Novel preconcentration technique for on-line coupling to high-speed narrow-bore capillary gas chromatography: sample enrichment by equilibrium (ab)sorption, I: Principles and theoretical aspects

In recent years, there has been substantial progress in the field of high-speed narrow-bore capillary gas chromatography (GC) in general, and in the development of (trans)portable gas chromatographs for fast and accurate analysis in field applications in particular. Due to the limited (concentration) sensitivity of instrumentation for high-speed (portable) GC, environmental applications of this technique frequently require a preconcentration step. The equilibrium (ab)sorption technique described in this article was found to be very promising for on-line coupling to high-speed narrow-bore capillary GC and field portable GC instruments. Enrichment factors up to at least 100 can be obtained rapidly without the use of complicated instrumentation. The new preconcentration technique is shown to have clear advantages over enrichment based on conventional adsorption, i.e. thermal desorption techniques. It can be carried out at ambient trapping temperatures, gives uniform desorption profiles, reduces water effects, uses inert adsorption materials and does not require a (cryogenic) refocusing step. Moreover, the new preconcentration method allows the enrichment factors to be predicted from tabulated chromatographic data, thereby facilitating calibration.