Sensitive square-wave voltammetric determination of tadalafil (Cialis®) in pharmaceutical samples using a cathodically pretreated boron-doped diamond electrode

•BDDE was for the first time employed in the determination of tadalafil.•The cathodic pretreatment improved the sensibility for tadalafil.•A very sensitive method was developed using SWV obtaining a LOD of 42.3 nmol L−1.•Voltammetric method was not statistically different from the chromatographic one.

This work presents the development of a novel voltammetric method for a sensitive, simple, fast and eco-friendly determination of tadalafil (TDL) using a cathodically pretreated boron-doped diamond electrode (CP-BDDE). Using cyclic voltammetry of TDL, this drug presented one irreversible and well resolved oxidation process at 0.905 V (vs Ag/AgCl (KCl 3.0 mol L−1)) in Britton-Robinson buffer solution (pH 4.0). A scan rate study demonstrated that TDL transport toward CP-BDDE is diffusion controlled and one proton and one electron are involved in its electrooxidation. Employing square-wave voltammetry under optimized parameters, there was a linear dependence of peak current and TDL concentration in the range of 0.15-1.28 μmol L−1 with a detection limit of 19.5 nmol L−1. The proposed method was successfully applied in TDL determination in pharmaceutical formulations. The results obtained with the voltammetric method were not statistically different from the comparative spectrophotometric method, at a 95% confidence level.

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