Electrochemical Oxidation of Pentoxifylline and its Analysis in Pure and Pharmaceutical Formulations at a Glassy Carbon Electrode

Abstract

The oxidative behavior of pentoxifylline was studied at a glassy carbon electrode in phosphate buffer solutions using cyclic and differential-pulse voltammetry. The oxidation process was shown to be irreversible over the pH range (3.0–9.0) and was diffusion controlled. The possible mechanism of the oxidation of pentoxifylline was investigated by means of cyclic voltammetry and UV-Vis spectroscopy. An analytical method was developed for the determination of pentoxifylline in phosphate buffer solution at pH 3.0 as a supporting electrolyte. The anodic peak current varied linearly with pentoxifylline concentration in the range 2.0 × 10^?8 M to 6.0 × 10^?7 M of pentoxifylline with a limit of detection (LOD) of 4.42 × 10^?10 M. The proposed method was applied to the determination of pentoxifylline in pure and pharmaceutical formulations.     

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.     

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.     

Voltammetric Determination of Dopamine in Human Serum and Urine at a Glassy Carbon Electrode Modified by Cysteic Acid Based on Electrochemical Oxidation of L ‐cysteine

Abstract

The voltammetric behavior of dopamine was studied at a glassy carbon electrode modified by cysteic acid, based on electrochemical oxidation of L ‐cysteine. The modified electrode showed strong electrocatalytic activity towards dopamine and good selectivity. In a phosphate buffer solution (pH 7.4), the anodic peak current obtain from the differential pulse voltammetry of dopamine was linearly dependent on its concentration in the range of 5×10^?9 to 4.0×10^?6mol · L^?1, with a detection limit of 2×10^?9mol · L^?1. The low‐cost modified electrode had been applied to the determination of dopamine in human serum and urine samples with satisfactory results.     

Voltammetric Behavior and Determination of Cinnarizine in Pharmaceutical Formulations and Serum

Abstract

The electrochemical reduction of cinnarizine was investigated by cyclic and linear sweep adsorptive voltammetry at glassy carbon electrode in Britton-Robinson buffers over the pH range 2.5–11.5. For analytical purposes, a well-defined adsorption-controlled cathodic peak was obtained at pH 2.5. By cathodic adsorptive linear sweep voltammetry, a linear calibration plot was obtained in the range of 2.0 × 10^?7 to 5.0 × 10^?6 mol L^?1 with detection limit of 9.0 × 10^?9 mol L^?1. The method was successfully applied to the determination of cinnarizine in commercial formulations with mean recovery and relative standard deviation of 100.24% and 1.46, respectively. The proposed method was also applied for drug determination in spiked serum samples by applying the standard addition method with a mean recovery of 97.80% and standard deviation of 3.06.     

A Validated Voltammetric Procedure for Quantification of the Antifungal Drug Griseofulvin in Bulk Form,Tablets, and Biological Fluids at a Mercury Electrode

Abstract

Griseofulvin is an antifungal antibiotic used to treat various pathogenic mycotic diseases. The voltammetric behavior of griseofulvin at a hanging mercury drop electrode in Britton‐Robinson buffers of pH 2–11.5 was studied and discussed. A fully validated sensitive square‐wave adsorptive cathodic stripping voltammetric procedure was described for direct determination of bulk griseofulvin substance. The procedure was based on the reduction of the >C?O double bond of griseofulvin molecule following its preconcentration onto a hanging mercury drop electrode in a Britton‐Robinson buffer of pH 10. Limits of detection (LOD) and quantitation (LOQ) of 5.8×10^?10 M and 1.93×10^?9 M bulk griseofulvin were achieved, respectively. The proposed stripping voltammetric procedure was successfully applied to assay griseofulvin in tablets and in spiked human serum and urine samples. LOD of 8.65×10^?10 M and 6.6×10^?9 M and LOQ of 2.88×10^?9 M and 2.2×10^?8 M griseofulvin in spiked human serum and urine samples, respectively, were achieved.     

Indirect Differential Pulse Voltammetric Determination of Aluminum Biological Samples in the Presence of 3, 4-Dihydroxyphenylalanine

ABSTRACT

Indirect differential pulse voltammetric (DPV) determination of aluminum in the presence of 3, 4-dihydroxyphenylalanine (L-dopa) with glass carbon electrode as working electrode has been described. The method relies on the decrease of DPV anodic peak current of L-dopa with the addition of Al^III The decreasing value of the peak current is linear with the increase of Al^III concentration. Under the optimum experimental conditions (pH 4.8, 6×10^?4 M L-dopa, 0.06M NaAc - HAc ¹buffer solution), the linear ranges are 4.0×10^?7 - 5.2×10^?6 M and 7.2×10^?6 - 4.5×10^?5 M. The relative standard deviation for 8×10^?6 M aluminum is 1.0% (n = 8) and the detection limit is 3.5×10^?7 M. A number of foreign species for interference have been studied. The method has been applied to determine aluminum in drinking water, synthetic renal dialysate and urine samples.     

