ACETALDEHYDE by HPLC: METHOD 3507, Issue 2, dated 15 August 1994 - Page 3 of 4
SAMPLE PREPARATION: 4. Tap bubbler stem lightly against bubbler body to drain contents into the body. If necessary, bring samples up to the 15-mL mark with distilled water. Swirl bubbler to mix contents well. Do not add solution collected in the trap to the sample. 5. Transfer a 5-mL aliquot to a 100-mL flask and bring to volume with HPLC mobile phase. CALIBRATION AND QUALITY CONTROL: 6. Calibrate daily with at least six working standards over the range 0.007 to 4 mg acetaldehyde per mL (0.1 to 60 mg acetaldehyde per sample). a. Add known amounts of calibration stock solution to Girard T solution in 10-mL volumetric flasks and dilute to the mark. Dilute 5 mL of each of these solutions to 100 mL with HPLC mobile phase. Prepare at least two blanks in the same manner. b. Analyze together with samples and blanks (steps 8 and 9). c. Prepare calibration graph (peak area vs. mg acetaldehyde per sample). 7. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph is in control. MEASUREMENT: 8. Set liquid chromatograph according to manufacturer’s recommendations and to conditions given on page 2507-1. Inject 50-µL sample aliquot with injection loop or autosampler. NOTE: If peak area is above the linear range of the working standards, dilute with HPLC mobile phase, reanalyze, and apply the appropriate dilution factor in calculations. 9. Measure peak area. CALCULATIONS: 10. Determine the mass, mg of acetaldehyde found in the sample ( ), and in the average media blank ( ). 11. Calculate concentration, , of acetaldehyde in the air volume sampled, (L): , mg/m³. EVALUATION OF METHOD: Method S345 was issued on March 16, 1979 [2], and validated over the range 170 to 670 mg/m³ at 21 °C and 756 mm Hg using a 60-L sample [1,5]. Overall precision, , was 0.053 with an average recovery of 101.2% representing a non-significant bias. The concentration of acetaldehyde was independently verified by calibrated gas chromatograph. Collection efficiency of a single bubbler was determined to be >0.998 when 61-L air samples were taken at 0.5 L/min in atmospheres containing 670 mg/m³ acetaldehyde. REFERENCES: [1] Backup Data Report, S345, Acetaldehyde, prepared under NIOSH Contract 210-76-0123 (unpublished). [2] NIOSH Manual of Analytical Methods, 2nd ed., Vol. 5, S345, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979). [3] Kuwata, K., M. Uebori and Y. Yamasaki. J. Chromatog. Sci., 17, 264–268 (1979). [4] Lipari, F. and S.J. Swarin. J. Chromatog., 247, 297–306 (1982). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
