Anodic Voltammetric Behavior and Determination of Antihistaminic Agent: Fexofenadine HCl

Abstract

A voltammetric study of the oxidation of fexofenadine HCl (FEXO) has been carried out at the glassy carbon electrode. The electrochemical oxidation of FEXO was investigated by cyclic, linear sweep, differential pulse (DPV), and square wave (SWV) voltammetry using glassy carbon electrode. The oxidation of FEXO was irreversible and exhibited diffusion‐controlled process depending on pH. The dependence of intensities of currents and potentials on pH, concentration, scan rate, nature of the buffer was investigated. Different parameters were tested to optimize the conditions for the determination of FEXO. For analytical purposes, a very well resolved diffusion‐controlled voltammetric peak was obtained in Britton‐Robinson buffer at pH 7.0 with 20% constant amount of methanol for DPV and SWV techniques. The linear response was obtained in supporting electrolyte in the ranges of 1.0×10^?6–2.0×10^?4 M with a detection limit of 6.6×10^?9 M and 5.76×10^?8 M and in serum samples in the ranges of 2.0×10^?6–1.0×10^?4 M with a detection limit of 8.08×10^?8 M and 4.97×10^?8 M for differential pulse and square wave voltammetric techniques, respectively. Only square wave voltammetric technique can be applied to the urine samples, and the linearity was obtained in the ranges of 2.0×10^?6–1.0×10^?4 M with a detection limit of 2.00×10^?7 M. Based on this study, simple, rapid, selective and sensitive two voltammetric methods were developed for the determination of FEXO in dosage forms and biological fluids. For the precision and accuracy of the developed methods, recovery studies were used. The standard addition method was used for the recovery studies. No electroactive interferences were found in biological fluids from the endogenous substances and additives present in tablets.     

Electrochemical investigation and determination of ceftazidime in pharmaceutical dosage forms and human urine

A voltammetric study of the oxidation of Ceftazidime (CEFT) has been carried out at the glassy carbon electrode by cyclic, differential pulse (DPV) and square wave (SWV) voltammetry. The oxidation of CEFT was irreversible and exhibited diffusion controlled process depending on pH. The oxidation mechanism was proposed and discussed. According to the linear relationship between the peak current and concentration, DPV and SWV voltammetric methods for CEFT assay in pharmaceutical dosage forms and human urine were developed. For analytical purposes, a well resolved diffusion controlled voltammetric peak was obtained in 0.1 M H₂SO₄ at 1.00 and 1.02 V for differential pulse and square wave voltammetric techniques, respectively. The linear response was obtained within the range of 4 × 10^?6?8 × 10^?5 M with a detection limit of 6 × 10^?7 M for differential pulse and 4 × 10^?6–2 × 10^?4 M with a detection limit of 1 × 10^?6 M for square wave voltammetric technique. The determination of CEFT in 0.1 M H₂SO₄ was possible over the 2 × 10^?6–1 × 10^?4 M range in urine sample for both techniques. The standard addition method was used for the recovery studies.     

Electroanalytical Determination of Opipramol in Pharmaceutical Preparations and Biological Fluids

Abstract

The electrooxidative behavior and determination of opipramol, a tricyclic compound for therapy of anxious-depressive states and general anxiety disorder, were investigated at a glassy carbon electrode using cyclic, linear sweep, differential pulse and Osteryoung square wave voltammetric techniques. The oxidation of opipramol was irreversible and exhibited a diffusion controlled process dependent on pH using a glassy carbon electrode. The oxidation mechanism on a glassy carbon electrode is proposed and discussed. The anodic process can be attributed to the oxidation of azepine and piperazine rings. Different parameters were tested to optimize the conditions for the determination of opipramol. The dependence of current intensities and potentials on pH, concentration, scan rate, and nature of the buffer was investigated as detailed. Opipramol in pH 3.7 acetate buffer presents a well-defined anodic response at + 0.86 V according to studies of the proposed method. The determination of opipramol was in pH 3.7 acetate buffer, which allowed quantitation over the 2 × 10^?6 to 2 × 10^?4 M range in the supporting electrolyte, 2 × 10^?6 to 6 × 10^?5 M range in the spiked serum sample, and 2 × 10^?6 to 1 × 10^?4 M range in the urine sample, for both techniques. The proposed method was applied to commercial drageés and average percente recovery was in agreement with that obtained by spectrophotometric comparison methods. The method was extended to the in vitro determination of opipramol in spiked human serum and urine.     

