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

The electrochemical behavior of labetalol (LBT) at a carbon paste electrode (CPE) and an ionic liquid 1-benzyl-3-methylimidazole hexafluorophosphate ([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 voltammetry (SWV). The experimental results showed that LBT at both the bare CPE and [BnMIM]PF6/CPE showed an irreversible oxidation process, but at [BnMIM]PF6/CPE its oxidation peak current increased greatly and the potential shifted negatively. The electrode reaction process is diffusion-controlled involving a one-electron transfer accompanied by the participation of one proton at [BnMIM]PF6/CPE. In addition, 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 7.0x10(-6)-1.0x10(-4) mol L-1 with a limit of detection (LOD, S/N=3) of 4.810x10(-8) mol L-1 and a limit of quantification (LOQ, S/N = 10) of 1.60x10(-7) mol L-1. The proposed method was successfully applied in the determination of the LBT content in commercial tablet samples.