Oxidation Of Captopril Research Articles

Voltammetric Detection of Captopril in a Commercial Drug Using a Gold‐Copper Metal‐organic Framework Nanocomposite Modified Electrode

AbstractWe report the application of an electrochemical sensor based on gold‐copper metal‐organic framework immobilized on the surface of a glassy carbon electrode to the detection of captopril (CAP), an angiotensin‐converting enzyme inhibitor. Cyclic voltammetric studies showed that the joint action of gold nanoparticles and copper‐1,3,5‐benzenetricarboxylate (Cu−BTC) enhanced the electrochemical response to the Cu‐captopril complex that is adsorbed onto the surface of the electrode. Release of gold nanoparticles from Au@Cu−BTC not only increased the conductivity of the electrode but also provided a more favorable environment for the deposition of reduced Cu that is catalytically renewed on the electrode surface. The anodic current of the Cu(II)−CAP oxidation peak varied linearly within two concentration ranges, namely 0.5 to 7.0 μmol L−1 and 10 to 2500 μmol L−1, with a limit of detection of 0.047 μmol L−1. The mean recovery for the determination of captopril in commercial tablets was 100.3 % suggesting that the method has considerable potential for future industrial applications.

Rutin as an Electrochemical Mediator in the Determination of Captopril using a Graphite Paste Electrode

AbstractA simple, rapid and sensitive cyclic voltammetry method is described for the determination of the antihypertensive drug captopril in aqueous solution using a graphite paste electrode with rutin as mediator. The catalytic role of rutin in the oxidation of captopril was confirmed by the increase observed in anodic peak current at+0.44 V vs. SCE in the presence of the mediator. Anodic peak current varied linearly with the concentration of captopril in the dynamic range 0.2 to 1.0 mmol L−1. The method exhibited a limit of detection of 89.4 μmol L−1 and a reproducibility of 1 %, values that are comparable with those exhibited by other methodologies employing electrodes without any modification. The recovery rate for the determination of captopril in a pharmaceutical sample was good (91.21 %) suggesting that the described analytical technique would be effective in industrial applications whilst offering a number of advantages over published cyclic voltammetric methods.

Electrocatalytic determination of captopril using a carbon paste electrode modified with N-(ferrocenyl methylidene) fluorene-2-amine and graphene/ZnO nanocomposite

A carbon paste electrode (CPE) was modified with N-(ferrocenylmethylidene) fluorene-2-amine and graphene/ZnO nanocomposite. The electrooxidation of captopril (CAP) at the surface of the modified electrode was studied using electrochemical approaches. The electrochemical study of the modified electrode, as well as its efficiency for the electrocatalytic oxidation of captopril, is described. The electrode was used to study the electrocatalytic oxidation of captopril, by cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV) as diagnostic techniques. It has been found that the oxidation of captopril at the surface of modified electrode occurs at a potential of about 340 mV less positive than that of an unmodified CPE. DPV of captopril at the electrochemical sensor exhibited two linear dynamic ranges (0.1?100.0 and 100.0?800.0 ?M) with a detection limit (3?) of 0.05 ?M.

Simple Real-time Voltammetric Method for Captopril Determination in Pharmaceutical Formulation

A novel voltammetric assay for captopril (CAP) determination by using an electrochemically pretreated pencil graphite electrode (PGE*) is presented. The electrochemical oxidation reaction of CAP was investigated with PGE* by using cyclic voltammetry and linear sweep voltammetry techniques. CAP was electrochemically inactive at the non-pretreated pencil graphite electrode surface, while a sharp anodic wave with an anodic peak potential at around 200 mV resulted by using the PGE*. According to kinetic studies upon the electrode behavior, a new reaction mechanism for electrochemical oxidation of captopril is proposed. The sensor was examined as a selective, simple and precise new electrochemical disposable electrode for the determination of CAP in pharmaceutical samples in complex medical cases associated with sleep apnea, with good results.

