Nano-gold (NG) modified glassy carbon electrodes (GCEs) were used for determination of epinephrine (EP) in the presence of high concentration ascorbic acid (AA) by cyclic voltammetry (CV). This modified electrode can...Nano-gold (NG) modified glassy carbon electrodes (GCEs) were used for determination of epinephrine (EP) in the presence of high concentration ascorbic acid (AA) by cyclic voltammetry (CV). This modified electrode can not only catalytically oxidize EP and AA, but also separate the catalytic peak potentials of EP and AA by about 183.5 mV. In pH = 7.0 ogisogate byffer solution, the linear range of epinephrine was 5 106 ~ 1 ?10-4 mol/L.展开更多
Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems,supporting electrolytes and pH using differential paise,square-wave and cyclic voltammetry.Based on its reduction behavior...Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems,supporting electrolytes and pH using differential paise,square-wave and cyclic voltammetry.Based on its reduction behavior,a direct differential pulse voltammetric method has been developed and validated for the determination of midazolam in parenteral dosage.Three welldefined peaks were observed in 0.1％ SLS,Britton-Robinson (BR) buffer of pH 2.5.The effect of surfaetants like sodium lauryl sulfate (SLS),cetyl trimethyl ammonium bromide (CTAB) and Tween 20 was studied.Among these surfactants SLS showed significant enhancement in reduction peak.The cathodic peak currents were directly proportional to the concentration of midazolam with correlation coetfficient of 0.99.展开更多
For the first time, sulfanilamide(SFD) was determined in otologic solution, human urine and serum by electroanalytical techniques on glassy carbon electrode(GCE). The cyclic voltammetry(CV) experiments showed an irrev...For the first time, sulfanilamide(SFD) was determined in otologic solution, human urine and serum by electroanalytical techniques on glassy carbon electrode(GCE). The cyclic voltammetry(CV) experiments showed an irreversible oxidation peak at t 1.06 V in 0.1 mol/L BRBS(p H ? 2.0) at 50 m V/s. Different voltammetric scan rates(from 10 to 250 m V/s) suggested that the oxidation of SFD on the GCE was a diffusioncontrolled process. Square-wave voltammetry(SWV) method under optimized conditions showed a linear response to SFD from 5.0 to 74.7 μmol/L(R ? 0.999) with detection and quantification limits of 0.92 and3.10 μmol/L, respectively. The developed SWV method showed better results for detection limit and linear range than the chronoamperometry method. It has been successfully applied to determine SFD concentration in pharmaceutical formulation, human urine and serum samples with recovery close to 100%.展开更多
A voltammetric sensor based on the electropolymerization of cobalt-poly(methionine)(Co-poly(Met)) on a glassy carbon electrode (GCE) was developed and applied for the determination of estriol by differential pulse vol...A voltammetric sensor based on the electropolymerization of cobalt-poly(methionine)(Co-poly(Met)) on a glassy carbon electrode (GCE) was developed and applied for the determination of estriol by differential pulse voltammetry (DPV) for the first time. The electrochemical properties of the Co-poly(Met)/GCE were analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the polymers on the GCE surface. The deposition of the Co-poly(Met) film on the GCE surface enhanced the sensor electronic transfer. CV studies revealed that estriol exhibits an irreversible oxidation peak at t0.58 V for the Co-poly(Met)/GCE (vs. Ag/AgCl reference electrode) in 0.10 mol/L Britton-Robinson buffer solution (pH=7.0). Different voltammetric scan rates (10-200 mV/s) suggested that the estriol oxidation on the Co-poly(Met)/GCE surface is controlled by adsorption and diffusion processes. Based on the optimized DPV conditions, the linear responses for estriol quantification were from 0.596 μmol/L to 4.76 μmol/L (R2 =0.996) and from 5.66 μmol/L to 9.90 μmol/L (R2 =0.994) with a limit of detection (LOD) of 0.0340 μmol/L and a limit of quantification (LOQ) of 0.113 μmol/L. The DPV-Co-poly(Met)/GCE method provided good intra-day and inter-day repeatability with RSD values lower than 5%. Also, no interference of real sample matrices was observed on the estriol voltammetric response, making the DPV-Copoly( Met)/GCE highly selective for estriol. The accuracy test showed that the estriol recovery was in the ranges 96.7%-103% and 98.7%-102% for pharmaceutical tablets and human urine, respectively. The estriol quantification in pharmaceutical tablets performed by the Co-poly(Met)/GCE-assisted DPV method was comparable to the official analytical protocols.展开更多
