On-line solid-phase extraction of cephalosporins

Using a single, on-line solid-phase sample clean-up procedure, serum concentrations of ten cephalosporins (cefaloridine, cefalotin, cefamandole, cefazolin, cefodizime, cefoperazone, cefoxitin, ceftizoxime, ceftriaxone and cefuroxime) were assayed on a C-18 column, using UV detection. Serum samples diluted with water were directly injected, without any sample preparation, into the extraction column (alkylamino packing) where the drugs were separated from the serum components. Using an on-line column-switching system, cephalosporins were transferred and separated on the analytical column by ion-pair high-performance liquid chromatography. The proposed method was rapid and efficient: it requires a small serum volume (10 mu l) and it can be automated. Recovery was nearly complete. Detection limits varied from 0.5 to 2 mu g/ml from extraction of 10 mu l Of serum. The method was highly specific even in the presence of other drugs commonly found in clinical samples and provides a rapid, simple technique suitable for use in routine microbiological practice. (C) 1998 Published by Elsevier Science B.V. All rights reserved.