Volatile organic compounds (VOCs) are compounds that evaporate easily at room temperature and have a boiling point less than 200°C. VOCs are analysed for using GC/MS headspace analysis where the analytes move from the aqueous phase into the gas phase above the sample. An aliquot of the gas phase is then taken and injected into the GC (gas chromatography) system for separation and detection by mass spectrometry. Advanced techniques such as DHS (dynamic headspace), TD (thermal desorption) and SBSE (stir bar sorptive extraction)/twister, have been developed over the past 30 years to improve extraction of analytes and improve sensitivity and detection limits. Using the Gerstel system and the techniques available with the instrument, coupled with a GC/MS with an EI source, a basic extraction and analytical procedure was developed for twister analysis. The sample volume and preparation time were optimised alongside the instrument TD, CIS (Cool injection system) and GC parameters to ensure clear chromatography and increased sensitivity. The method created could suitably extract clean water and effluent samples. The different techniques that Gerstel offer, both Dynamic headspace combined with thermal desorption and Twister combined with thermal desorption provided enhanced analysis of some VOC analytes compared to static headspace analysis. Twister extraction was more beneficial for analytes with high boiling points, low dielectric constants and high Log kow values.
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