Analysis of lamotrigine and its metabolites in human plasma and urine by micellar electrokinetic capillary chromatography

A reliable micellar electrokinetic capillary chromatographic method was developed and validated for the determination of lamotrigine and its metabolites in human plasma and urine. The variation of different parameters such as pH of the BGE and SDS concentration were evaluated in order to find optimal conditions. Best separation of the analyses was achieved at pH 9.5, 10 mM borate and 50 mM sodium dodecyl sulfate; melatonin was selected as the internal standard. Isolation of lamotrigine and its metabolites from plasma and urine was accomplished with an original solid-phase extraction procedure using hydrophilic lypophilic balance cartridges. Good absolute recovery of the analytes and satisfactory precision was obtained. The calibration plots for lamotrigine and its metabolites were linear over the 1 – 20 µg/mL concentration ranges. Sensitivity was satisfactory; in fact, the limit of detection and the limit of quantitation of lamotrigine are 500 ng/mL and 1 µg/mL, respectively. The application of the method to real plasma samples from epileptic patients under therapy with lamotrigine gave satisfactory results (in terms of accuracy and selectivity) and in agree with those obtained with a HPLC method.