Low temperature headspace desorption of volatile organic compounds trapped in air sampling solid-supports

Abstract

Environmental context. The monitoring of volatile organic compounds (VOCs) in air is of great importance for air quality on both local and global scales. The determination of VOCs can be carried out by gas chromatography–mass spectrometry (GC-MS) after active or passive sampling and (high temperature) thermal desorption. An attractive alternative would be to combine GC-MS with headspace (HS) systems as it allows simpler, faster, low temperature desorption. We present here the first report of HS-GC-MS for the determination of VOCs in air sampled using solid supports. Abstract. The use of a headspace (HS) for low temperature desorption of VOCs, previously sorbed from indoor air on solid supports, has been evaluated in order to improve the GC-MS determinations in environmental studies. Graphitised carbon black (GCB), Porapak and Tenax were considered in this study. The HS injector does not allow temperatures higher than 150°C, so there is no a complete desorption of VOCs. However highly volatile compounds were completely desorbed from Porapak and Tenax, but compounds of low volatility showed a strong retention with recoveries of 71–100% for Porapak and 59–100% for Tenax. All studied VOCs were quantitatively desorbed from GCB. Only 100 μL of the HS volume is injected in the chromatographic system. So in spite of the reduced sensitivity we are able to make replicate analyses on the same sampler. Additional experiments were performed using the proposed methodology for the analysis of aforementioned supports in passive and active sampling modes. In short, the proposed methodology reduces the energy consumed and makes it possible to determine the VOCs in air with reduced cost media. The developed methodology permits the determination of 32 VOCs with limits of detection values around 1 μg m–3 when actively sampling air at 50 mL min–1 for 2 h and using 100 mg solid sorbent.