Sensitive and Selective Voltammetric Determination of Ciprofloxacin Using Screen-printed Electrodes Modified with Carbon Black and Magnetic-molecularly Imprinted Polymer

This work reports the construction of screen-printed electrode (SPE) modified with carbon black (CB) and magnetic Fe₃O₄ nanoparticles coated with molecularly imprinted polymer (mag@MIP) based on an alternative low-cost approach. The proposed device was used for the sensitive and selective voltammetric determination of the antibiotic ciprofloxacin. The results obtained from cyclic voltammetry pointed to the improvement of the SPE response toward the irreversible oxidation of ciprofloxacin after the modification of the electrode surface with CB-based film and the magnetic preconcentration of mag@MIP containing adsorbed ciprofloxacin molecules. Compared to the non-molecularly imprinted sensor (mag@NIP), the presence of cavities selective for ciprofloxacin recognition in the mag@MIP nanoparticles accounted for the improvement in analytical signal of the molecularly imprinted sensor. The application of differential pulse voltammetry for ciprofloxacin determination yielded a linear response in the concentration range of 0.5 to 7.0 μmol L⁻¹. The repeatability and interference tests results showed that the proposed electrochemical sensor has good measurement accuracy and selectivity. The proposed device was applied for the voltammetric determination of ciprofloxacin in river water and synthetic urine samples, where recovery rates close to 100 % were recorded for all the samples. The quantification data obtained from the application of the proposed voltammetric method were quite consistent with those of the HPLC reference method.     

Single‐Wall Carbon Nanotube Paste Electrodes: a Comparison with Carbon Paste,Platinum and Glassy Carbon Electrodes via Cyclic Voltammetric Data

A new carbon electrode material, obtained by mixing single wall carbon nanotubes (SWNTs) with a mineral oil binder is studied. Carbon nanotube pastes show the special properties of carbon nanotubes combined with the various advantages of composite electrodes such as a very low capacitance (background current) and the possibility of an easy preparation, modification and renewal. A better knowledge of the characteristics of electrode reactions at carbon nanotube paste (CNTP) electrodes was obtained studying the electron transfer rates of various redox couples under different pretreatment conditions. A critical comparison with carbon paste (CP), platinum (Pt) and glassy carbon (GC) electrodes was also carried out. Capacitance and resistance values were also calculated for all electrodes investigated. Both untreated and treated CNTP electrodes showed a low resistance while the capacitance was markedly reduced with CNTP electrodes previously treated with concentrated nitric acid. An electrochemical pretreatment on CNTP electrodes was developed which showed an excellent result towards two‐electron quinonic structure species. After this treatment the heterogeneous standard rate constants for p‐methylaminophenol sulfate (MAP) and dopamine resulted to be significantly higher (2.1×10^?2 cm/s and 2.0×10^?2 cm/s, respectively) than those obtained with the other electrodes studied. Reproducibility, stability and storage characteristics of CNTP electrodes were also reported.     

Simultaneous Square‐Wave Voltammetric Determination of Paracetamol,Caffeine and Orphenadrine in Pharmaceutical Formulations Using a Cathodically Pretreated Boron‐Doped Diamond Electrode

An electroanalytical method for the simultaneous determination of paracetamol (PAR), caffeine (CAF), and orphenadrine (ORPH) using the square‐wave voltammetry (SWV) and a cathodically pretreated boron‐doped diamond electrode was developed. The method exhibits linear responses to PAR, CAF, and ORPH in the concentration ranges 5.4×10^?7–6.1×10^?5 M, 7.8×10^?7–3.5×10^?5 M, and 7.8×10^?7–3.5×10^?5 M, respectively, with detection limits of 2.3×10^?7 M, 9.6×10^?8 M, and 8.4×10^?8 M, respectively. The proposed method was successfully applied in the simultaneous determination of these analytes in pharmaceutical formulations.     

Voltammetric Determination of Phenoxybenzyl‐Type Insecticides at Chemically Modified Conducting Polymer‐Carbon Nanotubes Coated Electrodes

