IMPROVED DETERMINATION OF VOCS IN MARINE BIOTA BY USING ONLINE PURGE-AND-TRAP GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A Tekmar LSC-2000 Purge and Trap (P&T) apparatus was further modified in order to improve the on-line P&T gas chromatographic determination of volatile organic compounds (VOCs) in biological tissue. The standar d needle sparger of the Tekmar was replaced by a system consisting of two needles (purge gas in- and outlet) and a moisture trap. This modif ication allows a rapid throughput of samples and minimises the risk of contamination or losses. Addition of octan-1-ol proved successful in eliminating the severe sample foaming that generally occurs when biolo gical material is purged. For separation of the analytes a J&W DB-VRX column (60 m x 0.2.5 min id, 1.4 mu m film) was used, which allowed th e elimination of the cryofocusing step prior to injection. The method was tested for 13 priority VOCs and detection limits were obtained ran ging from 0.003 ng g(-1) (tetrachloromethane) to 0.16 ng g(-1) (m- and p-xylene) using single ion monitoring-mass spectrometry. The reproduc ibility was around 15% for most compounds and the recoveries were bett er than 80% for all analytes except 1,1-dichloroethane (59%). Although the method was originally validated for 13 VOCs, it was found;to be a pplicable for a broader range of VOCs and was tested on an eel from th e Scheldt estuary. Apart from the priority VOCs several other VOCs tur ned up rather unexpectedly in these samples. They were identified on t he basis of their mass spectra and quantified using selected ion monit oring.