Integrity of VOCs on Thermally Desorbable Solid Adsorbents

Summary

Volatile organic compounds (VOCs) are ubiquisly present in the atmosphere and depending on toxicity and concentration, potential adverse health effects may arise. As a result of these compounds ability to negatively inflict the human organism there is a great need to correctly characterize the atmospheric environments in which humans frequently reside. VOCs can be extracted from air by collection onto solid adsorbents either by diffusion or by pumping air through the sample media followed by solvent or thermal desorption prior to gas chromatographic (GC) determination. Thermal desorption is a technique with many advantages over solvent desorption because of superior sensitivity as the whole sample may be transferred to the GC and as sample treatment is kept to an absolute minimum. The VOCs investigated in this study were methylethylketone (MEK), methylisobutylketone (MIBK), benzene, toluene, perchloroethylene (PER), butylacetate, decane, limonene, - and -pinene. The solid adsorbents Tenax TA, Chromosorb 106 and Carbotrap were first optimized regarding method conditions (conditioning, desorption, calibration) prior to investigations into blank, blank build-up, storage stability (50 ng and 500 ng at 5 ºC and 20 ºC) as a function of time. The analytes were introduced into the GC by means of thermal desorption and detection was performed by mass spectrometry (MS). The blank levels and the blank build up on Carbotrap and Tenax TA have been investigated and found to be excellent with no signs of artefact development over time. Chromosorb 106, however, contains inherently more artefacts that build up over time. The stability of the analytes on the adsorbents over time was investigated and it was found that Chromosorb106 gave the overall best results with recoveries of 90 % or better for all analytes. Tenax TA and Carbotrap gave lower recoveries and were more influenced by variations in time, temperature and concentration. Refrigerated temperatures are best avoidedfor storage on Tenax TA but may increase the recovery of some compounds (e.g. butylacetate) on Carbotrap.