Electrochemical Reduction and Voltammetric Determination of Metronidazole Benzoate at Modified Carbon Paste Electrode

Abstract

A metalloporphyrin incorporated carbon paste sensor has been developed for the determination of metronidazole benzoate (MTZB). Zn(II) complex of 5,10,15,20-tetrakis (3-methoxy-4-hydroxy phenyl) porphyrin (TMHPP) was used as the active material. The MTZB gave a well-defined reduction peak at?0.713 V in 0.1 mol l^?1 phosphate buffer solution of pH around 7. Compared with bare carbon paste electrode (CPE), the TMHPP Zn(II) modified electrode significantly enhanced the reduction peak current of MTZB as well as lowered its reduction potential. Under optimum conditions the reduction peak current was proportional to MTZB concentration over the range 1 × 10^?3 mol l^?1 to 1 × 10^?5 mol l^?1. The detection limit was found to be 4.36 × 10^?6 mol l^?1. This sensor has been successfully applied for the determination of MTZB in pharmaceutical formulations and urine samples.     

Nafion‐Modified Glassy Carbon Electrode for Trace Determination of Indium

Abstract

A new method for determination of trace indium is proposed by the adsorption stripping voltammetry (ASV) using a Nafion‐modified glassy carbon electrode (NMGCE). This chemically modified electrode (CME) shows a better stability. A sensitive oxidation peak was observed, and the anodic peak potential is ca. ?0.548 V (vs. SCE). The influences of various experimental parameters on the current peak were completely studied. Under the optimized condition, the method has been applied to the determination of indium in water samples. There is a good linear relationship between the peak current (i_p) and indium(III) concentration in the range of 1.0×10^?9–1.0×10^?7 mol/l, and the limit of detection is 7.5×10^?10 mol/l.     

Voltammetric Determination of L‐Dopa Using a Carbon Nanotubes‐Nafion Modified Glassy Carbon Electrode

Abstract

A method for determination of L‐dopa by the adsorption stripping voltammetry (ASV) using a multiwalled carbon nanotubes (MWNTs)–Nafion modified glassy carbon electrode (GMGCE) was proposed. This chemically modified electrode (CME) shows a better stability. A sensitive oxidation peak was observed and the anodic peak potential is ca. 0.374V (vs. SCE). The influences of various experimental parameters on the current peak were completely studied. Under the optimized condition, the method has been applied to the determination of L‐dopa in samples. There is a good linear relationship between the peak current (i_p) and L‐dopa concentration in the range of 3.5×10^?7～1.5×10^?5 mol/L, with the limit of detection 5.0×10^?8 mol/L.     

Electrochemical Studies and Square‐Wave Adsorptive Stripping Voltammetry of Spironolactone Drug

Abstract

A sensitive and reliable stripping voltammetric method was developed to determine Spironolactone drug. This method is based on the adsorptive accumulation of the drug at a hanging mercury drop electrode and then a negative sweep was initiated, which yield a well defined cathodic peak at ?1000 mV versus Ag/AgCl reference electrode. To achieve high sensitivity, various experimental and instrumental variables were investigated such as supporting electrolyte, pH, accumulation time and potential, drug concentration, scan rate, frequency, pulse amplitude, convection rate and working electrode area. The monitored adsorptive current was directly proportional to the concentration of Spironolactone and it shows a linear response in the range from 1×10^?8 to 2.5×10^?7 mol l^?1 (correlation coefficient=0.999) and the detection limit (S/N=3) is 1.72×10^?10 mol l^?1 at an accumulation time of 90 sec. The developed AdSV procedure shows a good reproducibility, the relative standard deviation RSD% (n=8) at a concentration level of 1.5×10^?7 mol l^?1 was 1.4%, whereas the method accuracy was indicated via the mean recovery of 97.5%±2.04. Possible interferences by several substances usually present in the pharmaceutical formulations have been also evaluated. The applicability of this approach was illustrated by the determination of Spironolactone in pharmaceutical preparation and biological fluids such as serum and urine.     

Electrochemical Behavior and Application of Pirarubicin at Gold Nanoparticles–Modified Indium Tin Oxide Electrode

Abstract

A new type of gold nanoparticles–attached indium tin oxide electrode was made. By SEM and EDS, the as‐prepared gold nanoparticles–modified ITO electrode was characterized. This modified electrode has been used for the determination of pirarubicin (THP) in urine by cyclic voltammetry. Compared to a bare ITO electrode, the modified electrode exhibited a marked enhancement in the current response. Liner calibration curves are obtained in the range 5×10^?9mol/L～1.5×10^?6 mol/L with a detection limit of 1×10^?9 mol/L. The percentage of the recoveries ranged from 99.3% to 106.3%. The practical analytic utility of the method is illustrated by quantitative determination of THP in urine.     

