Voltammetric determination of cefpirome at multiwalled carbon nanotube modified glassy carbon sensor based electrode in bulk form and pharmaceutical formulation

A new, simple and low cost voltammetric method for the determination of cefpirome in pharmaceutical preparations has been developed using multiwalled carbon nanotube modified glassy carbon electrode (MWCNT), which showed stable response with enhanced selectivity and sensitivity over the bare glassy carbon electrode. A multiwalled carbon nanotube (MWCNT) modified glassy carbon electrode (GCE) is used for the simultaneous determination of cefpirome by differential pulse voltammetry and square wave voltammetry. Results indicated that cathodic peak of cefpirome is greatly improved at MWCNT modified GC electrode as compared with the bare GC electrode showing excellent electrocatalytic activity towards cefpirome reduction. Linear calibration curves are obtained over the concentration range 100-600 μg mL(-1) in Britton Robinson buffer at pH 4.51 with limit of detection (LOD) and limit of quantification (LOQ) are 0.647 μg mL(-1) and 2.159 μg mL(-1) using SWV and 5.540 μg mL(-1) and 18.489 μg mL(-1) using DPV, respectively. The described method is rapid and can be successfully applied for the determination of cefpirome in bulk form and pharmaceutical formulations.     

Voltammetric Determination of Neotame by Using Chitosan/Nickelnanoparticles/Multi Walled Carbon Nanotubes Biocomposite as a Modifier

A selective and simple biosensor was prepared by immobilizing chitosan/nickelnanoparticles/multi-walled carbon nanotubes biocomposite on the glassy carbon electrode surface for voltammetric quantification of neotame. The properties and morphology of the modified electrode surfaces were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX). Electro oxidation of neotame on this modified surface was examined through cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. The biocomposite modified surface (Chi/NiNPs/MWCNTs/GCE) proposed in this study showed good electrocatalytic activity for neotame with an improved voltammetric peak current at 1.004 V, unlike the bare glassy carbon electrode (GCE) surface and several other modified surfaces. Under optimum conditions, Chi/NiNPs/MWCNTs/GCE gave linear SWV responses at the range of 2 μM ∼50 μM for neotame with 0.84 μM determination limit. This voltammetric sensor was successfully employed for the quantification of neotame on food samples and showed long-term stability, advanced voltammetric behavior, and good repeatability. Selective, accurate, and precise determination of neotame highlight the importance of this electrode in monitoring the control of food additives and ensures attract a great deal of attention.     

Metal ion analysis in contaminated water samples using anodic stripping voltammetry and a nanocrystalline diamond thin-film electrode

Boron-doped nanocrystalline diamond thin-film electrodes were employed for the detection and quantification of Ag (I), Cu (II), Pb (II), Cd (II), and Zn (II) in several contaminated water samples using anodic stripping voltammetric (ASV). Diamond is an alternate electrode that possesses many of the same attributes as Hg and, therefore, appears to be a viable material for this electroanalytical measurement. The nanocrystalline form has been found to perform slightly better than the more conventional microcrystalline form of diamond in this application. Differential pulse voltammetry (DPASV) was used to detect these metal ions in lake water, well water, tap water, wastewater treatment sludge, and soil. The electrochemical results were compared with data from inductively coupled plasma mass spectrometric (ICP-MS) and or atomic absorption spectrometric (AAS) measurements of the same samples. Diamond is shown to function well in this electroanalytical application, providing a wide linear dynamic range, a low limit of quantitation, excellent response precision, and good response accuracy. For the analysis of Pb (II), bare diamond provided a response nearly identical to that obtained with a Hg-coated glassy carbon electrode.     