Electrochemical Determination and in silico Studies of Fludarabine on NH2 Functionalized Multiwalled Carbon Nanotube Modified Glassy Carbon Electrode

A sensitive voltammetric technique has been developed for the determination of Fludarabine using amine‐functionalized multi walled carbon nanotubes modified glassy carbon electrode (NH₂‐MWCNTs/GCE). Molecular dynamics simulations, an in silico technique, were employed to examine the properties including chemical differences of Fludarabine‐ functionalized MWCNT complexes. The redox behavior of Fludarabine was examined by cyclic, differential pulse and square wave voltammetry in a wide pH range. Cyclic voltammetric investigations emphasized that Fludarabine is irreversibly oxidized at the NH₂‐MWCNTs/GCE. The electrochemical behavior of Fludarabine was also studied by cyclic voltammetry to evaluate both the kinetic (k_s and E_a) and thermodynamic (ΔH, ΔG and ΔS) parameters on NH₂‐MWCNTs/GCE at several temperatures. The mixed diffusion‐adsorption controlled electrochemical oxidation of Fludarabine revealed by studies at different scan rates. The experimental parameters, such as pulse amplitude, frequency, deposition potential optimized for square‐wave voltammetry. Under optimum conditions in phosphate buffer (pH 2.0), a linear calibration curve was obtained in the range of 2×10^?7 M–4×10^?6 M solution using adsorptive stripping square wave voltammetry. The limit of detection and limit of quantification were calculated 2.9×10^?8 M and 9.68×10^?8 M, respectively. The developed method was applied to the simple and rapid determination of Fludarabine from pharmaceutical formulations.     

Comparison of Boron-Doped Diamond and Glassy Carbon Electrodes for Determination of Terbinafine in Pharmaceuticals Using Differential Pulse and Square Wave Voltammetry

This paper examines the electrochemical oxidation of terbinafine with the boron doped diamond and glassy carbon electrodes. The studies were performed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square-wave voltammetry (SWV). The supporting electrolytes, solution pH, the range of potentials, and the scan rates were optimized. Terbinafine was irreversibly oxidized in all electrolytes, yielding well-defined peaks in the positive potential range. The peak potential shifted towards less positive values as the solution pH increased. Voltammetric determination of terbinafine was performed under the optimized conditions. Using the boron doped diamond electrode, a linear relationship between current and concentration was obtained between 5.44 × 10^?7 and 5.18 and 10^?6 mol/L with SWV and between 7.75 · 10^?7 and 8.55 · 10^?6 mol/L by DPV. At the glassy carbon electrode, a linear relationship between 7.75 · 10^?7 and 8.55 · 10^?6 mol/L was obtained by SWV and between 7.75 · 10^?7 and 1.05 · 10^?5 mol/L by DPV. The sensitivity, precision, and selectivity of the procedures were evaluated. In order to check the practical application of the developed methods, the concentration of terbinafine was determined in pharmaceutical preparations.     

Electroanalytical Characteristics of Amisulpride and Voltammetric Determination of the Drug in Pharmaceuticals and Biological Media

The electrochemical oxidation of antipsychotic drug amisulpride (AMS) has been studied in pH range 1.8–11.0 at a stationary glassy carbon electrode by cyclic, differential pulse and square‐wave voltammetry. Two oxidation processes were produced in different supporting electrolyte media. Both of the oxidation processes were irreversible and exhibited diffusion controlled. For analytical purposes, very resolved voltammetric peaks were obtained using differential pulse and square‐wave modes. The linear response was obtained in the range of 4×10^?6 to 6×10^?4 M for the first and second oxidation steps in Britton‐Robinson buffer at pH 7.0 and pH 3.0 (20% methanol v/v), respectively, using both techniques. These methods were used for the determination of AMS in tablets. The first oxidation process was chosen as indicative of the analysis of AMS in biological media. The methods were successfully applied to spiked human serum, urine and simulated gastric fluid samples.     