The electrochemical reduction of three common insecticides such as cypermethrin (CYP), deltamethrin (DEL) and fenvalerate (FEN) was investigated at glassy carbon electrode (GCE), multiwalled carbon nanotubes modified GCE (MWCNT‐GCE), polyaniline (herein called as modifier M₁) and polypyrrole (herein called as modifier M₂) deposited MWCNT/GCE using cyclic voltammetry. Influences of pH, scan rate, and concentration were studied. The surface morphology of the modified film was characterized by scanning electron microscopy (SEM) and X‐ray diffraction analysis (XRD). A systematic study of the experimental parameters that affect differential pulse stripping voltammetry (DPSV) was carried out and the optimized experimental conditions were arrived at. The calibration plots were linear over the insecticide's concentration range 0.1–100 mg L^?1 and 0.05–100 mg L^?1 for all the three insecticides at MWCNT‐GCE and MWCNT(M₁)‐GCE respectively. The MWCNT(M₂)‐GCE performed well among the three electrode systems and the determination range obtained was 0.01–100 mg L^?1 for CYP, DEL and FEN. The limit of detection (LOD) was 0.35 μg L^?1, 0.9 μg L^?1 and 0.1 μg L^?1 for CYP, DEL and FEN respectively on MWCNT(M₂)‐GCE modified system. Suitability of this method for the trace determination of insecticide in spiked soil sample was also determined.     

Tellurium Film Electrodes Deposited on Carbon and Mesoporous Carbon Screen‐printed Substrates for Anodic Stripping Voltammetric Determination of Copper

The performance of screen‐printed electrodes modified in situ with tellurium film for the anodic stripping voltammetric (ASV) determination of Cu(II) is reported. It was found that two types of screen‐printed substrates, namely carbon and mesoporous carbon, were optimal for this application. The selected in situ tellurium film modified electrodes were applied for the square wave ASV determination of copper at μg L⁻¹ concentration levels. Well‐defined and reproducible Cu oxidation stripping peaks were produced at a potential more negative than the anodic dissolution of tellurium. The highest sensitivity of Cu determination was achieved in 0.05 M HCl containing 50 μg L⁻¹ Te(IV) after 300 s of accumulation at −0.5 V. Using the optimized procedure, a linear range from 2 to 35 μg L⁻¹ of Cu(II) was obtained with a detection limit of 0.5 μg L⁻¹ Cu(II) (S/N=3) for 300 s of deposition time. Both sensors, carbon TeF‐SPE and mesoporous carbon TeF‐SPE, were successfully applied for the quantification of Cu in a certified reference surface water sample.     

Electrocatalytic Oxidation and Voltammetric Determination of Nitrite on Hydrophobic Ionic Liquid‐Carbon Nanotube Gel‐Chitosan Composite Modified Electrodes

A novel room temperature ionic liquid (i.e., 1‐octyl‐3‐methylimidazolium hexafluorophosphate, OMIMPF₆)‐multiwall carbon nanotube (MWNT) gel‐chitosan (Chi) composite modified glassy carbon electrode (GCE) was fabricated and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (IR), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The OMIMPF₆‐MWNT gel‐Chi composite showed good conductivity, stability, and extraction effect due to the synergic action of OMIMPF₆, MWNT, and Chi. Furthermore, it was found that the OMIMPF₆‐MWNT gel‐Chi composite had strong electrocatalytic effect on the oxidation of nitrite and at the OMIMPF₆‐MWNT gel‐Chi/GCE nitrite could produce a very sensitive anodic peak. Under optimized conditions, the peak current was linear to nitrite concentration from 2.0×10^?8 to 6.0×10^?5 M. The detection limit was 1.0×10^?8 M. The electrode also exhibited acceptable stability, repeatability and selectivity. It was used successfully for the determination of nitrite in soil, sewage and sausage samples.     

Simultaneous Voltammetric Determination of Benzene,Toluene and Xylenes (BTX) in Water Using a Cathodically Pre‐treated Boron‐doped Diamond Electrode

An electrochemical method for the simultaneous determination of benzene, toluene and xylenes (BTX) in water was developed using square‐wave voltammetry (SWV). The determination of BTX was carried out using a cathodically pre‐treated boron‐doped diamond electrode (BDD) using 0.1 mol L^?1 H₂SO₄ as supporting electrolyte. In the SWV measurements using the BDD, the oxidation peak potentials of the total xylenes‐toluene and toluene‐benzene couples, present in ternary mixtures, display separations of about 100 and 200 mV, respectively. The attained detection limits for the simultaneous determination of benzene, toluene and total xylenes were 3.0×10^?7, 8.0×10^?7 and 9.1×10^?7 mol L^?1, respectively. The recovery values taken in ternary mixtures of benzene, toluene and total xylenes in aqueous solutions are 98.9 %, 99.2 % and 99.4 %, respectively.     

Voltammetric Determination of Cymoxanil and Famoxadone at Different Types of Carbon Electrodes

Differential pulse voltammetry (DPV) at a carbon fibre rod electrode (CFRE) and a capillary carbon paste electrode (CPE) have been used for the determination of pesticides cymoxanil and famoxadone, respectively. In the cathodic potential range, optimum conditions were found for the determination of cymoxanil by DPV at CFRE at pH 4 with limit of quantification (L_Q) of 5.9×10^?7 mol L^?1. In the anodic area, determination of famoxadone by DPV at CPE was performed at optimum pH 2 with L_Q=1.4×10^?7 mol L^?1. Practical applicability of the newly developed methods was verified on spiked samples of river water and soil.     