Anodic oxidation of etodolac and its square wave and differential pulse voltammetric determination in pharmaceuticals and human serum

A voltammetric study of the oxidation of etodolac has been carried out at the glassy carbon electrode. The electrochemical oxidation of etodolac was investigated by cyclic, linear sweep, differential pulse and square wave voltammetry using glassy carbon electrode. Different parameters were tested to optimize the conditions for the determination of etodolac. The dependence of intensities of currents and potentials on pH, concentration, scan rate, nature of the buffer was investigated. For analytical purposes, a very well resolved diffusion controlled voltammetric peak was obtained in Britton-Robinson buffer at pH 2.15 for differential pulse and square wave voltammetric techniques. The linear response was obtained in the ranges of 2.10(-6)-8.10(-5) M with a detection limit of 6.8x10(-7) and 6x10(-6)-8x10(-5) M with a detection limit of 1.1x10(-6) M for differential pulse and square wave voltammetric techniques, respectively. Based on this study, simple, rapid, selective and sensitive two voltammetric methods were developed for the determination of the etodolac in tablet dosage form and human serum.     

Voltammetric determination of antibacterial drug gemifloxacin in solubilized systems at multi-walled carbon nanotubes modified glassy carbon electrode

A sensitive electroanalytical method for determination of gemifloxacin in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at multi-walled carbon nanotubes modified glassy carbon electrode in the presence of CTAB. Solubilized system of different surfactants including SDS, Tween-20 and CTAB were taken for the study of electrochemical behaviour of gemifloxacin at modified electrode. The reduction peak current increases in the presence of CTAB while other surfactants show opposite effect. The modified electrode exhibits catalytic activity, high sensitivity, stability and is applicable over wide range of concentration for the determination of gemifloxacin. The mechanism of electrochemical reduction of gemifloxacin has been proposed on the basis of CV, SWV, DPV and coulometeric techniques. The proposed squarewave voltammetric method shows linearity over the concentration range 2.47-15.5 μg/mL. The achieved limits of detection (LOD) and quantification (LOQ) are 0.90 ng/mL and 3.0 ng/mL respectively.     

Construction of an electrochemical sensor based on the electrodeposition of Au-Pt nanoparticles mixtures on multi-walled carbon nanotubes film for voltammetric determination of cefotaxime

Mixtures of gold-platinum nanoparticles (Au-PtNPs) are fabricated consecutively on a multi-walled carbon nanotubes (MWNT) coated glassy carbon electrode (GCE) by the electrodeposition method. The surface morphology and nature of the hybrid film (Au-PtNPs/MWCNT) deposited on glassy carbon electrodes is characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode is used as a new and sensitive electrochemical sensor for the voltammetric determination of cefotaxime (CFX). The electrochemical behavior of CFX is investigated on the surface of the modified electrode using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable improvement in the oxidation peak current of CFX compared to glassy carbon electrodes individually coated with MWCNT or Au-PtNPs. Under the optimized conditions, the modified electrode showed a wide linear dynamic range of 0.004-10.0 μM with a detection limit of 1.0 nM for the voltammetric determination of CFX. The modified electrode was successfully applied for the accurate determination of trace amounts of CFX in pharmaceutical and clinical preparations.     

Genetic Algorithm Based Potential Selection in Simultaneous Voltammetric Determination of Isoniazid and Hydrazine by Using Partial Least Squares (PLS) and Artificial Neural Networks (ANNs)

The voltammetric behavior of isoniazid and hydrazine at an overoxidized polypyrrole modified glassy carbon electrode has been investigated. The obtained cyclic voltammograms showed that their oxidation peaks were overlapped and it is difficult to determine them individually from a mixture without separation. To overcome this limitation, a procedure was proposed for resolution of overlapped voltammetric signals from mixtures of isoniazid and hydrazine. In this procedure, genetic algorithm was used for the selection of potentials for partial least squares. A feed forward artificial neural network with back propagation error algorithm was used to process the nonlinear relationship between currents and concentrations of hydrazine and isoniazid. The proposed method was suitable for determination of isoniazid in pharmaceutical tablets and detection of hydrazine impurities in the same samples.     

