Comparison of three stationary phases in the separation of polyphenyls by liquid chromatography.

We present herein new analytical protocols for the separation and structural elucidation of polyphenyls. Three commercially available chromatographic stationary phases are compared in the separation of these non-polar, unfunctionalized, positional isomers. Baseline separation of nine terphenyl and quaterphenyl isomers is achieved in under ten minutes using a rapid gradient elution HPLC method. Complete separation of these, and a further five polyphenyls, is demonstrated. We finally present a linear correlation between solvent accessible surface area and the retention times of these closely related compounds.

Tetrabutylammonium methacrylate as a novel receptor for selective extraction of sulphonylurea drugs from biological fluids using molecular imprinting.

Glibenclamide (GLIB), an oral antidiabetic medication of the sulphonylurea drug family, was stoichiometrically imprinted using tetrabutylammonium methacrylate as the functional monomer, for the first time in molecular imprinting, and utilising the sulphonylurea affinity for carboxylate anions. Solution association between the drug and the novel functional monomer was studied by 1H-NMR titrations, whereby evidence of sulphonylurea deprotonation followed by the formation of "narcissistic" GLIB dimers was found when tested in CDCl3, while an affinity constant in excess of 105 L mol-1 was measured in DMSO-d6. Detailed analysis of GLIB binding on the subsequently prepared imprinted and non-imprinted polymers confirmed the deactivation of binding sites by exchange of a proton between GLIB and methacrylate, followed by extraction of the tetrabutylammonium counterion from the polymer matrix, resulting in overall reduced binding capacities and affinities by the imprinted material under equilibrium conditions. An optimised MI-SPE protocol, which included a binding site re-activation step, was developed for the extraction of GLIB from blood serum, whereby recoveries of up to 92.4% were obtained with an exceptional sample cleanup.

Selective solid-phase extraction sorbent for caffeine made by molecular imprinting.

A molecularly imprinted polymer (MIP) was prepared with caffeine as the template molecule. Thermal polymerisation (60 degrees C) was optimised, varying ratios of monomer, cross linker and template. The polymer was used as a solid-phase extraction (SPE) sorbent, for selective trapping and pre-concentration of caffeine. Caffeine was loaded on the MIP-SPE cartridge using different loading conditions (solvents, pH value). Washing and elution of the caffeine bound to the MIP was studied utilising different protocols. The extraction protocol was successfully applied to the direct extraction of caffeine from beverages and spiked human plasma.