Preparation and characterization of porous silica-coated multifibers for solid-phase microextraction

C18-bonded silica-coated multifibers were prepared and studied as a stationary phase for solid-phase microextraction (SPME). The porous multifiber SPME provided larger absorption capacity and higher absorption rate compared to a polymer-coated single fiber. Its absorption rate was 10 times higher than that of a commercial 100-microm poly(dimethylsiloxane) (PDMS)-coated fiber. Its high extraction efficiency enabled the positive identification of unknown compounds at sub-part-per-billion level in full-scan mode with a benchtop quadruple GC/MS. The desorption temperature indicated that the analyte interactions with the C18-bonded silica were stronger than those with the PDMS polymer. The dependence of the equilibration time on the molecular weight was not observed for the porous multifiber SPME. The boundary layer between the fiber coating and the sample matrix could be the absorption control step in SPME under mild agitation. The special experimental conditions in the porous multifiber SPME, such as air interference and polar organic solvent wetting, were investigated.