The validity of using bare graphite electrode for the voltammetric determination of paracetamol and caffeine

The validity of applying the readily available bare spectroscopic graphite electrode in the pharmaceutical analysis as a cost-effective, simple, and efficient alternative to the modified carbon-based electrodes was eval-uated in this work using paracetamol and caffeine as test analytes. The cyclic voltammetry study on their electrochemical behavior revealed that paracetamol and caffeine display well-expressed oxidation peaks at potentials of typically 0.51 V and 1.36 V vs. Ag, AgCl/KClsat, correspondingly and that their oxidation is an adsorption-controlled process. Then the bare spectroscopic graphite electrode was applied for the separate and individual determination of the test analytes by differential pulse adsorptive stripping voltammetry. Under optimized experimental conditions (3 min accumulation time, pH 5.0) the electrode exhibited a linear response to paracetamol in the range from 5 mu mol L-1 to 150 mu mol L-1 and to caffeine in the range from 5 mu mol L-1 to 60 mu mol L-1. The detection limit achieved (0.2 mu mol L-1 for each of the analytes) was found to be sufficient to carry out paracetamol and/or caffeine analysis in drugs. The results were validated by separate and individual paracetamol and caffeine determinations in commercial tablets with satisfactory recovery values (98.90-101.85 %). The presence of common pharmaceutical excipients did not affect the paracetamol and/or caffeine voltammetric response.