Plain Carbon Paste Electrode Research Articles

Enantioselective analysis of Moxifloxacin hydrochloride enantiomers with graphene-β-Cyclodextrin-nanocomposite modified carbon paste electrode using adsorptive stripping differential pulse Voltammetry

Enantioselective analysis of Moxifloxacin hydrochloride (MOX) enantiomers was investigated on carbon paste electrode (CPE) modified with chiral selector β-Cyclodextrin and graphene nanosheets (GNS) employing adsorptive stripping differential pulse voltammetric (AdSDPV) technique. Electrochemical chiral discrimination was obtained due to β-Cyclodextrin, which has 35 chiral centres as a binding site resulting in very tight fit inclusion complex based on host-guest interactions. Enantioselectivity of present electrode system of graphene nanosheets and β-cyclodextrin modified carbon paste electrode (GNS-β-CD-CPE) gives difference in anodic oxidation peak potential of enantiomers S,S-MOX and R,R-MOX at 1.039V and 0.917V in B.R buffer solution in pH 7 confirming successful enantiomer detection respectively. Various techniques such as X-Ray diffraction (XRD), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA) and Fourier transform infra red spectroscopy (FT-IR) were employed for characterization of electrode surface. The electrocatalytic response of MOX at GNS-β-CD-CPE was measured using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Electrical conductivity of modified electrode was investigated by electrochemical impedance spectroscopy (EIS) which indicates its good conductivity over plain CPE. The proposed enantioselective electrochemical sensor was highly efficient and capable of sensing optically active isomers of MOX which is the S,S-enantiomer from its potential chiral antipode R,R-MOX enantiomer with large difference of 122mV shift in peak potential which suggests great stereoselectivity is achieved due to chiral environment provided by chiral selector β-Cyclodextrin. Determination of percentage enantiomeric composition of S,S-MOX in racemic mixture extend future applications of chiral electroanalytical system of β-CD. In the present work, it is for the first time enantiomeric electrochemical recognition of multi-chiral drug with two chiral centres has been done voltammetrically.

DEVELOPMENT OF AN ELECTROCHEMICAL SENSOR MODIFIED WITH MWCNT-COOH AND MIP FOR DETECTION OF DIURON

An electrochemical sensor modified with a molecularly imprinted polymer (MIP) and carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH) was developed for the sensitive and selective detection of diuron in river water samples. An MIP was obtained by bulk polymerization using the best monomer (methacrylic acid) selected by computational simulation. The surface characteristics of the MIP and NIP (control polymer) samples were evaluated by means of surface area and pore volume determinations, using the BET method. The adsorption efficiency of the MIP was determined in adsorption tests that revealed high adsorption, relative to the control polymer. In addition, MWCNTs functionalized with carboxyl groups were used to enhance the performance of the sensor. Electrochemical studies of diuron using the MIP and MWCNT-COOH immobilized on a carbon paste electrode were performed with wave square voltammetry (SWV). The analytical parameters pH, buffer composition, and amounts of MWCNT-COOH and MIP were investigated and optimized. Excellent results were obtained with a linear range of between 5.2×10−8 and 1.25×10−6molL−1, detection limit of 9.0×10−9molL−1, and sensitivity of 5.1×105μALmol−1. The MWCNT-COOH-MIP/CPE showed an enhanced electrochemical response, with sensitivity 7.9-fold greater than for a plain carbon paste electrode (CPE). Application of the sensor using river water samples resulted in recoveries between 96.1 and 99.5% and RSD <5% (n=3), demonstrating the reliability of this device.

Simultaneous electro-catalytic oxidative determination of ascorbic acid and folic acid using Fe3O4 nanoparticles modified carbon paste electrode

The fabrication of magnetite (Fe3O4) nanoparticles modified carbon paste electrode (Fe3O4-CME) enabled facile electrochemical determination of ascorbic acid (AA) and folic acid (FA) using differential pulse voltammetry. Fe3O4 nanoparticles were synthesized by solution route and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer and scanning electron microscopy. The nanoparticles were found to have an average diameter of 22nm. The electrochemical signals showed that Fe3O4-CME enhanced the rate of oxidation of AA and FA by increasing the peak current with a corresponding decline of peak potential compared to carbon paste electrode which makes the oxidation process thermodynamically more favorable. The modified electrode had a good sensitivity toward simultaneous determination of AA and FA in a linear working range of 9.09×10−7–4.70×10−3M and 6.50×10−8–9.80×10−5M with corresponding detection limits of 2.51×10−7M and 2.01×10−9M for AA and FA respectively. Electrochemical impedance spectroscopy was employed to understand the enhancement of the Fe3O4 nanoparticles modified carbon paste electrode over plain carbon paste electrode.