N‐Doped Hollow Porous Carbon Spheres/Bismuth Hybrid Film Modified Electrodes for Sensitive Voltammetric Determination of Trace Cadmium

In this work, N‐doped hollow porous carbon spheres (N‐HPCSs) were synthesized by silicon dioxide template‐assisted polybenzoxazine (PB) coating strategy. The prepared N‐HPCSs have a smooth hollow ball structure surrounded by a well‐defined porous shell. Combining with in‐situ plating of Bi film, the N‐HPCSs were further fabricated a sensitive electrochemical platform for determination trace levels of Cd(II) by differential pulse anodic stripping voltammetry (DPASV). Under the optimized conditions, the Bi‐N‐HPCSs based sensor displays a linear response to Cd(II) over the range of 0.5 μg L⁻¹ to 150 μg L⁻¹. Meanwhile, the limit of detection (LOD, S/N=3) is estimated to be around 0.16 μg L⁻¹ for Cd(II), which is 31 times lower than the safety values set by United States Environmental Protection Agency (EPA) for the drinking water. Moreover, the proposed method was successfully applied to detection of Cd(II) in tap water and lake water, and the analytical results of the presented method are agreed well with inductively coupled plasma‐mass spectrometry (ICP‐MS) data. Due to the excellent analytical performance, the fabricated electrode is promised for future development in monitoring of cadmium pollution in the environment.     

Direct Voltammetric Determination of Redox‐Active Iron in Carbon Nanotubes

With the advances in nanotechnology over the past decade, consumer products are increasingly being incorporated with carbon nanotubes (CNTs). As the harmful effects of CNTs are suggested to be primarily due to the bioavailable amounts of metallic impurities, it is vital to detect and quantify these species using sensitive and facile methods. Therefore, in this study, we investigated the possibility of quantifying the amount of redox‐available iron‐containing impurities in CNTs with voltammetric techniques such as cyclic voltammetry. We examined the electrochemistry of Fe₃O₄ nanoparticles in phosphate buffer solution and discovered that its electrochemical behavior could be affected by pH of the electrolyte. By utilizing the unique redox reaction between the iron and phosphate species, the redox available iron content in CNTs was determined successfully using voltammetry.     

Selective Determination of Quercetin Using Carbon Nanotube‐Modified Electrodes

Electrochemical detection of quercetin has been carried out on glassy carbon electrodes modified with carbon nanotubes and Nafion (GC/Nafion‐CNT). GC/Nafion‐CNT electrodes did not show passivation effect that occurs on the unmodified electrodes and displayed better stability and reproducibility. Quercetin oxidation was most favorable in acidic conditions and current gradually decreased as the solution pH increased. No oxidation was observed when two ? OH groups in a catechol moiety were fully deprotonated. These electrodes enabled selective determination of quercetin in the presence of interfering species such as ascorbic acid, uric acid, glucose, and catechol in large excess. Quantification of quercetin in a yellow onion has been made and favorably compared with reported values. Good selectivity and high sensitivity obtained by Osteryoung sSquare‐wave voltammetry can open new possibilities of direct quercetin determination in vegetables with a minimal sample treatment.     

Utilization of Carbon Paste Electrodes for the Voltammetric Determination of Chlortoluron

Conventional (CPE) and miniaturized (m‐CPE) carbon paste electrodes consisting of a carbon paste filled capillary were used for differential pulse voltammetric determination of chlortoluron in samples of river water and soil, in the latter case after the extraction by methanol. Britton‐Robinson buffer pH 3 with low content of methanol was found to be optimal for the determination. The achieved determination limits were 2.8 µmol L^?1 and 0.34 µmol L^?1 in river water, and 3.1 and 4.3 µg g^?1 in soil, using CPE and m‐CPE, respectively.     

Simultaneous Anodic Adsorptive Stripping Voltammetric Determination of Luteolin and 3‐Hydroxyflavone in Biological Fluids Using Renewable Pencil Graphite Electrodes

Simultaneous anodic adsorptive stripping voltammetry was applied for selective and sensitive electrochemical determination of the flavones luteolin (LU) and the basic flavone core 3‐hydroxyflavone (3HF) using a renewable pencil graphite electrode (PGE). The increased separation of the anodic peak potential of LU and 3HF on a PGE surface together with the increased sensitivity renders their simultaneous determination feasible by square wave anodic adsorptive stripping voltammetry (SWAASV). The electrochemical parameters such as surface concentration (Γ), electron transfer coefficient (α), and the standard rate constant (k_s) of both LU and 3HF at a PGE were calculated. For simultaneous detection of both compounds by synchronous change of the concentration of LU and 3HF, the detection limits were 1.34 nM and 5.15 nM, respectively. The proposed procedure was successfully applied for the simultaneous detection of LU and 3HF in human serum and urine samples with satisfactory results.     

