Collection and Analysis of Airborne Carbonyls by On-Sorbent Derivatization and Thermal Desorption

摘要

The most commonly used method for analysis of airborne carbonyls is to collect the analytes on solid sorbents coated with a suitable derivatization agent, followed by solvent desorption and liquid injection for analysis by High Pressure Liquid Chromatography. We have explored a new approach by combining on-sorbent derivatization and thermal desorption to measure airborne carbonyls. Two derivatization agents, O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) and pentafluorophenylhydrazine (PFPH), are tested for their suitability for collecting carbonyls in the air. The derivatization agents are coated onto Tenax sorbent particles packed in a tube with identical dimensions to those of a Gas Chromatography (GC) injector liner. After sample collection, the carbonyl derivatives are released by in-injection port thermal desorption to a GC column for separation followed by mass spectrometric detection. The collection efficiencies of gaseous carbonyls, including formaldehyde, acetaldehyde, acrolein, benzaldehyde, 2-furfural, glyoxal, and methylglyoxal, at ppbv levels vary with the sampling flow rate and the amount of derivatization agent coating. PFBHA at ～127 nmol per tube collects the carbonyls with >92% collection efficiency at a flow rate of 20 ml/min. PFPH collects the airborne carbonyls more efficiently than PFBHA at the same flow rate. At a flow rate as high as 55 mL/min, PFPH at ～510 nmol per tube collects the carbonyls with >93% collection efficiency. The derivatization agents are thermally desorbed and eluted from the GC column without compromising the determination of any carbonyl derivatives at the levels used. Detection limits of low ppbv to sub-ppbv are achieved using the PFBHA coated sampling tubes for a sample air volume of 4.8 liters. This method is less labor intensive than the solvent desorption technique and avoids use of organic solvents.