Differential Pulse Techniques Research Articles

Electrochemical Behaviour of the Bactericidal Cefoperazone and its Selective Voltammetric Determination in Pharmaceutical Dosage Forms and Human Serum

Cefoperazone sodium is irreversibly oxidized at the glassy carbon electrode in various buffer systems and at different pH values using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. The oxidation of cefoperazone sodium was irreversible and exhibited diffusion controlled process depending on pH. A detailed oxidation mechanism was proposed and discussed. The dependence of peak current and potentials on pH, concentration, scan rate, nature of the buffer was investigated. According to the linear relationship between the peak current and the concentration, differential pulse (DPV) and square wave (SWV) voltammetric methods for cefoperazone sodium assay in pharmaceutical dosage forms and biological fluids were developed. The determination of cefoperazone sodium was proposed in phosphate buffer at pH 2.00, which allows quantitation over the 4x10 – 6 – 2x10 – 5 M and 4x10 – 6 – 6x10 – 5 M ranges in supporting electrolyte for DPV and SWV, respectively, and 4x10 – 6 – 2x10 – 5 M in spiked serum samples for both techniques. The repeatability, reproducibility, precision and accuracy of the methods in all media were investigated. Precision and accuracy of the developed method were used for the recovery studies. 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 pharmaceutical dosage form. Keywords: Cefoperazone, Dosage forms, Electrochemistry, Biological samples, Oxidation, Analysis

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 H 2SO 4 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.

Electrochemical behavior of vardenafil on glassy carbon electrode: Determination in tablets and human serum

The voltammetric behavior of vardenafil was studied on glassy carbon electrode using cyclic, differential pulse (DPV) and Osteryoung square-wave (OSW) voltammetric techniques. Vardenafil exhibited irreversible anodic waves over the pH range 1.00–12.00 in different supporting electrolytes. The current–concentration plot was rectilinear over the range from 4 × 10 −7 to 2 × 10 −5 M with correlation coefficient of 0.999. The wave was characterized as being irreversible and diffusion-controlled. The developed procedure was successfully applied to the determination of vardenafil in tablets and in spiked human serum. Furthermore, results obtained by the proposed method have been compared with high-performance liquid chromatographic method.

Anodic voltammetric behavior and determination of cefixime in pharmaceutical dosage forms and biological fluids

The voltammetric behavior of cefixime was studied using cyclic, linear sweep, differential pulse and square wave voltammetric techniques. The oxidation of cefixime was irreversible and exhibited diffusion controlled process depending on pH. The oxidation mechanism was proposed and discussed. Different parameters were tested to optimize the conditions for the determination of cefixime. The dependence of current intensities and potentials on pH, concentration, scan rate, nature of the buffer was investigated. According to the linear relationship between the peak current and the concentration, differential pulse (DPV) and square wave (SWV) voltammetric methods for cefixime assay in pharmaceutical dosage forms and biological fluids were developed. For the determination of cefixime were proposed in acetate buffer at pH 4.5, which allows quantitation over the 6 × 10 −6–2 × 10 −4 M range in supporting electrolyte and spiked serum sample; 8 × 10 −6–2 × 10 −4 M range in urine sample; 6 × 10 −6–1 × 10 −4 M range in breast milk samples for both techniques. The repeatability, reproducibility, precision and accuracy of the methods in all media were investigated. No electroactive interferences from the excipients and endogenous substances were found in the pharmaceutical dosage forms and in the biological samples, respectively.

Study of a Catalytic Mechanism in Additive Differential Pulse Techniques

AbstractThe new electrochemical double pulse technique, known as additive differential normal pulse voltammetry (ADNPV) when there is no restriction on the duration of both pulses, and additive differential pulse voltammetry (ADPV) when t2≪t1, has been applied to a pseudo‐first‐order catalytic mechanism. The expressions obtained here are applicable to planar and spherical electrodes, of any radius. This is of great interest since the size of the electrode plays an important role in the preponderating of diffusive and kinetics processes. The signal obtained with this technique presents the same morphological characteristics as the triple pulse technique, double differential pulse voltammetry (DDPV) and is more advantageous than DDPV and than the double pulse one, differential pulse voltammetry (DPV).

