Sensitive electrochemical determination of amlodipine in pharmaceutical tablets and human urine using a boron-doped diamond electrode

• For the first time, BDD electrode was used for the determination of amlodipine.
• Analyte yielded irreversible oxidation peak at +0.75 V vs. Ag/AgCl electrode.
• Significant analytical performance of the proposed method was obtained.
• Electrochemical sensor for drug quality control.
• Alternative to chemically-modified electrodes in this application.

For the first time, a boron-doped diamond electrode was used as a perspective electrochemical sensor for the sensitive determination of amlodipine, calcium channel blocker drug of 1,4-dihydropyridine type. Cyclic voltammetric studies indicated that the electrochemical oxidation of amlodipine is irreversible with single and well-shaped peak at a potential of +0.75 V (vs. Ag/AgCl/3 M KCl electrode) in Britton–Robinson buffer solution at pH 5. The effect of supporting electrolyte, pH and scan rate was also examined. The electrode reaction of amlodipine on boron-doped diamond electrode was shown to be a two-electron diffusion-controlled process. Under optimized conditions and using differential pulse voltammetry, the current response of amlodipine was proportional in a concentration range of 0.2–38 μM with two linear segments from 0.2 to 6 μM (R2 = 0.996) and from 6 to 38 μM (R2 = 0.998), respectively, with a limit of detection of 0.07 μM (28.6 μg L−1) and a good repeatability (relative standard deviation of 3.6% at 9.9 μM for n = 20). The practical applicability of the proposed method was demonstrated in the assessment of total content of amlodipine in pharmaceutical tablets with sufficient recoveries in the range of 101.3–104.1%. Additionally, a biological relevance of the developed procedure was demonstrated by analysis of model human urine samples with adequate recoveries (94.1% and 105.7%). The interference study revealed that the use of proposed method in this kind of analysis could be limited depending on the presence of particular excess of some common urinary compounds (uric acid, dopamine, ascorbic acid and glucose). The proposed methodology with boron-doped diamond electrode represents an effective and alternative tool instead of commonly used glassy carbon and chemically-modified electrodes for electrochemical determination of amlodipine.