The present study reports voltammetric reduction of nitazoxanide in Britton-Robinson （B-R） buffer by cyclic and square-wave voltammetry at glassy carbon electrode. A versatile fully validated voltammetric method for...The present study reports voltammetric reduction of nitazoxanide in Britton-Robinson （B-R） buffer by cyclic and square-wave voltammetry at glassy carbon electrode. A versatile fully validated voltammetric method for quantitative determination of nitazoxanide in pharmaceutical formulation has been proposed. A squrewave peak current was linear over the nitazoxanide concentration in the range of 20-140 ~tg/mL. The limit of detection （LOD） and limit of quantification （LOQ） was calculated to be 5.23 la~/mL and 17.45 la~/mL, respectively.展开更多
In this paper, the electrochendcal behavior of bavistin (MBC) on glassy carbon electrode is reported. In a base solution of pH=9.0 NH3-NH4Cl, a sensitive anodic peak was found by cyclic voltammetry. Differential pulse...In this paper, the electrochendcal behavior of bavistin (MBC) on glassy carbon electrode is reported. In a base solution of pH=9.0 NH3-NH4Cl, a sensitive anodic peak was found by cyclic voltammetry. Differential pulse stripping voltanunetry was applied for determing MBC in grains. The detection limit is 4×10-8mo/L.The recovery is from 91.3% to 95.7%. The method has advantages of simplicity and high sensitivity.展开更多
The electrochemical behavior of paclitaxel drug was studied at a glassy carbon electrode in phosphate buffer solutions using cyclic and differential-pulse voltammetric techniques.The oxidation process was shown to be ...The electrochemical behavior of paclitaxel drug was studied at a glassy carbon electrode in phosphate buffer solutions using cyclic and differential-pulse voltammetric techniques.The oxidation process was shown to be irreversible over the pH range(3.0e10.4)and was diffusion controlled.Effects of anodic peak potential(E_(p)),anodic peak current(Ipa),scan rate,pH,heterogeneous rate constant(k^(0)),etc have been discussed.A possible electrooxidation mechanism was proposed.An analytical method was developed for the determination of paclitaxel in phosphate buffer solution at pH¼7.0 as a supporting electrolyte.The anodic peak current varied linearly with paclitaxel concentration in the range 1.0×10^-(6)M to 1.0×10^-(5)M with a limit of detection(LOD)of 1.23×10^(-8)M and limit of quantification(LOQ)of 4.10×10^(-8)M.The proposed method was successfully applied to the determination of paclitaxel in pure and real samples.展开更多
A simple and rapid method was developed using cyclic, differential pulse and square wave voltammetric techniques for the determination of trace-level chalcone at a glassy carbon electrode. Chalcone could produce two a...A simple and rapid method was developed using cyclic, differential pulse and square wave voltammetric techniques for the determination of trace-level chalcone at a glassy carbon electrode. Chalcone could produce two anodic peaks at about 0.514 V and 1.478 V and a cathodic peak at about -0.689 V. The differential pulse voltammerty presents a good linear response as compared to square wave voltammetry in the range of 0.2 - 10 μM with a detection limit of 0.18 μM. The proposed method was used successfully for its quantitative determination in spiked human plasma and urine as real samples.展开更多
