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 PHENOL and p-CRESOL in urine: METHOD 8305, Issue 2, dated 15 August 1994 - Page 3 of 4 11. Transfer ca. 0.5 mL of the clear ether layer to a culture tube. Add a few milligrams of Na mix. Cap the tube and keep it at 0 °C prior to measurement to avoid evaporation.

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CALIBRATION AND QUALITY CONTROL: 12. Calibrate daily with combined working standards containing 0.5 to 300 µg phenol/mL solution and 0.5 to 500 µg p-cresol/mL solution. a. Add known amounts of phenol and p-cresol calibration stock solutions to pooled control urine in 100-mL volumetric flasks and dilute to the mark with pooled control urine. b. Process 5 mL of each working standard using the same procedure as for the samples (steps 6 through 11). c. Analyze working standards with urine samples and pooled control urines. d. Plot separate calibration graphs for phenol and p-cresol (ratio of peak area of analyte to peak area of nitrobenzene vs. µg analyte/mL solution).

MEASUREMENT: 13. Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 8305-1. Inject an aliquot of the extract from step 11 using solvent flush technique. 14. Measure peak areas. Divide the peak areas of phenol and p-cresol by the peak area of nitrobenzene on the same chromatogram.

CALCULATIONS: 15. Determine the phenol and p-cresol concentrations (µg/mL) in the urine sample from the calibration graphs. 16. Calculate the concentrations of phenol and p-cresol per gram of creatinine in the urine sample by dividing by the creatinine value obtained in step 5. Compare the results obtained on the pre- and post-shift samples for each worker.

GUIDES TO INTERPRETATION: The normal range for phenol found in this laboratory for human controls not exposed to benzene, phenol, or p-cresol was 4.5 to 20.7 mg phenol/g creatinine. The normal range found for p-cresol was 5.5 to 65 mg/g creatinine. It must be emphasized that laboratories should establish their own normal ranges using urine specimens from personnel not exposed to benzene, phenol, p-cresol or excessive amounts of dietary sodium benzoate (used as a preservative in some foods). Lauwerys [6] reported "tentative maximum permissible values" of 45 mg phenol/g creatinine for benzene exposures and 300 mg phenol/g creatinine for phenol exposures. No values were reported for p-cresol. The ACGIH Biological Exposure Index is 250 mg phenol/g creatinine [7].

EVALUATION OF METHOD: Ten spiked urine specimens containing phenol and p-cresol at concentrations of 10 and 50 µg/mL urine, respectively, were analyzed for each analyte. Precision ( Sr) for the ten spiked replicate urine samples was 0.128 for phenol and 0.091 for p-cresol.

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