Electrochemical behavior of labetalol at an ionic liquid modified carbon paste electrode and its electrochemical determination

Electrochemical behavior of labetalol (LBT) at carbon paste electrode (CPE) and an ionic liquid1-benzyl-3-methylimidazolehexafluorophosphate([BnMIM]PF6)modified carbon paste electrode([BnMIM]PF6/CPE)in Britton-Robinson buffer solution (pH 2.0) was investigated by cyclic voltammetry (CV) and square wave voltammetric (SWV). The experimental results showed that LBT at both the bare CPE and [BnMIM]PF6/CPEshowed an irreversible oxidation process, but at [BnMIM]PF6/CPE its oxidation peak current increased greatly and the oxidation peak potential shifted negatively. The electrode reaction process is a diffusion-controlled process involving one electron transferring accompanied by a participation of one proton at [BnMIM]PF6/CPE. At the same time, the electrochemical kinetic parameters were determined. Under the optimized electrochemical experimental conditions, the oxidation peak currents were proportional to LBT concentration in the range of 7.0 x 10-6-1.0 x 10-4 mol L-1 with the limit of detection(LOD, S/N=3) of 4.810 x 10-8 mol L-1and the limit of quantification(LOQ, S/N=10) of 1.60 x 10-7 mol L-1, respectively. The proposed method was successfully applied in the determination of LBT content in commercial tablet samples.