多组分有机物在玻碳电极上的伏安法测定

对乙酰氨基苯乙醚,氨基比林,乙酰氨基苯酚,氨基苯酚等４种有机物在玻碳电极上的伏安行为进行了研究。在０．１ｍｏｌ／Ｌ氢氧化钠溶液中得到４个灵敏度和分辨率良好的阳极氧化峰。Ｅｐ分别为０．６８,０．５１,０．２２－０．０６Ｖ（ｖｓ．ＡｇＣｌ／Ａｇ）左右,样品不需分离直接测定。     

碳纳米管修饰金电极检测特定序列DNA

利用化学偶联法将末端修饰氨基的寡聚核苷酸固定在表面修饰有羧基化碳纳米管(CNTs-COOH)的金电极表面, 制备新型核酸探针, 可以特异性结合目标单链寡聚核苷酸. 以阿霉素作为嵌合指示剂, 利用示差脉冲法测定杂交的结果. 经过实验条件的优化, 测定DNA浓度在1.0×10^－6～1.0×10^－9 mol/L呈良好的线性关系. 检测限为: 2.54×10^－10 mol/L. 碳纳米管特有的纳米结构对检测结果的放大作用, 提高了该传感器的检测限和灵敏度.     

Adsorptive Stripping Voltammetric Determination of 4‐Hexylresorcinol in Pharmaceutical Products Using Multiwalled Carbon Nanotube Based Electrodes

A sensitive electroanalytical method is presented for the determination of 4‐hexylresorcinol using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT‐BPPGE). This method is also extended to the use of a MWCNT modified screen‐printed electrode (MWCNT‐SPE), thereby demonstrating that this approach can easily be incorporated into a facile and inexpensive electrochemical sensor.     

Voltammetric Determination of Trace Antiepileptic Gabapentin with a Silver‐Nanoparticle Modified Multiwalled Carbon Nanotube Paste Electrode

For the first time, a novel carbon nanotube bed electrode impregnated with silver–nanoparticles (AgNPs) for the determination of trace amounts of gabapentin (GBP) is described. We synthesized the AgNPs via a new procedure. The voltammetric behavior of the electrode was investigated by cyclic voltammetry. There were linear relationships in the ranges from 3.1×10^?9 to 2.9×10^?2 M and from 1.0×10^?8 to 1.0×10^?2 GBP with square wave and differential pulse voltammetric peak currents, respectively. The detection limits were 5.6×10^?10 and 9.7×10^?9 M, respectively. The electrode showed excellent response over a period of 2 months and was successfully applied in human plasma and pharmaceutical capsular products.     

Voltammetric Analysis of Naproxen in Graphite Electrodes and Its Determination in Pharmaceutical Samples

The present work discuses new findings in the electrochemistry of naproxen over graphite electrodes. This new approach, allows the proposal of a simple and competitive low‐cost method to carry out naproxen’s voltammetric quantification. Naproxen’s indirect quantification through an adsorption anodic wave was performed at a graphite bar electrode using differential pulse voltammetry. An anodic current maximum was recorded at a potential of ?0.3 V referred to a saturated Ag/AgCl reference electrode. The calibration plot having a correlation coefficient of 0.990, sensibility of 4.19±0.62 µA cm³ µg^?1, with detection and quantification limits of 0.68 and 3.3 µg cm^?3, respectively.     

Simultaneous Voltammetric Determination of Heavy Metals by Use of Crown Ether‐modified Electrodes and Chemometrics

A three‐sensor array consisting of a graphite‐epoxy composite electrode (GEC), 4‐carboxybenzo‐18‐crown‐6‐GEC and 4‐carboxybenzo‐15‐crown‐5‐GEC was employed for the simultaneous determination of Cd(II), Pb(II) and Hg(II) by differential pulse anodic stripping voltammetry (DPASV). Sensors were firstly studied for the determination of Hg(II); secondly, peak current responses confirmed that all sensors showed differentiated response for the three considered metals. A response model was developed to resolve mixtures of Cd(II), Pb(II) and Hg(II) at the µg L^?1 level; Discrete Wavelet Transform was selected as preprocessing tool and artificial neural network used for the modelling of the obtained responses.     

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.