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This paper demonstrates, for the first time, the use of paper-based electrochemical devices coupled to external solid working electrodes. The paper-based electrochemical cells were fabricated using inexpensive and largely available office paper, according to a simple protocol that consists on the creation of hydrophobic barriers using paraffinized paper and preheated metal stamp. The counter and reference electrodes were integrated to the paper platform through the deposition of carbon and silver inks, respectively. The electrochemical paper analytical device (ePAD) was coupled to external glassy carbon rod electrode modified with reduced graphene oxide doped with Cu nanoparticles through meniscus configuration. The analytical usefulness of this electrochemical approach was demonstrated through the simultaneous determination of paracetamol and caffeine in biological samples. The analytes were successfully quantified in real urine samples and limits of detection of 24.6 nM (paracetamol) and 36.1 nM (caffeine) were obtained. The paper platform showed good stability (RSD of 1.07 % for the peak currents and 1.43 % for the peak potentials) and satisfactory performance. The use of solid electrodes coupled to paper electrochemical devices, firstly demonstrated here, opens new possibilities for the utilization of ePADs in electrochemistry and electroanalytical chemistry and offers advantages such as the extremely reduced consumption of reagents and the minimal generation of wastes. [ABSTRACT FROM AUTHOR]

As an alternative to noble metals, MoS2 has been recognized as promising active and earth abundant electrocatalyst for the hydrogen evolution reaction (HER). Here, we demonstrate novel 2H‐phase MoS2 nanoclusters as efficient electrocatalyst for HER, prepared via hydrothermal process without using additional reducing agents to precursors. The MoS2 nanoclusters coated carbon paper electrode shows Tafel slope of 103 mV dec−1 at voltage sweep rate of 2 mV s−1 for HER with onset potential and over‐potential (η10) of 0.132 and 0.212 V, respectively. The good catalytic performance can be attributed to large accessible electrochemically active surface area and sites along with easy transport of electrolyte due to hydrophilic nature of prepared MoS2 nanoclusters. [ABSTRACT FROM AUTHOR]

The present work describes the fabrication of paper-based analytical devices (μPADs) by immobilization of glucose oxidase onto the screen printed carbon electrodes (SPCEs) for the electrochemical glucose detection. The sensitivity towards glucose was improved by using a SPCE prepared from homemade carbon ink mixed with cellulose acetate. In addition, 4-aminophenylboronic acid (4-APBA) was used as a redox mediator giving a lower detection potential for improvement selectivity. Under optimized condition, the detection limit was 0.86 mM. The proposed device was applied in real samples. This μPAD has many advantages including low sample consumption, rapid analysis method, and low device cost. [ABSTRACT FROM AUTHOR]

N‐isopropylacrylamide was polymerized on the surface of copper‐plated carbon paper electrode by a novel redox initiation system composed of persulfate and copper nanoparticles, and the PNIPAAm−Cu NPs@CP film electrode was obtained. Cyclic voltammetry (CV) results showed that the electrode exhibits a reversible temperature, pH and glucose switchable electrical signal response through the ferrocene carboxylic acid (Fc(COOH)). With this basis, a 4‐current output logic gate system consisting of 3‐response inputs of temperature, pH, and glucose was fabricated and a corresponding logic circuit for 3‐input/4‐output ports was established. This work might provide a new avenue for the development of multi‐valued biologic systems. [ABSTRACT FROM AUTHOR]

In this work, the electrochemical determination of glutathione (GSH) using b-cyclodextrin (β-CD) modified carbon electrodes was carried out. Different methodologies were used to modify the electrodes. In the first part of this paper, we analyze and compare the ability of the electrodes to determine GSH using the different β-CD-modified electrodes and cyclic voltammetry. We found that the carbon paste electrode modified by potential sweeping was the best electrode for GSH determination; in addition, we found that an inclusion complex formed between β-CD deposited on the electrode surface and GSH. The formation constant for this complex was 2498.54 M@1 at 258C. Furthermore, we have also calculated thermodynamic parameters for the formation of the inclusion complex. In the second part of this paper, we analyze the effect of sweep rate and pH on the determination of GSH. The best results were obtained at a rate of 50 mVs-1 and a pH of 2.2. The β-CD-modified carbon paste electrode exhibits a linear response in a concentration range of 20 to 157 mM with a sensitivity of 1083.65 μAmM-1cm-2 and a detection limit of 3.92 μM. Finally, the electrode was used to determine the GSH concentration in Eichhornia crassipes root extract, and the concentration determination accuracy was validated by a well-known spectroscopic method. [ABSTRACT FROM AUTHOR]

This paper reports a dual immunosensor for the simultaneous determination of two important fertility‐related hormones: 17β‐estradiol, E2, and follicle‐stimulating hormone, FSH. The implemented method involves direct competitive (E2) or sandwich‐type (FSH) immunoassays carried out on magnetic microparticles (MBs) and amperometric detection at screen‐printed dual carbon electrodes (SPdCEs) involving the hydroquinone (HQ)/H2O2 system. The developed immune platform demonstrates LOD values of 6.88 pg mL−1 and 0.11 mIU mL−1 for E2 and FSH standards, respectively and usefulness for the determination in saliva samples collected from different volunteers, giving results in agreement with the conventional ELISA methodologies. [ABSTRACT FROM AUTHOR]

This paper presents a new application for a screen‐printed carbon electrode (SPCE) modified with chitosan (Cs) and manganese oxide (II). This new electrode (Cs‐MnOX/SPCE) was applied in the detection of tartrazine (TZ) by linear scan voltammetry (LSV). The anodic peak current for TZ increased by nearly 500 % compared with Cs/SPCE and unmodified SPCE. The surface of the electrode was characterized by cyclic voltammetry. The detection limit was 0.06 μmol/L. The relative standard deviations (RSDs) were between 1.0 and 6.0 % (n=15). The accuracy of the new method was evaluated with real samples spiked with known quantities of TZ. [ABSTRACT FROM AUTHOR]