Electro-catalytic oxidation and detection of hydrazine on a glassy carbon electrode,at pH 6.0,was studied by using alizarin red S as a homogeneous mediator.The overall number of electrons involved in the catalytic oxi...Electro-catalytic oxidation and detection of hydrazine on a glassy carbon electrode,at pH 6.0,was studied by using alizarin red S as a homogeneous mediator.The overall number of electrons involved in the catalytic oxidation of hydrazine and that involved in the rate-determining step were four and one,respectively.The interfering effect of some cations,anions and organic compounds were examined.Peak current for this process varied linearly with the square root of the scan rate.The kinetic parameters,such as the electron transfer coefficient(α) and catalytic rate constant(k) ,were determined using cyclic voltammetry,linear sweep voltammetry and chronoamperometry.The electro-catalytic response was optimized with regards to the pH,scan rate,hydrazine concentration and other variables.展开更多
Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper(Ⅱ) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine Cu + is shown to be ...Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper(Ⅱ) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine Cu + is shown to be adsorbed on the electrode surface in the presence of an excess of copper(Ⅱ). After accumulation period, hypoxanthine Cu + was stripped from the electrode surface and the anodic current coming near to the oxidation of Cu(Ⅰ) to Cu(Ⅱ) was measured. A linear calibration curve in the range of 5 nmol/L 1.5 mmol/L hypoxanthine, with a detection limit of 0.5 nmol/L hypoxanthine were obtained.展开更多
A differential pulse voltammetry (DPV) method for amantadine (AT) determination is developed. To this end, all the chemical and instrumental variables affecting the determination of amantadine are optimized. These stu...A differential pulse voltammetry (DPV) method for amantadine (AT) determination is developed. To this end, all the chemical and instrumental variables affecting the determination of amantadine are optimized. These studies have used three types of glassy-carbon electrode, first electrode which has not undergone surface modification or coating, to then modify the working electrode surface with two kinds of suspensions: graphene and graphene-cucurbit[7]uril (CB[7]). From studies of the mechanisms governing the electrochemical response of amantadine, it was concluded that it is an electrochemically system with a diffusive reduction phenomenon. Under optimal conditions and with the appropriate electrode modification, we proceed to study the relation between the peak intensity with the analyte concentration. Thus, we find that when the electrode surface is covered with graphene-CB[7], two linear sections are obtained, the first one in the concentration range of between 0.05 μg·mL﹣1 and 0.75 μg·mL﹣1;and the second one between 1.00 μg·mL﹣1 and 6.00 μg·mL﹣1, with Er (%) = 87 and R.S.D. = 0.94% (n = 10 at 0.5 μg·mL﹣1 level). The minimum detectable amount was 15 ng·mL﹣1 while a concentration of 44 ng·mL﹣1 was calculated as determination limit. The optimized method was applied to the determination of amantadine in biological fluids.展开更多
基金The authors gratefully acknowledge financial support from the Natural Science Foundation of Anhui Province and the Natural Science Foundation of Anhui Education Committee.
文摘Nano-gold (NG) modified glassy carbon electrodes (GCEs) were used for determination of epinephrine (EP) in the presence of high concentration ascorbic acid (AA) by cyclic voltammetry (CV). This modified electrode can not only catalytically oxidize EP and AA, but also separate the catalytic peak potentials of EP and AA by about 183.5 mV. In pH = 7.0 ogisogate byffer solution, the linear range of epinephrine was 5 106 ~ 1 ?10-4 mol/L.
文摘Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems,supporting electrolytes and pH using differential paise,square-wave and cyclic voltammetry.Based on its reduction behavior,a direct differential pulse voltammetric method has been developed and validated for the determination of midazolam in parenteral dosage.Three welldefined peaks were observed in 0.1％ SLS,Britton-Robinson (BR) buffer of pH 2.5.The effect of surfaetants like sodium lauryl sulfate (SLS),cetyl trimethyl ammonium bromide (CTAB) and Tween 20 was studied.Among these surfactants SLS showed significant enhancement in reduction peak.The cathodic peak currents were directly proportional to the concentration of midazolam with correlation coetfficient of 0.99.
