Equilibrium sorptive enrichment on poly(dimethylsiloxane) particles for trace analysis of volatile compounds in gaseous samples

A novel approach for sample enrichment, namely, equilibrium sorptive enrich ment (ESE), is presented. A packed bed of sorption (or partitioning) materi al is used to enrich volatiles from gaseous samples. Normally, air sampling is stopped before breakthrough occurs, but this approach is not very succe ssful for weakly retained compounds (volatiles) as early breakthrough occur s. In ESE, sampling is continued until all compounds of interest are in equ ilibrium with the sorptive material. This allows accurate sampling of volat iles and enrichment at the maximum attainable sensitivity. However, due to the equilibrium nature of ESE, it is limited to samples with a constant con centration over the sampling time. This requirement is easily met for those compounds with short equilibration times (volatiles), Because of the natur e of the sorption mechanism, which is basically dissolution, all compounds partition independently into the sorbent (stationary phase) and displacemen t effects do not occur. This is a great advantage over adsorption materials , Additionally, theory allows the calculation of enrichment factors from li terature retention indexes. Moreover, ESE also benefits from the features o f sorption materials such as a very high inertness and interference-free bl anks. The performance of ESE is illustrated with the analysis of several an alytes including the epoxides ethylene oxide and epichlorohydrin in real-li fe air sampling.