POLYCHLOROBENZENES: METHOD 5517, Issue 2, dated 15 August 1994 - Page 3 of 5 SAMPLE PREPARATION: 5. 6. 7. 8.
Place filter in one vial, front glass wool plug and sorbent section in another vial, and rear sorbent section and enclosing glass wool plugs in third vial. Add 2.0 mL hexane to each vial. Cap each vial. Allow to stand 30 min with ultrasonic agitation. Wash inside surfaces of filter holder with 2 to 3 mL hexane. Transfer washings to 5-mL volumetric flask and dilute to mark with hexane.
CALIBRATION AND QUALITY CONTROL: 9.
10.
11.
Calibrate daily with at least six working standards over the linear range of the detector. a. Prepare working standards by serial dilution of the calibration stock solution. b. Analyze together with samples and blanks (steps 12 and 13). c. Prepare calibration graph for each analyte (peak height or area vs. µg/mL analyte). Determine desorption efficiency (DE) over range of interest at least once for each lot of filters and sorbent used. Prepare three samplers at each of five levels plus three media blanks. a. Prepare known concentrations of the analytes in hexane. b. Inject a 5-µL aliquot directly onto the filter of an assembled sampler with a microliter syringe while drawing 12 L of analyte-free air through the sampler at 0.2 L/min. c. Separate filter holder and sorbent tube, seal, and allow to stand overnight. d. Desorb (steps 5 through 8) and analyze together with working standards (steps 12 and 13). NOTE: Significant amounts should be found on the filters and holders only at the higher loadings. See EVALUATION OF METHOD. e. Prepare graph of DE vs. µg of each analyte recovered. DE is the sum of amounts recovered from filter, holder, and sorbent sections divided by the amount taken. Analyze three quality control blind spikes and three analyst spikes to ensure that calibration graph and DE graph are in control.
MEASUREMENT: 12.
13.
Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 5517-1. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE 1: Under these conditions, approximate t rs are: 1,2,4-trichlorobenzene, 2.0 min; 1,2,4,5-tetrachlorobenzene, 3.3 min; pentachlorobenzene, 7.5 min. NOTE 2: If peak area is above range of working standards, dilute with hexane, reanalyze and apply appropriate dilution factor in calculations. Measure peak height or area.
CALCULATIONS: 14. 15.
16.
Determine the concentration, µg/mL, for each analyte, and multiply by the desorption volume, mL, and the dilution factor, if any, to calculate the mass, µg, recovered. Add the amounts recovered from filter, filter holder, sorbent front (W f), and sorbent back (W b) sections to determine the mass found in a field sample (W) or the average sampler blank (B), and correct for DE. NOTE: If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of each analyte in air volume sampled, V (L):
EVALUATION OF METHOD:
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