Physicochemical and electrochemical properties of hydroxyphenyl boronic acids(HPBAs) and their use in fluoride determinations were investigated. HPBAs were electropolymerized at pH 1.0–11.0 in 40–60 %(v/v) methanol‐buffer. Differential pulse voltammetry(DPV) determinations of fluoride (with 1.0×10−5–1.0×10−4 M linearity based on potential shift) using poly(HPBAs) glassy carbon electrodes(GCEs) have −45.49 to +34.40 % error range. Significance of raw DPV data for chemometric discrimination was investigated by principle component analysis. This is the first demonstration of fluoride determination with poly(HPBAs)GCEs and chemometric discrimination of pharmaceutical formulations so far. Due to the lack of experimental data in literature, current findings will make a contribution to literature. [ABSTRACT FROM AUTHOR]

This paper describes the development of an electrochemical sensor for carbendazim detection using a glassy carbon electrode modified with a new nanomaterial obtained from the synthesis of magnetite nanoparticles stabilized with ascorbic acid and β‐cyclodextrin. The nanoparticles were characterized and the sensor was evaluated by electrochemical impedance spectroscopy and square wave voltammetry. The calibration curves were linear for carbendazim concentration ranges of 3.33–13.29 μmol L−1 and 16.61–29.82 μmol L−1 with detection limits of 0.43 μmol L−1 and 2.34 μmol L−1, respectively. The proposed sensor represents a fast, efficient and low‐cost analytical tool for pesticide monitoring in natural waters. [ABSTRACT FROM AUTHOR]

Chirality exists everywhere in nature, so chiral recognition is also an extremely important field. This paper explores the recognition of amino acid configuration by an electrochemical chiral sensing platform constructed with carbon nanomaterials (carbon quantum dots (CQDs) as the substrate material) combined with chiral selectors (chitosan (CS)). CQDs/CS, which is bonded by intermolecular force, and CQDs‐CS, which is formed by covalent grafting through amidation, are selected as electrochemical chiral recognition materials, and a series of characterization methods are carried out to indicate the successful preparation of the materials, and then attached to the glass carbon electrode (GCE), forming a chiral sensing platform for amino acid enantiomers. The differential voltammetry (DPV) method was used to convert the chemical signal into electrical signal. The results showed that compared with CQDs/CS, CQDs‐CS had better enantiomer resolution to tryptophan (Trp), and the peak current ratio (IL/ID) was 2.28. [ABSTRACT FROM AUTHOR]

Dopamine (DA) is a crucial neurotransmitter in the central nervous system (CNS) of human and multicellular animal brains. In this paper, we report for the first time the synthesis of carbon black (C)/phosphotungstic acid (PWA) composites by doping PWA on carbon black nanoparticles by impregnation method. The synthesized materials were characterized using high‐resolution scanning electron microscopy (SEM), X‐ray diffraction spectroscopy (XRD) and Fourier transform infrared spectroscopy (FT‐IR). Glassy carbon electrodes (GCE) modified by C/PWA composites were used to detect dopamine. The electrochemical redox behavior of DA was studied with cyclic voltammetry (CV). Under optimized conditions, DA was detected by differential pulse voltammetry (DPV) and the calibration plot showed linearity (R2=0.9988) over the range of DA concentrations of 10 μM‐600 μM with a detection limit of 0.1 μM. The sensor's capability to detect DA in commercial DA injections in real time has been successfully demonstrated. [ABSTRACT FROM AUTHOR]

This paper reports the preparation of multiwalled carbon nanotubes/4,4′‐dihydroxybiphenyl (MWCNTs‐DHB) nanolayered composite as a new modifier for modification of carbon paste electrode (CPE/MWCNTs‐DHB). CPE/MWCNTs‐DHB shows linear responses for phenol in the concentrations range of 0.04–220 μM with a current sensitivity of 0.67 μA μM−1 and a detection limit of 8.0 nM (S/N=3). The electrode shows high selectivity, good repeatability (RSD=4.1 %), excellent reproducibility (RSD=3.5 %), and acceptable stability (91.2 % over one‐month storage). Moreover, the modified CPE exhibits appreciable recoveries (93.0–104.0 %) indicating its acceptable performance for determination of phenol in tap and river water samples. [ABSTRACT FROM AUTHOR]

In this paper, a glassy carbon electrode (GCE) was modified with polyzincon. The modified electrode was used as a simple, inexpensive and highly sensitive electrochemical sensor for the determination of organophosphorus pesticide fenitrothion. To fabricate the electrochemical sensor, GCE was immersed in 0.10 mmol L−1 zincon solutions at pH 7.0 and then successively scanned between −1.00 to 2.20 V ( vs. Ag/AgCl) at a scan rate of 70 mV s−1 for six cycles. The morphology and structure of the polyzincon were studied with atomic force microscopy and scanning electron microscopy. A comparison of the electrochemical behavior of fenitrothion on the unmodified and polyzincon modified-GCE showed that in the modified electrode not only the oxidation peak current increased, but also the overpotential shifted to lower one. The experimental conditions such as sample solution pH, accumulation potential, and time were optimized. The differential pulse voltammetric responses of fenitrothion at potential about −0.60 V was used for the determination of fenitrothion. The peak current increased with increasing the concentration of fenitrothion in the range of 5 to 8600 nmol L−1 with a detection limit of 1.5 nmol L−1. Finally, the electrochemical sensor was used for the analysis of fenitrothion in water and fruit samples. [ABSTRACT FROM AUTHOR]

This paper describes the preparation of a new sensor based on Zn-ferrite modified glassy carbon paste electrode and its electrochemical application for the determination of trace Cd(II) ions in waste waters using differential pulse anodic stripping voltammetry (DPASV). Different Zn/Ni ferrite nanoparticles were synthesized and characterized using scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). The prepared ferrite nanoparticles were used for the preparation of Zn-ferrite-modified glassy carbon paste electrode (ZnMGCPE) for determination of Cd(II) at nanomolar levels in waste water at pH 5. The different parameters such as conditions of preparation, Zn2+/Ni2+/Fe2+ ratio and electrochemical parameters, percentage of modifier, accumulation time, pH and accumulation potential were investigated. Besides, interference measurements were also evaluated under optimized parameters. The best voltammetric response was observed for ZnFe2O4 modifier, when the percentage of modifier was 3 %, accumulation time 9 min, pH of supporting electrolyte 5 and accumulation potential −1.05 V. Thus prepared electrode displays excellent response to Cd(II) with a detection limit of 0.38 ppb, and selective detection toward Cd(II) was achieved. [ABSTRACT FROM AUTHOR]

This paper describes the development of a new electrochemical sensor for 17β‐estradiol (E2) determination based on glassy carbon electrode (GCE) modified with molecularly imprinted polymer grafted onto iniferter‐multiwall carbon nanotubes surface (MIP‐MWCNT) and dihexadecyl‐hydrogen‐phosphate (DHP). The electrochemical method was based on closed‐circuit preconcentration of E2 in 0.1 mol L−1 phosphate buffer (pH 7.0) during 500 s. Upon preconcentration, E2 was determined by differential pulse voltammetry (DPV) exhibiting a limit of detection of 0.01 μmol L−1. The sensor exhibited higher selectivity toward E2 and it was applied for E2 determination in natural water samples, with accuracy attested by HPLC‐DAD. [ABSTRACT FROM AUTHOR]

This paper describes the electrochemical behaviors of Cd2+ and Pb2+ on the proposed mesoporous carbon microspheres/mefenamic acid/nafion modified glassy carbon electrode (MC/MA/Nafion/GC) studied by square wave anodic stripping voltammetry (SWASV). The prepared material is characterized by XRD, SEM, FTIR, RAMAN and BET analysis. Experimental parameters, such as the deposition potential and time, the pH value of buffer solution were optimized. Under the optimized conditions, the electrode responded linearly to Cd2+ and Pb2+ in the concentration range from 50 to 300 nM, and the detection limits were 24.2 and 11.26 nM respectively. The sensitivity determined was 0.0623 μA/nM (Cd2+) and 0.192 μA/nM (Pb2+). Multiple metal ion detection with clear demarcation of peaks was produced by the electrode. Moreover, the modified electrode has possessed good selectivity and reproducibility of Cd2+ and Pb2+ detection. We also investigated the interference of various anions and surfactants for the detection of Cd2+ and Pb2+ ions. Finally the modified electrode was used to detect the presence of metal ions in practical samples and the results obtained are comparatively good with respect to AAS. [ABSTRACT FROM AUTHOR]

Two novel carbon paste electrodes based on gentamicin-reineckate (GNS-RN)/multiwall carbon nanotubes (MWCNTs)/sodium tetraphenyl borate (NaTPB) or potassium tetraphenylborate (KTPB) for potentiometric determination of gentamicin sulfate were constructed. Our endeavors of lowering the detection limit for gentamicin ion-selective electrodes were described. The paper focused on gentamicin carbon paste electrodes based on GNS-RN as electroactive material, o-nitrophenyloctyl ether ( o-NPOE) as plasticizer and incorporation of MWCNTs and lipophilic anionic additives (NaTPB and KTPB) which lower the detection limit of the electrodes showing best results for determination of gentamicin ion. The characteristics of the electrodes, GNS-RN+NaTPB+MWCNTs (sensor 1) and GNS-RN+KTPB+ MWCNTs (sensor 2), were measured, showing favorable features as they provided measurements of the potential with near-Nernstian slopes of 29.6±0.3 and 29.1±0.3 mV/decade over the concentration range of 1.0×10−6-1.0×10−2 mol L−1 and pH ranges 3.0-8.2 and 3.0-8.0 in short response times (6.5 sec). Importantly, the electrodes had low detection limits of 3.0×10−7and 3.4×10−7 mol L−1 for the two sensors, respectively. The sensors showed high selectivity for gentamicin ion with respect to a large number of interfering species. The electrodes were successfully applied for the potentiometric determination of GNS ions in pure state, pharmaceutical preparations and human urine with high accuracy and precision. The results of this study were compared with some previously published data using other analytical methods. [ABSTRACT FROM AUTHOR]

This paper reports on the use of electrochemical impedance spectroscopy (EIS) allied to copper (II) for the determination of 2,4-dinitrophenylhydrazine (DNPH) at glassy carbon electrode (GCE). The experiment measurements were carried out in methanol at a potential of 0.3V versus Ag/AgCl. The Nyquist plots were modeled with a Randle equivalent circuit, by identifying the charge transfer resistance as the relevant concentration dependent parameter. These measurements show that the impedance spectra of DNPH increased by the formation of non-electroactive compound produced from specific interaction between DNPH and Cu (II), which will block the electron-transfer process of the redox probe. Therefore, the proposed methodology offers a detection limit of 4.0×10-8 molL-1. The proposed methodology was satisfactorily applied to determine DNPH in industrial water samples. [ABSTRACT FROM AUTHOR]

Vertically aligned conducting polymer nanowire arrays had great potential applications in supercapacitor electrode material and exhibited enhanced electrocatalytic behavior towards the reduction of nitrite. In this paper, a facial template-free approach to synthesize large arrays of vertically aligned polyaniline (PANI) nanowires on electrochemically pretreated glassy carbon electrodes was reported by using a galvanostatic current method. The asprepared large arrays of PANI nanowires had very narrow diameters and were oriented perpendicular to the substrate, which was a benefit to the ion diffusion when being used as the supercapacitor electrode. The highest specific capacitance of PANI nanowire arrays was measured and kept high at a large charge-discharge current density. Furthermore, it also can detect nitrite with ultrahigh sensitivity of 62.99 μA mM-1cm-2 and a remarkable fast response time of less 1 s. The results indicated that the vertically aligned PANI nanowires could dramatically enhance the electrochemical performance. [ABSTRACT FROM AUTHOR]

In this paper, bare glassy carbon electrode (GCE), multi‐walled carbon nanotubes (MWCNT/GCE) and reduced graphene oxide (RGO/GCE) were to verify the ciprofloxacin oxidation process. The RGO/GCE electrode provided a 9‐fold increase in the analytical signal and a potential displacement of 50 mV. A method using flow injection analysis with amperometric detection has been developed for simple and fast detection of ciprofloxacin in pharmaceutical formulations and bovine milk. The method presented adequate analytical characteristics, limit of detection (LOD<0.1 μmol L−1), simple sample treatment (only dilution supporting electrolyte), analytical frequency (110 analyzes per hour), satisfactory linear range (1–100 μmol L−1) and good precision (RSD<3%). The method was applied in six samples with satisfactory accuracy (recovery values in the range of 101 to 113 %). The ciprofloxacin contents were in agreement with the values provided by the drug labels, while the levels in the milk samples were below the LOD. The results obtained for both applications were statistically equivalent to the results obtained by liquid chromatography, at a 95 % confidence level. [ABSTRACT FROM AUTHOR]

This paper describes the development of a label‐free electrochemical immunosensor based on polyethyleneimine‐stabilized magnetite nanoparticles (MGNnP‐PEI) for the determination of microcystin‐LR (MC‐LR). MGNnP‐PEI was immobilized on the glassy carbon electrode (GCE) surface and employed as a platform for anchorage of the anti‐MC‐LR. Hydroquinone in solution was used as a redox probe. After optimization, the immunosensor exhibited a linear response to MC‐LR concentrations in the range of 0.1 to 500 ng mL−1 with a calculated detection limit of 0.053 ng mL−1. The immunosensor was satisfactorily applied in the quantification of MC‐LR in a water sample collected from a freshwater lagoon. [ABSTRACT FROM AUTHOR]

Aminoquinolines are widely used as antimalarial drugs and thus there is an ever increasing demand for their determination. In this paper, non‐traditional carbon film electrode developed in our laboratory (CFE) with easily replaceable carbon film was used for the determination of 5‐aminoquinoline (5‐AQ) and compared with well‐established commercially available carbon screen printed electrode (CSPE) and gold screen printed electrode (AuSPE). Electrochemical behavior of 5‐AQ was characterized by cyclic and differential pulse voltammetry. Differences in electrochemical behavior of 5‐AQ at different electrodes were evaluated. Determination of 5‐AQ was carried out by differential pulse, square wave, and direct current voltammetry. Practical applicability of the method was verified by direct determination of 5‐AQ in model samples of drinking and river water. Achieved limits of quantitation were in submicromolar concentrations. It was found out that novel CFE in terms of overall performance is in most aspects superior to routinely used commercially available CSPE and AuSPE. [ABSTRACT FROM AUTHOR]

Electrochemical behaviour of 12 icosahedral carboranes – ortho‐, meta‐ and para‐carborane with different exo‐skeletal substituents was investigated. The study was done using phosphate buffers, in some cases with 20 % and 30 % dimethyl sulfoxide (DMSO) addition to increase the solubility of studied compounds. Commercial glassy carbon electrode or home‐made screen printed electrodes were used. Distinct electrochemical responses were observed only for the ortho‐carborane and its exo‐skeletal derivatives. The study of different exo‐skeletal substituents on the electrochemical behaviour of the carboranes is crucial for the intended use of these compounds as electrochemical labels of biomolecules. [ABSTRACT FROM AUTHOR]

In this paper, a high‐sensitivity electrochemical sensor based on platinum (Pt) doped nickel oxide (NiO) nanoparticles and multi‐walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (Pt−NiO/MWCNTs/GCE) has been developed to determine piroxicam (PIR) and amlodipine (AML) simultaneously. The electrochemical behavior of PIR and AML at the proposed sensor has been investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) methods. Pt doped NiO nanoparticles were synthesized by the sol‐gel procedure and were investigated using X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM) techniques. DPV responses of PIR and AML increased linearly with their concentration in wide linear dynamic ranges of 0.6–320.0 μM and 1.0–250.0 μM, respectively. The limits of detection were 0.061 μM for PIR and 0.092 μM for AML. The excellent analytical figure of merits of the proposed modified electrode leads to application of it promising electrochemical sensor to determine PIR and AML in human serum and urine with satisfactory results. [ABSTRACT FROM AUTHOR]

This paper reports the development of a dual immunosensor using magnetic microcarriers (MBs) and amperometric transduction at dual screen‐printed carbon electrodes (SPdCEs) for the simultaneous determination of two biomarkers: interleukin‐13 receptor α2 (IL‐13Rα2) and E‐cadherin (E‐CDH), with both extracellular and soluble fraction; oncogenic and tumor suppressor markers, respectively, of great relevance in metastatic processes. The implemented methodology involved the formation of sandwich‐type immunocomplexes using specific capture antibodies immobilized onto carboxylic acid magnetic microbeads (HOOC‐MBs), and biotinylated detector antibodies labeled with streptavidin−horseradish peroxidase conjugates (Strep‐HRP). The amperometric detection was performed by addition of hydrogen peroxide in the presence of hydroquinone (HQ) as the redox mediator. The dual immunosensing platform provided linear calibration ranges suitable for the determination of both biomarkers in liquid and solid clinical specimens as well as excellent selectivity against other cancer biomarkers. This simple handling dual bioplatform was applied to the determination of the soluble and extracellular fraction of the target biomarkers in serum and paraffined‐embedded tissues from colorectal cancer (CRC) patients diagnosed at different tumor grade. The obtained results reveal great potential of this configuration to improve the reliability in diagnosing metastatic CRC. [ABSTRACT FROM AUTHOR]

Non‐enzymatic glucose sensor is greatly expected to take over its enzymatic counterpart in the future. In this paper, we reported on a facile strategy to construct a non‐enzymatic glucose sensor by use of NiCo2O4 hollow nanocages (NiCo2O4 HNCs) as catalyst, which was derived from Co‐based zeolite imidazole frame (ZIF‐67). The NiCo2O4 HNCs modified glassy carbon electrode (NiCo2O4 HNCs/GCE), the key component of the glucose sensor, showed highly electrochemical catalytic activity towards the oxidation of glucose in alkaline media. As a result, the proposed non‐enzymatic glucose sensor afforded excellent analytical performances assessed with the aid of cyclic voltammetry and amperometry (i–t). A wide linear range spanning from 0.18 μΜ to 5.1 mM was achieved at the NiCo2O4 HNCs/GCE with a high sensitivity of 1306 μA mM−1 cm−2 and a fast response time of 1 s. The calculated limit of detection (LOD) of the sensor was as low as 27 nM (S/N=3). Furthermore, it was demonstrated that the non‐enzymatic glucose sensor showed considerable anti‐interference ability and excellent stability. The practical application of the sensor was also evaluated by determination of glucose levels in real serum samples. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Glycated albumin (GHSA) is a medium‐term glycaemic control marker of diabetes, which can be used as an alternative to or together with glycated haemoglobin (HbA1c). Currently available methods for the measurement of GHSA are limited in clinical practice because they involve slow and cumbersome processes of sample preparation, proteolytic digestion, and thermal incubation, and they suffer from limited analytical performance, and/or a lack of normalization to total albumin (HSA) levels. In this paper, we developed a simple electrochemical biosensor to measure GHSA values based on two DNA aptamers that specifically bind to GHSA and HSA. We used square wave voltammetry (SWV) to measure binding of the target proteins to their specific biotinylated aptamers, which had been immobilised on separate streptavidin (STR)‐modified screen‐printed carbon electrodes (SPCEs), in the presence of the redox mediator ferricyanide (Fe(CN)63−). This electrochemical aptasensing system had a detection limit of 3 ng/ml for GHSA and 0.2 μg/ml for HSA. The results exhibited high selectivity for GHSA over other molecules present in the blood. The developed sensor was able to measure the amount of GHSA in plasma samples. A statistically significant difference was observed in the elevated plasma GHSA levels in diabetic versus non‐diabetic patients. Moreover, the trends in these GHSA levels were consistent with those obtained using the HbA1c test. The sensing system reported herein could be applied as a point‐of‐care‐testing (POCT) device for measurements of clinically relevant GHSA values. [ABSTRACT FROM AUTHOR]

Resveratrol is a phenolic compound that shows important biological antioxidant activities. In this paper, the electrochemical oxidation of iodide in the presence of resveratrol was investigated using both platinum and glassy carbon electrodes. The experimental results showed a diffusion controlled process for the oxidation of iodide to iodine, followed by the chemical reaction of iodine with resveratrol. The possible applicability of iodine‐mediated reaction in the quantitative analysis of resveratrol was studied, obtaining sensitivities of 0.98±0.03 and 4.22±0.20 μAμM−1 cm−2 using platinum and glassy carbon electrodes, respectively. The resveratrol content in a sample obtained from the extracellular medium of elicited suspension‐cultured cells of Vitis vinifera was evaluated and compared with data obtained by HPLC analysis, with good correlations. The signal of other compounds that may be present in the samples or they are precursors of the biosynthesis of trans‐resveratrol (L‐ascorbic, glycine, saccharose, tyrosine, cinnamic acid and p‐coumaric acid) was also evaluated, which shows lower interferences when using glassy carbon electrodes. [ABSTRACT FROM AUTHOR]

This paper describes the immobilization of nickel (II) phthalocyanine‐tetrasulfonic acid tetrasodium salt (NiTsPc) in 3‐n‐propyl(3‐methylpyridinium) silsesquioxane chloride (Si3Pic+Cl−). This hybrid material was synthetized and characterized by 29Si NMR CP‐MAS, FTIR and DRS. The modified material, designated as Si3Pic+Cl−/NiTsPc, was used to build carbon paste electrodes to determine sulfanilamide (SFL) by differential pulse voltammetry. The modified electrode showed a higher current response when compared to the bare carbon paste electrode. The evaluation of SFL was possible in the presence of salicylic acid, commonly used in solid ointment compositions in a high concentration. Theoretical calculations using density functional theory were done aiming to shed light at dimerization process at SFL. The oxidation peak increased with increasing concentrations of SFL in the range of 35–301 μmol L−1. The LOD and LOQ values obtained were 12 and 35 μmol L−1 of SFL, respectively. The novel electrochemical sensor was successfully applied for the determination of SFL in pet drug samples, urine and serum through the standard addition method. Validation was performed through a comparison with values obtained by the molecular absorption spectrometry method and there were no significant differences in the results, as confirmed by the statistical paired t‐test. This demonstrates the promise of a new approach for analytical application in clinical and drug samples of sulfonamide compounds. [ABSTRACT FROM AUTHOR]

In this paper, an electrochemical application of bismuth-film electrode (BiFE) fabricated via ex-situ electrodeposition onto a glassy carbon electrode for testosterone determination was investigated in aqueous and aqueous/ surfactant solutions. In cyclic voltammetry, the compound showed one irreversible and adsorption-controlled reduction peak. The BiFE revealed good linear response in the examined concentration range of 1 to 45 nmol L-1 testosterone in Britton-Robinson buffer, pH 5.0 containing 3 mmol L-1 cetyltrimethylammonium bromide. The limit of detection was 0.3 nmol L-1 (0.09 ng mL-1). Finally, the BiFE was satisfactorily applied for quantitation of testosterone in both pharmaceutical (oil-based ampoule) and biological (human urine) samples. [ABSTRACT FROM AUTHOR]

The paper reports the development of a new sensor based on Printex L6 (CPL6) carbon black modified with copper oxides (CuO/Cu2O) nanoparticles and its application towards the determination of Propylparaben (PP). In fact, it is the first report of its kind in the literature. The sensor was produced through the dispersion of CPL6 in dimethylformamide on glassy carbon electrode surface followed by CuO/Cu2O electrodeposition. The conditions of electrodeposition investigated included time and solution concentration of Cu (II). Morphological, structural and electrochemical characterizations of the sensor were performed. Under optimal conditions, wide linear range (1.0 to 35.0 μmol L−1) was obtained in the detection of PP. The detection limit obtained was 0.46 μmol L−1 (S/N=3). The CuO/Cu2O‐CPL6/GCE sensor was found to be as sensitive as the high performance liquid chromatography in the determination of PP in both cosmetic and river water samples, in addition to being reproducible and stable. [ABSTRACT FROM AUTHOR]

In this paper, we report an electrochemical material for nicotine detection in aqueous solution by using glassy carbon electrode (GCE) electrodeposited with Nickel(II) phthalocyanine‐tetrasulfonic acid tetrasodium salt (polyNiTSPc) in Tetra n‐bütil ammonium hydroxide (TnBAH) alkaline solution. The detection performance of the polyNiTSPc/GCE and the reaction mechanism of nicotine electro‐oxidation process is investigated using Cyclic Voltammetry (CV) and Square Wave Voltammetry (SWV) techniques in 0.1 M phosphate buffer solution (pH 7.5). The conductivity properties of the bare GCE and polyNiTSPc/GCE were analysed using Electrochemical impedance spectroscopy (EIS). The surface morphology of bare GCE and polyNiTSPc/GCE are characterized by Atomic Force Microscopy (AFM). PolyNiTSPc shows high catalytic activity for the electro‐oxidation of nicotine, with the limit of detection at 146 nM nicotine. PolyNiTSPc/GCE can be used as a biosensor with very low detection limit for nicotine. Electrode process for nicotine oxidation is diffusion controlled, including irreversible one‐electron transfer attributed to the nicotine/nicotine‐Δ1′,(5′)‐iminium ion conversion on the polyNiTSPc coated electrode. Electrochemical measurements indicated that the polyNiTSPc against nicotine plays a similar role as CYP2A6 enzyme which catalyses the intermediate reaction product of nicotine‐cotinine transformation in most mammalian species. [ABSTRACT FROM AUTHOR]

This paper describes the electrochemical determination of vitamin D2 (ergocalciferol) and D3 (cholecalciferol) in mixed organic/water solvent, using a glassy carbon electrode (GCE). The mixing ratio of organic/water solvent has an important influence on the electrocatalytic response of D vitamins on the surface of the glassy carbon electrode. Well-defined peaks for Vitamin D2 and D3 were observed in a 40 % ethanol/60 % water solution with lithium perchlorate as the support electrolyte. This study demonstrated that the glassy carbon electrode is highly sensitive for the determination of vitamin D2 and D3, with a limit of detection of 0.13 and 0.118 µmol L−1, respectively. No significant interference was seen for vitamins A, E and K in the detection of vitamin D. [ABSTRACT FROM AUTHOR]

This paper describes the development of a new sensor based on an ionic organic film. The amphiphilic molecule, 4-[(4-decyloxyphenyl)-ethynyl]-1-methylpyridinium iodide (10PyI), which has liquid-crystalline properties, was synthesized and applied in the construction of a GCE/10PyI sensor. Analytical parameters for caffeic acid, repeatability (4.8 %), reproducibility (2.8 %), linearity (two ranges: 9.9×10−7 to 3.8×10−5 mol L−1 and 4.7×10−5 to 9.9×10−5 mol L−1) and detection limits (9.0×10−7 mol L−1 and 8.7×10−6 mol L−1), were determined. The method was successfully applied in the determination of total phenolic compounds (TPC) in mate herb extracts. [ABSTRACT FROM AUTHOR]

This paper describes the development a novel ruthenium(II) complex-ZnO/CNTs modified carbon paste electrode (Ru(II)/ZnO/CNTs/CPE) for the electrocatalytic determination of ascorbic acid (AA). The objective of this novel electrode modification was to seek new electrochemical performances for the detection of AA, nicotinamide adenine dinucleotide (NADH) and folic acid (FA). The peak potentials recorded were 170, 500 and 830 mV vs. Ag/AgCl/KClsat for AA, NADH and FA, respectively. The peak currents were linearly dependent on AA, NADH and FA concentrations using square wave voltammetry (SWV) method at the ranges of 0.008-251, 1.0-650, and 3.0-700 µmol L−1, with detection limits of 0.005, 0.5, and 1.0 µmol L−1, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a rapid and sensitive modified electrode for the simultaneous determination of hydroquinone (HQ) and bisphenol A (BPA) is proposed. The simultaneous determination of these two compounds is extremely important since they can coexist in the same sample and are very harmful to plants, animals and the environment in general. A carbon paste electrode (CPE) was modified with silver nanoparticles (nAg) and polyvinylpyrrolidone (PVP). The PVP was used as a reducing and stabilizing agent of nAg from silver nitrate in aqueous media. The nAg‐PVP composite obtained was characterized by transmission electron microscopy and UV‐vis spectroscopy. The electrochemical behavior of HQ and BPA at the nAg‐PVP/CPE was investigated in 0.1 mol L−1 B−R buffer (pH 6.0) using cyclic voltammetry (CV) and square wave voltammetry (SWV). The results indicate that the electrochemical responses are improved significantly with the use of the modified electrode. The calibration curves obtained by SWV, under the optimized conditions, showed linear ranges of 0.09–2.00 μmol L−1 for HQ (limit of detection 0.088 μmol L−1) and 0.04–1.00 μmol L−1 for BPA (limit of detection 0.025 μmol L−1). The modified electrode was successfully applied in the analysis of water samples and the results were comparable to those obtained using UV‐vis spectroscopy. [ABSTRACT FROM AUTHOR]

