Characterization of quality assurance properties of biogenic volatile organic compounds with an emphasis on the breakthrough behavior, recovery, and temporal stability

Abstract

In this research, we investigated the breakthrough volume (BTV) and temporal performance of two types of sorbent tube (ST) sorbent beds toward 10 (target) biogenic volatile organic compounds (BVOCs) ((1) isoprene, (2) (+)-alpha-pinene, (3) camphene, (4) (+)-beta-pinene, (5) (+)-3-carene, (6) alpha-phellandrene, (7) alpha-terpinene, (8) (R)-(+)-limonene, (9) gamma-terpinene, and (10) p-cymene) and two (reference) anthropogenic volatile organic compounds (AVOCs) ((11) benzene and (12) toluene). The analysis of their vaporized liquid-phase working standards was carried out using thermal desorption-gas chromatography-mass spectrometry (TD-GC/MS). To this end, the performance of two ST types (CC (Carbopack C) and CBX (Carbopack C, Carbopack B, and Carbopack X)) was tested as a function of a few key variables, e.g., sorbent type, N-2 gas purge volume, and sampling temperature. The CBX ST gave recoveries of 100 +/- 10% at 60 degrees C for two BVOCs (camphene and alpha-terpinene). However, three compounds (isoprene, (+)-alpha-pinene, and (+)-beta-pinene) showed poor recoveries (0.7,59.3, and 11.3%,respectively), whilst p-cymene recorded an excess recovery (similar to 190%). In contrast, for the CC ST, BT for (+)-alpha-pinene and camphene increased with purge volume, while isoprene was not detected. Accordingly, the range of BTV5% and BTV50% values (L/g) for each compound with CC ST were 1.7 (toluene)-17 (camphene) and 15 (toluene) -570 ((+)-alpha-pinene), respectively. In summary, a three-bed CBX with the higher BTV is the preferred choice for environmental sampling for a wide range of BVOCs compared to a one-bed CC ST. The recovery of CBX ST for 10 out of 12 analytes (after >150 reconditioning/loading/TD cycles) remained constant in terms of response factor, while the response factors of isoprene and beta-pinene were highly variable. Both the present work and the reported literature recoveries showed similar and divergent results which are discussed in terms of high temperature on-sorbent reactions.