TOLUENE-2,4-DIISOCYANATE: METHOD 2535, Issue 2, dated 15 August 1994 - Page 3 of 5 SAMPLE PREPARATION: 5. 6.
Transfer front and back sections of reagent-coated glass wool to separate vials. Add 2 mL methanol. Seal vials. Place vials into ultrasonic bath for 3 min.
CALIBRATION AND QUALITY CONTROL: 7.
8.
Calibrate daily with at least six working standards over the range 0.3 to 80 µg 2,4-TDIU per sample (equivalent to 0.1 to 25 µg 2,4-TDI per sample). a. Prepare a series of standard solutions of 2,4-TDIU in methanol over the range of 0.15 to 40 µg/mL. b. Analyze together with samples and blanks (steps 9 and 10). c. Prepare calibration graph (peak area vs. µg 2,4-TDIU). Determine recoveries from samplers in the range 0.3 to 25 µg 2,4-TDI per sample. Prepare three samples at each of three levels plus three media blanks. NOTE: Recoveries should be quantitative. If recoveries are not quantitative, determine the reason for error. a. Prepare a series of standard solutions of 2,4-TDI in dichloromethane in the range 0.06 to 5 mg/mL. b. Connect a U-tube to the inlet of a sampler with a short piece of tubing. NOTE: The length of tubing should be minimal to prevent losses of TDI by adsorption or reaction on the inside wall of the tubing. c. Connect charcoal sorbent tube to inlet of U-tube (charcoal can adsorb contaminants of air which would react with 2,4-TDI). d. Draw ambient air through the charcoal tube, U-tube, and sampler with a sampling pump at 1 L/min. e. Place 5 µL of a standard solution of 2,4-TDI into the U-tube. f. Allow operation of the pump to continue for 20 min. g. Desorb (steps 5 and 6) and analyze with working standards (steps 9 and 10).
MEASUREMENT: 9. 10.
Establish chromatographic conditions indicated on page 2535-1. Inject sample aliquot manually or with autosampler. Measure peak area.
CALCULATIONS: 11.
12.
Determine the mass (µg) of 2,4-TDIU found on the sample front (W f) and back (W b) sections and in the average media blank front (B f) and back (B b) sections. NOTE: If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of 2,4-TDI in the air volume sampled, V (L):
where 0.310 = MW of 2,4-TDI/MW of 2,4-TDIU.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
