Voltammetric studies and assay of the anti-inflammatory drug ketoprofen in pharmaceutical formulation and human plasma at a mercury electrode

The electrochemical reduction of the anti-inflammatory drug ketoprofen was studied in a Britton-Robinson (B-R.) buffer series of pH 2–11 using dc-polarography, cyclic voltammetry, and coulometry techniques. The electrode reaction pathway of the drug at the dropping mercury electrode was proposed and discussed. A new adsorptive cathodic stripping square-wave voltammetric procedure was optimized for the assay of bulk drug in a B-R. buffer of pH 2.0. The peak current was linear with the drug concentration over the ranges 2 × 10–9 to 2 × 10–7 M of the bulk drug, using a 60 s accumulation time period at –0.6 V (vs. Ag/AgCl/KCls). The percentage recovery of the bulk drug was 99.57 ± 0.54 and a detection limit of 0.10 ng mL–1 was achieved. The proposed procedure was successfully applied for the assay of ketoprofen in pharmaceutical formulation (Ketofan®) and human plasma. The percentage recoveries were 99.66 ± 0.47 and 101.76 ± 0.64 in pharmaceutical formulation and human plasma, respectively. A detection limit of 0.14 ng mL–1 plasma was achieved which was below that reported in literature using the different analytical techniques.