High Resolution Mass Spectrometry Elucidation of Captopril’s Ozonation and Chlorination By-Products

The article evaluated the degradation of the captopril in aqueous solution after ozonation and chlorination. The process was continuously monitored focusing on the identification, mass spectrometry and elucidation of its by-products by applying direct infusion and high performance liquid chromatography, electrospray ionization high resolution mass spectrometry, in the negative ion mode. The cytotoxicity of its by-products solutions were evaluated with 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. It was observed through that after 30 min of ozonation and chlorination, there was complete oxidation of captopril, i.e., 100% removal efficiency. At these conditions, the rate of mineralization, by total organic carbon, was only 7.63% for ozonation and 6.40% for chlorination, evidencing the formation of degradation by-products. Ten captopril by-products were identified and their respective chemical structures elucidations are proposed. The treated samples and their by-products were nontoxic to HepG2 cells by MTT assay.

Cobalt hexacyanoferrate electrodeposited on electrode with the assistance of laponite: The enhanced electrochemical sensing of captopril

In this work, Co2+ ions were initially intercalated into the layers of laponite and then cobalt hexacyanoferrates (CoHCFe) were electrogenerated on the surface of laponite-Co2+ modified ITO via square wave voltammetry (SWV). At scan rate of 10mVs−1, the electrochemical response of the ITO/laponite/CoHCFe showed two pairs of well-defined redox peaks located about 0.44 and 0.672V vs.SCE, attributed to the redox reaction of CoII/CoIII and FeII/FeIII, respectively. The modified electrode was highly electrocatalytic to the captopril oxidation. Moreover, the ITO/laponite/CoHCFe exhibited an enhanced analytical performance for amperometric detection of captopril with two enlarged linear ranges from 3.0×10−7 to 1.27×10−4M and 1.63×10−4 to 3.76×10−4M and a low detection limit (0.29μM). The modified electrode was used for electrocatalytic determination of captopril in some real samples.

Voltammmetric Determination of Captopril Using Multiwall Carbon Nanotubes Paste Electrode in the Presence of Isoproterenol as a Mediator.

The electrocatalytic oxidation of captopril (CAP) was studied by modified carbon nanotubes paste electrode in the presence of isoproterenol (ISPT) using cyclic voltammetry (CV), chronoamperometry and square wave voltammetry (SWV). Also, the values of catalytic rate constant (k), and electron transfer coefficient (α) for CAP were calculated. The mechanism of CA electrochemical behavior at the modified electrode surface was analyzed by various electrochemical methods in the presence of mediator. The prepared modified electrode showed voltammetric responses with high sensitivity for CAP, making it very suitable for the detection of CAP at trace levels. Under the optimized conditions, the peak current was linear to CAP concentration over the concentration range of 0.3 to 90 μmol L(-1) using SWV. The detection limit was 0.1 μmol L(-1). The proposed method was successfully applied for the determination of CAP in the urine, tablet and patient urine samples.

Oxidation of captopril by hydrogen peroxide and peroxomonosulfate ion catalyzed by a ruthenium(III) complex: kinetic and mechanistic studies

The complex [RuIII(edta)(H2O)]− (edta4− = ethylenediaminetetraacetate) catalyzes the oxidation of captopril (CapSH) using primary oxidants, hydrogen peroxide (H2O2) and peroxomonosulfate (\( {\text{HSO}}_{5}^{ - } \)). The kinetics of the oxidation reaction were studied as a function of both oxidant (H2O2, \( {\text{HSO}}_{5}^{ - } \)) and substrate (CapSH) concentrations using stopped-flow and rapid scan stopped-flow techniques. Spectral and kinetic data are suggestive of a pathway involving rapid formation of the intermediate complex [RuIII(edta)(CapS)]2− followed by direct attack of the oxidant (H2O2 or \( {\text{HSO}}_{5}^{ - } \)) at the S atom of the coordinated CapS−. ESI–MS and HPLC analysis of the reaction products showed that captopril disulfide (CapSSCap) is the major oxidation product. A probable mechanism in agreement with the spectral and kinetic data is presented.

