Silicate-entrapped porous coatings for preparing high-efficiency solid-phase microextraction sorbents

We present a novel way to prepare SPME fibers using a silicate entrapment of porous particles, followed by derivatization using classical organosilane chemistry. The fibers provide a good platform for on-fiber derivatization of desired extraction phases while providing porosity necessary for high extractions capacities. The porous network was created using potassium silicate and porous silica particles. Fibers derivatized using n-butyl, n-octyl, n-octadecyl and n-triacontyl groups were shown to extract benzodiazepines successfully. The coatings were determined to have an average thickness of ca. 8 microm, as determined by a scanning electron microscope, permitting equilibrium times as fast as 2 min. The fibers also showed very good ruggedness towards a vast range of solvents and prolonged use. It was determined that greater extraction efficiencies could be obtained using triacontyl as an extraction phase. The C18 and C30 fibers were also found to provide good linearity (>0.99) for the model analytes over two orders of magnitude, with limits of detection in the sub ng mL(-1) levels. C30 fibers were used to establish a correlation between structurally diverse beta-blockers and their literature reported Log P values. The C30 fibers provided a good correlation (R(2)=0.9255) between beta-blockers ranging in hydrophobicity from Log P(literature) 0.16-4.15 and their respective experimentally determined Log K(spme) values.