Electrochemical Behavior of Vinpocetine at Carbon Paste Electrodes Modified with Calixarenes

Electrochemical behavior of vinpocetine at a plain carbon paste electrode and paste electrodes modified with different calixarenes and ammonium metavanadate was studied by means of cyclic and differential pulse voltammetry. The effect of pH and scan rate on the response at both plain and modified carbon paste electrodes has been revealed. Modification of an electrode with a mixture of ammonium metavanadate and some calixarenes led to considerable decrease of background current along with sensitivity increase as compared to an unmodified carbon paste electrode or an electrode modified with calixarenes only. For the most effective electrode composition, the linear working range was shown to be 2.10−8–6.10−6 M with a detection limit of 5.10−9 M.

Voltammetric Sensing of Phosphoproteins Using a Gallium(III) Acetylacetonate-Modified Carbon Paste Electrode

The voltammetric detection of phosphoproteins was developed using a gallium(III) acetylacetonate-modified carbon paste electrode. Because phosphate groups of the protein interacted with the gallium(III) ion, the protein was accumulated on the electrode surface. A hexaammine ruthenium(III) ion, which combined with the functional groups, was used to monitor the interaction. When phosvitin and hexaammine ruthenium(III) ions were incubated in 0.1 M acetate buffer (pH 3.2), a reduction peak of hexaammine ruthenium(III) ion at the electrode decreased as the concentration of the protein increased. In contrast, an increase in the peak current was observed with a plain carbon paste electrode. These results were caused by a competitive reaction of the phosphate groups with the hexaammine ruthenium(III) and gallium(III) ions. In the presence of α-, β- and κ-caseins, the electrode response decreased due to the order of the numbers of phosphate groups. This method could be applied to the sensing of phosphoproteins at the 10(-10) M level.

Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk

An electrochemical method based on potentiometric stripping analysis (PSA) employing a hexathia 18C6 (HT18C6) and rice husk (RH) modified carbon paste electrode (HT18C6–RH-CPE) has been proposed for the subnanomolar determination of antimony. The characterization of the electrode surface has been carried out by means of scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. By employing HT18C6–RH-CPE, a 12-fold enhancement in the PSA signal (d t/d E) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, d t/d E (s V −1) was proportional to the Sb(III) concentration in the range of 1.42 × 10 −8 to 6.89 × 10 −11 M ( r = 0.9944) with the detection limit (S/N = 3) of 2.11 × 10 −11 M. The practical analytical utilities of the modified electrode were demonstrated by the determination of antimony in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limit and excellent reproducibility. Moreover, the results obtained for antimony analysis in commercial and real samples using HT18C6–RH-CPE and those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are in agreement at the 95% confidence level.

Potentiometric stripping analysis of bismuth based on carbon paste electrode modified with cryptand [2.2.1] and multiwalled carbon nanotubes

An electrochemical method based on potentiometric stripping analysis (PSA) employing a cryptand [2.2.1] (CRY) and carbon nanotube (CNT) modified paste electrode (CRY–CNT-PE) has been proposed for the subnanomolar determination of bismuth. The characterization of the electrode surface has been carried out by means of scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronocoulometry (CC). It was observed that by employing CRY–CNT-PE, a 9-fold enhancement in the PSA signal ( dt/ dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/ dE (s/V) was proportional to the Bi(III) concentration in the range of 5.55 × 10 −8 to 9.79 × 10 −11 M ( r = 0.9990) with the detection limit (S/N = 3) of 3.17 × 10 −11 M. The practical analytical utilities of the modified electrode were demonstrated by the determination of bismuth in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as a simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. Moreover, the results obtained for bismuth analysis in commercial and real samples using CRY–CNT-PE and those obtained by atomic absorption spectroscopy (AAS) are in agreement at the 95% confidence level.