Electroanalytical characteristics of piribedil and its differential pulse and square wave voltammetric determination in pharmaceuticals and human serum

The electrochemical oxidative behavior of piribedil (PR) was described. It was investigated by cyclic, linear sweep, differential pulse (DPV) and square wave (SWV) voltammetric techniques. The redox behavior of PR was found irreversible. Different parameters were tested to optimize the conditions for the determination of PR. The dependence of intensities of currents and potential on pH, concentration, scan rate, nature of the buffer was investigated. Two sensitive methods for the measurement of PR were described. For analytical purposes, a very well resolved diffusion controlled voltammetric peak was obtained in 0.1 M H 2SO 4 and pH 5.7 acetate buffer. The determination peaks are obtained at 1.27 and 0.95 V for differential pulse and 1.29 and 0.97 V for SWV in 0.1 M H 2SO 4 and pH 5.7 acetate buffer, respectively. The linear response was obtained in the ranges of 2×10 −6–1×10 −3 M in 0.1 M H 2SO 4 and 2×10 −6–8×10 −4 M in pH 5.7 acetate buffer for both techniques. The proposed techniques were successfully applied to the determination of PR in tablet dosage forms and human serum. Excipients did not interfere in the determination. The necessary statistical validation reveals that the proposed methods are free from significant systematic errors.

Multistep Electrode Processes in Double Potential Step Techniques

A rigorous analytical solution for linear diffusion corresponding to the double potential step problem for a reversible multistep process is derived. The expressions obtained are valid for any value of the formal potentials of each step and can be applied to any double pulse technique without restriction on the duration of both pulses. Differential pulse techniques are applied to the study of reversible processes with different number of steps.

Voltammetric Analysis of Alfuzosin HCl in Pharmaceuticals, Human Serum and Simulated Gastric Juice

The electrochemical oxidation of alfuzosin was investigated by cyclic, linear sweep, differential pulse and square-wave voltammetry at glassy carbon disk electrode. Alfuzosin hydrochloride showed a well-defined anodic wave in Britton-Robinson and phosphate buffers over the pH range 2–7.5. For analytical purposes, a very well resolved diffusion controlled voltammetric peak was obtained in phosphate buffer at pH 6.0 for differential pulse and square-wave voltammetric techniques. The linear response was obtained in the ranges of 6×10−7 M – 1×10−4 M for both tecniques. Detection limits were found 1.56×10−7 M for DPV and 6.2×10−8 M for SWV. Based on this study, simple, rapid, selective and sensitive two voltammetric methods were developed for the determination of the alfuzosin in tablet dosage form, human serum and simulated gastric juice.

Study of an EE mechanism using double potential step techniques

An analytical solution corresponding to the double potential step problem for a reversible EE mechanism is presented. This solution is applicable to any double pulse technique without restrictions on the duration of the first and second potential steps and is valid when several species are initially present in the solution. The influence of the duration of the two pulses on the characteristic of the current–potential curves on differential and reverse double pulse techniques in static and dynamic electrodes is also discussed.

Study of an EE mechanism in additive differential pulse techniques

Additive differential pulse techniques are applied to the study of a reversible EE mechanism. Analytical solutions are obtained in additive differential normal pulse voltammetry (ADNPV) and in additive differential pulse voltammetry (ADPV). The usefulness of these techniques in obtaining accurate simultaneous determinations of the formal potentials of both electrochemical steps when they are not completely separated is discussed and also applied to the study of the reduction of pyrazine in aqueous acid media. Excellent agreement between experimental results and theoretical predictions has been found.

Electrochemical study of fluvastatin sodium--analytical application to pharmaceutical dosage forms, human serum, and simulated gastric juice.

