Optimization of a solid sorbent dynamic personal air sampling method for aldehydes

A solid sorbent personal dynamic air sampling method for aldehydes using chemisorption with 20 percent (w/w) O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) on Tenax TA has been optimized for several aldehydes. The method for formaldehyde was developed after optimization for valeraldehyde and acrolein. The effects of temperature, intermittent exposure, and flow rate on sampling efficiency were investigated. Vapors of known concentrations were generated in Tedlar gas bags by syringe injection. Aldehyde chemisorption by reaction with 200-mg coated solid sorbent in a Pyrex Tube (7-cm length, 7-mm OD, and 5-mm ID) occurred during dynamic collection with a personal sampling pump operated at 10, 50, or 100 mL/min. The oxime derivatives were 81-87 percent desorbed by shaking with hexane for two minutes or more, resulting in coefficients of variation ranging between 4-7 percent. Aliquots were then injected for gas chromatographic analysis on a nonpolar capillary column with mass spectrometric or 63Ni electron capture detection. Formaldehyde at 8 ppm-hours equivalent to the permissible exposure limit (PEL) concentration was sampled with a recovery of 94 +/- 4 percent at 50.0 +/- 0.5 mL/min. Valeraldehyde and acrolein at their PELs showed no significant differences (P < 0.05) in recoveries at different relative humidities (1 and 90%), temperatures (1, 25, and 40 degrees C), or intermittent sampling protocol. The sampler capacity at 75 percent recovery was at a PFBHA:aldehyde molar ratio of 12:1 at 10.0 +/- 0.1 mL/min, 17:1 at 50.0 +/- 0.5 mL/min, and 26:1 at 100 +/- 1 mL/min.