National Institute for Occupational Safety and Health

“ SAMPLE PREPARATION: 5.
Place the charcoal from the front and back sorbent tubes in separate vials. Discard the glass wool and foam plugs. 6.
Add 1.0 mL 2-propanol to each vial. Attach crimp cap to each vial. 7.
Allow to stand overnight with occasional agitation. CALIBRATION AND QUALITY CONTROL: 8.
Calibrate daily with at least five working standards over the range 0.4 to 20 mg dibromodifluoro­ methane per sample. NOTE:
Prepare the working standards in a cold room or cold box. a. Add known amounts of cold (<0 °C) difluorodibromomethane to 2-propanol in 10-mL volumetric flasks and stopper. ”

“ 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 2-propanol, reanalyze, and apply the appropriate dilution factor in calculations. 12. ”

“ NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition DIFLUORODIBROMOMETHANE: METHOD 1012, Issue 2, dated 15 August 1994 - Page 3 of 4
b. Allow standards to come to room temperature, and dilute to the mark. c. Analyze together with samples and blanks (steps 11 and 12) . d. Prepare calibration graph (peak area vs. mg difluorodibromomethane) . 9.
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. a. ”