This short review discusses how sorbent-packed focusing traps can be used to enhance sensitivity for headspace and headspace-SPME sampling of trace-level VOCs and SVOCs, thus allowing more (and better-quality) information to be obtained from every sample. Options covered include the use of larger headspace extraction volumes, repeat extractions from a single vial, and lowsplit or splitless analysis. Each option is illustrated with data acquired on the automated Centri® sample extraction and enrichment platform for GC–MS. Also discussed are the advantages that trapping offers for water management.
It is well-known that analyte recovery and sensitivity for static (or equilibrium) headspace analysis of liquid or solid samples by GC–MS is affected by a number of sample preparation parameters. These include agitation speed, sampling time, incubation temperature and (for aqueous samples) ionic strength. In addition, sampling of headspace onto solid-phase microextraction (SPME) fibers is affected by the type of fiber (single-phase or multi-phase) and issues of analyte polarity.
Once these factors are optimised and the type of detector has been decided, any further gains in sensitivity need to come from the sample delivery system itself. This can be done by changing the method parameters to increase the on-column loading of the sample – for example, through adjustment of the headspace extraction volume and concentration, and use of low-split or splitless injection. However, most headspace instruments provide very limited ability to change these parameters, without degrading peak shape/symmetry, response and resolution.
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