Improved determination of VOCs in marine biota by using on-line purge and trap-gas chromatography-mass spectrometry

Abstract

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 standard needle sparger of the Tekmar was replaced by a system consisting of two needles (purge gas in- and outlet) and a moisture trap. This modification 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 biological material is purged. For separation of the analytes a J&W DB-VRX column (60 m × 0.25 mm id, 1.4 µm film) was used, which allowed the elimination of the cryofocusing step prior to injection. The method was tested for 13 priority VOCs and detection limits were obtained ranging from 0.003 ng g–1 (tetrachloromethane) to 0.16 ng g–1 (m- and p-xylene) using single ion monitoring-mass spectrometry. The reproducibility was around 15% for most compounds and the recoveries were better than 80% for all analytes except 1,1-dichloroethane (59%). Although the method was originally validated for 13 VOCs, it was found to be applicable for a broader range of VOCs and was tested on an eel from the Scheldt estuary. Apart from the priority VOCs several other VOCs turned up rather unexpectedly in these samples. They were identified on the basis of their mass spectra and quantified using selected ion monitoring.