Membrane solid-phase microextraction--a new concept of sorbent preparation.

A new sorption system for isolation/enrichment of polar organic analytes from aqueous samples was obtained by substantial modification of the solid-phase microextraction (SPME) probe. In this system, polar sorbents are separated from the sample by a hydrophobic membrane. The new membrane SPME (M-SPME) probe was made utilizing polyethylene glycol (PEG) (molecular weight = 20 kDa) and polydimethylsiloxane (PDMS) as the membrane material. In this probe, PEG behaves as a pseudo-liquid at the extraction stage, whereas, up to now, it has mainly been used as a cross-linked solid adsorbent. It has been found that such M-SPME fiber may be successfully used at the sample pretreatment stage. It is sufficiently robust and thermally stable; the latter feature permits the usage of thermal desorption for the liberation of analytes. Comparison of our probe with the commercially available polyacrylic (PA) SPME fiber, using a mixture of phenols and gas chromatography as the final determination technique, demonstrated the highly effective nature of the new sorptive system; ca. 10 times higher than in the case of the PA fiber.