Voltammetric behaviour of antimalarial drug artesunate in solubilized systems

The voltammetric behaviour of artesunate is studied at glassy carbon electrode in different buffer systems using square wave, differential pulse and cyclic voltammetric techniques. The peak current is linear with the drug concentration in the range 4.0-40 μg mL(-1) for serum, plasma and urine. The mean percentage recoveries of the drug, urine, plasma and serum samples are 98.6-100.2%. No electroactive interferences from the excipients and endogenous substance could be observed in the pharmaceutical dosage forms and in biological samples.     

Sonoelectroanalytical detection of lead at a bare copper electrode

The sonochemically facilitated, mercury free detection of Pb2+ at a copper electrode has been investigated as a means of simplifying the quantification of this important analyte and to minimise the interference of copper ion. The procedure relies upon maximising the formation of Pb-Cu intermetallic compounds leading to the emergence of a single, easily quantifiable stripping signal. Linear responses to Pb2+ were obtained with a sensitivity comparable to that obtained at a bare glassy carbon electrode. Interference from Cu2+, Zn2+ and Cd2+ was assessed on the copper electrode with no appreciable change in the Pb2+ voltammetric profile observed. In contrast, bare glassy carbon showed a significant change in Pb2+ voltammetric profile as Cu2+ was added, due to the formation of intermetallic species.     

Voltammetric determination of coenzyme Q10 in pharmaceutical dosage forms

A simple and rapid voltammetric method has been developed for the quantitative determination of coenzyme Q(10) (CoQ(10)) in pharmaceutical preparations. Studies with differential pulse voltammetry (DPV) were carried out using a glassy carbon electrode (GCE) in a mixed solvent containing 80 vol.% acetic acid and 20 vol.% acetonitrile. A well-defined reduction peak of CoQ(10) was obtained at -20 mV vs. Ag/AgCl. The voltammetric technique applied provides a precise determination of CoQ(10) using the multiple standard addition method. The statistical parameters and the recovery study data clearly indicate good reproducibility and accuracy of the method. The accuracy of the results assessed by recovery trials was observed to be within the range of 101.1% to 102.5%. The detection and quantification limits were found to be 0.014 mM (12 mg L(-1)) and 0.046 mM (40 mg L(-1)), respectively. An analysis of real samples containing CoQ(10) showed no interferences with common additives and excipients, such as unsaturated fatty acids and soya lecithin. The method proposed does not require any pretreatment of the pharmaceutical dosage forms. A spectrophotometric determination of CoQ(10) in real samples diluted in mixtures containing ethanol and n-hexane was also performed for comparison.     

Challenge Approach of an Inexpensive Electrochemical Sensor for Rapid Selective Determination of two Non‐classical β‐Lactams in Presence of Different Degradants and Interference Substances

An inexpensive stability−indicating anodic voltammetric method for rapid determination of two non‐classical β ‐lactam antibiotics; Meropenem (MP) and Ertapenem (EP) has been developed and validated. The method was based on the enhancement of voltammetric response at a disposable graphite pencil electrode (GPE). Differential pulse voltammetric (DPV) method was developed for quantification of both drugs in B−R buffer solution (pH 2.0) at GPE. The GPE displayed very good voltammetric behavior with significant enhancement of the peak current compared to glassy carbon electrode (GCE). Stress stability studies were performed using 0.5 M of either HCl or NaOH and H₂O₂. Mass and infrared spectroscopy were used for identification of degradants and their pathways were illustrated. Under optimal conditions, the peak currents showed a linear dependence with drug concentrations. The achieved limits of detection (LOD) were 1.23, 2.07 and 1.50 μM for MP and two waves of EP, respectively. The developed voltammetric method was successfully applied for direct determination of MP and EP in drug substances, pharmaceutical vials and in presence of either their corresponding hydrolytic, oxidative‐degradants or interfering substances with no potential interferences. The differential pulse voltammograms were highly advantageous and applicable in QC laboratories for rapid, selective micro‐determination of MP and EP.     

