Improved determination of VOCs in marine biota by using on-line 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 etermination 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 minimizes the risk of contamination or losses. Addition of 1-octanol 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 i.d., 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 (tetrachloromethane) to 0.16 ng/g (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 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

Improved determination of VOCs in marine biota by using on-line 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 etermination 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 minimizes the risk of contamination or losses. Addition of 1-octanol 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 i.d., 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 (tetrachloromethane) to 0.16 ng/g (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 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

Volatile organic compounds in various marine organisms from the southern North Sea

The concentration levels of 12 priority volatile organic compounds (VOCs) were determined in two species of vertebrates and four species of invertebrates from sampling stations in the Southern North Sea, using a modified Tekmar LSC 2000 purge and trap system coupled to GC-MS. In general, concentration levels of VOCs found in this study were of the same order of magnitude as those previously reported in the literature. The concentrations of the chlorinated hydrocarbons (CHCs), with the exception of chloroform, tended to be lower than those of the monocyclic aromatic hydrocarbons (MAHs). The experimental data were statistically evaluated using both cluster and principal component analysis (PCA). From the results of cluster analysis and PCA, no specific groups could be distinguished on the basis of geographical, temporal or biological parameters. However, based on the cluster analysis and the PCA, the VOCs could be divided into three groups, C2-substituted benzenes, CHCs and benzene plus toluene. This division could be related to different types of sources. Finally, it was shown that organisms can be used to monitor the presence of VOCs in the marine environment and the observed concentrations levels were compared with proposed safety levels

Measurement of volatile organic compounds in sediments of the Scheldt estuary and the southern North Sea

The concentrations and distribution of 13 priority volatile organic compounds (VOCs) were determined in sediments of the Scheldt estuary and the Belgian continental shelf, using a modified Tekmar LSC 2000 purge-and-trap system coupled to GC-MS. The method allows a sample intake of up to 50 g wet weight and detection limits are between 0.003 ng/g (tetrachloromethane) and 0.16 ng/g (m- and p-xylene). The repeatability (n = 5) varied between 4% (benzene) and 17% (toluene) and the recoveries ranged from 59% (1,1-dichloroethane) to 99% (tetrachloromethane). Because of the nature of the contaminants, special attention was paid to analyte losses and contamination of the samples during storage aboard the research vessel. Spiked sediment samples were prepared in the laboratory and stored aboard under the same conditions as the environmental samples. The recoveries for these samples varied between 94 and 130%, which suggests that storage had no adverse effect on the samples. No detectable VOC concentrations were found for most of the sampling stations. However, in the Antwerp harbour area, significant concentrations of VOCs were found. The sorption behaviour as predicted from laboratory equilibrium partitioning experiments gives an indication of the in situ partitioning behaviour of VOCs. Although VOCs in sediments should, in general, not be regarded as a major problem in the marine environment, high local concentrations may be a cause of concern

Laser-induced fluorescence detection at 266 nm in capillary electrophoresis Polycyclic aromatic hydrocarbon metabolites in biota

The separation of five phenolic polycyclic aromatic hydrocarbon metabolites (hydroxy-PAHs) has been performed by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) using a 30 mM borate buffer (pH 9.0) containing 60 mM sodium dodecyl sulfate and varying concentrations of γ-cyclodextrin (γ-CD). A concentration of 12.5 mM γ-CD was found to provide a baseline separation of the five hydroxy-PAHs. We applied conventional fluorescence and laser-induced fluorescence (LIF) detection, using a new, small-size, quadrupled Nd–YAG laser emitting at 266 nm. The best limits of detection, in the low ng/ml range, were achieved using LIF detection. For all analytes, linearity was observed up to ca. 100 ng/ml. As an application, conjugated pyrene metabolites in hepatopancreas samples from the terrestrial isopods Oniscus asellus and Porcellio scaber were separated and detected. Finally, flatfish bile samples from individuals exposed to polluted sediment or crude oil, which were part of an interlaboratory study, were analyzed by CD-MEKC with conventional fluorescence and LIF detection to determine the 1-hydroxypyrene concentrations.The authors wish to thank the Dutch Foundation for the Advancement of Science (NOW) for financial support and equipment (grant No. 344-006). Also, the technical assistance of Mr. J. Buijs is much appreciated

Practical fast gas chromatography : methods, instrumentation and applications

Minimal time of operation in gas chromatography (GC) has been a research topic ever since the introduction of GC. Today, revived interest in fast GC is seen to be driven by applications, such as process control and high-throughput analysis, or by the desire to reduce the costs of operation and ownership in routine analysis. Numerous options exist for speeding up GC separations. Which option to select depends strongly on the application under study. The first step should always be to see if it is possible to trade resolution for time. If this approach fails, the concept of "resolution-normalised conditions" comes into play. An overview of options for faster chromatography and a system for classifying chromatograms are brought together to give guidelines for speeding up specific applications. The practical consequences of implementing these options are discussed and the instrumental requirements are outlined. Applications of the various methods for faster GC are given