POLYNUCLEAR AROMATIC HYDROCARBONS by GC: METHOD 5515, Issue 2, dated 15 August 1994 - Page 4 of 7
10.
sorbent section and the middle glass wool plug to a second culture tube. c. Add 5.0 mL toluene to each culture tube. Cap the culture tubes. d. Allow samples to stand for 30 min. Swirl occasionally. Filter all sample extracts through an 0.45-µm membrane filter.
CALIBRATION AND QUALITY CONTROL: 11.
12.
13.
Calibrate daily with at least six working standards. a. Dilute aliquots of calibration stock solution with toluene in 10-mL volumetric flasks (e.g., to 5, 1, 0.2, 0.05, and 0.005 µg/mL). b. Intersperse working standards and samples in the measurements. c. Prepare calibration graphs (peak area vs. µg of each PAH per sample). Recovery and desorption efficiency. a. Determine recovery (R) from filters and desorption efficiency (DE) from sorbent tubes at least once for each lot of filters and sorbent tubes used in the range of interest. (1) Filters. Using a microliter syringe or micropipette, spike four filters at each of five concentration levels with calibration stock solution. Allow the filters to dry in the dark overnight. Analyze the filters (steps 8, 10, and 14 through 16). Prepare graphs of R vs. amounts found. NOTE: This step may not be used for some highly adsorptive particulate matrices for which calibration by the method of standard additions may be more accurate. (2) Sorbent tubes. Transfer an unused front sorbent section to a culture tube. prepare a total of 24 culture tubes in order to measure DE at five concentration levels plus blanks in quadruplicate. Using a microliter syringe or micropipette, add calibration stock solution directly to sorbent. Cap culture tubes and allow to stand overnight in the dark. Analyze (steps 9, 10, and 14 through 16). Prepare graphs of DE vs. amounts found. b. Check R and DE at two levels for each sample set, in duplicate. Repeat determination of R and DE graphs if checks do not agree to within ±5% of DE graph. Analyze at least three field blanks for each sample medium.
MEASUREMENT: 14. 15. 16.
Set GC according to manufacturer's recommendations and to the conditions on page 5515-1. Inject sample aliquot. Start temperature program. Measure peak areas. NOTE 1: Approximate retention times appear in Table 4. NOTE 2: If peak area is above the calibration range, dilute with appropriate solvent, reanalyze, and apply dilution factor in calculations. NOTE 3: If sample has many interferences, additional sample cleanup may be necessary. Many cleanup procedures have been published. Liquid-liquid partitioning between cyclohexane and nitromethane [6,7] is widely used, but other techniques may be more appropriate for specific samples.
CALCULATIONS: 17.
18.
Read the mass, µg (corrected for R or DE) of each analyte found on the filter (W) and front sorbent (W f) and back sorbent (W b) sections, and on the average media blank filter (B) and front sorbent (B f) and back sorbent (B b) sections from the calibration graphs. Calculate concentration, C (mg/m 3), in air as the sum of the particulate concentration and the vapor concentration using the actual air volume sampled, V (L).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
