GLYCIDOL: METHOD 1608, Issue 2, dated 15 August 1994 - Page 3 of 4
9.
10.
c. Prepare calibration graph (peak area vs. mg glycidol). Determine desorption efficiency (DE) at least once for each batch of charcoal used for sampling in the calibration range (step 8). 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 of glycidol directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight in refrigerator at 4 °C. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. mg glycidol recovered. Analyze three quality control blind spikes and three analyst spikes to insure 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 1608-1. 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 tetrahydrofuran, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area.
CALCULATIONS: 13.
14.
Determine the mass, mg (corrected for DE) of glycidol 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 glycidol in the air volume sampled, V (L):
EVALUATION OF METHOD: Method S70 was issued on February 14, 1975 [2], and validated over the range 73 to 310 mg/m 3 at 21 °C and 768 mm Hg using a 50-L sample [1]. Overall precision, SˆrT was 0.080 with an average recovery of 0.953, representing a non-significant bias. The concentration of glycidol was independently verified using a total hydrocarbon analyzer calibrated with gas mixtures of glycidol in air. Desorption efficiency was 0.92 in the range 3.8 to 15.0 mg per sample. Desorption efficiencies using carbon disulfide or methylene chloride were much lower. Samples appeared unstable at room temperature. The breakthrough volume (where the concentration of glycidol in the effluent from the 100-mg charcoal bed was 5% of that in the influent) was 152 L; this was determined by sampling dry air containing 300 mg/m 3 glycidol at 0.93 L/min.
REFERENCES: [1]
[2] [3]
Documentation of the NIOSH Validation Tests, S70, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185 (1977), available as GPO Stock #017-033-00231-2 from the Superintendent of Documents, Washington, DC 20402. NIOSH Manual of Analytical Methods, 2nd. ed., V. 2, S70, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-B (1977). Occupational Health Guidelines for Chemical Hazards, Glycidol, U.S. Department of Health and Human Services, Publ. (NIOSH) 81-123 (1981), available as GPO Stock #017-033-00337-8 from NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
