Direct Simultaneous Determination of α‐ and β‐Naphthol Isomers at GC‐Electrode Modified with CNTs Network Joined by Pt Nanoparticles Through Derivative Voltammetry

The semi‐derivative technique was adopted to improve the resolution and surfactant was added to sample solution to enhance the sensitivity, α‐ and β‐naphthol isomers could be determined directly and simultaneously at glassy carbon electrode modified with carbon nanotubes network joined by Pt nanoparticles. In 0.1 mol L^?1 HAc‐NaAc buffer solution (pH 5.8), the linear calibration ranges were 1.0×10^?6 to 8.0×10^?4 mol L^?1 for both α‐ and β‐naphthols, with detection limits of 5.0×10^?7 for α‐ and 6.0×10^?7 mol L^?1 for β‐naphthol. The amount of naphthol isomers in artificial wastewater has been tested with above method, and the recovery was from 98% to 103%.     

Ionic Organic Film Sensor for Determination of Phenolic Compounds

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.     

Determination of Atrazine in Natural Water Samples by Differential Pulse Adsorptive Stripping Voltammetry Using a Bismuth Film Electrode

A new method using differential pulse adsorptive stripping voltammetry for the determination of atrazine (ATZ) in natural water samples using a bismuth film electrode (BiFE) is proposed. The calibration curve was linear in the atrazine concentration range from 6.7×10^?7 to 2.0×10^?5 mol L^?1, with a limit of detection (LOD) of 1.4×10^?7 mol L^?1. The proposed electrode was applied for atrazine determination with satisfactory results compared with a high‐performance liquid chromatography method (HPLC).     

Voltammetric Determination of Acibenzolar‐S‐Methyl Using a Renewable Silver Amalgam Film Electrode

Acibenzolar‐S‐methyl (ASM) is a novel fungicide applied for crop protection. A renewable silver amalgam film electrode was used for the determination of ASM in pH 3.4 Britton? Robinson buffer using square wave adsorptive stripping voltammetry (SW AdSV). The parameters of the method were optimized. The electroanalytical procedure made possible to determine ASM in the concentration range of 5×10^?8–3×10^?7 mol L^?1 (LOD=4.86×10^?9, LOQ=1.62×10^?8 mol L^?1). The effect of common interfering pesticides and heavy metal ions was checked. The validated method was applied in ASM determination in spiked water samples.     

Voltammetric Determination of 3‐Nitrofluoranthene and 3‐Aminofluoranthene at Boron Doped Diamond Thin‐Film Electrode

The voltammetric behavior of 3‐nitrofluoranthene and 3‐aminofluoranthene was investigated in mixed methanol‐water solutions by differential pulse voltammetry (DPV) at boron doped diamond thin‐film electrode (BDDE). Optimum conditions have been found for determination of 3‐nitrofluoranthene in the concentration range of 2×10^?8–1×10^?6 mol L^?1, and for determination 3‐aminofluorathnene in the concentration range of 2×10^?7–1×10^?5 mol L^?1, respectively. Limits of determination were 3×10^?8 mol L^?1 (3‐nitrofluoranthene) and 2×10^?7 mol L^?1 (3‐aminofluoranthene).     

Simultaneous Differential Pulse Voltammetric Determination of Ascorbic Acid and Caffeine in Pharmaceutical Formulations Using a Boron‐Doped Diamond Electrode

A cathodically pretreated boron‐doped diamond electrode was used for the simultaneous anodic determination of ascorbic acid (AA) and caffeine (CAF) by differential pulse voltammetry. Linear calibration curves (r=0.999) were obtained from 1.9×10^?5 to 2.1×10^?4 mol L^?1 for AA and from 9.7×10^?6 to 1.1×10^?4 mol L^?1 for CAF, with detection limits of 19 μmol L^?1 and 7.0 μmol L^?1, respectively. This method was successfully applied for the determination of AA and CAF in pharmaceutical formulations, with results equal to those obtained using a HPLC reference method.     

Simultaneous Determination of Thallium and Lead on a Chemically Modified Electrode with Langmuir– Blodgett Film of a p‐tert‐Butylcalix[4]arene Derivative

A new voltammetric sensor, Langmuir–Blodgett (LB) film of a p‐tert‐butylcalix[4]arene derivative modified glassy carbon electrode, was designed and successfully used in simultaneous determination of Tl⁺ and Pb²⁺ by square‐wave anodic stripping voltammetry. Under the optimum experimental conditions, this newly developed sensor reveal good linear response for Tl⁺ and Pb²⁺ in the concentration range of 3×10^?8–4×10^?6 mol L^?1 and 2×10^?7–2×10^?5 mol L^?1 respectively. The detect limits are 2×10^?8 mol L^?1 for Tl⁺ and 8×10^?8 mol L^?1 for Pb²⁺. Using proposed method, Tl⁺ and Pb²⁺ in environment samples were determined with satisfactory results.     

