Pharmacokinetic Study of Amlodipine in Human Urine Using On-Line Coupled Isotachophoresis-Capillary Zone Electrophoresis with Diode Array Detection

The present work illustrates possibilities of column coupling capillary electrophoresis (CE-CE) combined with fiber-based diode array detection (DAD) for the direct quantitative determination of trace drug (amlodipine, AML), in biological multicomponent ionic matrices (human urine). Capillary isotachophoresis (ITP) served as an ideal injection technique in CE-CE. Moreover, ITP provided an effective on-line sample pretreatment before a capillary zone electrophoresis (CZE) separation. Enhanced separation selectivity, due to the combination of different separation mechanisms (ITP vs. CZE, carboxyethyl-β-cyclodextrine as a complexing buffer additive in CZE), enabled to obtain a pure analyte zone, suitable for its detection and quantitation. The DAD, unlike single wavelength UV detection, enabled to characterize the purity of the analyte zone. A processing of the raw DAD spectra (the background correction and smoothing procedure) was essential, when a trace analyte signal was evaluated. Obtained results indicated pure zone of interest confirming effective ITP-CZE separation process. The proposed ITP-CZE-DAD method was characterized by favorable performance parameters (sensitivity, linearity, precision, recovery, accuracy, robustness, selectivity) and was successfully applied to a pharmacokinetic study of AML.