Altered electrochemistry of oxcarbazepine on cathodically treated boron-doped diamond electrode: Selective detection by pulsed amperometric detection coupled to flow-injection analysis

This work presents a novel electrochemical method for the determination of oxcarbazepine (OXC) in urine and pharmaceutical samples using a flow injection analysis (FIA) system coupled to multiple-pulse amperometric (MPA) detection on a boron-doped diamond electrode (BDDE). The unique voltammetric profile of OXC on the BDDE, consisting of two electrochemical oxidation processes between +1.6 and +1.8 V versus Ag/AgCl/3.0 mol L−1 KCl generating cationic radical species that undergo two electrochemical reduction processes at −0.2 and −1.0 V, was used for the application of MPA detection for the selective detection of OXC in biological samples. Briefly, OXC determination consisted in the application of a three-potential waveform: (1) at +1.7 V/200 ms, generator potential pulse for oxidation of OXC; (2) at −1.1 V/30 ms, collector potential pulse for reduction of the generated product and OXC quantification; (3) at −1.3 V/300 ms, potential pulse for cleaning the BDDE. This strategy enabled OXC determination in urine free from the interference of ascorbic and uric acids. The method showed high repeatability (RSD < 1.0% for injections of 100 μmol L−1 OXC), high analytical frequency (65 determinations per hour), wide working linear range (from 2.0 to 80.0 μmol L−1) with a limit of detection of 0.42 μmol L−1 under optimized FIA conditions (sample loop: 200 μL and flow rate: 3.5 mL min−1), and recovery values close to 100% in all analyses.