Square‐Wave Voltammetry Applied to the Analysis of the Dye Marker,Solvent Blue 14, in Kerosene and Fuel Alcohol

The purpose of this paper is to develop an electroanalytical method based on square‐wave voltammetry (SWV) for the determination of the solvent blue 14 (SB‐14) in fuel samples. The electrochemical reduction of SB‐14 at glassy carbon electrode in a mixture of Britton‐Robinson buffer with N,N‐dimethylformamide (1 : 1, v/v) presented a well‐defined peak at?0.40 V vs. Ag/AgCl. All parameters of the SWV technique were optimized and the electroanalytical method presented a linear response from 1.0×10^?6 to 6.0×10^?6 mol L^?1 (r=0.998) with a detection limit of 2.90×10^?7 mol L^?1. The developed method was successfully utilized in the quantification of the dye SB‐14 in kerosene and alcohol samples with average recovery from 93.00 to 98.10%.     

Nanostructured Alpha‐Nickel Hydroxide Electrodes for High Performance Hydrogen Peroxide Sensing

Nanostructured alpha‐nickel hydroxide (α‐Ni(OH)₂) immobilized on a Fluorine‐doped Tin Oxide (FTO) surface was explored for the construction of hydrogen peroxide amperometric Flow Injection Analysis (FIA) sensors. Their notable electrocatalytic activity and heterogeneous electron‐transfer rate were confirmed by the appearance of a broad and intense peak associated with the oxidation of hydrogen peroxide and the enhancement of sensibility in hydrodynamic conditions. The α‐Ni(OH)₂ electrodes exhibited a broad dynamic range (5×10^?6 to 1×10^?3 mol L^?1), low detection limit (2×10^?7 mol L^?1), good repeatability (RSD=1.29 % for 20 successive analyses), and a sensitivity greater than 500 µA mmol^?1 L^?1 cm^?2.     

A Novel Voltammetric Method for the Determination of Maleic Acid Using Silver Amalgam Paste Electrode

An efficient voltammetric method was developed for the determination of maleic acid at a silver amalgam paste electrode (AgA‐PE) in Britton–Robinson buffer pH 2.0. The experimental parameters, such as pH of Britton–Robinson buffer, type of the supporting electrolyte and activation of the electrode surface were optimized. Under the optimal conditions, a linear response was observed over the 2×10^?6–1×10^?4 mol L^?1 maleic acid concentration range, determination limit being 5×10^?7 mol L^?1. A highly stable response, with a relative standard deviation (RSD) of 1.6% for 45 repetitive measurements of 1×10^?4 mol L^?1 maleic acid showed that there was no apparent surface passivation indicating the suitability of the method. The method was successfully applied for direct determination of maleic acid in drinking and river water.     

Chemometric Strategies to Develop a Nanocomposite Electrode for Simultaneous Determination of Ascorbic Acid,Dopamine, and Uric Acid

A simple and sensitive method for simultaneously measuring dopamine (DA), ascorbic acid (AA), and uric acid (UA) using a poly(1‐aminoanthracene) and carbon nanotubes nanocomposite electrode is presented. The experimental parameters for composite film synthesis as well as the variables related to simultaneous determination of DA, AA, and UA were optimized at the same time using fractional factorial and Doehlert designs. The use of carbon nanotubes and poly(1‐aminoanthracene) in association with a cathodic pretreatment led to three well‐defined oxidation peaks at potentials around ?0.039, 0.180 and 0.351 V (vs. Ag/AgCl) for AA, DA, and UA, respectively. Using differential pulse voltammetry, calibration curves for AA, DA, and UA were obtained over the range of 0.16–3.12×10^?3 mol L^?1, 3.54–136×10^?6 mol L^?1, and 0.76–2.92×10^?3 mol L^?1, with detection limits of 3.95×10^?5 mol L^?1, 2.90×10^?7 mol L^?1, and 4.22×10^?5 mol L^?1, respectively. The proposed method was successfully applied to determine DA, AA, and UA in biological samples with good results.     