Electrochemical Study of Interaction Between Clozapine and DNA and Its Analytical Application

Abstract

The interaction between clozapine (CLZ) as an orally administrated antipsychotic drug with double stranded calf thymus DNA (dsDNA) was investigated at electrode surface using differential pulse voltammetry (DPV). Activated carbon paste electrode (CPE) was modified with dsDNA and used for monitoring the changes of the characteristics peak of CLZ in 0.05 M acetate buffer (pH 4.3). The adsorptive stripping voltammetry on dsDNA‐modified carbon paste electrode (dsDNA‐CPE) was used for determination of very low concentration of CLZ. Under optimal conditions, the oxidation peak current is proportional to CLZ concentration in the range of 7×10^?9?1.2×10^?6 mol l^?1 with a detection limit of 1.5×10^?9 mol l^?1 for 180 s accumulation time by DPV. The proposed dsDNA‐CPE was successfully used for determination of CLZ in human serum samples with recovery of 97.0±2.5%.     

A Direct Chemiluminescence Method for the Determination of Prulifloxacin Using Tris-(4,7-Diphenyl-1,10-Phenanthrolinedisulfonic Acid) Ruthenium(II)–Cerium(IV) System

Abstract

A simple, rapid, injection chemiluminescence method is described for the determination of prulifloxacin, a commonly used antibiotic. A strong chemiluminescence signal was detected when a mixture of the analyte and tris-(4,7-diphenyl-1,10-phenanthrolinedisulfonic acid)ruthenium(II) was injected into cerium(IV) sulfate. The chemiluminescence signal is proportional to the concentration of prulifloxacin in the range 4.0 × 10^?8–9.0 × 10^?6 mol L^?1. The detection limit is 1.0 × 10^?8 mol L^?1, and the relative standard deviation is 2.2% (n = 11) for the determination of 8.0 × 10^?7 mol L^?1 prulifloxacin. The proposed method was successfully applied to the determination of prulifloxacin in pharmaceutical preparations in capsules, spiked serum, and urine samples.     

Voltammetric Determination of Proguanil in Malarone and Spiked Urine with a Renewable Silver Amalgam Film Electrode

Electrochemical properties of proguanil were investigated by a voltammetric method (SWV) using a renewable silver amalgam film electrode. The influence of buffer pH as well as potential amplitude, frequency, and step potential was studied. The repeatability, precision and recovery of the developed method were examined. The reduction peak current was used for proguanil voltammetric determination in the range 1×10^?7–6×10^?6 mol L^?1, LOD=2.9×10^?8 mol L^?1, LOQ=9.7×10^?8 mol L^?1. The standard addition method was used to determine proguanil in a commercial formulation (Malarone) and in spiked urine.     

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.     

Sensitive Determination of Prulifloxacin by Its Fluorescence Enhancement on Terbium(III)–Sodium Dodecylbenzene Sulfonate System

Abstract

A terbium-sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of prulifloxacin (PUFX). It was found that SDBS significantly enhanced the fluorescence intensity of the PUFX–Tb³⁺ complex (about 13-fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 290 nm and 545 nm, pH 8.0, 4.0 × 10^?5 mol L^?1 terbium(III), and 4.0 × 10^?4 mol L^?1 SDBS. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of PUFX over the range 6.0 × 10^?8 to 2.0 × 10^?6mol L^?1 with a correlation coefficient of 0.9991. The detection limit (S/N = 3) was determined as 8.5 × 10^?9 mol L^?1. This method has been successfully applied for the determination of PUFX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range, and good stability. The luminescence mechanism of the system was also discussed in detail. In the fluorescence system of PUFX–Tb³⁺–SDBS, SDBS acted not only as the surfactant but also as the energy donor.     

Determination of Carbendazim by Adsorptive Stripping Differential Pulse Voltammetry Employing Glassy Carbon Paste Electrode Modified with Graphene and Amberlite XAD 2 Resin

Graphene nanosheets (GNS) and amberlite XAD‐2 (XAD2) modified glassy carbon paste electrode (GNS‐XAD2‐GCPE) were fabricated for voltammetric determination of Carbendazim (MBC). GNS was synthesized by Hummer’s method and characterized by SEM, EDAX, and XRD techniques. After optimizing the analytical conditions in 0.4 M citrate buffer (pH 4.0), the peak current was found to be linear in the range of 8.36×10^?9 to 4.13×10^?6 M (r=0.9986) with detection limit of 3.14×10^?9 M (S/N=3) by AdSDPV. The method was validated for the determination of MBC in soil, fruit, blood serum, urine, waste and ground water samples with satisfactory recoveries.     

Single-Sweep Voltammetric Determination of Tamoxifen at Carbon Paste Electrode

Abstract

A single-sweep voltammetric method was proposed for the determination of tamoxifen. The proposed method took advantage of both the accumulation of carbon paste electrode toward tamoxifen and the rapidity of single-sweep voltammetry. In HAc-NaAc (pH 4.1) buffer/methanol (85:15 v/v) mixed solution, an irreversible oxidation peak of tamoxifen was observed at 1.1 V (versus SCE). The second-order derivative peak current of tamoxifen and its concentration plots were rectilinear over the range of 7.0 × 10^?10 ～ 3.0 × 10^?8 mol · l^?1 with a detection limit of 1.0 × 10^?10 mol · l^?1 without any preconcentration. The proposed method was evaluated by analyzing tamoxifen citrate tablets, which was characterized by rapidity and higher sensitivity.