Differential Pulse Stripping Voltammetric Determination of Paracetamol and Phenobarbital in Pharmaceuticals Assisted by Chemometrics

A voltammetric method, aided by chemometrics, was developed for the simultaneous determination of paracetamol and phenobarbital in pharmaceuticals. Both of these analytes gave well‐defined oxidation peaks in the Britton–Robinson buffer (pH 5.72) when analyzed by differential pulse‐stripping voltammetry (DPSV) at a glassy carbon electrode. The experimental conditions were optimized: 200 mV—deposition potential, 160 s—deposition time, 4 mV—increment potential, 50 mV—amplitude, and 60 ms—pulse width. Under these selected conditions, the oxidation current had a linear relationship with concentration of paracetamol [ranges: 0.09–0.93 mg l−1 (r 2 = 0.999) and 0.9–11.7 mg l−1 (r 2 = 0.999)], and phenobarbital [1.0–22.0 mg l−1 (r 2 = 0.999)]. Due to the overlapping voltammograms from the two analytes, two chemometrics methods, partial least squares (PLS), and principal component regression (PCR), were used for building calibration models from voltammograms of mixtures. These models were applied for prediction of the analytes from unknown samples. It was found that the two chemometrics methods gave good results for analysis of mixtures of these two compounds. The proposed method was verified by an established HPLC method, and its practical application was demonstrated with the determination of paracetamol and phenobarbital in several commercial tablets with satisfactory results.