Electrochemical Oxidation and Determination of Theophylline at a Carbon Paste Electrode Using Cetyltrimethyl Ammonium Bromide as Enhancing Agent

Abstract

The oxidation of theophylline was studied at a carbon paste electrode in the presence of cetyltrimethyl ammonium bromide by cyclic and differential pulse voltammetry. The results indicated that the electrochemical responses of theophylline are apparently improved by cetyltrimethyl ammonium bromide, due to the enhanced accumulation of theophylline at carbon paste electrode surface. Under optimal conditions the peak current was proportional to theophylline concentration in the range of 8.0 × 10^?7 to 2.0 × 10^?4 M with a detection limit of 1.85 × 10^?7 M by differential pulse voltammetry. The proposed method was applied to the determination of theophylline in tablet and urine samples.     

Electrochemical studies of determination of C.I. Direct Red 80 based on a gold nanoparticles-modified carbon paste electrode

In this paper, a simple, convenient and sensitive electrochemical method has been developed for the determination of C.I. Direct Red 80. A gold nanoparticle modified carbon paste electrode was fabricated and used for study and sensitive determination of Direct Red 80 by cyclic voltammetry and differential pulse voltammetry. The overall analysis involved a two-step procedure: an accumulation step under open-circuit conditions, followed by voltammetric measurements of Direct Red 80 in a 0.1?M phosphate buffer solution at pH?=?3.0. The experimental conditions, such as the medium, pH and accumulation time, were optimised. The oxidation peak current was proportional to the concentration of Direct Red 80 from 5.0?×?10^?8 to 5.0?×?10^?7?M and 5.0?×?10^?7 to 3.0?×?10^?6?M, and the detection limit was 1.15?×?10^?8?M (S/N?=?3). The proposed method was used to detect Direct Red 80 in natural water and sewage with good accuracy.     

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.     

β‐Cyclodextrin Incorporated Carbon Nanotube Paste Electrode as Electrochemical Sensor for Nifedipine

In this work a carbon paste electrode modified with multiwalled carbon nanotubes/β‐cyclodextrin (MWCNTs/β‐CD) was constructed and applied to the determination of nifedipine. The electrochemical behavior of nifedipine at this electrode was investigated using cyclic voltammetry and differential pulse voltammetry. Characterization of the modified electrode was conducted with electrochemical impedance spectroscopy and scanning electron microscopy. After adsorption of nifedipine on the MWCNTs/β‐CD paste electrode at 0.0 V for 6 min, a well defined reduction peak was produced in sodium hydroxide of 0.05 M. The calibration curve was linear from 7.0×10^?8 to 1.5×10^?5 M. The detection limit was obtained as 2.5×10^?8 M. The results demonstrated that this electrochemical sensor has excellent sensitivity and selectivity. This sensor was applied for determination of nifedipine in drug dosage and blood serum with excellent recoveries.     

Determination of Tetracycline by Microdroplet Hydrodynamic Adsorptive Voltammetry Using a Multiwalled Carbon Nanotube Paste Rotating Disk Electrode

A novel and simple method is proposed for the determination of tetracycline by adsorptive voltammetry in a droplet using a carbon nanotube paste rotating disk electrode (CNTP-RDE). An enhanced electrochemical oxidation response of tetracycline was observed in pH 8.2 supporting electrolyte by the addition of a long-chain cationic surfactant, such as benzyldimethyltetradecylammonium chloride (zephiramine). Under the optimized experimental conditions, the calibration curve was linear across a tetracycline concentration range from 1.0?×?10^?7 to 2.0?×?10^?6 M. The limit of detection and sensitivity were 4.0?×?10^?8 M and 0.9358?A M^?1, respectively. This method was successfully employed for the determination of tetracycline in milk samples.     

