample front and back sorbent sections, and in the average media blank front and back  sorbent sections. NOTE:	If >  /10, report breakthrough and possible sample loss. 14.	Calculate concentration,, of TTE in the air volume sampled, (L): , mg/m³. EVALUATION OF METHOD: Method S129 was issued on May 9, 1975 [3], and validated with generated atmospheres using calibrated syringe drive and independent verification by gas chromatography [2]. Average recovery was 100.3% (18 samples) in the range 3300 to 14200 mg/m³ for 1.5-L samples. Breakthrough (effluent = 5% of test concentration) occurred after sampling for 60 min at 0.046 L/min from an atmosphere containing 14500 mg/m³ 1,1,2-trichloro-1,2,2-trifluoroethane in dry air. Desorption efficiency for 18 samples of SKC lot 105 activated coconut charcoal spiked with 5.6 to 23 mg 1,1,2-trichloro-1,2,2-trifluoroethane averaged 1.01 with = 0.02. Sample stability was not determined. REFERENCES: [1]	 Pendergrass, S.M., Method Development Efforts, NIOSH/DPSE Analytical Sequence #6937, 6956, and 6916A (unpublished) NIOSH/MRSB (1989). [2]	 Documentation of the NIOSH Validation Tests, S129, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185 (1977), available as Stock No. PB 274-248 from NTIS, Springfield, VA 22161. [3]	 NIOSH Manual of Analytical Methods, 2nd ed., Vol. 2, S129, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-B (1977).

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition