Poly(Taurine‐Glutathione)/Carbon Nanotube Modified Glassy Carbon Electrode as a New Levofloxacin Sensor

A new highly sensitive and selective electrochemical levofloxacin sensor based on co‐polymer‐carbon nanotube composite electrode was developed. Taurine and Glutathione were electrochemically co‐polymerized on multiwalled carbon nanotubes modified glassy carbon electrode (Poly(TAU‐GSH)/CNT/GCE) and used as a levofloxacin sensor in pH 6 phosphate buffer solution. The new composite electrode surfaces were characterized by scanning electron microscopy, atomic force microscopy and electrochemical impedance spectroscopy. Under the optimized conditions, two linear segments were obtained for increasing LEV concentrations between 20 nmol L^?1‐1 μmol L^?1 and 1.5 μmol L^?1‐55 μmol L^?1 LEV with a detection limit of 9 nmol L^?1 using amperometry. Poly(TAU‐GSH)/CNT/GCE exhibited high sensitivity, selectivity with good stability. The new sensor was employed for real samples of LEV tablets and urine. Promising results were obtained with good accuracy which were also in accordance with LC‐MS/MS analysis.     

Sensitive Voltammetric Determination of Bisphenol A Based on a Glassy Carbon Electrode Modified with Copper Oxide‐Zinc Oxide Decorated on Graphene Oxide

A highly sensitive and selective chemical sensor was prepared based on metallic copper‐copper oxides and zinc oxide decorated graphene oxide modified glassy carbon electrode (Cu?Zn/GO/GCE) through an easily electrochemical method for the quantification of bisphenol A (BPA). The composite electrode was characterized via scanning electron microscopy (SEM), X‐Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of BPA in Britton‐Robinson (BR) buffer solution (pH 7.1) was examined using cyclic voltammetry (CV). Under optimized conditions, the square wave voltammetry (SWV) response of Cu?Zn/GO/GCE towards BPA indicates two linear relationships within concentrations (3.0 nmol L^?1?0.1 μmol L^?1 and 0.35 μmol L^?1?20.0 μmol L^?) and has a low detection limit (0.88 nmol L^?1). The proposed electrochemical sensor based on Cu?Zn/GO/GCE is both time and cost effective, has good reproducibility, high selectivity as well as stability for BPA determination. The developed composite electrode was used to detect BPA in various samples including baby feeding bottle, pacifier, water bottle and food storage container and satisfactory results were obtained with high recoveries.     

Electrochemical Detection of Nitrite in Meat and Water Samples Using a Mesoporous Carbon Ceramic SiO2/C Electrode Modified with In Situ Generated Manganese(II) Phthalocyanine

Mesoporous carbon ceramic SiO₂/50 wt % C (S_BET=170 m² g^?1), where C is graphite, were prepared by the sol‐gel method. The materials were characterized using N₂ sorption isotherms, scanning electron microscopy, and conductivity measurements. The matrix was used as support for the in situ immobilization of Mn(II) phthalocyanine (MnPc) on their surface. XPS was used to determine the Mn/Si atomic ratios of the MnPc‐modified materials. Pressed disk electrodes were prepared with the MnPc‐modified matrix, and tested as an electrochemical sensor for nitrite oxidation. The linear response range, sensitivity, detection limit and quantification limit were 0.79–15.74 µmol L^?1, 17.31 µA L µmol^?1, 0.02 µmol L^?1 and 0.79 µmol L^?1, respectively, obtained using cyclic voltammetry. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation was 1.7 % for 10 measurements of a solution of 12.63 µmol L^?1 nitrite. The sensor employed to determine nitrite in sausage meat, river and lake water samples showed to be a promising tool for this purpose.     

Development and application of the tartrazine voltammetric sensors based on molecularly imprinted polymers

A modified glassy carbon electrode was prepared as an electrochemical voltammetric sensor based on molecularly imprinted polymer film for tartrazine (TT) detection. The sensitive film was prepared by copolymerization of tartrazine and acrylamide on the carbon nanotube-modified glassy carbon electrode. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. Under the optimum conditions, two dynamic linear ranges of 8?×?10^?8 to 1?×?10^?6?mol?L^?1 and 1?×?10^?6 to 1?×?10^?5?mol?L^?1 were obtained, with a detection limit of 2.74?×?10^?8?mol?L^?1(S/N?=?3). This sensor was used successfully for tartrazine determination in beverages.     

Electrochemical Sensor for Sensitive Determination of Ga(III) Ion Based on β‐Cyclodextrin Incorporated Multi‐walled Carbon Nanotubes and Imprinted Sol‐gel Composite Film

A novel sensor for detection of trace gallium ion [Ga(III)] was created by stepwise modification of a gold electrode with β‐cyclodextrin (β‐CD)/multi‐walled carbon nanotubes (MWCNTs) and an ion imprinted polymer (IIP). The sensor surface morphology was characterized by scanning electron microscopy. The electrochemical performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The sensor displayed excellent selectivity towards the target Ga(III) ion. Meanwhile, the introduced MWCNTs displayed noticeable catalytic activity, and β‐CD demonstrated significant enrichment capacity. A linear calibration curve was obtained covering the concentration range from 5.0×10^?8 to 1.0×10^?4 mol·L^?1, with a detection limit of 7.6×10^?9 mol·L^?1. The proposed sensor was successfully applied to detect Ga(III) in real urine samples.     

Gold Nanoparticles Modified Electrode for the Determination of an Antihypertensive Drug

The nature of binding between Terazosin (TR) and gold nanoparticles (Au‐Nps) is investigated using UV‐vis and fluorescence spectroscopies, cyclic voltammetry, SEM, and EIS. The results suggest that Au‐Nps are effective carriers for TR. An electrochemical sensor for TR is introduced using Au‐Nps electrodeposited on carbon paste electrode. The effect of parameters including pH and scan rate on the response was investigated. A linear range from 8.0×10^?9 to 5.4×10^?5 mol L^?1 with correlation coefficient of 0.9995 and detection limit of 1.2×10^?10 mol L^?1 was obtained. This sensor was used for determining TR spiked in urine, and excellent recovery results are achieved.     

Direct Determination of Paracetamol in Environmental Samples Using Screen‐printed Carbon/Carbon Nanofibers Sensor – Experimental and Theoretical Studies

The paper describes the first electrochemical method (differential pulse adsorptive stripping voltammetry, DPAdSV) using a screen‐printed sensor with a carbon/carbon nanofibers working electrode (SPCE/CNFs) for the direct determination of low (real) concentrations of paracetamol (PA) in environmental water samples. By applying this sensor together with DPAdSV, two linear PA concentration ranges from 2.0×10^?9 to 5.0×10^?8 mol L^?1 (r=0.9991) and 1.0×10^?7–2.0×10^?6 mol L^?1 ( r=0.9994) were obtained. For the accumulation time of 90 s, the limit of detection was 5.4×10^?10 mol L^?1. Moreover, the SPCE/CNFs sensor and the DPADSV procedure for PA determination are potentially applicable in field analysis. The process of PA adsorption at the SPCE/CNFs surface was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and theoretical studies. In the theoretical study of the interaction of CNF and PA, the first species was modelled by graphene‐like clusters containing up to 37 rings. It was found that the preferable orientation of PA is parallel to the carbon surface with the binding energy of about ?68 kJ/mol calculated by symmetry‐adapted perturbation theory (SAPT). Both the selectivity and the accuracy of the developed sensor for real sample analysis were also investigated using Polish river and sea samples.     

Fabrication of Superoxide Dismutase (SOD) Imprinted Poly(ionic liquid)s via eATRP and its Application in Electrochemical Sensor

Superoxide dismutase (SOD) plays an important role in nearly all living cells. In this study, SOD imprinted poly(ionic liquid)s (SIPILs) were prepared on the surface of the bare Au electrode modified with nano‐palladium and nano‐gold (Au/nPd/nAu/SIPILs). SIPILs was synthesized with 1‐vinyl‐3‐propyl imidazole sulfonate ionic liquids as functional monomers via electrochemically mediated atom transfer radical polymerization (eATRP) catalyzed by SOD. The Au/nPd/nAu/SIPILs was examined by cyclic voltammetry (CV), scanning electron microscope (SEM), energy‐dispersive spectrometer (EDS) and X‐ray photoelectron spectroscopy (XPS). The Au/nPd/nAu/SIPILs was also used as an electrochemical sensor to determine SOD by differential pulse voltammetry (DPV). Under the optimal conditions, the detection range of SOD was from 1.0×10^?8 to 1.0×10² mg L^?1 with a limit of detection of 8.90×10^?9 mg L^?1 (S/N=3). Compared with other methods, the sensor based on SIPILs had the broader linear range and lower detection limit.     

Effect of Different Carbon Blacks on the Simultaneous Electroanalysis of Drugs as Water Contaminants Based on Screen‐printed Sensors

For the construction of the sensor, three different carbon black (CB) materials (VULCAN XC72R, BLACK PEARLS 4750 and CB N220) were explored as modifying nanomaterial. Firstly, the electrochemical activity of the each SPE modified was compared by cyclic voltammetry and electrochemical impedance spectroscopy technique, using [Fe(CN)₆]^3?/4? as redox couple. After demonstrating that electrodes modified with different types of CB were characterized by improved electrochemical performances when compared with bare electrodes, and among them, electrodes modified with CB BP4750 is characterised by slightly better electrochemical properties, this type of electrode was used for the development of the analytical method. By applying SWV technique in 0.2 mol L^?1 phosphate buffer (pH 3.0), the obtained analytical curves for ACP and LVF were found linearly from 4.0 to 80.0 μmol L^?1 and from 0.90 to 70.0 μmol L^?1 with limit of detection of 2.6 μmol L^?1 and 0.42 μmol L^?1 for ACP and LVF, respectively. Finally, the quantification of these drugs in river water was evaluated using the new here‐proposed sensor by recovery method in spiked samples, obtaining satisfactory recovery values. The results achieved demonstrated that the developed analytical tool is of great analytical interest being easy to use, cost‐effective, miniaturized, and thus suitable for low cost on site analysis.     

A new voltammetric sensor for the determination of sulfite in water and wastewater using modified-multiwall carbon nanotubes paste electrode

The electrochemical response of a modified-carbon nanotubes paste electrode with p-aminophenol was investigated as an electrochemical sensor for sulfite determination. The electrochemical behaviour of sulfite was studied at the surface of the modified electrode in aqueous media using cyclic voltammetry and square wave voltammetry. It has been found that under the optimum condition (pH 7.0) in cyclic voltammetry, the oxidation of sulfite occurs at a potential about 680?mV less positive than that of an unmodified-carbon nanotubes paste electrode. Under the optimized conditions, the electrocatalytic peak current showed linear relationship with sulfite concentration in the range of 2.0?×?10^?7–2.8?×?10^?4?mol?L^?1 with a detection limit of 9.0?×?10^?8?mol?L^?1 sulfite. The relative standard deviations for ten successive assays of 1.0 and 50.0?µmol?L^?1 sulfite were 2.5% and 2.1%, respectively. Finally, the modified electrode was examined as a selective, simple and precise new electrochemical sensor for the determination of sulfite in water and wastewater samples.     

Electrochemical Determination of Dicofol at Nickel Nanowire Modified Poly(p‐aminophenol) Film Electrode

An electrochemical sensor was fabricated by construction of nickel nanowires on the surface of poly(p‐aminophenol) (PPAP) modified glassy carbon electrode. The electrochemical response of dicofol, a known pesticide and used for agricultural activities such as cyclic voltammetry and differential pulse voltammetry, were investigated and the results were compared with those obtained unmodified electrodes. Following the optimization of NaOH concentration, polymerization cycle number, Ni nanowire amount, the linear range for the dicofol was studied and found as 0.83–30.7 μmol L^?1 (R²=0.9981) at Ni/PPAP/GCE with a 0.08 μmol L^?1 detection limit according to S/N=3. Finally, the proposed Ni/PPAP/GCE sensor was successfully applied for the dicofol analysis in soil samples. The characterization of the developed surface was carried out by scanning electron microscopy and X‐Ray photoelectron spectroscopy.     

A Sensitive Sensor Based on Single‐walled Carbon Nanotubes: Its Preparation,Characterization and Application in the Electrochemical Determination of Drug Clorsulon in Milk Samples

Within this paper, a glassy carbon electrode modified with single‐walled carbon nanotubes (SWCNTs?GCE) was prepared, and employed for the determination of clorsulon (Clo), which is a frequently used veterinary drug against common liver fluke. The comprehensive topographical and electrochemical characterizations of bare GCE and SWCNTs?GCE were performed by atomic force microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. Significantly enhanced electrochemical characteristics of SWCNTs?GCE toward a ferrocyanide/ferricyanide redox couple was observed when compared to bare GCE. Further, the prepared sensor was applied for the voltammetric determination of Clo, which was electrochemically investigated for the first time in this work. Voltammetric experiments were performed using square‐wave voltammetry with optimized parameters in phosphate buffer solution, pH 6.8, which was selected as the most suitable medium for the determination of Clo. The corresponding current at approx. +1.1 V increased linearly with Clo concentration within two linear dynamic ranges of 0.75–4.00 μmol L^?1 (R²=0.9934) and 4.00–15.00 μmol L^?1 (R²=0.9942) with a sensitivity for the first calibration range of 0.76 μA L μmol^?1, a limit of detection of 0.19 μmol L^?1, and a limit of quantification of 0.64 μmol L^?1. The developed method was subsequently applied for quantitative analysis of Clo in milk samples with results proving high repeatability and recovery.     

A Sensitive Sensor Based on CuTSPc and Reduced Graphene Oxide for Simultaneous Determination of the BHA and TBHQ Antioxidants in Biodiesel Samples

A novel and sensitive electrochemical sensor was developed for the simultaneous determination of the butylated hydroxyanisole (BHA) and tert‐butylhydroquinone (TBHQ) antioxidants in biodiesel samples employing the differential pulse voltammetry (DPV). In this sense, a glassy carbon electrode (GCE) modified with copper (II) tetrasulfonated phthatocyanine immobilized on reduced graphene oxide (CuTSPc/rGO) allowed the detection of BHA and TBHQ at potentials lower than those observed at unmodified electrodes. The sensor was characterized by cyclic voltammetry (CV) and linear scan voltammetry (LSV). After optimization of the experimental parameters, the analytical curves for simultaneous determination of BHA and TBHQ by DPV technique demonstrated an excellent linear response from 0.1 to 500 µmol L^?1 with detection limit of 0.045 µmol L^?1 for TBHQ and 0.036 µmol L^?1 for BHA. Finally, the proposed method was successfully applied in the simultaneous determination of BHA and TBHQ in six biodiesel samples, and the results obtained were found to be similar to those obtained using the HPLC method with agreement at 95 % confidence level.     

MWCNT‐modified Electrode for Voltammetric Determination of Allura Red and Brilliant Blue FCF in Isotonic Sport Drinks

A fast and simple electrochemical sensor is presented for the determination of allura red and brilliant blue in isotonic sport drinks, using a glassy carbon electrode modified with multi‐walled carbon nanotubes. The electrochemical behavior of the colorants was studied by cyclic and differential pulse voltammetry in 0.1 M PBS, pH 7.0. The solution pH, the amount of nanomaterial on the surface of the electrode and the accumulation time of each colorant were optimized. Under the optimal conditions, the sensor exhibited a linear response to allura red and brilliant blue with detection limits of 7 μg L^?1 and 52 μg L^?1, respectively. The sensor was applied to the analysis of commercial isotonic sports drinks that contain individual or mixed colorants, showing good sensitivity and reproducibility. The results were compared with a chromatographic method showing that the levels of colorants are low and did not show a risk for a consumer's health.     

An Electrochemical Sensor Based on Reduced Graphene Oxide,Gold Nanoparticles and Molecular Imprinted Over‐oxidized Polypyrrole for Amoxicillin Determination

An electrochemical sensor for amoxicillin (AMX) detection based on reduced graphene oxide (RGO), molecular imprinted overoxidized polypyrrole (MIOPPy) modified with gold nanoparticles (AuNPs) is described in this work. The electrochemical behavior of the imprinted and non‐imprinted polymer (NIP) was carried out by cyclic voltammetry (CV) and impedance spectroscopy (IS). The structure and morphology of the prepared MIP sensor were characterized by scanning electron microscopy (SEM), UV‐Visible, Fourier transform infrared spectroscopy (FTIR) and its experimental parameters such as monomer and template concentration, pH buffer solution, incubation time of AMX and AuNPs, scan rate as well as electropolymerization scan cycles were optimized to improve the performance of the sensor. The peak current obtained at the MIP electrode was proportional to the AMX concentration in the range from 10^?8 to 10^?3 mol L^?1 with a detection limit and sensitivity of 1.22 10^?6 mol L^?1 (Signal to noise ratio=3) and 2.52×10^?6 μAmol^?1 L, respectively. It was also found that this sensor exhibited reproducibility and excellent selectivity against molecules with similar chemical structures. Besides, the analytical application of the AMX sensor confirms the feasibility of AMX detection in milk and human serum.     

Direct Electrochemical Determination of Glyphosate at Copper Phthalocyanine/Multiwalled Carbon Nanotube Film Electrodes

A copper phthalocyanine/multiwalled carbon nanotube film‐modified glassy carbon electrode has been used for the determination of the herbicide glyphosate (Gly) at ?50 mV vs. SCE by electrochemical oxidation using differential pulse voltammetry (DPV). Cyclic voltammetry and electrochemical impedance spectroscopy showed that Gly is adsorbed on the metallic centre of the copper phthalocyanine molecule, with formation of Gly‐copper ion complexes. An analytical method was developed using DPV in pH 7.4 phosphate buffer solution, without any pretreatment steps: Gly was determined in the concentration range of 0.83–9.90 μmol L^?1, with detection limit 12.2 nmol L^?1 (2.02 μg L^?1).     

Electrochemical sensor for determination of aflatoxin B1 based on multiwalled carbon nanotubes-supported Au/Pt bimetallic nanoparticles

A sensitive and selective imprinted electrochemical sensor for the determination of aflatoxin B₁ (AFB₁) was constructed on a glassy carbon electrode by stepwise modification of functional multiwalled carbon nanotubes (MCNTs), Au/Pt bimetallic nanoparticles (Au/PtNPs), and a thin imprinted film. The fabrication of a homogeneous porous poly o-phenylenediamine (POPD)-grafted Au/Pt bimetallic multiwalled carbon nanotubes nanocomposite film was conducted by controllable electrodepositing technology. The sensitivity of the sensor was improved greatly because of the nanocomposite functional layer; the proposed sensor exhibited excellent selectivity toward AFB₁ owing to the porous molecular imprinted polymer (MIP) film. The surface morphologies of the modified electrodes were characterized using a scanning electron microscope. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. A linear relationship between the sensor response signal and the logarithm of AFB₁ concentrations ranging from 1?×?10^?10 to 1?×?10^?5 mol L^?1 was obtained with a detection limit of 0.03 nmol L^?1. It was applied to detect AFB₁ in hogwash oil successfully.     