Simultaneous Determination of Hydroquinone and Catechol at a Glassy Carbon Electrode Modified with Multiwall Carbon Nanotubes

A simply and high selectively electrochemical method for simultaneous determination of hydroquinone and catechol has been developed at a glassy carbon electrode modified with multiwall carbon nanotubes (MWNT). It was found that the oxidation peak separation of hydroquinone and catechol and the oxidation currents of hydroquinone and catechol greatly increase at MWNT modified electrode in 0.20 M acetate buffer solution (pH 4.5). The oxidation peaks of hydroquinone and catechol merge into a large peak of 302 mV (vs. Ag/AgCl, 3 M NaCl) at bare glassy carbon electrode. The two corresponding well‐defined oxidation peaks of hydroquinone in the presence of catechol at MWNT modified electrode occur at 264 mV and 162 mV, respectively. Under the optimized condition, the oxidation peak current of hydroquinone is linear over a range from 1.0×10^?6 M to 1.0×10^?4 M hydroquinone in the presence of 1.0×10^?4 M catechol with the detection limit of 7.5×10^?7 M and the oxidation peak current of catechol is linear over a range from 6.0×10^?7 M to 1.0×10^?4 M catechol in the presence of 1.0×10^?4 M hydroquinone with the detection limit of 2.0×10^?7 M. The proposed method has been applied to simultaneous determination of hydroquinone and catechol in a water sample with simplicity and high selectivity.     

Electrocatalytic determination of propranolol hydrochloride at carbon paste electrode based on multiwalled carbon-nanotubes and γ-cyclodextrin

A carbon paste electrode based on γ-cyclodextrin–carbon nanotube composite (γ-CD–CNT–CME) was developed for the determination of propranolol hydrochloride (PRO). The electrochemical behaviour of PRO was investigated employing cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse adsorptive stripping voltammetry (DPAdSV). Surface morphology of the electrode has been studied by means of scanning electron microscopy. The results revealed that the oxidation of PRO is facilitated at γ-CD–CNT–CME. Under the optimized conditions in Britton–Robinson buffer pH 1.5, the peak currents were found to vary linearly with their concentrations in the range of 1.42 × 10^?7 to 4.76 × 10^?5 M. A detection limit (S/N = 3) of 4.01 × 10^?8 M was obtained for PRO by means of DPAdSV. The proposed method was employed for the determination of PRO in pharmaceutical formulations, urine and blood serum samples.     

A Selective and Sensitive Method for Simultaneous Determination of Traces of Paracetamol and p‐Aminophenol in Pharmaceuticals Using Carbon Ionic Liquid Electrode

A reliable and simple electrochemical method has been proposed for the simultaneous determination of paracetamol (PAR) and p‐aminophenol (PAP) in pharmaceutical formulations. The oxidation and reduction peak potentials in cyclic voltammetry (CV) for PAR on carbon ionic liquid electrode (CILE) were occurred at 370 and 225 mV vs. Ag/AgCl, respectively at pH 7.0, while those for PAP on CILE appeared at 128 mV and 68 mV, respectively at the scan rate of 0.05 V s^?1. In comparison to the conventional carbon paste electrode, the apparent reversibility and kinetics of the electrochemical reactions of PAR and PAP were significantly improved on CILE. In differential pulse voltammetric technique, the peak potentials for PAR and PAP appeared at 345 and 130 mV, respectively, with the peak separation of 215 mV, sufficient for their simultaneous determination in samples containing these two species. The proposed method was used for simultaneous determination of PAR and PAP in tablets. PAR and PAP can be determined in the ranges of 2.0×10^?6–2.2×10^?3 M and 3.0×10^?7–1.0×10^?3 M, with the detection limits of 5.0×10^?7 and 1.0×10^?7 M (calculated by 3σ), respectively. The relative standard deviations for the determination of PAR and PAP were less than 2%.     

Electro‐oxidation and Determination of Tripelennamine Hydrochloride at MWCNT‐CTAB Modified Glassy Carbon Electrode

An electrochemical method for the determination of tripelennamine hydrochloride (TPA) using cetyltrimethylammoniumbromide‐multiwalled carbon nanotubes modified glassy carbon electrode (MWCNT‐CTAB/GCE) was developed. Because of good electrical conductivity of MWCNT and catalytic behavior of CTAB, new electrode significantly enhances the sensitivity for the detection of TPA. Parameters such as amount of modifier suspension, scan rate, pH of measure solution, heterogeneous rate constant were investigated. The electrode exhibits a linear potential response in the range of 1.0×10^?8 M to 3.0×10^?6 M with a detection limit of 2.38× 10^?9 M. The modified electrode was successfully applied to the determination of TPA in pharmaceutical and real samples.     

Electrochemical Behavior and Determination of Phenylephrine at Silicate Nanotubes Modified Electrode

A novel Silicate nanotubes (SNTs) modified glass carbon (GC) electrode was prepared and used to study the electrochemcial behavior of phenylephrine (PHE) and determine it. The enhanced electrochemical response of PHE at SNTs modified electrode was observed as compared with bare GC electrode. This proposed method displayed a broad linear range and a lower detection limit for PHE. The linear range was from 8 × 10^?8 M to 2 × 10^?5 M with the detection limit of 1 × 10^?8 M. The electrode could be easily regenerated and exhibited high stability and good selectivity. This method was successfully applied to the determination of PHE in drug samples with satisfactory result. The strategy presented here opens a new way for the development of nanoelectronic devices or electrochemical sensors based on SNTs.     

Simultaneous Determination of Ascorbic Acid,Dopamine and Uric Acid at Pt Nanoparticles Decorated Multiwall Carbon Nanotubes Modified GCE

A modified electrode was fabricated by electrochemically deposition of Pt nanoparticles on the multiwall carbon nanotube covered glassy carbon electrode (Pt nanoparticles decorated MWCNT/GCE). A higher catalytic activity was obtained to electrocatalytic oxidation of ascorbic acid, dopamine, and uric acid due to the enhanced peak current and well‐defined peak separations compared with both, bare and MWCNT/GCE. The electrode surfaces were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). Individual and simultaneous determination of AA, DA, and UA were studied by differential pulse voltammetry. The detection limits were individually calculated for ascorbic acid, dopamine, and uric acid as being 1.9×10^?5 M, 2.78×10^?8 M, and 3.2×10^?8 M, respectively. In simultaneous determination, LODs were calculated for AA, DA, and UA, as of 2×10^?5 M, 4.83×10^?8 M, and 3.5×10^?7 M, respectively.     

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 Analysis of D‐Penicillamine Using a Carbon Paste Electrode Modified with Ferrocene Carboxylic Acid

The electrochemical behavior of D ‐penicillamine (D ‐PA) studied at the surface of ferrocene carboxylic acid modified carbon paste electrode (FCAMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found that under optimum condition (pH 7.00), the oxidation of D ‐PA at surface of such an electrode is occurred about 420 mV less positive than that an unmodified carbon paste electrode (CPE). The catalytic oxidation peak current was linearly dependent on the D ‐PA concentration and a linear calibration curve was obtained in the ranges 7.5×10^?5 M – 1.0×10^?3 M and 6.5×10^?6 M?1.0×10^?4 M of D ‐PA with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (3σ) were determined as 6.04×10^?5 M and 6.15×10^?6 M. This method was also used for the determination of D ‐PA in pharmaceutical preparation (capsules) by standard addition method.     

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.     

Electrocatalytic Characteristics of Ferrocenecarboxylic Acid Modified Carbon Paste Electrode in the Oxidation and Determination of L‐Cysteine

The electrochemical behavior of L ‐cysteine studied at the surface of ferrocenecarboxylic acid modified carbon paste electrode (FCMCPE) in aqueous media using cyclic voltammetry and double step potential chronoamperometry. It has been found that under optimum condition (pH 7.00) in cyclic voltammetry, the oxidation of L ‐cysteine is occurs at a potential about 580 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α and catalytic reaction rate constant, K′_h were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of L ‐cysteine showed a linear dependent on the L ‐cysteine concentration and linear calibration curves were obtained in the ranges of 10^?5 M–10^?3 M and 4.1×10^?8 M–3.7×10^?5 M of L ‐cysteine concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (2δ) were determined as 2.4×10^?6 M and 2.5×10^?8 M by CV and DPV methods. This method was also examined for determination of L ‐cysteine in some samples, such as Soya protein powder, serum of human blood by using recovery and standard addition methods.     