Electrochemical Behavior of Carvedilol and Its Adsorptive Stripping Determination in Dosage Forms and Biological Fluids

Carvedilol is used in the management of hypertension and angina pectoris and as an adjunct to standard therapy in symptomatic heart failure. The electrochemical oxidation of carvedilol was investigated using cyclic, linear sweep voltammetry at a glassy carbon electrode. In cyclic voltammetry, in all values of pH, the compound shows two irreversible oxidation peaks. These two peaks are related to the different electroactive part of the molecule. First and second peak currents were found as diffusion and adsorption controlled, respectively. Using second oxidation step, two voltammetric methods were described for the determination of carvedilol by differential pulse adsorptive stripping voltammetry (AdSDPV) and square‐wave adsorptive stripping voltammetry (AdSSWV) at a glassy carbon electrode. Accumulation of carvedilol was found to be optimized in 0.2 M H₂SO₄ solution following 275 second accumulation time at open circuit condition. Under optimized conditions, the current showed a linear dependence with concentration in the range between 2×10^?7 M and 2×10^?5 M in supporting electrolyte and in the range between 2×10^?7 M and 1×10^?5 M in spiked human serum samples for both methods. These methods were successfully applied for the analysis of carvedilol pharmaceutical dosage forms and spiked human serum samples. The repeatability and reproducibility of the methods for all media were determined. Precision and accuracy were also found. No electroactive interferences from the tablet excipients and endogenous substances from biological material were found.     

Electrochemical evaluation and determination of antiretroviral drug fosamprenavir using boron-doped diamond and glassy carbon electrodes

Fosamprenavir is a pro-drug of the antiretroviral protease inhibitor amprenavir and is oxidizable at solid electrodes. The anodic oxidation behavior of fosamprenavir was investigated using cyclic and linear sweep voltammetry at boron-doped diamond and glassy carbon electrodes. In cyclic voltammetry, depending on pH values, fosamprenavir showed one sharp irreversible oxidation peak or wave depending on the working electrode. The mechanism of the oxidation process was discussed. The voltammetric study of some model compounds allowed elucidation of the possible oxidation mechanism of fosamprenavir. The aim of this study was to determine fosamprenavir levels in pharmaceutical formulations and biological samples by means of electrochemical methods. Using the sharp oxidation response, two voltammetric methods were described for the determination of fosamprenavir by differential pulse and square-wave voltammetry at the boron-doped diamond and glassy carbon electrodes. These two voltammetric techniques are 0.1 M H₂SO₄ and phosphate buffer at pH 2.0 which allow quantitation over a 4 × 10⁻⁶ to 8 × 10⁻⁵ M range using boron-doped diamond and a 1 × 10⁻⁵ to 1 × 10⁻⁴ M range using glassy carbon electrodes, respectively, in supporting electrolyte. All necessary validation parameters were investigated and calculated. These methods were successfully applied for the analysis of fosamprenavir pharmaceutical dosage forms, human serum and urine samples. The standard addition method was used in biological media using boron-doped diamond electrode. No electroactive interferences from the tablet excipients or endogenous substances from biological material were found. The results were statistically compared with those obtained through an established HPLC-UV technique; no significant differences were found between the voltammetric and HPLC methods.     