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.     

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.     

Voltammetric Determination of Nifedipine on Carbon Nanotubes‐Modified Glassy Carbon Electrode: A new Application to Dissolution Test Studies

We report the adsorptive voltammetric determination of nifedipine on multiwalled carbon nanotubes (MWCNT)‐modified glassy carbon electrode (GCE). Nifedipine was adsorbed on the MWCNT and then reduced using linear sweep and cyclic voltammetry (LSV and CV). Parameters such as pH and accumulation time were tested. The MWCNT‐modified GCE showed enhanced currents and good signal‐to‐noise characteristics in comparison with the bare GCE. Consecutive measurements with the modified electrode were highly repeatable and reproducible. The MWCNT/GCE was used for the determination of nifedipine and is recommended for quantitation in dissolution test studies. In this study we have tested normal and extended‐release pharmaceutical formulations of nifedipine using USP apparatus 2 and tracking the released drug in solution by the proposed voltammetric method. The main advantage of the voltammetric determination is the feasibility to detect the drug in‐situ avoiding tedious intermediate steps such as filtration, collection and replenishment of sample solutions. This work seeks to demonstrate the feasibility of applying voltammetric techniques in dissolution test studies.     

Selective Voltammetric Detection of Uric Acid in the Presence of Ascorbic Acid at Well‐Aligned Carbon Nanotube Electrode

The voltammetric behaviors of uric acid (UA) and L ‐ascorbic acid (L ‐AA) were studied at well‐aligned carbon nanotube electrode. Compared to glassy carbon, carbon nanotube electrode catalyzes oxidation of UA and L ‐AA, reducing the overpotentials by about 0.028 V and 0.416 V, respectively. Based on its differential catalytic function toward the oxidation of UA and L ‐AA, the carbon nanotube electrode resolved the overlapping voltammetric response of UA and L ‐AA into two well‐defined voltammetric peaks in applying both cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which can be used for a selective determination of UA in the presence of L ‐AA. The peak current obtained from DPV was linearly dependent on the UA concentration in the range of 0.2 μM to 80 μM with a correlation coefficient of 0.997. The detection limit (3δ) for UA was found to be 0.1 μM. Finally, the carbon nanotube electrode was successfully demonstrated as a electrochemical sensor to the determination of UA in human urine samples by simple dilution without further pretreatment.     

Modification of the Electrode Surface by Ag Nanoparticles Decorated Nano Diamond‐graphite for Voltammetric Determination of Ceftizoxime

A modified glassy carbon electrode with a film of nano diamond? graphite nano mixture decorated with Ag nanoparticles (AgNPs? NDG/GCE) was constructed and used for sensitive voltammetric determination of ceftizoxime (CFX). Morphology of AgNPs? NDG/GCE has been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental variables such as deposited amount of the modifier suspension, pH of the supporting electrolyte and accumulation potential and time were optimized by monitoring of CV and LSV responses of CFX. The results illustrate that AgNPs? NDG/GCE exhibits an excellent electrocatalytic effect in the electro‐oxidation of CFX that leads to a considerable improvement in the corresponding anodic peak current. This also allows the development of a highly sensitive voltammetric sensor for the determination of CFX in pharmaceutical and clinical samples. Under the optimum conditions, the modified electrode showed a linear response to the concentration of CFX in the range of 0.02–7 µM with detection limit of 6 nM. The prepared modified electrode has some remarkable electrochemical properties such as simple preparation, high sensitivity, excellent repeatability and reproducibility and long‐term stability.     

