High-performance liquid chromatography with a column-switching system and capillary electrophoresis for the determination of ibuprofen in plasma

Quantitative aspects of high-performance liquid chromatography with a column-switching system (CS-HPLC) and capillary electrophoresis (CE) were investigated for the determination of ibuprofen in plasma. For CSS-HPLC, 100 mu l of plasma was directly injected onto the column system for the three separation steps: (1) deproteinization and fractionation of plasma samples with a polymer-coated mixed-function phase column, (2) concentration with an intermediate column and (3) final separation with a main column. For CE, a mixture of 50 mu l of plasma and 1 ml of acetonitrile was centrifuged and the supernatant was introduced onto the capillary (66 cm x 50 mu m I.D.; 62 cm to detector) at 20 degrees C. Run buffer was 250 mM sodium berate buffer (pH 8.5) and applied electric field was 379 V cm(-1). Linear dynamic ranges were 0.1-250 mu g ml(-1) in CSS-HPLC and 1-1000 mu g ml(-1) in CE. Intra-day and inter-day coefficients of variation were less than 5.6% and 6.5% for CSS-HPLC, 6.3% and 6.5% for CE, respectively. The limits of detection (S/N = 3) for CSS-HPLC and CE were 25 ng ml(-1) and 300 ng ml(-1), respectively. CSS-HPLC was superior in simplicity and sensitivity, while CE was better in efficiency, rapidity, and cost. (C) 1998 Elsevier Science B.V. All rights reserved.