Mechanism of the Oxidation of Captopril by Diperiodatoargentate(III) in Aqueous Alkali: A Reaction Kinetics Study

Kinetics of the oxidation of captopril by diperiodatoargentate(III) in aqueous alkaline medium was studied spectrophotometrically in the visible region. The kinetics of oxidation was found to be first order in diperiodatoargentate(III) and to have a fractional order in the captopril concentration. Added periodate, alkali and one of the reaction products, silver(I), showed retarding effects on the rate of reaction. The oxidation product of captopril was identified as captopril disulfide, which was characterized by its IR and LC–ESI–MS spectra. It was observed that the reaction products, silver(I) and captopril disulfide, interacted to yield a silver(I)–captopril disulfide complex and this was confirmed by its LC–ESI–MS spectrum. Based on the kinetics results and other parameters, a suitable mechanism for oxidation of captopril by diperiodatoargentate(III) has been proposed in which an intermediate complex between oxidant and substrate results from the preceding step before generation of a free radical in a slow step. The rate law was derived and reaction constants have also been determined. The active species of the silver(III)–periodate complex was determined to be monoperiodatoargentate(III).

Preparation, Characterization and Electrochemical Application of ZnO‐CuO Nanoplates for Voltammetric Determination of Captopril and Tryptophan Using Modified Carbon Paste Electrode

Abstract2‐chlorobenzoyl ferrocene, was synthesized and used to construct a modified ZnO‐CuO nanoplates modified carbon paste electrode. The electrooxidation of captopril at the surface of the modified electrode was studied. Under the optimized conditions, the square wave voltammetric (SWV) peak current of captopril increased linearly with captopril concentration in the range of 5.0×10−7 to 9.0×10−4 M and detection limit of 90.0 nM was obtained for captopril. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for captopril oxidation were also determined. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of captopril and tryptophan which makes it suitable for the detection of captopril in the presence of tryptophan in real samples.

Fabrication of Ru–Pd bimetallic monolayer on nanoporous gold film electrode with excellent electrocatalytic performance towards captopril oxidation

This paper describes a simple and novel method to construct ruthenium–palladium (RuPd) bimetallic thin films by coating thin layer of RuPd metals on the nanoporous gold film (NPGF) electrode. The codeposition of Ru and Pd was done through oxidation of copper underpotential deposition (UPD) layer by Ru and Pd ions. This low RuPd-loading electrode (RuPdNPGF) behaved as the nanostructured bimetallic RuPd for the detection of captopril (CAP). Whereas at the surface of the bare electrode an electrochemical activity for CAP cannot be observed, a very sharp anodic peak of the potential of −0.295V (vs. Ag/AgCl) in pH=7.0 is obtained using the prepared RuPdNPGF electrode. RuPdNPGF exhibited an excellent performance toward electrochemical oxidation of CAP without any additional mediator showing a significant decrease in the anodic over potential, a high sensitivity and a low detection limit (1.25×10−9M) for CAP. Under the optimized conditions, the amperometric of CAP showed two linear ranges for determination of CAP: 2.50×10−9 to 4.75×10−7M CAP and 2.5×10−6 to 3.25×10−5M CAP. The results show that the RuPdNPGF electrode exhibited a selective, rapid response, good stability with excellent precision (RSD=2.19%).

Application of new ferrocene derivative for electrocatalytic determination of captopril using multiwall carbon nanotube modified carbon paste electrode

A carbon-paste electrode modified with the N-4,4'-azodianiline (ferrocenyl Schiff base) and with multiwall carbon nanotubes was used as a highly sensitive and fairly selective electrochemical sensor for trace level determination of captopril. This modified electrode shows very efficient electrocatalytic activity for anodic oxidation of captopril via substantially decreasing of anodic overpotential. The measurements carried out by application of electrochemical impedance spectroscopy, differential pulse voltammetry, cyclic voltammetry and chronoamperometry. It has been found that under optimum conditions, the oxidation of captopril occurs at potential less positive than the unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient (α) and rate constant for chemical reaction between captopril and redox sites in the modified electrode were 0.31 and 1.82 ×102 cm3 mol-1 s-1, respectively. The catalytic peak current was linearly dependent on the captopril concentration in the range of 0.1-625.0 µmol L-1 with a detection limit of 0.03 µmol L-1. Finally, the modified electrode was examined as a selective, simple, and a precise new electrochemical sensor for the determination of captopril in real sample, such as urine, with satisfactory results. KEY WORDS: Captopril, N-4,4'-azodianilineferrocene, Modified carbon paste electrode, Multiwall carbon nanotubes Bull. Chem. Soc. Ethiop. 2015, 29(1), 149-156DOI: http://dx.doi.org/10.4314/bcse.v29i1.14

