Page:NIOSH Manual of Analytical Methods - 5034.pdf/4

 TRIBUTYL PHOSPHATE: METHOD 5034, Issue 1, dated 15 August 1994 - Page 4 of 4 CALIBRATION AND QUALITY CONTROL: 8.

9.

10.

Calibrate daily with at least six working standards over the range of 2 to 1000 µg per sample. a. Add known amounts of calibration stock solution to 10-mL volumetric flasks and dilute to volume with diethyl ether. b. Analyze working standards together with samples and blanks (steps 11 and 12). This will minimize the effect of variations in FPD response with time. NOTE 1: The FPD response is very sensitive to minor variations in hydrogen flow rate and, therefore, it is recommended that calibration standards be carefully interspersed with the samples. NOTE 2: Use of an internal standard is recommended to minimize errors caused by sample solvent evaporation and FPD response variations. c. Prepare a calibration graph of area vs. µg of tributyl phosphate per 10 mL of sample. Determine recovery in the concentration range of interest for each lot of filters used for sampling. Prepare three filters at each of five levels plus three media blanks. a. Spike aliquot of calibration solution onto each filter. b. After air-drying, extract filters with 10 mL diethyl ether (steps 5 through 7). c. Analyze together with working standards (steps 11 and 12). d. Prepare graph of recovery vs. µg tributyl phosphate. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and recovery graph are in control.

MEASUREMENT: 11.

12.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 5034-1. Inject 5-µL sample aliquot using solvent flush technique or with autosampler. NOTE: If peak area is above linear range of the calibration graph, dilute with diethyl ether, analyze, and apply appropriate dilution factor in calculations. Measure peak area.

CALCULATIONS: 13. 14.

Determine mass, µg (corrected for recovery), of tributyl phosphate found in the sample (W) and the average media blank (B). Calculate concentration of tributyl phosphate in the actual air volume sampled, V (L):

EVALUATION OF METHOD: This method was evaluated over the range 2.7 to 12.6 mg/m 3 at 19 C and pressure of 761 mm Hg with 100-L air samples [1]. Overall sampling and measurement precision, SˆrT, was 0.076. The average collection efficiencies for test concentrations of 12.6 mg/m 3 and 9.3 mg/m 3 were 100.0% and 99.6%, respectively. The average recovery from filters spiked in the range 234 µg to 973 µg per filter was 100.4%. Therefore, there is no significant bias in the method. No tests of sample stability during storage were conducted.

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