Direct HPLC analysis of ketoprofen in horse plasma applying an ADS-restricted access-phase

Making up part of the unique family of restricted access materials (RAM) th e Lichrospher ADS (alkyl-diol silica) sorbents have been developed as speci al packing materials for precolumns used for LC-integrated sample processin g of biofluids. The advantage of such phases consists of direct injection o f untreated biological fluids without sample clean-up and elimination of th e protein matrix together with an an-column enrichment. The plasma samples, with internal standard phenacetin added (not essential), were brought onto the precolumn (C-18 ADS, 25 mu m, 25 x 4 mm i.d.) using a phosphate buffer , 0.1 M, pH 7.0. After washing with the buffer, the ADS column was backflus hed with the mobile phase phosphate buffer 0.05 M pH 7.0: acetonitrile (80: 20), thus transporting the analytes onto a reversed-phase column Ecocart 12 5-3 HPLC cartridge with a LiChrocart 4-4 guard column, both packed with LiC hrospher 5 mu m 100 RP-18; after separation detection was performed in UV a t 260 nm. Essential features of the method include the novel precolumn pack ing, the absence of sample pretreatment, a quantitave recovery, good precis ion and accuracy, as well as a considerable reduction of analysis time comp ared to conventional manual methods applied in bioavailability studies. Cop yright (C) 1999 John Wiley & Sons, Ltd.