Application of the restricted-access precolumn packing material alkyl-diolsilica in a column-switching system for the determination of ketoprofen enantiomers in horse plasma

The group of LiChrospher ADS (alkyl-diol silica) sorbents that make part of a unique family of restricted-access materials, have been developed as spe cial packings for precolumns used in the LC-integrated sample processing of biofluids. The advantage of these sorbents lies in the direct injection of untreated biological fluids, that is without sample clean-up, the eliminat ion of the protein matrix with a quantitative recovery together with an on- column enrichment. The present method is based on previous work applying UV detection at 260 nm for ketoprofen determinations. Plasma samples introduc ed to the ADS precolumn using a 0.1 M phosphate buffer, pH 7.0. After washi ng with the buffer the ADS column was backflushed with the mobile phase 0.0 1 M phosphate buffer-6% (v/v) 2-propanol-5 mM octanoic acid at a pH of 5.5, thus transporting the analytes to the chiral-HSA (human serum albumin) (10 0X4.0 mm) column where the separation of the ketoprofen enantiomers was ach ieved with a resolution factor of 1.4. The developed column-switching metho d was fully applicable to plasma injections. (C) 2000 Elsevier Science B.V. All rights reserved.