MEK, TOLUENE, and ETHANOL in blood: METHOD 8002, Issue 2, dated 15 August 1994 - Page 3 of 4
CALIBRATION AND QUALITY CONTROL: 7.
8.
9. 10.
11.
Prepare working standard solutions. Pipet 2 mL from each of the calibration stock solutions into separate 200-mL volumetric flasks. Dilute to the mark with deionized water. The resultant concentrations are 38.1 and 38.6 µg/mL for toluene and MEK, respectively; and 1.58 mg/mL for ethanol. Prepare fresh standards every 92 h. Make blood standards at 5 different concentrations ranging from 0 to 8 µg MEK and toluene/mL blood and from 0 to 500 µg ethanol/mL blood. Add aliquots of the working standards to 2 mL blood with a microliter syringe. Prepare fresh blood standards every 92 h and store at 4 °C. Analyze the blood standards (steps 3 through 6 and 12 through 14). Plot the concentrations (µg/mL) vs. the ratio of the peak areas of each analyte to the peak areas of the internal standard (isobutanol) on the same chromatogram to establish the calibration graph. Include a blood control with each run.
MEASUREMENT: 12. 13.
14.
Heat the sealed vial in a block heater at 60 °C for 15 min. Remove a 1-mL aliquot of the head space vapor inside the sealed vial with a heated 60 °C gastight syringe and inject into the gas chromatograph. NOTE: Temperature control of blood and syringe is very important for accurate results. Heat the gas-tight syringe to 60 °C in an oven. Measure the peak areas. Divide the peak area for each analyte by the peak area for the internal standard on the same chromatogram.
CALCULATIONS: 15.
Determine the concentrations of MEK, toluene, and ethanol in blood from the calibration graph.
GUIDES TO INTERPRETATION: 1. Blood-alcohol analyses are usually reported in mg/dL or % w/v blood alcohol concentration (BAC). Thus, a BAC may be reported as 300 µg/mL or 30 mg/dL, or 0.03 g/dL, or 0.03% w/v. Legal blood alcohol concentrations are reported in reference [3]. 2. Single toluene inhalation exposures of 50 and 100 ppm in air for 3 h produced average blood (human) toluene concentrations of 1.6 and 3.9 ppm, respectively [4]. Another study reported blood toluene levels ranging from 4.1 to 7.3 ppm for exposure to 200 ppm toluene in air [5]. 3. The Biological Exposure Index for toluene is 1 mg/L in end-of-shift venous blood [6].
EVALUATION METHOD: 1. Ten spiked replicate blood samples at the blood concentration of 1 µg/mL for MEK and toluene and 10 µg/mL for ethanol were analyzed. The precision data obtained for each analyte were 9.5, 9.8, and 5.6%, respectively. 2. Average recoveries of 10 replicate blood samples for MEK, toluene and ethanol were 90, 93 and 98%, at 3 µg/mL of MEK, 2 µg/mL toluene, respectively, and 0.05 mg/mL of ethanol, respectively, in pooled blood.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
