Page:NIOSH Manual of Analytical Methods - 5043.pdf/3

 p-TOLUENESULFONIC ACID: METHOD 5043, Issue 1, dated 15 January 1998 - Page 3 of 4 Prepare three filters at each of five concentration levels plus three media blanks. a. Place 13-mm glass fiber filters into 4-mL vials. b. With a microliter syringe, fortify each filter with a known amount of the calibration stock solution. c. Allow the uncapped vials to stand overnight at room temperature. d. Prepare and analyze with working standards (steps 5 through 8, and steps 12 and 13). e. Prepare graph of R vs. µg of analyte recovered. 11. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration and recovery graphs are in control.

MEASUREMENT: 12. Set high performance liquid chromatograph to manufacturer’s recommendations and to conditions given on page 5043-1. Inject 100-µL aliquot manually or with autosampler. NOTE: If peak area is above the range of the working standards, dilute with desorbing solution, reanalyze, and apply appropriate dilution factor in calculations. 13. Measure peak area or height forp-toluenesulfonic acid.

CALCULATIONS: 14. Determine the mass, µg (corrected for R), of analyte found on the filter (W) and the average media blank (B). 15. Calculate the concentration, C, ofp-toluenesulfonic acid in the air volume sampled, V (L):

C

W

B V

, mg/m 3

EVALUATION OF METHOD: Average recoveries ofp-toluenesulfonic acid after fortification of 13-mmglass fiber filters with 3-, 6-, 10-, and 15-µg quantities of the compound were 1.02, 0.96, 1.04 and 0.96, respectively; precision r was 0.046 (23 samples, pooled). After 29 days of storage at room temperature, the average recovery of 3-µg quantities of p-toluenesulfonic acid from glass fiber filters was 1.03; rSwas 0.023 (5 samples). The purpose of the 2% isopropanol in samples and standards was to prevent possible deterioration of p-toluenesulfonic acid by bacteria during storage.

ALTERNATIVE METHOD: As an alternative to the glass fiber filters, air samples ofp-toluenesulfonic acid canbe collected in midget impingers containing isopropanol at 1 L/min. After sampling, the impinger solution is transferred to a 20-mL glass vial and transported to the laboratory. The vial is placed onto a heating plate maintained at 80C, and the isopropanol is evaporated to dryness with a gentle stream of nitrogen (total evaporation time is about 1.5 hours). A 2-mL aliquot of 2% isopropanol in water is added to the vial, and the vial is placed into an ultrasonic bath for 30 seconds. Then the vial is tilted in order to wet the inside wall of the vial. Solution is filtered through a PTFE membrane syringe filter and is ready for analysis according to the method described above.

EVALUATION OF ALTERNATIVE METHOD: Isopropanol was found to evaporate from the midget impinger during air sampling. Air at room temperature was drawn at 1 L/min through an impinger containing 20 mL of isopropanol. After 1 hour of pump operation, NIOSH Manual of Analytical Methods (NMAM), Fourth Edition