Page:NIOSH Manual of Analytical Methods - 1012.pdf/2

 DIFLUORODIBROMOMETHANE: METHOD 1012, Issue 2, dated 15 August 1994 - Page 2 of 4

EQUIPMENT:

REAGENTS: 1.	2-Propanol, chromatographic grade. 2.	Difluorodibromomethane.* 3.	Nitrogen, purified. 4.	Hydrogen, prepurified. 5.	Air, filtered, compressed.
 * See SPECIAL PRECAUTIONS.

1.	Sampler: two glass tubes in series, each with both ends flame sealed, 7 cm long, 6-mm OD, 4-mm ID, each containing 150 mg of 20/40 mesh activated (600 °C) coconut shell charcoal; four plastic caps for sealing after use. A silylated glass wool plug precedes the charcoal beds and a 3-mm urethane foam plug follows the charcoal beds. NOTE:	A pair of two-section (100 mg/50 mg) tubes may be used. 2.	Personal sampling pump, 0.01 to 0.2 L/min, with flexible connecting tubing. 3.	Gas chromatograph, FID, integrator, and column (page 1012-1). 4.	Vials, 2-mL, glass, with PTFE-lined septa and crimp seals. 5.	Syringe, 10-µL, readable to 0.1 µL. 6.	Volumetric flask, 10-mL. 7.	Pipets, 1.0-mL. 8.	Cold room or cold box for preparing standards at 0 °C or lower. 9.	Syringes, gas-tight, 10- and 100-µL.

SPECIAL PRECAUTIONS: Difluorodibromomethane does not have adequate warning properties [3]. SAMPLING: 1.	Calibrate each personal sampling pump with a representative sampler in line. 2.	Break the ends of the front and back sorbent tubes immediately before sampling. Connect the tubes with a short piece of plastic tubing and attach sampler to personal sampling pump with flexible tubing. 3.	Sample at an accurately known flow rate between 0.01 and 0.2 L/min for a total sample size of 2.5 to 10 L. 4.	Separate the two sorbent tubes. Cap the ends of each tube with plastic (not rubber) caps and pack securely for shipment. 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. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition