Voltammetric Determination of 4‐Nitrophenol and 5‐Nitrobenzimidazole Using Different Types of Silver Solid Amalgam Electrodes – A Comparative Study

The voltammetric behavior of two genotoxic nitro compounds (4‐nitrophenol and 5‐nitrobenzimidazole) has been investigated using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at a polished silver solid amalgam electrode (p‐AgSAE), a mercury meniscus modified silver solid amalgam electrode (m‐AgSAE), and a mercury film modified silver solid amalgam electrode (MF‐AgSAE). The optimum conditions have been evaluated for their determination in Britton‐Robinson buffer solutions. The limit of quantification (L_Q) for 5‐nitrobenzimidazole at p‐AgSAE was 0.77 µmol L^?1 (DCV) and 0.47 µmol L^?1 (DPV), at m‐AgSAE it was 0.32 µmol L^?1 (DCV) and 0.16 µmol L^?1 (DPV), and at MF‐AgSAE it was 0.97 µmol L^?1 (DCV) and 0.70 µmol L^?1 (DPV). For 4‐nitrophenol at p‐AgSAE, L_Q was 0.37 µmol L^?1 (DCV) and 0.32 µmol L^?1 (DPV), at m‐AgSAE it was 0.14 µmol L^?1 (DCV) and 0.1 µmol L^?1 (DPV), and at MF‐AgSAE, it was 0.87 µmol L^?1 (DCV) and 0.37 µmol L^?1 (DPV). Thorough comparative studies have shown that m‐AgSAE is the best sensor for voltammetric determination of the two model genotoxic compounds because it gives the lowest L_Q, is easier to prepare, and its surface can be easily renewed both chemically (by new amalgamation) and/or electrochemically (by imposition of cleaning pulses). The practical applicability of the newly developed methods was verified on model samples of drinking water.     

Analytical Potentialities of Carbon Nanotube/Silicone Rubber Composite Electrodes: Determination of Propranolol

A new composite electrode based on multiwall carbon nanotubes (MWCNT) and silicone‐rubber (SR) was developed and applied to the determination of propranolol in pharmaceutical formulations. The effect of using MWCNT/graphite mixtures in different proportions was also investigated. Cyclic voltammetry and electrochemical impedance spectroscopy were used for electrochemical characterization of different electrode compositions. Propranolol was determined using MWCNT/SR 70 % (m/m) electrodes with linear dynamic ranges up to 7.0 µmol L^?1 by differential pulse and up to 5.4 µmol L^?1 by square wave voltammetry, with LODs of 0.12 and 0.078 µmol L^?1, respectively. Analysis of commercial samples agreed with that obtained by the official spectrophotometric method. The electrode is mechanically robust and presented reproducible results and a long useful life.     

Anodic Stripping Voltammetric Determination of Mercury(II) in Water Using a 4‐Tert‐Butyl‐1‐(Ethoxycarbonylmethoxy)Thiacalix[4]Arene Modified Glassy Carbon Electrode

A glassy carbon electrode coated the film of 4‐tert‐butyl‐1‐(ethoxycarbonylmethoxy)thiacalix[4]arene is designed for the determination of trace amounts of Hg²⁺. Compared with bare glassy carbon electrode, the modified electrode can improve the measuring sensitivity of Hg²⁺. Under the optimum experimental condition, the modified electrode in 0.1 mol L^?1 H₂SO₄ + 0.01 mol L^?1 KCl solution shows a linear voltammetric response in the range of 8.0 × 10^?9 ～ 3.0 × 10^?6 mol L^?1 with detection limit 5.0 × 10^?9 mol L^?1 for Hg²⁺. The high sensitivity, selectivity, and stability of modified electrode also prove its practical application for a simple, rapid and economical determination of Hg²⁺ in water samples.     

Palladium Particles‐Impregnated Natural Phosphate Electrodes for Electrochemical Determination of Mercury in Ambient Water Samples

We present here a simple procedure for the determination of mercury(II) using differential pulse anodic stripping voltammetry (DPASV) at palladium particles‐impregnated natural phosphate modified carbon paste electrodes (Pd‐NP‐CPE). The surface of modified electrode was characterized using SEM, infrared spectroscopy, X‐ray diffraction and electrochemical analysis. All experimental variables involved in the voltammetric stripping method were optimized. The detection limit was found to be 4.99×10^?8 mol L^?1 (S/N=3) that is not different to the permitted value for Hg(II) in water reported by the Environmental Protection Agency (EPA). The proposed electrode exhibits good applicability for monitoring Hg(II) in tap and wastewater.     

Selective Determination of Zn2+ Ion in Various Environmental,Biological and Medicinal Plant Samples Using a Novel Coated Graphite Electrode

Novel Zn²⁺ ion‐selective PVC based coated graphite electrodes were fabricated using the ionophores N‐((1H‐indol‐3‐yl)methylene)thiazol‐2‐amine (I₁), N‐((1H‐indol‐3‐yl)methyl)‐thiazol‐2‐amine (I₂) and 1‐((1H‐indol‐3‐yl)methylene)urea (I₃). Their potentiometric performance was examined in dependence of the addition of plasticizers and anion excluders and compared. It is found that the coated graphite electrode with the composition I₁:KTpClPB:o‐NPOE:PVC=9 : 1.5 : 51 : 38.5 is the best with respect to the wide working concentration range (4.2×10^?8–1.0×10^?1 mol L^?1), low detection limit (1.6×10^?8 mol L^?1) and wide pH range of 3.0–8.0. The proposed electrode was successfully applied to quantify Zn²⁺ in various environmental, biological and medicinal plant samples and used as indicator electrode.     

Application of Polymer‐Modified Hanging Mercury Drop Electrode in the Indirect Determination of Certain β‐Lactam Antibiotics by Differential Pulse,Ion‐Exchange Voltammetry

A selective and sensitive polymer‐modified electrode was developed for β‐lactam antibiotics (cefaclor, amoxycillin and ampicillin) present in formulated and blood plasma samples for the quantitative analysis in aqueous environment. The detection was made using an ion‐exchange voltammetric technique, in differential pulse mode, on poly(N‐chloranil N,N,N′,N′‐tetramethylethylene diammonium dichloride)‐modified hanging mercury drop electrode of a three‐electrode system (PAR Model 303A) attached with a Polarographic Analyzer/Stripping Voltammeter (PAR Model 264A). Antibiotics, which are electroinactive compounds, were essentially converted to their electroactive oxazolone analogues through acid treatment under drastic conditions (0.1 mol L^?1 HCl, ～85 °C, 2 h). These analytes in the form of their respective oxazolones were indirectly analyzed by oxazolone entrapment in the polymeric film through ion‐exchange process at modified electrode surface (accumulation potential ?0.20 V (vs. Ag/AgCl), accumulation time 120 s, pH 7.4, KH₂PO₄‐NaOH buffer (ionic strength 0.1 mol L^?1), scan rate 10 mV s^?1, pulse amplitude 25 mV). The limit of detection of cefaclor‐derived oxazolone was found to be 2.12 nmol L^?1 (0.82 ppb, S/N 3, RSD 3.21%) in terms of cefaclor (a representative β‐lactam) concentration.     

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).     

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.     

Electrochemical Determination of Sunscreens Agents in Cosmetic Using Square Wave Voltammetry

Sunscreen agents and in particular UV filters are compounds added in different cosmetic formulations, that has the function of preventing damage caused by sun exposition. Therefore, this paper proposes the development of a simple, fast and reliable electroanalytical method utilizing square wave voltammetry (SWV) to the determination of Benzophenone‐3 (BZ‐3), camphor 4‐methylbenzylidene (MBC) and 2‐ethylhexyl‐4‐methoxycinnamate (OMC) in cosmetic samples. The electrochemical system consisted of a cell with three electrodes: work – gold electrode modified, reference – Ag/AgCl_(sat) and auxiliary – platinum, using as supporting electrolyte 4.0 mL of Britton Robinson Buffer 0.04 mol L^?1 (pH=4.0), 1.0 mL of methanol and 5.50×10^?4 mol L^?1 of cetyltrimethylammonium bromide (CTAB). The method was validated using three commercial sunscreen samples and the results showed recovery values between 83 and 98 %. The average values found for the analysed samples were 3.49 % m/m (728 mg L^?1) to BZ‐3, 0.56 % m/m (113 mg L^?1) to MBC and 0.99 % m/m (208 mg L^?1) to OMC. The detection (DL) and quantification (QL) limits were 0.47 mg L^?1 and 1.56 mg L^?1 to BZ‐3, 0.77 mg L^?1 and 2.58 mg L^?1 to MBC and 0.78 mg L^?1 and 2.59 mg L^?1 to OMC, respectively. The sunscreen protector samples were also evaluated by high‐performance liquid chromatography (HPLC) demonstrating a good correlation between the results and compared the results with allowed concentration.     

Simultaneous Voltammetric Determination of Zn(II), Pb(II), Cu(II), and Hg(II) in Ethanol Fuel Using an Organofunctionalized Modified Graphite‐Polyurethane Composite Disposable Screen‐Printed Device

A disposable screen‐printed device containing working, auxiliary, and reference electrodes is proposed for the simultaneous voltammetric determination of Zn(II), Pb(II), Cu(II), and Hg(II) in ethanol fuel. The working electrode was printed using an ink modified with 2‐benzothiazole‐2‐thiol organofunctionalized SBA‐15 silica, in order to increase sensitivity. The performance of this electrode was compared with that of bare and SBA‐15‐modified electrodes. After optimizing the experimental parameters, the device was applied in determination of the analytes in commercial ethanol fuel samples, using 0.10 mol L^?1 KCl/ethanol ratios of 30 : 70 (v/v), with [H⁺]=10^?5 mol L^?1. After 5 min of preconcentration at ? 1.3 V (vs. pseudo‐Ag/AgCl), four well‐resolved signals were obtained, enabling simultaneous determination of the four analytes using a differential pulse anodic stripping voltammetry (DPASV) procedure. The limits of detection were 0.30, 0.065, 0.030, and 0.046 µmol L^?1 for Zn(II), Pb(II), Cu(II), and Hg(II), respectively. The results of these analyses were in agreement with those obtained using graphite furnace atomic absorption spectroscopy (GFAAS) for Pb(II), Cu(II), and Hg(II), and high‐resolution continuum source flame atomic absorption spectrometry (HR‐CS‐FAAS) for Zn²⁺, at a 95 % confidence level. Analytes originally present in the samples could be detected, and the interference of some cations and anions was evaluated.     

Sol—Gel Derived Carbon Ceramic Electrode Bulk—Modified with Tris（1,10—phenanthroline—5,6—dione） iron （Ⅱ）Hexafluorophosphate and Its Use as an Amperometric Iodate Sensor

A surface‐renewable tris(1, 10‐phenanthroline‐5, 6‐dione) iron (D) hexafluorophosphate (FePD) modified carbon ceramic electrode was constructed by dispersing FePD and graphite powder in methyltrimethoxysilane (MTMOS) based gels. The FePD‐modified electrode presented pH‐dependent voltammetric behavior, and its peak currents were diffusion‐controlled in 0.1 mol/L Na₂SO₄ + H₂SO₄ solution (pH = 0.4). In the presence of iodate, dear electrocatalytic reduction waves were observed and thus the chemically modified electrode was used as an amperometric sensor for iodate in common salt. The linear range, sensitivity, detection limit and response time of the iodate sensor were 5 × 10^?6–1 × 10^?2 mol/L, 7.448 μA·L/ mmol, 1.2 × 10^?6 mol/L and 5 s, respectively. A distinct advantage of this sensor is its good reproducibility of surface‐renewal by simple mechanical polishing.     

Electroanalytical Studies of Chromone Based Ionophores for the Selective Determination of Arsenite Ion

Two chemosensors 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐(2‐phenylhydrazone), [I₁] and 4H‐1‐benzopyran‐3‐carboxaldehyde, 4‐oxo‐, 3‐[2‐(2,4‐dinitrophenyl)hydrazone], [I₂] with hydrazone‐NH group as binding site have been shown excellent selectivity for arsenite ion. It is confirmed by the UV‐vis titration that I₂ is more selective than I₁. The performance of the coated graphite electrode (CGE) was found to be better than polymeric membrane electrode (PME) in terms of linear range of 4.89×10^?7–1.0×10^?1 mol L^?1, low detection limit of 8.31×10^?8 mol L^?1 and short response time. The proposed sensors were also used to determine the arsenite ion in different water samples.     