Electrochemical Investigations of the Anticancer Drug Idarubicin Using Multiwalled Carbon Nanotubes Modified Glassy Carbon and Pyrolytic Graphite Electrodes

The effect of surface modifications on the electrochemical behavior of the anticancer drug idarubicin was studied at multiwalled carbon nanotubes modified glassy carbon and edge plane pyrolytic graphite electrodes. The surface morphology of the modified electrodes was characterized by scanning electron microscopy. The modified electrodes were constructed for the determination of idarubicin using adsorptive stripping differential pulse voltammetry. The experimental parameters such as supporting electrolyte, pH, accumulation time and potential, amount of carbon nanotubes for the sensitive assay of idarubicin were studied as details. Under the optimized conditions, idarubicin gave a linear response in the range 9.36×10^?8–1.87×10^?6 M for modified glassy carbon and 9.36×10^?8–9.36×10^?7 M for modified edge plane pyrolytic graphite electrodes. The detection limits were found as 1.87×10^?8 M and 3.75×10^?8 M based on modified glassy carbon and edge plane pyrolytic graphite electrodes, respectively. Interfering species such as ascorbic acid, dopamine, and aspirin showed no interference with the selective determination of idarubicin. The analyzing method was fully validated and successfully applied for the determination of idarubicin in its pharmaceutical dosage form. The possible oxidation mechanism of idarubicin was also discussed. The results revealed that the modified electrodes showed an obvious electrocatalytic activity toward the oxidation of idarubicin by a remarkable enhancement in the current response compared with bare electrodes.     

Anodic Oxidation of α‐Lipoic Acid at a Glassy Carbon Electrode and Its Determination in Dietary Supplements

Abstract

Direct electrochemistry of alpha‐lipoic acid (ALA) was performed at a glassy carbon electrode using cyclic, differential pulse and square wave voltammetry over a wide range of pH. The oxidation of ALA is an irreversible process, pH independent, and involves the charge transfer of one electron. The diffusion coefficient of ALA was calculated from the results obtained at pH 6.9 in 0.1 M phosphate buffer and was shown to be D ₀=1.1×10^?5 cm² s^?1. The limits of detection (LOD) and quantification (LOQ) calculated from the results obtained at this pH are 1.8 and 6.1 µM, respectively.

The lipoic acid content in two dietary supplements samples, a syrup containing ALA and capsules of ALA, has been determined directly at the glassy carbon electrode by differential pulse voltammetry using the standard addition method.     

Determination of the Anticancer Drug Sorafenib in Serum by Adsorptive Stripping Differential Pulse Voltammetry Using a Chitosan/Multiwall Carbon Nanotube Modified Glassy Carbon Electrode

Adsorptive stripping differential pulse voltammetry (AdSDPV) was applied to the assay of sorafenib in human serum sample. Cyclic voltammetry at a carbon based screen printed electrode (SPE) permitted to detect the irreversible oxidation of SOR with formation of a new compound reversibly oxidized at a lower potential. Quantitative assays were realized using a chitosan/carboxylic acid functionalized multiwalled carbon nanotube modified glassy carbon electrode in 0.1 M phosphate buffer pH 7.0 in the presence of 50 % methanol. The AdSDPV method provided two linear responses within the concentration ranges 1×10^?8–8×10^?8 M and 1×10^?7–8×10^?7 M in serum with LOQ and LOD of 3.2×10^?9 and 9.6×10^?10 of lower linear range, respectively. The recovery of sorafenib in spiked serum was 97.5 %.     

Electrochemical Determination of Anti-Hyperlipidemic Drug Ezetimibe Based on its Oxidation on Solid Electrodes

Ezetimibe is the first of a new class of drugs that selectively inhibits cholesterol absorption in the small intestine and reduces plasma LDL cholesterol. In this study, electrochemical oxidation of ezetimibe was investigated on carbon based electrodes and a single and irreversible peak at both electrodes was observed. A linear response was detected between 2 × 10^?6 and 8 × 10^?5 M with glassy carbon electrode and between 2 × 10^?6 and 2 × 10^?4 M with a boron-doped diamond electrode in 0.1 M H₂SO₄ supporting electrolyte. The proposed methods were successfully applied for the determination of ezetimibe from pharmaceutical dosage forms and human serum samples.     

