Study Of In-tube SPME And Its On-line Coupling To Capillary GC For Trace Analysis In Aqueous Samples

Kinds of extraction methods based on principle of solid-phase microextraction are the most rapidly developed sample preparation techniques in the last fifteen years. It has the merits such as solvent-free, simple operation as well as easy hyphenation to analytical instruments. However, for addressing the more and more strict demanding of analysis, it is still crucial to improve the techniques to facilitate the sensitivity, accuracy, availability and automated operation.Based on kinetic extraction principle, a device of in-tube solid-phase microextraction on-line coupling to HRGC (On-line ITSPME-HRGC), is designed and validated for the trace analysis of contaminants in water. A 5 m x 0.53 mm I.D. 1.2 [am OV-1 phase capillary column is used as the in-tube extractor, through which aqueous samples were driven during the extraction process. The extractor is fast heated and purged by auxiliary carrier gas for desorption of the analytes, which is then transferred through a micro T-piece and a heated lOOfxm I.D fused silica tube onto a retention gap in a GC. There is no switching valve between the extractor and the injection port of GC to avoid possible adsorption of target compounds, and to reduce the cost of the device.The extraction and the analysis of trace contaminants such as alkanes, PAHs, phosphorus containing pesticides and chlorinated pesticides were realized using On-line ITSPME-HRGC. Compared to the classical SPME, the on-line ITSPME system can dramatically increase enrichment factor and reduce the lowest detectionlimits of interested analytes by 20 to 70 times, while the extraction time is only within 40 minutes. The reproducibility of quantitation as well as the availability is good due to the on-line operation of overall analytical process. The cost per sample for an analysis is the same as that of classical fiber SPME, or even lower in the long run owing to the use of ordinary valve and conventional GC column extractor.Fluid-dynamic effects and other influencing factors of ITSPME were studied. The kinetic model of extraction process was put forward, and also the extraction equation was set up to illustrate the influence of sampling rate of extraction.In chapter 4, a simple method based on the technique of capillary column switching-back flushing was developed for the analysis of more complex samples both from direct injection or ITSPME. A detailed analysis of aromatics in gasoline was tested to examine the two-dimensional method. The sample was first separated on an OV-2330 or FFAP polar pre-column and then back flushed onto a non-polar analytical column. The early eluting components from pre-column and the components of interest (aromatics plus heavier compounds) eluting from analytical column are all directed to the same flame ionization detector through a 'T' piece, which permits quantitative analysis of aromatic hydrocarbons in gasoline by corrected factor normalization method. Real live samples were analyzed, and the reproducibility of the quantitative analysis is <5% RSD. The operation is simple and easy since the switching time window of the method is ? seconds.