Electrochemical Characterization and Rapid Voltammetric Determination of Riluzole in Pharmaceuticals and Human Serum

The electrochemical oxidation of riluzole was investigated using cyclic and linear sweep voltammetry. Under optimized conditions, current and concentration showed linear dependence in Britton Robinson buffer at pH 3.00 for boron doped diamond and pH 3.00 phosphate buffers for glassy carbon electrodes. Differential pulse and square wave voltammetry were used for the determination of riluzole levels in serum samples and pharmaceutical formulations. The limit of detections were found as 5.25 × 10^?7 M and 8.26 × 10^?8 M for glassy carbon electrode and 1.78 × 10^?7 M and 8.42 × 10^?8 M for boron-doped diamond electrodes, in serum samples, using differential pulse and square wave methods, respectively.     

Electropolymerization of Acid Chrome Blue K on Glassy Carbon Electrode for the Determination of Curcumin

Acid chrome blue K (ACBK) was electropolymerized on the surface of a glassy carbon electrode (GCE) by cyclic voltammetric sweep in the potential range from –0.2 to 0.9 V. The characteristic of poly‐ACBK film was studied by different methods such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. This modified electrode showed excellent electrocatalytic response to curcumin with the increase of the electrochemical responses. Under the optimal conditions a good linear voltammetric response could be obtained over the range of 1.0 × 10^?7‐7.0 × 10^?5 M and the detection limit was got as 4.1 × 10^?8 M (S/N = 3). The method was successfully applied for the determination of curcumin in human urinev samples.     

Electrochemical Studies of the Interaction of 2‐Nitroacridone with DNA and Determination of DNA

A new acridone derivate 2‐nitroacridone (NAD) was synthesized and a new method of electrochemical probe has been proposed for the determination of salmon sperm DNA based on its interaction with NAD. The electrochemical behavior of interaction of NAD with DNA was investigated on glassy carbon electrode (GCE). In the presence of DNA, the peak current of NAD decreases and the peak potential shifts to a more positive potential without appearance of a new peak. The binding ratio between NAD and salmon sperm DNA was calculated to be 2 : 1 and the binding constant was 3.19×10⁵ L/mol. The decrease of the peak current (ΔI_p) of NAD was proportional to the concentration of DNA in the range from 1.55×10^?7 M to 2.02×10^?6 M with the detection limit of 3.10×10^?8 M, and DNA of synthetic sample was determined satisfactorily. Additionally, the binding mechanism was preliminarily discussed. The mode of interaction between NAD and DNA was found to be intercalation binding.     

Electrochemical behavior of adriamycin at an electrode modified with silver nanoparticles and multi-walled carbon nanotubes, and its application

An electrochemical sensor has been constructed for the determination of adriamycin (ADM) that is based on a glassy carbon electrode modified with silver nanoparticles and multi-walled carbon nanotubes with carboxy groups. The modified electrode was characterized by scanning electron microscopy and exhibits a large enhancement of the differential pulse voltammetric response to ADM. Signals are linear with the concentrations of ADM in the range from 8.2?×?10^?9 M to 19.0?×?10^?9 M, with a detection limit of 1.7?×?10^?9 M. The sensor is highly reproducible and exhibits excellent stability. It was to detect calf thymus DNA.     

Electrocatalytic Oxidation and Voltammetric Determination of Hydrazine on the Tetrabromo‐p‐Benzoquinone Modified Carbon Paste Electrode

The electrochemical properties of hydrazine studied at the surface of a carbon paste electrode spiked with p‐bromanil (tetrabromo‐p‐benzoquinone) using cyclic voltammetry (CV), double potential‐step chronoamperometry and differential pulse voltammetry (DPV) in aqueous media. The results show this quinone derivative modified carbon paste electrode, can catalyze the hydrazine oxidation in an aqueous buffered solution. It has been found that under the optimum conditions (pH 10.00), the oxidation of hydrazine at the surface of this carbon paste modified electrode occurs at a potential of about 550 mV less positive than that of a bar carbon paste electrode. The electrocatalytic oxidation peak current of hydrazine showed a linear dependent on the hydrazine concentrations and linear analytical curves were obtained in the ranges of 6.00×10^?5 M–8.00×10^?3 M and 7.00×10^?6 M–8.00×10^?4 M of hydrazine concentration with CV and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3σ) were determined as 3.6×10^?5 M and 5.2×10^?6 M by CV and DPV methods. This method was also used for the determination of hydrazine in the real sample (waste water of the Mazandaran wood and paper factory) by standard addition method.