A unipolar pulse electrodeposition method was employed to controllably synthesize nanosheet type NiCo LDH. The effect of concentration rate of Ni(NO3)2/Co(NO3)2 preparation solution on crystalline structure, morphology and supercapacitive performance was investigated systematically. Experimental found that the morphology and composition of NiCo LDH was highly depend on the Ni2+/Co2+ molar ratios of preparation solution; and the obtained Ni0.76Co0.24 LDH materials showed small nanosheet size and uniform distribution on carbon fiber electrode. Ni0.76Co0.24 LDH electrode was evaluated for supercapacitor application, which revealed a high specific capacitances of 2189.8 and 1908.8 F g−1 at the current density of 1 and 30 A g−1 respectively and a good cycle stability, retaining 70.3 % of the initial capacitance after 20000 charge and discharge cycles at 50 A g−1. Moreover, the Ni0.76Co0.24 LDH electrode exhibits a high energy density of 76 Wh Kg−1 at a power density of 250 W Kg−1 and a high power density of 7500 W Kg−1 at energy density of 66 Wh Kg−1. The as-prepared Ni0.76Co0.24 LDH as positive electrode for asymmetric supercapacitor exhibits excellent energy density of 4.1 Wh Kg-1 at a power density of 4000 W Kg-1 [ABSTRACT FROM AUTHOR]

Three tumor biomarkers (homovanillic acid (HVA), vanillylmandelic acid (VMA), and 5-hydroxyindole-3-acetic acid (5-HIAA)) have been determined by differential pulse voltammetry (DPV) at screen-printed carbon electrodes (SPCEs). As an optimum medium for all three analytes, Britton-Robinson buffer (0.04 mol ⋅ L−1, pH 3.0) was used. Dependencies of the peak current on the concentration of a biomarker were linear in the concentration range from 0.2 to 100 μmol ⋅ L−1 for all the tested compounds, with the limits of quantification 0.8 μmol ⋅ L−1 for homovanillic acid, 0.2 μmol ⋅ L−1 for vanillylmandelic acid, and 0.4 μmol ⋅ L−1 for 5-hydroxyindole-3-acetic acid. Moreover, it was verified that the newly developed methods can be used for simultaneous determination of HVA and VMA in mixture. [ABSTRACT FROM AUTHOR]

In this study, a differential pulse voltammetry method was designed for the simultaneous determination of etodolac and thiocolchicoside in a tablet dosage form. This method is a sensitive, costless and reproducible one initially designed for the simultaneous determination of etodolac and thiocolchicoside using bare/unmodified glassy carbon electrode in the presence of sodium dodecyl sulfate. At optimized conditions, the method showed linear responses with etodolac and thiocolchicoside concentration in the range of 1 μM to 80 μM. The limits of detection and quantification were calculated as 0.11 μM and 0.38 μM for etodolac and 0.20 μM and 0.67 μM for thiocolchicoside, respectively. [ABSTRACT FROM AUTHOR]

A molecularly imprinted polymer (MIP) sensor was successfully constructed on glassy carbon electrode for the determination of 1‐naphthol (1‐Nph). The sensor was constructed by electropolymerization on bare GCE in the presence of the target molecule. The recognition of 1‐Nph was conducted indirectly using [Fe(CN)6]3−/4− as redox probe. The MIP sensor presented wide linear working range and limit of detection of 1.5×10−9 mol L−1. The MIP sensor was applied for the determination of 1‐Nph in oilfield produced water. The results obtained showed good selectivity and sensitivity of the proposed sensor in terms of 1‐Nph quantification. [ABSTRACT FROM AUTHOR]

In this work, a glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes functionalized with carboxylic groups (MWCNT−COOH) was used to determine the hormone estrone in seawater samples. Modification of the electrode was optimized using three successive 10‐μL aliquots of the MWCNT−COOH dispersion in ethanol (1 : 5 mL). The cyclic voltammetry results showed an oxidation peak at 0.59 V with characteristics of an irreversible process, pH dependent and controlled by adsorption of species. The results of square‐wave voltammetry showed that the intensities of peak currents for the MWCNT−COOH/GCE were about 2.5 times higher than for GCE. The calibration curve showed a linearity of 0.9981 and a sensitivity of 0.1521 μA/mol L−1. The limits of detection and quantification were 0.117 and 0.392 μmol L−1, respectively. The recovery obtained using seawater samples was 91%, indicating the applicability of the method in marine environments. [ABSTRACT FROM AUTHOR]

An electrochemical sensor based on poly‐ethionine (Poly‐ET) film modified glassy carbon electrode was developed for sensitive and simultaneous sensing of dopamine (DA) and paracetamol (PA). The electropolymerization of ethionine monomer was carried out to modify the electrode. The modified electrode was characterized by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The Poly‐ET/GCE exhibited excellent electrocatalysis towards the sensing of DA and PA. Poly‐ET/GCE showed a linear increase of current response with increase concentration of DA and PA ranging from 0.1 μM–60 μM and 0.1 μM–180 μM, respectively. The LODs were found to be 7 nM and 18 nM (S/N=3) for DA and PA, respectively. This electrochemical sensor was successfully utilized for the detection of DA and PA in pharmaceutical samples. [ABSTRACT FROM AUTHOR]

The synthesis of NiO/NiCo2O4 nanoparticles by an eco‐friendly, fast, simple and cost‐effective approach employing Urtica extract is reported in this study. The NiO/NiCo2O4 nanocomposite were characterized using VSM, FTIR, XRD, and SEM techniques. Moreover, to construct a modified carbon paste electrode, NiO/NiCo2O4 were employed and this sensor was used for dopamine (DA) detection. Using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques, the electrochemical behavior of dopamine at the NiO/NiCo2O4/CPE was investigated. Analysis of dopamine, with a limit of detection (LOD) equal to 0.04 μM, in the concentration range of 0.1–100.0 μM, was facilitated by NiO/NiCo2O4/CPE. Moreover, the satisfactory selectivity for DA determination in the presence of uric acid (UA) and ascorbic acid (AA), was obtained. The suggested new sensor displayed a good reproducibility, sensitivity, and stability for determination of DA in drug and biological samples. [ABSTRACT FROM AUTHOR]

