Ruthenium Hexacyanoferrate (III) Modified Glassy Carbon Electrode for Determination of Captopril

Abstract

A glassy carbon electrode modified with a ruthenium (III) hexacyanoferrate film was investigated for the determination of captopril in pharmaceutical formulations. The RuOHCF film was deposited on the surface of the electrode after applying 50 successive cycles and subsequent stabilization in a mixture of NaNO3 0.50 mol L−1+HCl 0.050 mol L−1 used as supporting electrolyte. The main processes responsible for the redox electrode response are attributed to the system RuII/RuIII/RuIV, and appeared at −0.080, 0.86 and 1.01 V (vs. SCE). The redox process at −0.080 V was selected for the determination of captopril in the present study, once it provided higher sensibility and occurs in a lower potential than the other ones which can prevent interferences. The experimental parameters used in the determination of the analyte, using differential pulse voltammetry were optimized: pulse amplitude: 50 mV, scan rate: 5 mV s−1 and potential window: −0.5 to 0.2 V (vs. SCE). The analytical application of the sensor in real samples demonstrated a linear range between 0.060 and 0.80 µmol L−1 (r=0.998) with a detection limit of 0.047 µmol L−1. A mechanism based on co‐precipitation of captopril and the Ru (III) complex in the film is presented once the signal of the RuII/III redox couple decreases with increasing the analyte concentration. Recoveries of 99 to 100 % were achieved in pharmaceutical samples and the proposed procedure agreed with the HPLC official method within 95 % confidence level, according to the t‐Student test.

Gold Nanoparticles/Biphenol–biphenoquinone for Ultra‐trace Voltammetric Determination of Captopril

“…It is important to mention that for BOH, pKa 1 =pKa 2 =9.7 [15], and for CP, p K a 1 =3.7 (for −COOH) and p K a 2 =9.8 (for −SH) [16]. Accordingly, in agreement with previous literature, the electrochemical process at the surface of CPE/Au NPs−BOH−BQ was proposed [16–17] (eqs. 1–3…”

“…Furthermore, a study was conducted to compare the proposed modified electrode with the previous literature. Based on table 1S, it was demonstrated that the suggested sensor exhibits lower D.L and comparable linear range pointing to the fact that the suggested sensor is a more appropriate one for the determination of CP [4a, [17][18].…”