ETHYL ACETATE: METHOD 1457, Issue 2, dated 15 August 1994 - Page 3 of 4 9.
10.
11.
Determine desorption efficiency (DE) at least once for each lot of charcoal used for sampling in the calibration range (step 8). Prepare three tubes at each of five concentrations plus three media blanks. Determine desorption efficiency (DE) for each lot of charcoal tubes used for sampling in the calibration range (step 9). a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount 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 together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. µg ethyl acetate recovered. Analyze three quality control blind spikes and three analyst spikes to insure that the calibration graph and DE graph are in control.
MEASUREMENT: 12.
13.
Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 1457-1. 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 with CS 2, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak area.
CALCULATIONS: 14.
15.
Determine the mass, µg (corrected for DE), of ethyl acetate 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 ethyl acetate in the air volume sampled, V (L), at the sampling site:
EVALUATION OF METHOD: Method S49 [2] was evaluated over the range of 704 to 2950 mg/m 3 for 6-L samples at 23 °C and a pressure of 759 mm Hg. The overall sampling and analytical precision ( SˆrT) was 0.058 with an average recovery of 97.9% and the breakthrough capacity was found to be 25 mg of ethyl acetate [5]. The method was updated later for a lower range (40.5 to 810 µg/sample) with a capillary column [1]. Desorption efficiencies ranged from 44.5% to 87.5% with an analytical precision ( Sr) of 0.058. Samples of ethyl acetate on coconut charcoal are stable for 6 days at 5 °C with a recovery of 91.0% based on samples analyzed immediately after collection [1].
REFERENCES: [1] [2]
S.M. Pendergrass, Ethyl Acetate Method Development (unpublished report), NIOSH/MRSB, 1990, NIOSH Seq. Report 7716-F (unpublished, Feb. 5, 1993). NIOSH Manual of Analytical Methods, 2nd ed., V. 2, S49, U.S. Dept. of Health, Education, and Welfare, Publ. (NIOSH) 77-157B (1977).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