Potentiometric Study of Coated Graphite Electrode and Polymeric Membrane Electrode for the Determination of Sm3+ Ion

Preliminary studies on the two Schiff bases N2‐((3H‐indol‐3‐yl)methylene)‐6‐phenyl‐1,3,5‐triazine‐2,4‐diamine (L₁) and N2,N4‐bis((3H‐indol‐3‐yl)methylene)‐6‐phenyl‐1,3,5‐triazine‐2,4‐diamine (L₂) have shown that they can act as Sm³⁺ selective electrodes. The performances of a polymeric membrane electrode and a coated graphite electrode based on L₂ were compared and the CGE proved to be better, as it shows a low detection limit of 1.8×10^?8 mol L^?1, a Nernstian slope of 19.6±0.4 mV decade^?1 of activity with a response time of 11 s in the pH range of 3.0–9.0. The CGE was used to determine Sm³⁺ in medicinal plants and soil samples. It was also used to determine fluoride ions in mouthwash samples and in toothpaste.     

Flow-Injection Electrochemiluminescence Detecting Rifampicin Based on Its Sensitizing Effect

Introduction Rifampicin, a semi synthetic compound, is used primarily in the treatment of tuberculosis, and it is also an excellent amistaphyloco antibiotic when used in combination with other antibiotics, so it is very useful clinically.1 Therefore, the determination of rifampicin has attracted much attention. From now on, techniques for the determination of rifampicin have been primarily based on spectrophotometry,2 double-wavelength thin-layer scan,3 chemiluminescence,4 high performance liq…     

Differential Pulse Voltammetric Determination of Selenocystine and Selenomethionine Using SAM nanoSe0/Vc/SeCys‐Film Modified Au Electrode

The SAM nanoSe⁰/Vc/SeCys‐film modified Au electrode has been prepared to determine selenocystine and selenomethionine. The AFM and SEM showed the special three‐dimensional (3D) network structure of the sol‐gel films. The affinity between nanoparticles and biomolecules created special chemical characters analyzed by the XRD and fluorescence. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The modified films partly had resistance in the charge transduction of Fe(CN) , but the less electron‐transfer resistance. Differential pulse voltammetric (DPV) determination of selenoamino acids using SAM nanoSe⁰/Vc/SeCys‐film modified Au electrode was presented. In PBS (pH 7.0)+0.1 mol L^?1 NaClO₄ solution, selenoamino acids yielded a sensitive reduction peak at about +400±50 mV. The peak current had a linear relationship with the concentration of selenoamino acids in the range of 5.0×10^?8–1.0×10^?5 mol L^?1, and a 3σ detection limit of selenoamino acids was 1.2×10^?8 mol L^?1. The relative standard deviation of DPV signals of 0.50×10^?6 mol L^?1 selenoamino acids was 3.8% (n=8) using the same electrode and was 4.4% (n=5) when using three modified electrodes prepared at different times. The content of selenoamino acids in the organo‐selenium powder were determined by DPV. The results showed 71.5 μg g^?1 of SeCys and 65.1 μg g^?1 of SeMet in the organo‐selenium powder.     

Lead Determination by Anodic Stripping Voltammetry Using a p‐Phenylenediamine Modified Carbon Paste Electrode

Carbon paste electrodes were modified by mixing appropriate amounts of the monomers o‐phenylendiamine, p‐phenylendiamine and m‐phenylendiamine (o‐PD, p‐PD and m‐PD) into a graphite powder‐paraffin oil matrix. The electropolymerization of the incorporated phenylendiamine was then carried out in a carbon paste electrode in acidic medium by cyclic voltammetry between ?0.30 V and +0.90 or under constant potential. The modified carbon paste electrodes (MCPEs) obtained by this electropolymerization method were found to be useful for trace determination of Pb²⁺ in aqueous solutions. Lead(II) was first preconcentrated on the modified electrodes by complexation with the modifier, and the electrode was then transferred to an electrochemical cell. The best results in terms of sensitivity and detection limit were obtained with poly p‐phenylenediamine (poly (p‐PD)). For a 10‐min preconcentration time, the calibration plot was linear from 5×10^?8 mol L^?1 to 10^?5 mol L^?1, with r²=0.999 and relative standard deviation equal to 5%. However, the lowest lead concentration that could be detected was 10^?9 mol L^?1. Interference from metal ions like Cd(II), Hg(II), Zn(II), Fe(II) and Cu(II) was also studied.     

