Exploiting the high oxidation potential of carisoprodol on a boron-doped diamond electrode: an improved method for its simultaneous determination with acetaminophen and caffeine.

A boron-doped diamond electrode (BDDE) was employed for the first time in the development of a voltammetric method for the simultaneous determination of acetaminophen (ACT), caffeine (CAF) and carisoprodol (CAR). CAR presents a high oxidation potential (2.0 V) and this electrode is suitable for this purpose due to its wide electrochemical potential window. The anodic peak potentials of ACT, CAF and CAR oxidation on the BDDE were found to be 0.980 V, 1.50 V and 2.03 V (vs. Ag/AgCl (3.0 mol L KCl)), respectively, by cyclic voltammetry. After optimization of the analytical conditions employing BDDE at pH 6.0 in a Britton-Robinson buffer solution, square-wave voltammetry (SWV) was applied to the simultaneous determination, by which the peak currents for the three molecules were found to vary linearly with their concentrations in the range of 2.99-283 μmol L for ACT, 2.99-84.8 μmol L for CAF and 19.9-207 μmol L for CAR, with detection limits of 0.768 μmol L, 0.771 μmol L, and 3.11 μmol L, respectively. The proposed method was employed for the simultaneous determination of the three molecules in pharmaceutical formulations and the results were successfully validated with a comparative spectrophotometric method. The use of BDDE showed advantages such as low cost, suitable linearity for simultaneous quantification in real samples, no adsorption problems, and possessing rapidity and excellent reproducibility. This electrode represents a suitable electrochemical sensor for the routine analysis of these drugs.