Electro-oxidation of captopril at a gold electrode and its determination in pharmaceuticals and human fluids

Gold electrode was used for the oxidation of captopril in phosphate buffer solution pH 3.6 to study the influence of several physico-chemical parameters like potential, scan rate, pH and concentration by cyclic, linear sweep and differential pulse voltammetry.

Spectroscopic investigation on kinetics and mechanistic aspects to electron-transfer process into quinolinium dichromate oxidation of a high blood pressure drug captopril in acidic medium

This study investigated on kinetics of oxidation of captopril by QDC was studied spectrophotometrically in acidic medium along with its mechanistic pathway. Such studies are greatly helpful in gaining an insight into the interaction of metal ions through the study of the mechanistic pathway of CPL in redox reactions. The oxidative product of captopril was found to be captopril disulfide was separated, and identified by FT-IR. A suitable free radical mechanism was proposed. The reaction exhibited first-order kinetics with respect to [oxidant] and fractional order in CPL. Consequently, the interaction between the complex species and CPL is supported kinetic orders of reaction by spectrophotometric verification, positive entropy of activation and the first-order rate constant increased with the increase in the dielectric constant and increase ionic strength of the medium. The reaction constants involved in the mechanism were computed and the overall activation parameters were evaluated which lend support to the proposed mechanism.

Kinetics and mechanism of oxidation of captopril by diperiodatocuprate(III) in aqueous alkaline medium

Captopril is a sulfur containing drug which inhibits angiotensin-converting enzyme. Its kinetics of oxidation were studied spectrophotometrically using diperiodatocuprate(III) in aqueous alkali. Major oxidative product of captopril was identified as captopril disulfide along with trace amount of the hydrolyzed product, l-proline. Kinetics of oxidation was found to be first order each in [oxidant] and [reductant]. Rate of reaction was decreased by increasing [OH−], whereas added periodate retarded the rate. Other kinetic parameters viz., ionic strength, dielectric constant, temperature effect, and intervention of free radical were also studied. Activation parameters like E A, ΔH #, ΔS #, ΔG #, and log A were calculated. A suitable mechanism was proposed. Rate law for proposed mechanism was derived and verified. Reaction constants involved in various steps of mechanism were evaluated and used to regenerate first-order experimental rate constants at various experimental conditions.

Fabrication of a highly sensitive amperometric sensor using 1,4-phenylene-N,N′-bis (O,O-diphenylphoramidate)/CdS quantum dots/multi-walled carbon nanotubes for nanomolar detection of captopril

A novel modified glassy carbon electrode (GCE) based on a new synthesized compound 1,4-phenylene-N,N′-bis (O,O-diphenylphoramidate) (PDPP), l-cysteine capped CdS quantum dots (CdS-QDs) and multi-walled carbon nanotubes (MWCNTs) was prepared. After studying the redox properties of the modified electrode by cyclic voltammetry, it was used as an electrochemical sensor for oxidation of captopril (CAP). Combination of CdS-QDs and MWCNTs with PDPP considerably improved the current response of the GCE towards electrocatalytic oxidation of CAP. Under hydrodynamic conditions (stirred solutions) at a fixed potential, oxidation current was proportional to the CAP concentration and calibration plot was linear over the concentration range of 0.05–90μM and detection limit was found to be 15nM. The results of applying the proposed amperometric sensor for the determination of CAP in spiked urine and tablet were also encouraging.