We report the application of an electrochemical sensor based on gold‐copper metal‐organic framework immobilized on the surface of a glassy carbon electrode to the detection of captopril (CAP), an angiotensin‐converting enzyme inhibitor. Cyclic voltammetric studies showed that the joint action of gold nanoparticles and copper‐1,3,5‐benzenetricarboxylate (Cu−BTC) enhanced the electrochemical response to the Cu‐captopril complex that is adsorbed onto the surface of the electrode. Release of gold nanoparticles from Au@Cu−BTC not only increased the conductivity of the electrode but also provided a more favorable environment for the deposition of reduced Cu that is catalytically renewed on the electrode surface. The anodic current of the Cu(II)−CAP oxidation peak varied linearly within two concentration ranges, namely 0.5 to 7.0 μmol L−1 and 10 to 2500 μmol L−1, with a limit of detection of 0.047 μmol L−1. The mean recovery for the determination of captopril in commercial tablets was 100.3 % suggesting that the method has considerable potential for future industrial applications. [ABSTRACT FROM AUTHOR]

A novel electrode was fabricated for the quantitation of Fe2+ ion. It was based on the covalent attachment of the gemifloxacin molecule (the recognition element) to the surface of MWCNTs to be incorporated as an electroactive material. Linear response of Fe2+ ions was found in the concentration range of 1×10−2 mol L−1 to 1×10−8 mol L−1 with a Nernstian slope of 30.37 ±0.3 (mV/decade) and attained a stable response within 5 s. The sensor exhibited LOD value of 4.8×10−9 mol L−1. It was applied in the monitoring of Fe2+ concentration in multi‐vitamins tablets, tap water and milk samples with acceptable recovery ranged from 94.00 % to 102.00 %. [ABSTRACT FROM AUTHOR]

In the present paper a voltammetric sensor based on glassy carbon electrode (GCE) and cobalt phthalocyanine (CoPc)/multiwalled carbon nanotube (MWCNT) composite has been successfully prepared for uric acid (UA) determination in real samples. The electrochemical behavior of UA at the GCE-CoPc/MWCNT has been evaluated by employing cyclic voltammetry. The charge transfer coefficient, α, and the charge transfer rate constant, κs, for electron transfer between CoPc/MWCNT and GCE were calculated as 0.49 and 19.5±0.51 s−1, respectively. Under optimized conditions (pH 7.0 in 0.10 mol L−1 phosphate buffer) the best technique was the square wave voltammetry and responds linearly to UA from 0.2 up to 1.0 mmol L−1 (r=0.997) and 1.25 up to 4.0 mmol L−1 (r=0.991) with limits of detection and quantification of 0.26 and 0.86 mmol L−1, respectively. The developed method was successfully applied for UA determination in real samples of human urine. The modified electrode exhibits sensitive and stable responses and does not show interferences in presence of dopamine and ascorbic acid. [ABSTRACT FROM AUTHOR]

This paper describes a rapid and sensitive method for determination of the hair dye Basic Blue 41 in wastewater samples using screen-printed carbon electrodes modified with graphene (SPCE/Gr). The method is based on the reversible reduction of azo groups of the dye at potential of −0.23 V/−0.26 V, where both the anodic and cathodic currents increased 1,300 % when compared to screen-printed carbon (SPCE) and glassy carbon electrodes (GCE). The optimization of a square wave voltammetric method was performed by means of 23 factorial design, Doehlert matrix and multi-response assays, and the best parameters were: frequency (54.8 Hz), step potential (6 mV), pulse amplitude (43.7 mV) and pH 4.5. The analytical curve was constructed from 3.00×10−8 to 2.01×10−6 mol L−1, with detection and quantification limits of 5.00×10−9 and 1.70×10−8 mol L−1, respectively. The repeatability of the method evaluated for 10 consecutive measurements at concentrations of 1.70×10−7 mol L−1 and 1.70×10−6 mol L−1, showed relative standard deviation of 3.56 and 0.57 %, respectively. The sensor based in SPCE/Gr was successfully applied in wastewater samples collected from a drinking water treatment plant and validated by comparison with HPLC-DAD method with good accuracy. [ABSTRACT FROM AUTHOR]

This paper describes the development of a reduced graphene oxide (RGO), carbon nanotube (CNT) and Co(II) complex (cobalt(II) bis (benzoylacetone) eth-ylenediimino) (CBE) modified carbon paste electrode (CPE) for simultaneous determination of isoprenaline (IP), captopril (CAP) and tryptophan (Try). A pair of well-defined redox peaks of Co(II) complex were obtained through a direct electron transfer between the Co(II) complex and the CPE. The proposed sensor showed very efficient electrocatalytic activity for anodic oxidation of IP in a 0.1 M phosphate buffer solution (pH 7.0). Square wave voltammetry (SWV) exhibited two linear dynamic ranges of 0.125-30.0 µM and 30.0300.0 µM for IP. The detection limit for IP was found to be 50 nM. The proposed sensor was successfully applied for the determination of IP in real samples such as human blood serum, urine and IP ampoule. [ABSTRACT FROM AUTHOR]

A fast, simple and costless methodology without sample pre‐treatment is proposed for the discrimination of beers. It is based on cyclic voltammetry (CV) using commercial carbon screen‐printed electrodes (SPCE) and includes a correction of the signals measured with different SPCE units. Data are submitted to partial least squares discriminant analysis (PLS−DA) and support vector machine discriminant analysis (SVM−DA), which allow a reasonable classification of the beers. Also, CV data from beers can be used to predict their alcoholic degree by partial least squares (PLS) and artificial neural networks (ANN). In general, non‐linear methods provide better results than linear ones. [ABSTRACT FROM AUTHOR]