Electroanalytical Characterization of Verapamil and its Voltammetric Determination in Pharmaceuticals and Human Serum

Abstract

The electrooxidative behavior and determination of Verapamil HCl, one of the class IV anti‐arrhythmic agent, on a glassy carbon disc electrode were investigated for the first time by using cyclic, differential pulse (DPV), and Osteryoung square wave voltammetry (OSWV). Verapamil showed an irreversible oxidation behavior at all pH values and buffers studied. From the electrochemical response, the main oxidation step was found to be related to the methoxy group on the phenyl ring. DPV and OSWV were used to generate peak current versus concentration curves for verapamil. A linear response was obtained in the range comprised between 8×10^?7 and 1×10^?4 M for both techniques with detection limit of 1.61×10^?7 M for DPV and 1.33×10^?7 M for OSWV. The repeatability and reproducibility of the methods for all investigated media (such as supporting electrolyte and serum samples) were determined. Precision and accuracy were also checked in all media. The methods were proposed for the determination of verapamil in dosage forms adopting both DPV and OSWV modes. The methods were extended to the in vitro determination of verapamil in spiked serum samples. No electroactive interferences from the endogenous substances were found in human plasma.     

Voltammetric Determination of Adrenaline Using a Poly(1‐Methylpyrrole) Modified Glassy Carbon Electrode

A voltammetric method using a poly(1‐methylpyrrole) modified glassy carbon electrode was developed for the quantification of adrenaline. The modified electrode exhibited stable and sensitive current responses towards adrenaline. Compared with a bare GCE, the modified electrode exhibits a remarkable shift of the oxidation potentials of adrenaline in the cathodic direction and a drastic enhancement of the anodic current response. The separation between anodic and cathodic peak potentials (ΔEp) for adrenaline is 30 mV in 0.1 M phosphate buffer solution (PBS) at pH 4.0 at modified glassy carbon electrodes. The linear current response was obtained in the range of 7.5 × 10^?7 to 2.0 × 10^?4 M with a detection limit of 1.68 × 10^?7 M for adrenaline by square wave voltammetry. The poly(1‐methypyrrole)/GCE was also effective to simultaneously determine adrenaline, ascorbic acid and uric acid in a mixture and resolved the overlapping anodic peaks of these three species into three well‐defined voltammetric peaks in cyclic voltammetry. The modified electrode has been successfully applied for the determination of adrenaline in pharmaceuticals. The proposed method showed excellent stability and reproducibility.     

Polymer-modified glassy carbon electrode for the electrochemical detection of quinine in human urine and pharmaceutical formulations

Glassy carbon electrode was modified by electropolymerization of 4-amino-3-hydroxynaphthalene sulfonic acid. Cyclic voltammetric study of quinine showed higher current response at the modified electrode compared to the bare and activated glassy carbon electrodes in pH 7.0 phosphate buffer solution. Under optimized conditions, a calibration curve was obtained by square wave voltammetry at the modified electrode. The linear relationship between the peak current and the concentration of quinine in the range of 1.0?×?10^?7 to 1.0?×?10^?5 M was I _pa (in microamperes)?=?6.26C (in micromolars)?+?0.2997 (R ²?=?0.999). The detection limit calculated (S/N?=?3) was 1.42?×?10^?8 M, which is much lower than similar reports. The method was successfully applied for the determination of quinine in spiked human urine, and pharmaceutical formulations and recovery values >90 % were obtained.     

An Electrochemical Sensor Based on Silver Nanoparticles‐Benzalkonium Chloride for the Voltammetric Determination of Antiviral Drug Tenofovir

A simple voltammetric nanosensor was described for the highly sensitive determination of antiviral drug Tenofovir. The benzalkonium chloride and silver nanoparticles were associated to build a nanosensor on glassy carbon electrode. Surface characterictics were achieved using scanning electron microscopic technique. The voltammetric measurements were performed in pH range between 1.0 and 10.0 using cyclic, adsorptive stripping differential pulse and adsorptive stripping square wave voltammetry. The linear dependence of the peak current on the square root of scan rates and the slope value (0.770) demonstrated that the oxidation of tenofovir is a mix diffusion‐adsorption controlled process in pH 5.70 acetate buffer. The linearity range was found to be 6.0×10⁻⁸–1.0×10⁻⁶ M, and nanosensor displayed an excellent detection limit of 2.39×10⁻⁹ M by square wave adsorptive stripping voltammetry. The developed nanosensor was successfully applied for the determination of Tenofovir in pharmaceutical dosage form. Moreover, the voltammetric oxidation pathway of tenofovir was also investigated at bare glassy carbon electrode comparing with some possible model compounds (Adenine and Adefovir).     