Flow injection determination of hydrogen peroxide using diperiodatoargentate- and diperiodatonickelate-luminol chemiluminescence

A novel chemiluminescence (CL) method for the determination of hydrogen peroxide is described. Method is based on the transition metals in highest oxidation state complex, which include diperiodatoargentate (DPA) and diperiodatonickelate (DPN) and show excellent sensitisation on the luminol-H₂O₂ CL reaction with low luminol concentration in alkaline medium. In particular, the sensitiser which was previously reported (such as Co²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Fe³⁺, Cr³⁺, KIO₄, K₃Fe(CN)₆ etc.) to be unobserved CL due to poor sensitisation with such low concentration of luminol which makes the method hold high selectivity. Based on this observation, the detection limits were 6.5?×?10^?9?mol?L^?1 and 1.1?×?10^?8?mol?L^?1 hydrogen peroxide for the DPN- and DPA-luminol CL systems, respectively. The relative CL intensity was linear with the hydrogen peroxide concentration in the range of 2.0?×?10^?8–6.0?×?10^?6?mol?L^?1 and 4.0?×?10^?8–4.0?×?10^?6?mol?L^?1 for the DPN- and DPA-luminol CL systems, respectively. The proposed method had good reproducibility with a relative standard deviation of 3.4% (8.0?×?10^?7?mol?L^?1, n?=?7) and 1.0% (2.0?×?10^?6?mol?L^?1, n?=?7) for the DPN- and DPA-luminol CL systems, respectively. A satisfactory result has been gained for the determination of H₂O₂ in rainwater and artificial lake water by use of the proposed method.     

Electrochemical Behaviors of Adenosine‐5′‐triphosphate on Molecular Wire Modified Carbon Paste Electrode and Its Sensitive Detection

A new electrochemical method was proposed for the determination of adenosine‐5′‐triphosphate (ATP) based on the electrooxidation at a molecular wire (MW) modified carbon paste electrode (CPE), which was fabricated with diphenylacetylene (DPA) as the binder. A single well‐defined irreversible oxidation peak of ATP appeared on MW‐CPE with adsorption‐controlled process and enhanced electrochemical response in a pH 3.0 Britton‐Robinson buffer solution, which was due to the presence of high conductive DPA in the electrode. The electrochemical parameters of ATP were calculated with the electron transfer coefficient (α) as 0.54, the electron transfer number (n) as 1.9, the apparent heterogeneous electron transfer rate constant (k_s) as 2.67 × 10^?5 s^?1 and the surface coverage (Γ_T) as 4.15 × 10^?10 mol cm^?2. Under the selected conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0 × 10^?7 mol L^?1 to 2.0 × 10^?3 mol L^?1 with the detection limit as 1.28 × 10^?8 mol L^?1 (3σ) by sensitive differential pulse voltammetry. The proposed method showed good selectivity without the interferences of coexisting substances and was successful applied to the ATP injection samples detection.     

Electrocatalytic Oxidation of Acyclovir on Poly(p‐Aminobenzene Sulfonic Acid) Film Modified Glassy Carbon Electrode

Acyclovir is an antiviral effective drug active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p‐aminobenzene sulfonic acid (p‐ABSA) in phosphate buffer solution (PBS). The polymer film‐modified electrode was used to electrochemically detect acyclovir. Polymer film showed excellent electrocatalytic activity for the oxidation of acyclovir. The anodic peak potential value of the acyclovir at the poly(p‐ABSA) modified glassy carbon electrode was 950 mV obtained by DPV. A linear calibration curve for DPV analysis was constructed in the acyclovir concentration range 2×10^?7–9×10^?6 mol L^?1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 5.57×10^?8 and 1.85×10^?7 mol L^?1 respectively. The proposed method exhibits good recovery and reproducibility.     

Preparation of Cobalt Oxide Nanoclusters/Overoxidized Polypyrrole Composite Film Modified Electrode and Its Application in Nonenzymatic Glucose Sensing

A cobalt oxide nanocluster/overoxidized polypyrrole composite film electrochemical sensing interface was fabricated by two step electrochemical method. The electrochemical properties and electrocatalytic activity of the resulting modified electrode were also studied carefully. The results showed that this modified electrode exhibited good stability, good anti‐interference ability, as well as high electrocatalytic activity to the oxidation of glucose. The linear range for the amperometric determination of glucose was 2.0×10^?7–2.4×10^?4 mol L^?1 and 2.4×10^?4–1.4×10^?3 mol L^?1 with a detection limit of 5.0×10^?8 mol L^?1 (S/N=3), respectively. The sensitivity was 1024 µA mM^?1 cm^?2.     

Stripping Voltammetric Determination of Zirconium with Complexing Preconcentration of Zirconium(IV) at a Morin‐Modified Carbon Paste Electrode

A sensitive, selective and economic stripping voltammetry is described for the determination of trace amounts of zirconium at a morin‐modified carbon paste electrode (morin‐MCPE). Zirconium(IV) can be preconcentrated on the surface of the morin‐MCPE due to forming the Zr(IV)–morin complex. The complex produces two second‐order derivative anodic peaks at 0.69 V (vs. SCE) and 0.75 V when linear‐scanning from 0.0 to 1.0 V. The optimum analytical conditions are: 2.2 mol L^?1 HCl, 0.0 V accummulation potential, 90 s accummulation time, 250 mV s^?1 scan rate. A linear relationships between the peak currents at 0.75 V and the Zr(IV) concentration are in the range of 2.0×10^?8 to 3.0×10^?6 mol L^?1. The detection limit is 1.0×10^?8 mol L^?1 (S/N=3) for 120 s accumulation. The RSD for determination of 4.0×10^?7 mol L^?1 Zr(IV) is 4.8% (n=8). The proposed method has been applied to determine zirconium in ore samples, unnecessarily extracted.     

Simultaneous Determination of Dopamine and Ascorbic Acid Using the Nano‐Gold Self‐Assembled Glassy Carbon Electrode

Electrochemical behavior of dopamine (DA) was investigated at the gold nanoparticles self‐assembled glassy carbon electrode (GNP/LC/GCE), which was fabricated by self‐assembling gold nanoparticles on the surface of L ‐cysteine (LC) modified glassy carbon electrode (GCE) via successive cyclic voltammetry (CV). A pair of well‐defined redox peaks of DA on the GNP/LC/GCE was obtained at E_pa=0.197 V and E_pc=0.146 V, respectively. And the peak separation between DA and AA is about 0.2 V, which is enough for simultaneous determination of DA and AA. The peak currents of DA and AA were proportional with their concentrations in the range of 6.0×10^?8–8.5×10^?5 mol L^?1 and 1.0×10^?6–2.5×10^?3 mol L^?1, with the detection limit of 2.0×10^?8 mol L^?1 and 3.0×10^?7 mol L^?1 (S/N=3), respectively. The modified electrode exhibits an excellent reproducibility, sensibility and stability for simultaneous determination of DA and AA in human serum with satisfactory result.     

Effect of Pulse Width of Square Potential to Remove Silver Interference in the Determination of Mercury(II)

A graphite electrode modified with silver (Ag‐CPE) has been applied to detect mercury(II) using differential pulse voltammetry (DPV). Under optimized conditions, the calibration curve is linear in the range from 5.0×10^?8 mol L^?1 to 1.0×10^?4 mol L^?1 of mercury(II). The detection limit was found to be 3.38×10^?8 mol L^?1 with a relative standard deviation (RSD) of 2.25 % (n=8). The proposed method was successfully applied for the detection of mercury(II) in leachate samples. The Ag‐CP composites were characterized using X‐ray diffraction (XRD), BET adsorption analysis and scanning electron microscopy (SEM).     

Indirect Voltammetric Determination of Aluminum in Environmental and Biological Samples in the Presence of the Aluminum Chelating Drugs

A simple indirect method using aluminum chelating drugs as electroactive complexation ligands for the voltammetric determination of aluminum in environmental and biological samples on glassy carbon working electrode is studied. In the range of pH 8–9, desferrioxamine (DFO), 1,2‐dimethy‐3‐hydroxypyrid‐4‐one (Hdmp), 3‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one (Hma) and 2,3‐dihydroxypyridine (DHP) yielded good anodic peaks. It was demonstrated that the decrease of the anodic peak current of the drugs was linear with the increase of aluminum concentration. Among them, Hdmp was found the best complexible ligand and chosen for the voltammetric determination of aluminum with EDTA as chelant, which was used for masking most of the interferences. Under the optimum experimental conditions, the linear range for determination of Al by Hdmp was 5×10^?7–3×10^?5 mol L^?1 Al(III), the detection limit was 2×10^?7 mol L^?1, and the relative standard deviation for 3×10^?6 mol L^?1 Al(III) was 2.6% (n=7). The proposed method was applied to the determination of Al in real water samples and biological samples. The Al concentration in serum samples can be measured directly without time‐consuming digestion pretreatment.     

Determination of Ethambutol in Aqueous Medium Using an Inexpensive Gold Microelectrode Array as Amperometric Sensor

In this paper, gold microelectrode array (Au‐MEA) were employed to determination of ethambutol in aqueous medium. Au‐MEA was constructed with an electronic microchip integrated circuit. The standard curve (analytical curve) was constructed for a single microelectrode (ME) in a concentration range of 5.0×10^?5 to 2.0×10^?3 mol L^?1, allowing estimation of both the limit of detection (LOD) (4.73×10^?5 mol L^?1) and the limit of quantification (LOQ) (1.57×10^?4 mol L^?1) for ethambutol. When the MEA was utilized, the LOD and LOQ were 1.55×10^?7 and 5.18×10^?7 mol L^?1, respectively. Our results indicated that Au‐MEA can be utilized as amperometric sensors for ethambutol determination in aqueous media.