基金UFESCNPq,CAPES(23068719374/2017-70)FAPES(54693900/2011,54694442/2011,60125730/2012,53671880/2011)for the financial support
文摘For the first time, sulfanilamide(SFD) was determined in otologic solution, human urine and serum by electroanalytical techniques on glassy carbon electrode(GCE). The cyclic voltammetry(CV) experiments showed an irreversible oxidation peak at t 1.06 V in 0.1 mol/L BRBS(p H ? 2.0) at 50 m V/s. Different voltammetric scan rates(from 10 to 250 m V/s) suggested that the oxidation of SFD on the GCE was a diffusioncontrolled process. Square-wave voltammetry(SWV) method under optimized conditions showed a linear response to SFD from 5.0 to 74.7 μmol/L(R ? 0.999) with detection and quantification limits of 0.92 and3.10 μmol/L, respectively. The developed SWV method showed better results for detection limit and linear range than the chronoamperometry method. It has been successfully applied to determine SFD concentration in pharmaceutical formulation, human urine and serum samples with recovery close to 100%.
基金CNPq (454438/2014-1)CAPES+1 种基金FINEPFAPEMIG for the financial support to this work
文摘A voltammetric sensor based on the electropolymerization of cobalt-poly(methionine)(Co-poly(Met)) on a glassy carbon electrode (GCE) was developed and applied for the determination of estriol by differential pulse voltammetry (DPV) for the first time. The electrochemical properties of the Co-poly(Met)/GCE were analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the polymers on the GCE surface. The deposition of the Co-poly(Met) film on the GCE surface enhanced the sensor electronic transfer. CV studies revealed that estriol exhibits an irreversible oxidation peak at t0.58 V for the Co-poly(Met)/GCE (vs. Ag/AgCl reference electrode) in 0.10 mol/L Britton-Robinson buffer solution (pH=7.0). Different voltammetric scan rates (10-200 mV/s) suggested that the estriol oxidation on the Co-poly(Met)/GCE surface is controlled by adsorption and diffusion processes. Based on the optimized DPV conditions, the linear responses for estriol quantification were from 0.596 μmol/L to 4.76 μmol/L (R2 =0.996) and from 5.66 μmol/L to 9.90 μmol/L (R2 =0.994) with a limit of detection (LOD) of 0.0340 μmol/L and a limit of quantification (LOQ) of 0.113 μmol/L. The DPV-Co-poly(Met)/GCE method provided good intra-day and inter-day repeatability with RSD values lower than 5%. Also, no interference of real sample matrices was observed on the estriol voltammetric response, making the DPV-Copoly( Met)/GCE highly selective for estriol. The accuracy test showed that the estriol recovery was in the ranges 96.7%-103% and 98.7%-102% for pharmaceutical tablets and human urine, respectively. The estriol quantification in pharmaceutical tablets performed by the Co-poly(Met)/GCE-assisted DPV method was comparable to the official analytical protocols.
文摘The present study reports voltammetric reduction of nitazoxanide in Britton-Robinson （B-R） buffer by cyclic and square-wave voltammetry at glassy carbon electrode. A versatile fully validated voltammetric method for quantitative determination of nitazoxanide in pharmaceutical formulation has been proposed. A squrewave peak current was linear over the nitazoxanide concentration in the range of 20-140 ~tg/mL. The limit of detection （LOD） and limit of quantification （LOQ） was calculated to be 5.23 la~/mL and 17.45 la~/mL, respectively.
文摘In this paper, the electrochendcal behavior of bavistin (MBC) on glassy carbon electrode is reported. In a base solution of pH=9.0 NH3-NH4Cl, a sensitive anodic peak was found by cyclic voltammetry. Differential pulse stripping voltanunetry was applied for determing MBC in grains. The detection limit is 4×10-8mo/L.The recovery is from 91.3% to 95.7%. The method has advantages of simplicity and high sensitivity.
基金One of the author(J.I.Gowda)thanks UGC,New Delhi,for the award of Research Fellowship in Science for Meritorious Stu-dents(RFSMS).