The oxidation of fluvastatin sodium on a glassy carbon electrode has been studied by use of a variety of voltammetric techniques. Different conditions were investigated to optimize the determination of fluvastatin sodium. The dependence of the intensities of currents and potentials on pH, concentration, scan rate, and nature of the buffer was investigated. Oxidation of fluvastatin sodium was found to be diffusion-controlled and irreversible. The best results for the determination of fluvastatin sodium were obtained by using differential pulse and square-wave voltammetric techniques in Britton-Robinson buffer at pH 10.04. Differential pulse and square-wave voltammetry at a glassy carbon electrode resulted in linear calibration in the range 8x10(-6) to 6x10(-4) mol L(-1) and detection limits of 1.07x10(-6) and 7.99x10(-7) mol L(-1), respectively. The proposed methods were successfully applied to the determination of the drug in capsules and biological fluids. Excipients did not interfere with the determination. Statistical validation revealed that the methods were free from significant systematic errors.

Electroanalysis of Endosulfan and o -Chlorophenol in Polypyrrole Coated Glassy Carbon Electrode

Electroanalysis of endosulfan, an important organochlorine pesticide and o -chlorophenol, a toxic pollutant was carried out with polypyrrole coated glassy carbon electrode. Pyrrole was electropolymerised on glassy carbon electrode potentiostatically at 0.9 V. Cyclic voltammogram, square wave voltammogram, differential pulse stripping voltammogram and square wave stripping voltammogram under their optimum experimental conditions were obtained for the determination of both compounds. On polypyrrole coated electrode, higher peak current response was observed with differential pulse and squarewave stripping techniques. Comparatively better analytical signal was noticed with square waveform than the differential pulse form. Optimum stripping voltammetric conditions were arrived and the calibration plot was made. The determination limit is 2.457 2 10 m 3 and 23.346 mM for endosulfan and 7.779 2 10m 3 and 26.916 mM for o-chlorophenol.

Determination of trace bismuth by solid phase extraction and anodic stripping voltammetry in non-aqueous media

The voltammetric characteristics of Bi(III) oxinate at the mercury electrode in chloroform are investigated. Anodic stripping voltammetry (ASV) for the determination of trace bismuth was developed in chloroform, using the differential pulse technique to strip the amalgamated bismuth from hanging mercury drop electrode (HMDE). The experimental variables such as scan rate of electrode potential, deposition potential, deposition time and stirring speed were optimized. The linear range of calibration graph and the detection limit were 5×10 −8 to 5×10 −6 and 3.5×10 −9 M for Bi(III), respectively. Preceded by a preconcentration stage by solid phase extraction using octylsilane (RP-8) cartridge and subsequent elution by chloroform, the detection limit of the method is improved in 4.5×10 −10 M. The suitability of the proposed method for determination of trace bismuth in real sample was established by the analysis of a metallic aluminum sample.

Voltammetric determination of doxazosin in tablets using rotating platinum electrode.

This study describes the voltammetric behaviour of doxazosin molecule based on the oxidation on the surface of platinum electrode in the stationary and rotating conditions and determine doxazosin in the tablets by differential pulse technique at only rotating condition. The experiments were carried out in the supporting electrolyte consisting of 0.2 M KCl and 0.2 M buffer solution in 10% (v/v) ethanol. The effect of initial potential was investigated and no adsorption effect was observed during use of +500 mV. The influence of pH on the peak current and peak potential was examined and the most symmetrical peaks were obtained at 0.5 M H2SO4 for rotating conditions. In the rotation range of 50-1000 rpm and up to 1.0x10(-5) M doxazosin, the factor affecting the voltammetric current was diffusional. The effect of rate of potential was tested between 2 and 20 mV for the stationary condition and the character of current was found to be diffusional up to 3x10(-5) M concentration of doxazosin solutions. The voltammetric determination of doxazosin in tablets was realised in the optimum rotating system conditions and depending on the statistical evaluations, acceptable results were obtained. Therefore, the method proposed in this study is practical, sensitive and accurate for the analysis of doxazosin in the quality control laboratories.

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 6.8×10 −7 and 6×10 −6–8×10 −5 M with a detection limit of 1.1×10 −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.

