Page:NIOSH Manual of Analytical Methods - 2003.pdf/3

 1,1,2,2-TETRABROMOETHANE: METHOD 2003, Issue 2, dated 15 August 1994 - Page 3 of 4 SAMPLE PREPARATION: 5. 6. 7.

Place the front and back sorbent sections of the sampler tube in separate vials. Discard the glass wool and foam plugs. Add 1.0 mL THF to each vial. Attach crimp cap to each vial. Allow to stand 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 8.

9.

10.

Calibrate daily with at least six working standards over the range 0.1 to 4 mg 1,1,2,2-tetrabromoethane per sample. Working standard should be prepared fresh daily. a. Add known amounts of calibration stock solution to THF in 10-mL volumetric flasks and dilute to the mark. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (peak area or height vs. mg 1,1,2,2-tetrabromoethane). Determine desorption efficiency (DE) at least once for each batch of silica gel used for sampling in the calibration range (step 8). Prepare three tubes at each of five levels plus three media blanks. a. Place aliquots of DE stock solution into a U-tube partly immersed in a temperature bath at about 75 °C, and draw air through the U-tube into media blank samplers with a pump at 0.2 to 1 L/min. NOTE: Although values of DE for the original method [2] are based on liquid spikes, values of DE should be determined for vapor spikes. Values of DE for liquid and vapor spikes may be different [4]. b. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). NOTE: If breakthrough occurs with the vapor spikes, determine DE using liquid spikes. c. Prepare a graph of DE vs. mg 1,1,2,2-tetrabromoethane recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph is in control.

MEASUREMENT: 11.

12.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2003-1. 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 THF, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak area or peak height.

CALCULATIONS: 13.

14.

Determine the mass, mg (corrected for DE) of 1,1,2,2-tetrabromoethane 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 1,1,2,2-tetrabromoethane in the air volume sampled, V (L):

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94