Development of a Carbon Paste Electrode Containing Benzo-15-Crown-5 for Trace Determination of the Uranyl Ion by Using a Voltammetric Technique

The interaction of macrocyclic compounds like crown ethers and UO2(2+) has been studied by electrochemical methods. A modified carbon paste electrode incorporating benzo-15-crown-5 (B15C5) was used to evaluate the electron transfer reaction of UO2(2+) by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Electrochemical impedance studies showed that charge transfer resistance was less for the B15C5-modified electrode than for the plain carbon paste electrode (PCPE). On the basis of these observations, a UO2(2+)-sensitive crown ether chemically modified electrode (CME) for trace analysis was fabricated and investigated in aqueous solutions. It was found that a 5% B15C5-CME for UO2(2+) showed a better voltammetric response than did the PCPE. UO2(2+) could be quantified at sub-microg/mL levels by differential pulse voltammetry with a detection limit of 0.03 microg/mL. By differential pulse adsorptive stripping voltammetry, UO2(2+) could be quantified in the working range of 0.002-0.2 microg/mL, with a detection limit of 1.1 microg/L. Simultaneous determination of UO2(2+), Pb(2+), and Cd(2+) was possible. The method was successfully applied to the determination of UO2(2+) in synthetic, as well as real, samples; the results were found to be comparable to those obtained by inductively coupled plasma-atomic emission spectroscopy.

Electrochemical behaviour of pyridoxine hydrochloride (vitamin B6) at carbon paste electrode modified with crown ethers

The electrochemical behaviour of pyridoxine hydrochloride (pyridoxine HCl) at the plain carbon paste electrode and the electrode modified with oxa crown ether has been studied using voltammetric and impedance measurements. The macrocycles used as modifiers were 18-crown-6, dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6 and dibenzo-24-crown-8, out of which DB18C6 gave better response for pyridoxine HCl. Tris buffer (pH 10.3) was chosen as an appropriate medium among the several supporting electrolytes of varying pH studied. The characterization of the DB18C6-modified electrode (CME-DB18C6) using kinetic parameters such as number of electrons (n) and electron transfer coefficient (α) is studied by cyclic voltammetry. Electrochemical impedance spectroscopic measurements obtained confirm the current enhancement over the modified electrode. Analytical applications of this electrode have been studied for the determination of pyridoxine HCl. A sensitive linear working range of 0.6 to 100 μg cm−3 with a detection limit of 0.4 μg cm−3 by differential pulse voltammetry was observed for pyridoxine HCl on CME-DB18C6. However, on decreasing the scan rate to 5 mV s−1, the detection limit lowered to 0.2 μg cm−3. Interference from some vitamins like thiamine hydrochloride, riboflavin, nicotinamide, para-aminobenzoic acid, cyanocobalamin, folic acid and d-biotin and amino acid l-tryptophan was studied, and simultaneously, riboflavin, thiamine hydrochloride and pyridoxine HCl were determined over the modified electrode, CME-DB18C6. The modified electrode is successfully used for the determination of pyridoxine HCl in multivitamin pharmaceutical preparations.

Electrochemical behavior of folic acid at calixarene based chemically modified electrodes and its determination by adsorptive stripping voltammetry

Voltammetric behavior of folic acid at plain carbon paste electrode and electrode modified with calixarenes has been studied. Two peaks for irreversible oxidation were observed. Out of the three calixarenes chosen for modification of the electrodes, p- tert-butyl-calix[6]arene modified electrode (CME-6) was found to have better sensitivity for folic acid. Chronocoulometric and differential pulse voltammetric studies reveal that folic acid can assemble at CME-6 to form a monolayer whose electron transfer rate is 0.00273 s −1 with 2-electron/2-proton transfer for the peak at +0.71 V against SCE. An adsorption equilibrium constant of 5 × 10 3 l/mol for maximum surface coverage of 2.89 × 10 −10 mol/cm 2 was obtained. The current is found to be rectilinear with concentration by differential pulse voltammetry. However, linearity in the lower range of concentration 8.79 × 10 −12 M to 1.93 × 10 −9 M with correlation coefficient of 0.9920 was achieved by adsorptive stripping voltammetry. The limit of detection obtained was found to be 1.24 × 10 −12 M. This method was used for the determination of folic acid in a variety of samples, viz. serum, asparagus, spinach, oranges and multivitamin preparations.