Differential pulse anodic stripping voltammetry of copper in dichloromethane: application to the analysis of human hair

The voltammetric characteristics of copper(II)–bis(acetylacetone)ethylenediimine (Cu(II)–BAE) complex in dichloromethane at the mercury electrode are investigated. Anodic stripping voltammetry (ASV) for the determination of trace-copper was developed in dichloromethane, using the differential pulse technique to strip the amalgamated copper from the hanging mercury drop electrode (HMDE). The experimental variables such as scan rate of electrode potential, deposition potential, deposition time and stirring speed of the solution were optimized. The linear range of calibration graph and the detection limit were 5 × 10 −8–10 −6 M and 1.6 × 10 −8 M of Cu(II), respectively. Preceded by wet ashing of the sample and solvent extraction of Cu(II)–BAE complex into dichloromethane, the method was used for the determination of copper in human hair as a typical example of application.

Voltammetric, spectrofluorimetric and spectrophotometric methods to determine flufenamic acid

Simple, rapid and sensitive voltammetric, spectrofluorimetric and spectrophotometric methods for determination of flufenamic acid (FF) in bulk powder and capsule dosage form are presented. The methods are based on the cyclisation reaction of FF with concentrated sulphuric acid to produce the corresponding acridone derivative. The voltammetric method is based on the adsorptive stripping differential pulse (DP) technique. The acridone derivative is determined over the concentration range of 8–60 ng ml −1 using adsorptive preconcentration at the hanging mercury drop electrode (HMDE). The lower detection limit was found to be 1.02 ng ml −1. The fluorimetric and spectrophotometric methods are based on the measurement of the fluorescence intensity at 450 nm ( λ ex=400 nm)and peak-to-peak measurements of the first- (D 1) and second-derivative (D 2) curves, respectively. Beer’s law is obeyed over the concentration ranges of 2–20 ng ml −1 and 0.2–8.0 μg ml −1 for the fluorimetric and spectrophotometric measurements, respectively. The three methods were proved to be accurate and reproducible as indicated by a relative standard deviation of <2%.

Adsorptive stripping square-wave voltammetric behavior of insulin

The adsorptive stripping voltammetric behavior of bovine insulin has been studied by both differential pulse and square-wave techniques, leading to analytical methodologies for its determination in aqueous samples and pharmaceutical preparations. The application of a square-wave mode for the stripping of adsorbed bovine insulin has proved to be much more sensitive, yielding signals 20 times larger than those obtained by applying a differential pulse scan. The precision obtained for the voltammetric method, at a concentration level as low as 0.77 mg L–1 of the protein, was found to be 1.45% (RSD., n = 8) by SWS and 2.20% (RSD., n = 8) by DPS. The pharmaceutical product Actrapid containing biosynthetic human insulin was analyzed by both methods.

Determination of Nifuroxazide in Human Serum by Adsorptive Stripping Voltammetry

The adsorption behavior of nifuroxazide on a hanging mercury drop electrode (HMDE) was critically examined using cyclic voltammetry and differential pulse techniques. The effect of different parameters on the accumulation behavior of the adsorbed species was tested. Thus, a sensitive stripping voltammetry procedure for the determination of nifuroxazide with an adsorptive accumulation on the surface of HMDE has been developed. Under optimal conditions a detection limit of 5×10-9 Mand a linear calibration graph in the range 2×10-8 - 1×10-7 M were obtained. The precision, expressed by the relative standard deviation, was 2.8% (n=10) at 1×10-7 M. The method was successfully applied for the analysis of nifuroxazide in serum.

Differential pulse anodic stripping voltammetry of lead (lI) benzoylacetonate in chloroform: Application to the analysis of free-lead gasoline and gas oil samples

The voltammetric characteristics of lead(II) benzoylacetonate in chloroform at the mercury electrode are investigated. The conditions for nearly reversible reduction of lead(II) were optimized. Anodic stripping voltammetry for the determination of trace-lead was developed using differential pulse technique to strip amalgamed lead from hanging mercury drop electrode. The experimental conditions, such as scanning rate of electrode potential and deposition time of lead were optimized. The calibration graph was linear over concentration range 5×10 −8–10 −6 M of lead(II). The detection limit was 2.5×10 −9 and the relative standard deviation for the determination of 4×10 −7 M Pb(II) was 2%. Preceded by decomposition of organolead compounds with concentrated nitric acid, then ashing at 300°C and a solvent extraction of Pb(II) benzoylacetonate in chloroform, the suitability of the proposed method for the determination of lead in free-lead gasoline and gas oil was demonstrated as a typical example of application.