Silica Modified Carbon Paste Electrode Research Articles

Spot on Gold Nanoparticles/Silica Modified Electrode for Rapid Sensitive Determination of Dinoprostone

A novel simple and selective electrochemical procedure is utilized for the determination of Dinoprostone (DIN) in drug substance and pharmaceutical preparation with good recovery and without interference with other excipient. Herein, the electrochemical sensing platform based upon preparing gold nanoparticle sensor on silica modified carbon paste electrode. The surface morphology of the modified electrode was characterized by scanning electron microscope. Different experimental conditions, including electrode composition, effect of pH and scan rate were estimated carefully by cyclic voltammetry to obtain the highest electrochemical response. By using square wave voltammetry a good linear response was obtained in the range of, 2 x 10-5-4 x10-4 mol L-1, and 2 x 10-7-1.6 x 10-4 mol L-1, with low detection limit of 5 x 10-6 mol L-1, and 4.9 x 10-8 mol L-1 by CPE and GNP/SMCPE respectively. The obtained results are in good agreement with those obtained by official method. No electrochemical method was reported before for determination of DIN. The developed method was simple, rapid, economic and challenging to green analytical chemistry.

A simple and sensitive portable system for a rapid evaluation of bisphenol A contamination in potable and environmental waters using a mesoporous silica-modified carbon paste electrode

ABSTRACTIn this work, two ordered mesoporous silicas (HMS and SBA-15) were prepared and incorporated into carbon paste electrodes (CPEs) to obtain mesostructured sensors for a rapid determination of bisphenol A (BPA) in waters by voltammetric techniques. The materials were characterised by nitrogen adsorption-desorption measurements, transmission electron microscopy and scanning electron microscopy. The electrochemical properties of the modified carbon paste electrodes were studied by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Results showed that the sensor modified with HMS (HMS-CPE) exhibited strong adsorption activity toward the oxidation of BPA, with a well-defined voltammetric peak at +0.6 V. Moreover, the HMS-CPE exhibited a wider linearity range, from 0.44 to 3.5 μM BPA, with a detection limit of 61 nM (S/N = 3) and good reproducibility by DPV. The enhanced performance of the HMS-CPE could be attributed to its high surface area, with a 3 D wormhole-like channel structure that favoured an excellent accessibility, high adsorption capacity and faster adsorption rate of BPA. This novel sensor was coupled to a portable system and successfully applied for a rapid determination of BPA in tap, mineral, well and river water samples with good recovery, ranging from 98 ± 12 to 103 ± 7%.

Voltammetric Determination of Lidocaine and Its Toxic Metabolite in Pharmaceutical Formulation and Milk Using Carbon Paste Electrode Modified with C18 Silica

A new voltammetric method was developed for simultaneous determination of lidocaine hydrochloride (LH) and its toxic metabolite (2, 6-dimethylaniline (DMA)) based on their oxidation and adsorption on C18 silica modified carbon paste electrode (SMCPE). Several experimental factors including the effect of pH, scan rate, percentage of silica, accumulation potential and time were studied and the optimum conditions were found to be: pH 11 ± 0.10 using Britton Robinson buffer, 100 mV/s scanning rate, −0.6V accumulation potential, 150 s accumulation time and 5% C18 silica. Under the optimized conditions, applying square wave voltammetry (SWV) displayed two signals for DMA and LH at 0.56 and 0.87 V, respectively. The method revealed satisfactory results in terms of linearity (7.94 × 10−6 to 1.07 × 10−4 M) for LH and (1.20 × 10−6 to 1.07 × 10−5 M) for DMA, accuracy, and precision. The limit of detection was found to be 2.19 × 10−6 and 2.15 × 10−7 M for LH and DMA in pure forms, respectively. The developed SWV method was further applied for the assay of LH in its pharmaceutical dosage form and DMA in spiked milk samples.

Nano-silica modified electrode as a sensor for the determination of mefenamic acid - A voltammetric sensor

Electrochemical oxidation of mefenamic acid was investigated at the surface of carbon paste electrode with silica nanoparticles as an modifier. The electrode surface was characterized by using SEM and TEM. Voltammetric behaviour of mefenamic acid was studied using cyclic voltammetric method. A nano silica modified carbon paste electrode was used to investigate the electrochemical oxidation of mefenamic acid. Comparison of bare carbon paste electrode and silica nanoparticles modified carbon paste electrode, it was observed that the modified electrode has advantage of high sensitivity and selectivity with low detection limit. Effect of supporting electrolyte (phosphate buffer, I = 0.2 M) solution in the range, 3.0 – 11.2 pH was investigated and found that pH 5 is suitable for the investigations. In addition, effect of scan rate variations was studied to calculate some of the physiochemical properties. An electrode reaction mechanism was proposed and differential pulse voltammetric method was developed for the analytical application. Further, the applicability of the proposed method was investigated for pharmaceutical dose form and human urine samples.

Simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode

A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0μM–1.0mM range for hydroquinone with the detection limit of 1.2μM and from 30.0μM–1.0mM for catechol with the detection limit of 1.1μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples.

A nano sized functionalized mesoporous silica modified carbon paste electrode as a novel, simple, robust and selective anti-diabetic metformin sensor

A novel, simple, selective and robust sensor has been developed for the electrochemical determination of metformin (MET) using anodic stripping voltammetry. The sensor was designed by incorporating of a nano sized mesoporous silica material functionalized by copper ion (SBA-15-Cu(II)) in the carbon paste electrode (CPE). The sensitivity of the sensor was improved by increasing the accumulation of MET on the surface of the electrode through complex with copper ions. The synthesized SBA-15-Cu(II) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Under optimized conditions, the modified electrode exhibited a linear response over the MET concentration range of 0.1–65μM, with a detection limit of 30nM. Also, the applicability of the method to the direct assays of the pharmaceutical and biological fluid real samples was investigated.

Simultaneous determination of aminophenol isomers based on functionalized SBA-15 mesoporous silica modified carbon paste electrode

The electrochemical behaviors of aminophenol (AP) isomers at amino-functionalized SBA15 modified carbon paste electrode (NH2-SBA15/CPE) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in Britton–Robinson buffer solutions (pH 9.0). The results demonstrated that the NH2-SBA15/CPE exhibited a strong electrocatalytic performance toward aminophenol isomers, and the oxidation peak potential of each analyte in aminophenol isomers mixtures could be well separated. A selective method was developed for the determination of ortho-(o-), meta-(m-) and para-(p-) aminophenol simultaneously, without any chemical separations. Under the optimized conditions, the linear range was 0.3–18μmolL−1 for o-aminophenol, 0.3–16μmolL−1 for m-aminophenol and 0.1–12μmolL−1 for p-aminophenol, respectively, with detection limit of 0.05μmolL−1 for o- and m-aminophenol, 0.02μmolL−1 for p-aminophenol. The proposed method was applied to quantitatively determine aminophenol isomers in river sample with satisfactory recoveries.

Highly sensitive determination of capsaicin using a carbon paste electrode modified with amino-functionalized mesoporous silica

Mesoporous silica (MS) and amino-functionalized mesoporous silica (NH2-FMS) were prepared and characterized using the techniques of transmission electron microscopy (TEM) and nitrogen adsorption–desorption. Voltammetry was used to investigate the electrochemical behavior of capsaicin at the amino-functionalized mesoporous silica, which was modified through carbon paste electrode (NH2-FMS/CPE). NH2-FMS/CPE showed better performance for the electrochemical oxidation of capsaicin, when compared with bare carbon paste electrode (CPE) and mesoporous silica modified carbon paste electrode (MS/CPE). We optimized the experimental conditions influencing the determination of capsaicin. Under optimal conditions, the oxidation peak current was proportional to capsaicin concentration in the range of 0.040–0.40μmolL−1and 0.40–4.0μmolL−1, when the detection limit was 0.020μmolL−1 (S/N=3). The above method was successfully applied to determine capsaicin in hot pepper samples, yielding satisfactory results. The spiked recoveries were in the range of 93.1–100.7%.

Electrochemical behavior and simultaneous determination of dihydroxybenzene isomers at a functionalized SBA-15 mesoporous silica modified carbon paste electrode

The simultaneous voltammetric determination of dihydroxybenzene isomers was investigated using cyclic and differential pulse voltammetries at the amino-functionalized SBA-15 mesoporous silica-modified carbon paste electrode (NH2-SBA15/CPE) in phosphate buffer solution (pH 6.0). The NH2-SBA15/CPE showed a larger peak current and higher selectivity for the dihydroxybenzene isomers in comparison with the bare carbon paste electrode (CPE) and SBA-15 mesoporous silica-modified carbon paste electrode (SBA15/CPE). The oxidation peak potential difference between hydroquinone (HQ) and catechol (CC) was 115mV and was 396mV between catechol and resorcinol (RC). This indicated that catechol, resorcinol and hydroquinone could be identified entirely at the NH2-SBA15/CPE. Under the optimized conditions, the amperometric currents were linear over ranges from the following: 0.8–160μmolL−1 for hydroquinone, 1.0–140μmolL−1 for catechol and 2.0–160μmolL−1 for resorcinol. The detection limits were 0.3, 0.5 and 0.8μmolL−1, respectively. The proposed electrode can be applied to the simultaneous determination of dihydroxybenzene isomers in mixtures without previous chemical or physical separations.

