Simultaneous determination of antihypertensive drugs by flow injection analysis using multiple pulse amperometric detection with a cathodically pretreated boron-doped diamond electrode

• Hydrochlorothiazide (HTZ) and enalapril (ENP) were simultaneously determined for the first time.
• Flow injection analysis and multiple pulse amperometric detection were used.
• The electrochemistry method used a cathodically pretreated BDD electrode.
• The developed method was applied for determination of analytes in pharmaceutical formulations.
• The obtained results are in agreement with those of a comparative HPLC method.

A flow injection analysis (FIA) and multiple pulse amperometric detection (MPA) using a cathodically pretreated boron-doped diamond electrode (CPT-BDD) were employed for simultaneous determination of the antihypertensive drugs hydrochlorothiazide (HTZ) and enalapril (ENP). A dual-potential waveform as a function of time, previously optimized, was used: Edet.1 = + 1.50 V / 150 ms (pulse potential at which HTZ was oxidized) and Edet.2 = + 1.80 V / 150 ms (pulse potential at which oxidation of both analytes – HTZ and ENP – occurs). The analytical curves presented good linearity from 0.40 to 8.00 μmol L− 1 for HTZ and from 0.03 to 1.00 μmol L− 1 for HTZ, and the detection limits were 0.20 μmol L− 1 for HTZ and 0.01 μmol L− 1 for ENP. The proposed flow method presented an analytical frequency of 89 determinations per hour, good precision and accuracy, was successfully applied to the simultaneous determination of HTZ and ENP in pharmaceutical samples and the results obtained using the FIA–MPA method were in agreement with those obtained using a comparative method (HPLC) at a 95% confidence level.

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