Chemometrics-assisted electrochemical determination of dextromethorphan hydrobromide and phenylephrine hydrochloride by carbon paste electrode

In this paper, multivariate curve resolution-alternating least squares (MCR-ALS) was applied for simultaneous determination of phenylephrine (PHE) and dextromethorphan (DEX) at the surface of bare carbon paste electrode (CPE). PHE and DEX are present in most the cold pharmaceuticals, and their voltammetric peaks have a high overlap that makes difficult or impossible their simultaneous electrochemical determinations without further experiments like modification of electrode, applying analytical techniques other than differential pulse voltammetry (DPV), or cyclic voltammetry. In this study, DEX and PHE were quantified on the surface of CPE without any further purification or modification. After recording DPV signals from thirty-three samples from these drugs and correcting potential shifts, MCR-ALS was applied to resolve overlapped peaks of these pharmaceuticals and quantitative determination of them in mixtures. Equality constraint was applied as a constraint during optimization and led to unique results from MCR-ALS. This study is the first report of using equality constraint in the analysis of first-order electrochemical data. The detection limit was determined, which was 1.79 μM for DEX and 1.93 μM for PHE, respectively. The main advantages of this method are its simplicity, low cost, and its speed since there is no need to modify electrode.