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The electrochemical behavior of atorvastatin and amlodipine at a glassy carbon electrode has been studied using different voltammetric techniques. First derivative of the ratio voltammetric methods for determination of amlodipine and atorvastatin in tablets in the presence of the other compound has been described. This technique depends on the measuring of first derivative of the ratio voltammograms of each concentration as a function of the increased concentrations. DP and SW voltammetric methods depend on first derivative of the ratio-voltammetry by measurements of the selected potentials for amlodipine and atorvastatin. The linear response was within the range of 4 Â 10 À6 -1 Â 10 À4 M for amlodipine and 2 Â 10 À6 -1 Â 10 À4 M for atorvastatin. The proposed methods have been extensively validated.

The electrochemical oxidation of formoterol fumarate (formoterol) has been carried out in aqueous solution in the pH range of 1.5–10.0 by cyclic, linear sweep, differential‐pulse and square‐wave voltammetry. The diffusion controlled nature of the waves was established. The mechanism of oxidation was discussed. Two voltammetric techniques for the determination of formoterol in 0.5 M sulfuric acid which allow quantitation over the 8×10−6–6×10−5 M range for both methods were proposed. Based on this study simple, rapid and selective two voltammetric methods were developed for the determination of formoterol in capsule dosage form and human serum.

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A detailed study of the electrochemistry of ambroxol at a glassy carbon electrode was carried out in the pH range 1.8 ± 11.0 in aqueous solution using cyclic and differential pulse voltammetry. The compound was oxidized irreversibly at high positive potentials resulting in the formation of a chemical product at less positive potentials, which was more readily oxidized than the parent compound. In addition, a differential pulse voltammetric method was proposed for the determination of the drug in different pharmaceutical formulations, and in drug dissolution studies.