文摘The electrochemical behavior of paclitaxel drug was studied at a glassy carbon electrode in phosphate buffer solutions using cyclic and differential-pulse voltammetric techniques.The oxidation process was shown to be irreversible over the pH range(3.0e10.4)and was diffusion controlled.Effects of anodic peak potential(E_(p)),anodic peak current(Ipa),scan rate,pH,heterogeneous rate constant(k^(0)),etc have been discussed.A possible electrooxidation mechanism was proposed.An analytical method was developed for the determination of paclitaxel in phosphate buffer solution at pH¼7.0 as a supporting electrolyte.The anodic peak current varied linearly with paclitaxel concentration in the range 1.0×10^-(6)M to 1.0×10^-(5)M with a limit of detection(LOD)of 1.23×10^(-8)M and limit of quantification(LOQ)of 4.10×10^(-8)M.The proposed method was successfully applied to the determination of paclitaxel in pure and real samples.
文摘A simple and rapid method was developed using cyclic, differential pulse and square wave voltammetric techniques for the determination of trace-level chalcone at a glassy carbon electrode. Chalcone could produce two anodic peaks at about 0.514 V and 1.478 V and a cathodic peak at about -0.689 V. The differential pulse voltammerty presents a good linear response as compared to square wave voltammetry in the range of 0.2 - 10 μM with a detection limit of 0.18 μM. The proposed method was used successfully for its quantitative determination in spiked human plasma and urine as real samples.
文摘Electro-catalytic oxidation and detection of hydrazine on a glassy carbon electrode,at pH 6.0,was studied by using alizarin red S as a homogeneous mediator.The overall number of electrons involved in the catalytic oxidation of hydrazine and that involved in the rate-determining step were four and one,respectively.The interfering effect of some cations,anions and organic compounds were examined.Peak current for this process varied linearly with the square root of the scan rate.The kinetic parameters,such as the electron transfer coefficient(α) and catalytic rate constant(k) ,were determined using cyclic voltammetry,linear sweep voltammetry and chronoamperometry.The electro-catalytic response was optimized with regards to the pH,scan rate,hydrazine concentration and other variables.
文摘Nanomolar levels of the hypoxanthine in NaOH electrolyte cantaining copper(Ⅱ) can be determined by anodic stripping voltammetry at a glassy carbon electrode. In the present article hypoxanthine Cu + is shown to be adsorbed on the electrode surface in the presence of an excess of copper(Ⅱ). After accumulation period, hypoxanthine Cu + was stripped from the electrode surface and the anodic current coming near to the oxidation of Cu(Ⅰ) to Cu(Ⅱ) was measured. A linear calibration curve in the range of 5 nmol/L 1.5 mmol/L hypoxanthine, with a detection limit of 0.5 nmol/L hypoxanthine were obtained.
文摘A differential pulse voltammetry (DPV) method for amantadine (AT) determination is developed. To this end, all the chemical and instrumental variables affecting the determination of amantadine are optimized. These studies have used three types of glassy-carbon electrode, first electrode which has not undergone surface modification or coating, to then modify the working electrode surface with two kinds of suspensions: graphene and graphene-cucurbit[7]uril (CB[7]). From studies of the mechanisms governing the electrochemical response of amantadine, it was concluded that it is an electrochemically system with a diffusive reduction phenomenon. Under optimal conditions and with the appropriate electrode modification, we proceed to study the relation between the peak intensity with the analyte concentration. Thus, we find that when the electrode surface is covered with graphene-CB[7], two linear sections are obtained, the first one in the concentration range of between 0.05 μg·mL﹣1 and 0.75 μg·mL﹣1;and the second one between 1.00 μg·mL﹣1 and 6.00 μg·mL﹣1, with Er (%) = 87 and R.S.D. = 0.94% (n = 10 at 0.5 μg·mL﹣1 level). The minimum detectable amount was 15 ng·mL﹣1 while a concentration of 44 ng·mL﹣1 was calculated as determination limit. The optimized method was applied to the determination of amantadine in biological fluids.
