Simultaneous voltammetric determination of paracetamol and caffeine and ascorbic acid and caffeine in pharmaceutical formulations using a boron doped diamond electrode

In this study the development of eletroanalytical procedures for paracetamol, ascorbic acid (AA) and caffeine in pharmaceutical formulations using a boron doped diamond (BDD) and differential pulse voltammetry (DPV) is described. Initially, the cyclic voltammograms of paracetamol, AA and caffeine were separately obtained with the potentials of anodic peaks of oxidation of each one of these analytes equals to 0.80 V, 0.92 V and 1.47 V, respectively. The effect of electrochemical pre-treatment of the BDD electrode in voltammetric measurements was the purpose of this study, as well. The parameters of square wave voltammetry and differential pulse voltammetry were also studied and optimized for each analyte. In the first developed procedure, it was determined both paracetamol and caffeine in pharmaceutical formulations using the BDD electrode and differential pulse voltammetry after optimization of experimental conditions. The analytical curves were linear in the paracetamol and caffeine concentration intervals, ranging from 5.0 x 10-7 mol L-1 to 8.3 x 10-5 mol L-1 with detection limit equal to 4.9 x 10-7 mol L-1 for paracetamol and 3.5 x 10-8 mol L-1 for caffeine. The relative standard deviation of paracetamol and caffeine for the intra-day repeatability was 0.7% and 0.2% respectively, and the inter-day repeatability was 5.1% and 1.4% respectively. The quantification of paracetamol and caffeine in pharmaceutical formulations using a BDD electrode showed results in agreement with those results obtained using a chromatographic method at a 95% confidence level. Subsequently, a second procedure was developed for the simultaneous determination of AA and caffeine in pharmaceutical formulations using the BDD electrode and differential pulse voltammetry, after optimization of experimental conditions. The analytical curves were linear in the concentrations ranging from 5.0 x 10-6 mol L-1 to 1.9 x 10-4 mol L-1 for AA and 2.0 x 10-6 mol L-1 to 1.0 x 10-4 mol L-1 for caffeine with detection limits of 2.6 x 10-7 mol L-1 for AA and 2.4 x 10-8 mol L-1 for caffeine. The relative standard deviation of AA and caffeine for the intra-day repeatability was 0.5% and 0.2% respectively, and the inter-day repeatability was 5.9% and 8.7% respectively. Quantification of AA and caffeine in pharmaceutical formulations using a BDD electrode showed results in accordance with the results obtained using a chromatographic method at a 95% confidence level. (AU)