DIOXANE: METHOD 1602, Issue 2, dated 15 August 1994 - Page 3 of 4 a.
9.
10.
Add known amounts of dioxane to eluent in 10-mL volumetric flasks and dilute to the mark. By serial dilution, prepare solutions containing 0.01 to 7 mg dioxane/mL. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (ratio of peak area of analyte to peak area of internal standard vs. mg dioxane). 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 levels plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount (1 to 20 µL) of dioxane or DE 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. mg dioxane 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 1602-1. 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 eluent, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak area. Divide the peak area of analyte by the peak area of internal standard on the same chromatogram.
CALCULATIONS: 13.
14.
Determine the mass, mg (corrected for DE) of dioxane 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 dioxane in the air volume sampled, V (L):
EVALUATION OF METHOD: Method S360 [4] was issued on March 14, 1975, and validated over the range 155 to 651 mg/m 3 using atmospheres generated by calibrated syringe pump [1]. Desorption efficiency averaged 0.88 in the range 1.8 to 7.3 mg dioxane per sample. Breakthrough was observed when a test atmosphere containing 651 mg/m 3 of dioxane in dry air was sampled at 0.19 L/min for 210 min (40-L air sample volume). The front section held 26 mg of dioxane. Precision and accuracy are listed on page 1602-1. A similar method, without internal standard, was collaboratively tested in the range 6 to 190 ppm dioxane [2,8].
REFERENCES: [1] Documentation of the NIOSH Validation Tests, S360, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185 (1977), available as GPO Stock #017-033-00231-2 from NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