Electroanalytical Studies on Cobalt(II) Ion‐Selective Sensor of Polymeric Membrane Electrode and Coated Graphite Electrode Based on N2O2 Salen Ligands

Poly(vinyl chloride)‐based membranes of salen ligands, 2‐((E)‐((1R,2S)‐2‐((E)‐5‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4‐tert‐butyl phenol (S₁) and 2‐((E)‐((1R,2S)‐2‐((E)‐3,5‐di‐tert‐butyl‐2‐hydroxybenzylideneamino)cyclohexylimino)methyl)‐4,6‐di‐tert‐butylphenol (S₂) were fabricated and explored as cobalt(II) selective electrodes. The performance of the polymeric membrane electrode (PME) and coated graphite electrode (CGE) were compared and it was observed that CGE showed a wide working concentration range of 1.1×10^?8 to 1.0×10^?1 mol L^?1 with a limit of detection of 7.0×10^?9 mol L^?1 exhibiting the Nernstian slope 29.6 mV/decade of activity in the pH range 3.0–9.0. It was used for the determination of cobalt(II) ions in water, soil, beer, pharmaceutical samples and medicinal plants and would be used as an indicator electrode in potentiometric titration with EDTA.     

Chemical Speciation of Antimony(III and V) in Water by Adsorptive Cathodic Stripping Voltammetry Using the 4‐(2‐Thiazolylazo) – Resorcinol

A simple adsorptive cathodic stripping voltammetry method has been developed for antimony (III and V) speciation using 4‐(2‐thiazolylazo) – resorcinol (TAR). The methodology involves controlled preconcentration at pH 5, during which antimony(III) – TAR complex is adsorbed onto a hanging mercury drop electrode followed by measuring the cathodic peak current (I_p,c) at ?0.39 V versus Ag/AgCl electrode. The plot of I_p,c versus antimony(III) concentration was linear in the range 1.35×10^?9–9.53×10^?8 mol L^?1.The LOD and LOQ for Sb(III) were found 4.06×10^?10 and 1.35×10^?9 mol L^?1, respectively. Antimony(V) species after reduction to antimony(III) with Na₂SO₃ were also determined. Analysis of antimony in environment water samples was applied satisfactorily.     

A Novel Glucose Biosensor Based on Palladium Nanoparticles and Its Application in Detection of Glucose Level in Urine

IntroductionThelevelofglucoseinbloodorurineindicateshyper andhypoglycaemia ,bothofwhichcanresultfromavarietyofendocrinedisorders .1 4 Therapidandreliabledetermi nationofglucoselevelisaroutineprojectinclinicchem istry.Urinesamplesaresaferandmoreconvenientthanbloodones .Meanwhile ,theconcentrationofglucoseinserumiscloselyassociatedwiththatinurine .2 4 Eventhoughglucoseelectrodeshavebeensuccessfullyusedinseruminclinicalapplication ,thequestionstillremainedofhowtodetecttheglucoselevelinurine ,wh…     

Electrocatalytic Reduction of Peroxy Disulfate on the Palladized Aluminum Electrode Modified by Prussian Blue: Application to the Analysis of Decolorizing Powders

The mechanism of catalytic reduction of peroxydisulfate on the palladized aluminum electrode modified by Prussian blue (PB/Pd‐Al) was studied. The charge transfer‐rate limiting step as well as overall reduction reaction of S₂O₈^2? is found to be a one‐electron and two‐electron abstraction respectively. The modified electrode is exploited for the hydrodynamic amperometry of peroxydisulfate. It is found that the calibration graph is linear in the S₂O₈^2?concentration range 5×10^?6–1.5×10^?3 mol L^?1. The detection limit of the method was 2.4×10^?6 mol L^?1 S₂O₈². The method was successfully used for the determination of S₂O₈^2? in decolorizing powders