RESUMO
A new micellar electrokinetic capillary chromatography method (MEKC) is proposed for the determination of ibuprofen and tetrazepam in human urine samples over a concentration range of therapeutic interest. A fused silica capillary (60 cm x 75 microm) is used. Ibuprofen and tetrazepam are detected via UV detection at 220 and 228 nm, respectively. Separation is performed at 25 degrees C and at a separation voltage of 30 kV, with 15 mM borate buffer (pH 10.2) containing 40 mM sodium dodecylsulfate as the electrolyte solution. Under these conditions the analytes were separated in <11 min. Sulfamethazine is used as an internal standard. Prior to determination, the samples are purified and enriched by means of an extraction-preconcentration step with a preconditioned C18 cartridge and by eluting the compounds with methanol. Good linearity, accuracy, precision, robustness and solution stability were achieved for the technique. Detection limits of 200 microg L(-1) for ibuprofen and 300 microg L(-1) for tetrazepam were obtained. These analytes were then determined in real urine using the technique.