Quantitative Analysis of Irbesartan in Pharmaceuticals and Human Biological Fluids by Voltammetry

Abstract

A differential pulse (DP) and square wave (SW) voltammetric techniques were developed for the determination of irbesartan. The electrochemical behavior of irbesartan was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) at the hanging mercury drop electrode (HMDE). Different parameters were tested to optimize the conditions of the determination. It was found that in the range of 8 × 10^?6–1 × 10^?4 M, the currents measured by both of methods presented a good linear property as a function of the concentration of irbesartan. In addition, validation parameters, such as reproducibility, sensitivity, and recovery were evaluated as well. The slope of the log Ip- log ν linear plot was 0.58 indicating the diffusion control for 0.5 M sulphuric acid without the need for separation or complex sample preparation, since there was no interference from the excipients and endogenous substances.

The methods were successfully applied to the analysis of irbesartan in the pharmaceutical tablet formulations and in human serum samples.     

An electroanalytical study of the anticancer drug dacarbazine

The electrochemical behaviour of dacarbazine [5-(3,3-dimethyl-1-triazenyl) imidazole-4-carboxamide; DTIC] was investigated by Tast and differential pulse polarography (d.p.p.) at the dropping mercury electrode, by cyclic and differential pulse voltammetry at the hanging mercury drop electrode and by anodic voltammetry at the glassy carbon electrode. Calibration graphs were obtained for 2×10^?8?2×10^?5 M DTIC by d.p.p., for 5×10^?9?1×10^?5 M by adsorptive stripping voltammetry ar a hanging mercury drop electrode, and for 1?10×10^?5 M by high-performance liquid chromatography with oxidative amperometric detection at a glassy carbon electrode. The methods are compared and applied to determine DTIC added to blood serum after a simple clean-up procedure.     

Effects of covalent versus non-covalent interactions on the electrocatalytic behavior of tetracarboxyphenoxyphthalocyanine in the presence of multi-walled carbon nanotubes

Tetracarboxyphenoxy phthalocyanine was covalently linked to multi-walled carbon nanotubes and the conjugate was used for modification of glassy carbon electrodes for the detection of hydrogen peroxide. The electrocatalytic behavior was examined by cyclic voltammetry, square wave voltammetry, and rotating disk electrode. The results show that covalent linking is attractive in terms of high detecting currents, low overpotential, and high catalytic rate constants. Very low detection limits were observed with CoTCPhPc-DAMN-MWCNT(linked)-GCE at 0.33 nM. The resulting catalytic rate constant was 1.1 × 10³ M^?1s^?1.     

Preparation,Characterization and Analytical Applications of a New and Novel Electrically Conducting Polymer

In this study, a glassy carbon electrode (GC) was modified with an electropolymerized film of 1‐naphthylamine (1‐NAP) with a subsequent overoxidation treatment in 0.2 M sodium hydroxide solution. This polymer p‐1‐NAPox film coated GC electrode was used for the selective determination of dopamine (DA) in the presence of a triple concentration of ascorbic acid (AA).These studies were performed using cyclic voltammetry and square‐wave voltammetry at physiological pH. p‐1‐NAPox shows an attractive permselectivity, a marked enhancement of the current response and antifouling properties when compared to a bare GC electrode activated in basic media. With a preconcentration time of 3 minutes at open circuit, linear calibration plots were obtained for DA in buffer solution (pH 7.4) over the concentration range from 1×10^?6–1×10^?4 M with a detection limit of 1.59×10^?7 M.