ACROLEIN: METHOD 2501, Issue 2, dated 15 August 1994 - Page 3 of 4 CALIBRATION AND QUALITY CONTROL: 9.
Calibrate daily with at least six standards covering the range of the samples. a. Weigh ten 120-mg portions of the coated sorbent into 4-mL vials with septum caps. If the bulk coated sorbent is not available, remove the front section from 10 unused samplers (media blanks). b. Inject aliquots of the calibration stock solution into the vials at six different levels and allow to stand overnight at room temperature. Prepare two standards at each level. c. Desorb (steps 7 and 8) and analyze together with samples and blanks (steps 10 and 11). d. Prepare calibration graph (peak area or height vs. concentration of acrolein, µg/mL). NOTE: The calibration procedure used in this method does not require a desorption efficiency (DE) correction to be made. If DE is needed, see the APPENDIX.
MEASUREMENT: 10. Set gas chromatograph to conditions given on page 2501- 1. Set air and hydrogen flows on the nitrogen specific detector to manufacturer's specifications. Inject 1-µL sample aliquot. 11. Measure peak area or peak height. Acrolein derivative t r = 3.6 min and t r for 2-(hydroxymethyl)piperidine = 10.7 min for these conditions. CALCULATIONS: 12. Read the µg/mL of acrolein found in the sample front (W f) and back (W b) sorbent sections from the calibration graph and multiply by the desorption volume, 2 (mL). Calculate concentration, C (mg/m 3), of acrolein in the air volume sampled, V (L): NOTE: Because the working standards are prepared on media blanks, no additional blank correction is necessary.
EVALUATION OF METHOD: The method was evaluated over the range of 0.12 to 1.5 mg/m 3 using 24-L samples. Average desorption efficiencies were ca. 1.0 for all levels studied. Mean recovery was 107%, representing an insignificant bias in the method [1]. Concentration of the generated acrolein vapor was independently verified by a modification of P&CAM 211 by Shell Development Co. [3]. No breakthrough was observed for an 8-h sample at 0.10 L/min (48 L) of a 4.5 mg/m 3 of acrolein at 80% RH. The method has been used by three separate analysts at NIOSH and no intralaboratory bias was observed. Measurement precision ( Sr) was not determined. Overall accuracy was ± 29%; therefore, the method does not meet the ± 25% criterion for a valid method. REFERENCES: [1] Kennedy, E.R., O'Connor, P.F., Gagnon, Y.T. "Determination of Acrolein in Air as an Oxazolidine Derivative by Gas Chromatography," Anal. Chem. 56(12):2120-2123 (1984). [2] NIOSH Manual of Analytical Methods, 2nd ed., V. 1, P&CAM 118 and 211, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-A (1977). [3] Shell Development Company Analytical Department. Determination of Acrolein in Air, Bubbler/Colorimetric Method, SRC 11A11/79, Shell Development Company Westhollow Research Center. METHOD WRITTEN BY: Eugene R. Kennedy, Ph.D. and Paula Fey O'Connor, NIOSH/DPSE. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
