Porous layer solid phase microextraction using silica banded phases

In this paper, solid phase microextraction (SPME) using porous layer-coated fibers is reported. Bonded silica particles (5 mu m diameter), which are typically used for reversed-phase high-performance liquid chromatography, were fixed onto the surface of metal wires using high-temperature adhesives. The adsorption and desorption properties of the new porous layer SPME fibers were investigated using aromatic hydrocarbon test compounds, and the results were compared with those of commercially available polymer-coated fused silica fibers. It was found that the desorption time using the porous layer fibers wsa less than 10 s, which provides high chromatographic efficiency without cryogenic trapping. The total mass of toluene adsorbed from a 0.1 ppm aqueous solution on a fiber with a 30 mu m C-8 porous layer was 8 times larger than that obtained using a fiber with a 100 mu m thick polydimethylsiloxane coating. It was also found that the selectivity of the porous layer in SPME greatly depends on the properties of the bonded particles. Both C-8 and C-18 bonded phases were evaluated. The stability of the resultant porous layer coatings for SPME was investigated by introduction into a GC injector at different temperatures. It was found that the new porous layers were very stable for thermal desorption below 250 degrees C; however, some monomers were released from the epoxy glue at 300 degrees C.