Viscosity and binder composition effects on tyrosinase-based carbon paste electrode for detection of phenol and catechol

The systematic study of the effect of binder viscosity on the sensitivity of a tyrosinase-based carbon paste electrode (CPE) biosensor for phenol and catechol is reported. Silicon oil binders with similar (polydimethylsiloxane) chemical composition were used to represent a wide range of viscosities (10–60 000 mPa s −1 at 25°C) while minimizing polarity effects. The highest response for both phenol and catechol was achieved using a silicon oil binder of intermediate viscosity (100 mPa s −1). The binder viscosity showed no appreciable effect on the direct oxidation of phenol and catechol using a plain CPE, suggesting the involvement of diffusion kinetics in the binder matrix for the enzyme-based CPE. The effect of the relative binder concentration in the carbon paste was measured over the range of 30–70%. Optimal results were obtained using 40% silicon oil. For comparison of the viscosity effects observed with the carbon paste electrode (CPE) containing silicon oil, other low and high viscosity mineral oils and paraffin waxes were also examined.

Improved selective electrocatalytic oxidation of phenols by tyrosinase-based carbon paste electrode biosensor

Tyrosinase-based carbon paste electrodes are evaluated with respect to the viscosity and polarity of the binder liquids. The electrodes constructed using a lower viscosity mineral oil yielded a greater response to phenol and catechol than those using a higher viscosity oil of similar chemical composition. Despite its relatively high viscosity, the use of silicon oil Si PS 086 as carbon paste binder resulted in a 2-fold increase over Si AR 200 and a 4–6 fold increase (over mineral oils) in responses to phenol, p-chlorophenol, and p-cresol. Also reported is the enhanced enzyme electrode response to phenol and catechol resulting from pre-oxidation of these substrates using a plain carbon paste electrode in a series (in-line) dual electrode configuration.

A polarographic investigation on interactions between cu(ii) ions and natural degradation products of a herbicide atrazine

AbstractA study was performed to investigate the possible formation of coordination compounds between Cu(II), Cd(II), Zn(II), and Pb(II) ions and natural degradation products of atrazine (ATR) desisopropylatrazine (DIA), desethylatrazine (DEA), and desethyldesisopropylatrazine (DEIA), as well as parent compound ATR itself and the related s‐triazine herbicide prometryne (PRO). By using polarographic and voltammetric titrations of a metal ion with a ligand and vice versa, at mercury drop or plain carbon paste electrode, only a formation of coordination compounds involving Cu(II) ions, of a type CuL2 (L = DEA, DIA, and PRO) and CuL (L = DEIA) in aqueous solutions at pHs above 4, were observed. By applying an indirect polarographic method with ligand exchange (EDTA), a conditional stability constant of CuDEIA was determined, and the value β CcuDEIA = 12.7 was obtainted.

Catalytic-voltammetric determination of the antioxidant tert-butylhydroxyanisole (BHA) at a nickel phthalocyanine modified carbon paste electrode

The voltammetric behaviour of the antioxidant tert-butylhydroxyanisole (BHA), at a carbon paste electrode modified with the electron mediator nickel phthalocyanine, is described, and a method for the determination of this antioxidant, based on its oxidation on the modified electrode, is proposed. Cyclic voltammograms showed a well-defined oxidation peak for BHA slightly shifted towards less positive potentials with respect to that obtained at the plain carbon paste electrode. The peak current measured at the modified electrode is considerably higher than that obtained at the unmodified electrode. A modifier percentage of 2%, a methanol percentage of 2% and a 0.1 mol/HClO 4 medium were chosen as working conditions. The i p vs v 1 2 plot obtained by linear sweep voltammetry showed a linear relationship over the whole scan rate range studied (5–2000 mV/sec) which is typical of a diffusion-controlled current. Using differential pulse voltammetry at ΔE = 50 mV, linear calibration graphs were obtained in the concentration ranges 1.0–30.0, 0.10–1.0 and 0.02–0.10 mg/l BHA. The detection limit was 0.0036 mg/l (2.0 × 10 −8 mol/l). Interferences from other substances commonly present in commercial antioxidant mixtures were tested. The developed method was applied to the determination of BHA in spiked potato flakes.

Tropolone Modified Carbon Paste Electrodes For Trace Measurements of Tin

Abstract Tin-sensitive chemically modified electrodes were constructed by incorporating the ligand tropolone into the carbon paste matrix. Tin is rapidly collected onto the electrodes and the resulting surfaces are characterized by cyclic and differential pulse voltammetry. the differential pulse peak current, at-0.81V, is ca. 40-fold larger than the corresponding peak at the plain carbon paste electrode. Linear calibration curves are obtained for tin concentrations ranging from 4 to 52 mg/l. the detection limit is 0.2 mg/l. Rapid renewal of the surface allows use of a single electrode in multiple determinations. the relative standard deviation (at the 7 mg/l level) is 2.0%. Interference effects are reported.