Selective monitoring of Cu (II) species using a silica modified carbon paste electrode

The incorporation of silica particles within carbon paste leads to improved amperometric detection of copper(II) in ammoniacal medium. The enhanced sensitivity was attributed to the accumulation of copper(II) by adsorption on the ionised surface silanol groups of silica. The sensor was found to be highly selective to copper(II) with respect to alkali and alkaline earth metal cations and transition metal–ammonia complex species. The improved selectivity was explained by the strong silanolate–copper interactions, leading to appreciable accumulation even in high ionic strength media, as ascertained by measurements performed in synthetic ground and sea waters. Moreover, cyclic voltammetry using the silica modified carbon paste electrode was applied to the in situ investigation of copper(II) sorption processes on silica. Various silica-based materials were used to shed useful insights into these sorption processes, in relation to their capacity for copper(II) as well as their specific surface area and porosity.

Silica‐modified carbon paste electrode for copper determination in ammoniacal medium

AbstractThe silica modified carbon paste electrode (SMCPE) was applied to the voltammetric detection of copper(II) at trace level after its accumulation under open‐circuit conditions. As demonstrated by cyclic voltammetric experiments, silica particles displayed an attractive ability to efficiently preconcentrate trace copper(II) from ammonia solution, according to a combined acid‐base and complexation reaction: 2 (SiOH) + Cu(NH3) ⇌ (SiO)2Cu(NH3)2 + 2 NH. The analytical procedure involved four successive steps: the preconcentration during a given period of time at open circuit in the ammoniated analyte solution, the medium exchange of the electrode (washed with water) to a pure electrolyte solution (0.1 M HNO3), a 30 s electrolysis for reducing the accumulated CuII species, and the square wave voltammetric determination. Experimental parameters affecting either the uptake of copper(II) or its voltammetric detection at SMCPE were explored, including the solution pH and ionic strength, the ammonia concentration in the preconcentration medium, the preconcentration time, the deposition potential and duration, the anodic stripping scan mode or the silica loading into the paste. A detection limit of 2 × 10−9 M has been achieved after 10 min preconcentration (from a 0.5 M NH3 medium), as determined for a signal‐to‐noise ratio of 3, and a linear calibration plot was obtained in the 5 × 10−9 M to 5 × 10−6 M concentration range. The relative standard deviation (n = 8) for the determination of a 5 × 10−7 M Cu11 sample was 8%.

Anodic voltammetric assay of the herbicide Metamitron on a carbon paste electrode

The electrochemical oxidation of Metamitron in Britton-Robinson buffer (pH = 11.70) was examined using a silica modified carbon paste electrode (Si-MCPE). The results proved that the oxidation of Metamitron is irreversible and that the peak has adsorption characteristics. A mechanism, based on the oxidation of the amine group, is proposed. The influence of several instrumental and accumulation variables on the adsorptive stripping response has been evaluated using differential pulse (DPV) and square wave voltammetry (SWV Osteryoung’s method) as redissolution techniques; in both cases, a voltammetric peak is obtained at 0.482 V (DPV) and 0.341 V (SWV). The results from the SWV measurements lead to a poor sensitivity. On the contrary, under optimum conditions the AdS-DPV oxidation peak gave a linear response in the range 8 to 80 × 10–7 mol/l Metamitron solutions with a variation coefficient of 2.26% (4 × 10–6 mol/l, n = 10) and a detection limit of 3.7 × 10–7 mol/l. A method is proposed to determine Metamitron in natural water.

Utilization of a silica-modified carbon paste electrode for the direct determination of todralazine in biological fluids

Todralazine [ethyl 2-(-1-phthalazinyl)hydrazinecarboxylate] was determined by using a carbon paste electrode modified with silica. Todralazine is adsorbed on the electrode and determined in 0.1 mol 1−1 KNO3 (pH 1.8) by differential-pulse voltammetry. The adsorption can be carried out in open circuit or by applying a fixed potential (0.8 V vs. Ag/AgCI). The detection limits are about 4 × 10−7 and 3 × 10−8 mol 1−1, respectively. The method can be applied to the determination of todralazine in human urine. It is possible to determine directly 2.3 μg ml−1 of todralazine in urine with a relative standard deviation of 1.1% (n = 5)