Fabrication of a nanostructured TiO2/carbon nanotube composite electrode for voltammetric and impedimetric determination of NTO explosive in the water and soil samples

An electrochemical oxidation route was developed for sensitive and selective assay of nitrotriazolone (NTO) explosive in some environmental samples on a multi-walled carbon nanotube (MWCNTs)/TiO₂ nanocomposite paste electrode, for prevention of the analytical interference of conventional reducible energetic compounds. Detailed evaluations were made for the electrochemical behaviour of NTO on the modified electrode by adsorptive stripping voltammetry, electrochemical impedance spectroscopy (EIS) and chronoamperometry techniques in the pH range of 2.0–10.0. Parameters such as diffusion coefficient constant of NTO were calculated, and various experimental conditions were also optimised. Under optimal conditions the calibration curve had two linear dynamic ranges of 130.0–3251.5 μg L^?1 and 6.5–26.0 mg L^?1 with a detection limit of 26.0 μg L^?1 (0.2 μmol L^?1) and precision of <3%. This electrochemical sensor was further applied to determine NTO in real soil and water samples with satisfactory results.     

Preparation of Molecularly Imprinted Electrochemical Sensor for Detection of Vincristine Based on Reduced Graphene Oxide/Gold Nanoparticle Composite Film

An innovative molecularly imprinted electrochemical sensor was fabricated based on reduced graphene oxide (RGO) and gold nanocomposite (Au) for rapid detection of vincristine (VCR). The RGO‐Au composite membrane was obtained via direct one‐step electrodeposition technique of graphene oxide (GO) and chloroauric acid (HAuCl₄) on the surface of a glassy carbon electrode (GCE) by means of cyclic voltammetry (CV) in the potential range between ?1.5 and 0.6 V in phosphate buffer solution (PBS) of pH 9.18, which is capable of effectively utilizing its superior electrical conductivity, larger specific surface area due to its synergistic effect between RGO and Au. The molecularly imprinted polymers (MIPs) were synthesized on the RGO‐Au modified glassy carbon electrode surface with VCR as the template molecular, methyl acrylic acid (MAA) as the functional monomer, and ethylene glycol maleic rosinate acrylate (EGMRA) as a cross‐linker. The performance of the sensor was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) in detail. Under the optimum conditions, the fabricated sensor exhibited a linear relationship between oxidation peak current and VCR concentration over the range of 5.0×10^?8–5.0×10^?6 mol·L ^minus;1 with a correlation coefficient of 0.9952 and a detection limit (S/N=3) of 2.6×10^minus;8 mol·L^minus;1. The results indicated that the imprinted polymer films exhibited an excellent selectivity for VCR. The imprinted sensor was successfully used to determine VCR in real samples with recoveries of 90% –120% by using the standard addition method.     

Bismuth Nanoparticles@Porous Silicon Nanostructure,Application as a Selective and Sensitive Electrochemical Sensor for the Determination of Thioridazine

A bismuth@porous silicon (Bi/PSi) nanostructure is fabricated and used as a new highly sensitive electrochemical sensor for measurement of thioridazine. For this purpose, commercial silicon powder is converted to porous silicon using metal‐assisted chemical etching method. Then, bismuth nanoparticles are deposited on the surface of the porous silicon that synthesized in the previous step. The effects of pH and instrumental parameters are studied on the sensor response. After optimization of the parameters, differential pulse voltammetry is used to determine sub‐micro molar amounts of thioridazine. The Linear region of the electrochemical sensor is in the range of 0.1 to 260 μmol L⁻¹ thioridazine with a detection limit of 0.03 μmol L⁻¹, when Bi/PSi/CNTPE is used as an electrochemical sensor. The precision and accuracy of the sensor is evaluated. The Bi/PSi/CNTPE is used as an appropriated tool for accurate measurement of low amounts of thioridazine in real samples with satisfactory results.