title: On-line coupling of solid-phase extraction and capillary electrophoresis for the determination of cefoperazone and ceftiofur in plasma.
abstract: We present a method for determining two cephalosporins (cefoperazone and ceftiofur) in plasma by on-line solid-phase extraction (SPE)-capillary zone electrophoresis (CZE) with a T-split interface. Using this interface, a part of the SPE elution plug containing the cephalosporins is injected while the rest of the sample is flushed to waste. SPE was carried out using a C(18) micro-precolumn and the cephalosporins presented good retention properties with breakthrough volumes above 1 ml. Using a desorption volume of 426 nl of acetonitrile, recoveries were 75 and 90%, for cefoperazone and ceftiofur, respectively. The resulting elution volume was about 1.8 microl. A deproteinization step was included prior to SPE for the analysis of plasma samples with recoveries of 90 and 57% for cefoperazone and ceftiofur, respectively. With UV detection at 254 nm, linear relationships between the injected concentration and peak area was measured between 10 and 500 ng ml(-1) for standards, and 200 and 1500 ng ml(-1) for plasma samples. Intra-day (n=5) and inter-day (n=5) peak area repeatability were lower than 12% RSD. The detection limits obtained for spiked plasma (100 ng ml(-1) cefoperazone and ceftiofur) are sufficient for applying the method to pharmacokinetic studies.
authors.affiliation: Department of Biomedical Analysis, Faculty of Science, Utrecht University, Sorbonnelaan 16, NL-3584 CA Utrecht, The Netherlands. patricia.puig@urv.cat
authors.forename: Patricia
authors.initials: P
authors.lastname: Puig
authors.forename: F W Alexander
authors.initials: FW
authors.lastname: Tempels
authors.forename: Francesc
authors.initials: F
authors.lastname: Borrull
authors.forename: Marta
authors.initials: M
authors.lastname: Calull
authors.forename: Carme
authors.initials: C
authors.lastname: Aguilar
authors.forename: Govert W
authors.initials: GW
authors.lastname: Somsen
authors.forename: Gerhardus J
authors.initials: GJ
authors.lastname: de Jong
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000097:blood*; D002417:Cattle; D002438:Cefoperazone / Q000097:blood*; D002511:Cephalosporins / Q000097:blood*; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D002438:Cefoperazone; C053503:ceftiofur