Square wave voltammetric determination of captopril in liquid phase using N-(4-hydroxyphenyl)-3,5-dinitrobenzamide modified ZnO/CNT carbon paste electrode as a novel electrochemical sensor

The electrocatalytic oxidation of captopril (CAP) has been studied by N-(4-hydroxyphenyl)-3,5-dinitrobenzamide (N-HPDB) modified ZnO/CNT nanocomposite carbon paste electrode (N-HPDB/ZnO/CNTs/CPE). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry were used to investigate the suitability of N-HPDB as a mediator for the electrocatalytic oxidation of CAP in aqueous solution. The catalytic reaction rate constant, kh was calculated (2.28×103M−1s−1) using chronoamperometry. The square wave voltammetric (SWV) peak currents of the electrode increased linearly with the corresponding CAP concentration in the range of 5.0×10−8M–8.0×10−4M with a detection limit of 1.0×10−8M.

Electrochemical determination of captopril in the presence of acetaminophen, tryptophan, folic acid, and l-cysteine at the surface of modified carbon nanotube paste electrode

A novel carbon paste electrode (CPE) modified with 2,2′-[1,7–heptanediylbis(nitrilomethylidene)]-bis(4-hydroxyphenol) (DHB) and carbon nanotubes (CNTs) was prepared. At first, the redox properties of the modified electrode were studied by cyclic voltammetry (CV). Then, the modified electrode was used as an electrochemical sensor for oxidation of captopril (CAP). Under the optimum pH of 7.0, the overpotential of CAP oxidation decreases about 120 mV at modified electrode than unmodified CPE. Differential pulse voltammetry (DPV) of CAP at the electrochemical sensor exhibited two linear dynamic ranges (7.0–100.0 and 100.0–2,500.0 μM) with a detection limit (3σ) of 2.43 μM. DPV was used for determination of CAP in the presence of acetaminophen (AC) and tryptophan (Trp), CAP in the presence of folic acid (FA), and CAP in the presence of l-cysteine (l-Cys) by the electrochemical sensor. The proposed electrochemical sensor was used for the determination of these substances in real sample.

Electrocatalytic determination of captopril in real samples using NiO nanoparticle modified (9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)-4-ethylbenzene-1,2-diol carbon paste electrode

Synthesis and application of NiO nanoparticles (NiO/NPs) and (9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)-4-ethylbenzene-1,2-diol (DED) as high sensitive sensors for voltammetric determination of captopril (CAP) using carbon paste electrode has been reported in this work. The synthesized nanoparticles were characterized by different methods such as TEM and XRD. The electrochemical oxidation of CAP on the new NiO/NPs (9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido)-4-ethylbenzene-1,2-diol carbon paste electrode (NiO/NPs/DED/CPE) has been carefully studied. Under the best experimental conditions selected, the calibration curve for CAP was linear in the concentration range from 0.035 to 550μmolL−1 and a detection limit of 0.007μmolL−1 was obtained. The influence of pH and potential interfering substances on the determination of CAP were studied. Electrochemical impedance spectroscopy (EIS) was used to study the charge transfer properties at the electrode–solution interface. Finally, the sensor was examined as a selective, simple, and precise new electrochemical sensor for the determination of CAP in real samples, such as drugs and urine.

Voltammetric determination of captopril using a novel ferrocene-based polyamide as a mediator and multi-wall carbon nanotubes as a sensor

A modified carbon paste electrode was prepared by incorporating multi-wall carbon nanotubes with a ferrocene-based polyamide (FDADO-IPC). A mixture of fine graphite powder with 10 wt % of multi-wall carbon nanotubes was applied to the preparation of the carbon paste (by dispersing in paraffin) that was finally modified with a ferrocene polyamide complex. The electrocatalytic oxidation of captopril (CAP) was investigated on the surface of the FDADO-IPC multi-wall carbon nanotubes modified carbon paste electrode (FDADO-IPC-MCNTPE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CHA) and chronocoloumetry (CHC). Using the modified electrode, the kinetics of CAP electrooxidation was considerably enhanced by lowering the anodic overpotential through a catalytic fashion. A linear dynamic range of 0.2–200 μM for CAP was obtained in buffered solutions at pH 7.0. The detection limit was 0.08 μM. Differential pulse voltammetry as a simple, rapid, sensitive, and selective method was developed for the determination of CAP in tablet and human urine without any treatment.