Electro-oxidation and determination of trazodone at multi-walled carbon nanotube-modified glassy carbon electrode

A simple and rapid electrochemical method was developed for the determination of trace-level trazodone, based on the excellent properties of multi-walled carbon nanotubes (MWCNTs). The MWCNT-modified glassy carbon electrode was constructed and the electrochemical behavior of trazodone was investigated in detail. The cyclic voltammetric results indicate that MWCNT-modified glassy carbon electrode can remarkably enhance electrocatalytic activity towards the oxidation of trazodone in neutral solutions. It leads to a considerable improvement of the anodic peak current for trazodone, and allows the development of a highly sensitive voltammetric sensor for the determination of trazodone. Trazodone could effectively accumulate at this electrode and produce two anodic peaks at about 0.73 V and 1.00 V. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the trazodone determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit are 0.2-10 μM and 24 nM, respectively for trazodone. The proposed method was successfully applied to trazodone determination in pharmaceutical samples. The analytical performance of this sensor has been evaluated for detection of analyte in urine as a real sample.     

Electroanalytical investigation and determination of pefloxacin in pharmaceuticals and serum at boron-doped diamond and glassy carbon electrodes

The anodic behavior and determination of pefloxacin on boron-doped diamond and glassy carbon electrodes were investigated using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. In cyclic voltammetry, pefloxacin shows one main irreversible oxidation peak and additional one irreversible ill-defined wave depending on pH values for both electrodes. The results indicate that the process of pefloxacin is irreversible and diffusion controlled on boron-doped diamond electrode and irreversible but adsorption controlled on glassy carbon electrode. The peak current is found to be linear over the range of concentration 2 × 10⁻⁶ to 2 × 10⁻⁴ M in 0.5 M H₂SO₄ at about +1.20 V (versus Ag/AgCl) for differential pulse and square wave voltammetric technique using boron-doped diamond electrode. The repeatability, reproducibility, precision and accuracy of the methods in all media were investigated. Selectivity, precision and accuracy of the developed methods were also checked by recovery studies. The procedures were successfully applied to the determination of the drug in pharmaceutical dosage forms and humans serum samples with good recovery results. No electroactive interferences from the excipients and endogenous substances were found in the pharmaceutical dosage forms and biological samples, respectively.     

Sensitive detection of sulfanilamide by redox process electroanalysis of oxidation products formed in situ on glassy carbon electrode

This paper reported a simple method for sulfanilamide determination by redox process electroanalysis of oxidation products (SFDox) formed in situ on glassy carbon electrode. The CV experiments showed a reversible process after applied E _acc = + 1.06 V and t _acc = 1 s, in 0.1 mol L^?1 BRBS (pH = 2.0) at 50 mV s^?1. Different voltammetric scan rates (from 10 to 450 mV s^?1) suggested that the redox peaks of SFDox on the glassy carbon electrode (GCE) is an adsorption-controlled process. Square-wave voltammetry (SWV) method optimized conditions showed a linear response to SFD from 3.00 to 250.0 μmol L^?1 (R = 0.998) with a limit of detection of 0.638 μmol L^?1 and limit of quantification of 2.0 μmol L^?1. The developed the SWV method was successfully used in the determination of SFD pharmaceutical formulation and human serum. The SFD quantification results in pharmaceutical obtained by SWV-GCE were comparable to those found by official analytical protocols.     

Voltammetric Determination of Arsenic with Modified Glassy Carbon Electrode

In this study, glassy carbon electrode modified with nano gold‐crystal violet film has been used to detect arsenite (As (III)) in a model system and in groundwater samples. The modified electrode was characterized by scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS). Using voltammetric measuring technique, linear response was obtained in a concentration range of 2.0–22.0 μM. The arsenite concentrations in groundwater samples varied between 2.4 μM to 4.8 μM. The sensitivity of the modified electrode for As (III) detection was 5.6 μA/μM cm² and 0.8 μM concentration was found as lower limit of detection (LOD). The accuracy of the method was checked with standard method anodic stripping voltammetry (ASV). Groundwater samples were characterized with dynamic (DLS) and electrophoretic (ELS) light scattering measurements which have shown that particles present in different samples differ in size distribution and zeta potential which did not interfere with As (III) detection.