TRIORTHOCRESYL PHOSPHATE: METHOD 5037, Issue 1, dated 15 August 1994 - Page 3 of 4
9.
10.
NOTE: Triorthocresyl phosphate is very viscous and thus difficult to measure with a microliter syringe. b. Add known amounts of calibration stock solution to 10-mL volumetric flasks and dilute to volume with diethyl ether. c. 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. d. Prepare a calibration graph of area vs. µg of triorthocresyl 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 triorthocresyl 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 5037-1. Inject 5-µL sample aliquot using solvent flush technique or with an autosampler. NOTE: If peak area is above the 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 triorthocresyl phosphate found in the sample (W) and the average media blank (B). Calculate concentration (C) of triorthocresyl phosphate in the actual air volume sampled, V (L):
EVALUATION OF METHOD: This method was evaluated over the range 29 to 170 µg/m 3 at 19 °C and pressure of 761 mm Hg with 100-L air samples [1]. Overall sampling and measurement precision, SˆrT, was 0.086. The average collection efficiencies for test concentrations of 0.17, 0.19, and 3.8 mg/m 3 were 98.8%, 98.7%, and 99.5%, respectively. The average recovery from filters spiked in the range 5.85 µg to 23.4 µg per filter was 101.3%. Therefore, there is no significant bias in either the sampling or analytical method. No tests of sample stability during storage were conducted.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
