Determination of Sunset Yellow using a carbon paste electrode modified with a nanostructured resorcinol-formaldehyde resin

This article describes an electrochemical sensor for the dye additive Sunset Yellow (SY). It consists of a carbon paste electrode modified with nanostructured resorcinol-formaldehyde (RF) resin. The RF resin warrants strong signal enhancement and a strongly increased oxidation peak currents of SY at 0.66 V (vs. SCE). The effects of pH value, amount of RF polymer, accumulation potential and time were optimized. The sensor has a linear response to SY in the 0.3 to 125 nM concentration range, and the limit of detection is 0.09 nM after a 2-min accumulation time. The electrode was applied to the analysis of samples of wastewater and drinks, and the results are consistent with those obtained by HPLC.

Nanostructured resorcinol-formaldehyde (RF) resin was prepared and used as a material for electrochemical determination of Sunset Yellow.

     

Determination of gold using clay modified carbon paste electrode

Sorption of gold(III) chlorocomplexes was studied by means of a carbon paste electrode modified with montmorillonite. Anionic exchange behavior was found in chloride media with low ionic strength. Anionic sorption of [AuCl4]- can be used as a preconcentration step to the determination of Au(III). Linear calibration dependences were found in the concentration range 4.06 x 10(-6) - 1.22 x 10(-5) mol/L Au(III) after 5 min of sorption and in the range 8.12 x 10(-7) - 6. 1 x 10(-6) mol/L after 10 min of sorption. Interferences of several anions and cations were studied. Model samples of table water were analyzed.     

Determination of hydroxylamine using a carbon paste electrode modified with graphene oxide nano sheets

A carbon paste electrode that was chemically modified with 3-(4'-amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid (3,4-AA) was used as a selective electrochemical sensor for the detection of hydroxylamine. Cyclic voltammetry (CV), choronoamperometry (CHA) and square wave voltammetry (SWV) were used to investigate oxidation of hydroxylamine in aqueous solution. Under optimized concentration the electrocatalytic oxidation current peak for hydroxylamine increased linearly with concentration in the range of 0.025–10.0 μM. The detection limits for hydroxylamine was 0.012 μM. Finally, the modified electrode was applied to detection hydroxylamine in water samples.     

酞菁钴修饰碳糊电极对微量苯酚的测定

研究了苯酚在酞菁钴修饰碳糊电极上的电化学行为,提出了催化反应的机理,并以此为依据,用伏安法以酞菁钴修饰碳糊电极为工作电极测定了微量苯酚.在pH 8.7的磷酸盐缓冲溶液(PBS)中,苯酚在0.61 V(对SCE)出现一氧化峰,该峰电流与苯酚的浓度在5.0×10-7～1.0×10-4 mol/L之间呈线性关系,检出限为1.0×10-7 mol/L.此法可用于工业废水中苯酚的测定.     

Determination of cadmium(II) using carbon paste electrode modified with a Cd-ion imprinted polymer

We have synthesized cadmium(II) ion-imprinted polymers (IIP) and non-imprinted polymers (NIP) using 1-(2-pyridylazo)-2-naphthol as a ligand. The materials were used to prepare a carbon paste electrode for the determination of Cd(II). Polymerization was performed with (a) methacrylic acid as a functional monomer, (b) ethyleneglycol dimethacrylate as the crosslinking monomer, and (c) 2,2′-azobis(isobutyronitrile) as the initiator. Imprinted cadmium ion was removed from the polymeric matrix using nitric acid. The measurements were carried out in an closed circuit after accumulation at ?1.2?V, this followed by electrolysis of the accumulated Cd(II) by voltammetric scanning from ?1.0 to ?0.6?V. The parameters governing the response of the electrode were studied. Under optimized conditions, the response of the electrode is linear in the range from 2.0 to 200?ng?mL^?1. The detection limit is 0.31?ng?mL^?1. The relative standard deviations are ±3.4 and ±2.1?% for 7 successive determinations of 20.0 and 50.0?ng?mL-1 of Cd(II), respectively. The method was applied to the determination of cadmium (II) in water and food samples.

Determination of trace amounts of silver with a chemically modified carbon paste electrode

A method for the determination of trace amounts of silver with a chemically modified carbon paste electrode is described. The modified electrode is prepared by simply mixing a chelating resin (a polythioether backbone and dioxymonosulphur polyethylene polyimines in the side-chain polymer) with graphite powder and Nujol oil. By immersing the electrode in a silver sample solution (pH = 6.5–7.5), silver can be adsorbed on the electrode surface and then determined by voltammetry in a separate blank solution. The response depends on the concentration of silver and the preconcentration time. For a preconcentration time of 5 min, the detection limit is about 3 × 10^?10 M and the linear range is from 5 × 10^?10 to 1 × 10^?7 M with a relative standard deviation of 4%. Many common metal ions have no or little effect on the determination of silver. The recommended procedure was applied to the determination of trace amounts of silver in waste water.     

Electrocatalytic Determination of the antibiotic Levofloxacin using modified carbon paste electrode with a poly-murexide thin film voltammetrically

In this work, a simple, cheap, sensitive, and selective modified carbon paste electrode is proposed for the electroanalytical determination of Levofloxacin (LEVO), the drug used to treat pneumonia caused by coronavirus. The electrochemical polymerization method was applied to create a thin poly-murexide film (POMUR) on the bare carbon paste electrode (BCPE) surface to enhance its electrocatalytic activity. The peak current response of LEVO obtained by POMUR/CPE was increased by 14.2 μA compared to BCPE. Scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques were employed to characterize BCPE and POMUR/CPE. Under the optimal experimental circumstances, the prepared sensor was capable of determining LEVO with a low limit of detection (LOD) of 7.18 nM (S/N = 3) for a linear dynamic range of 25 – 1 × 10³ nM utilizing differential pulse voltammetry (DPV). Moreover, the practical applicability of POMUR/CPE for determining LEVO in pharmaceutical formulations and biological samples (human serum) demonstrated high sensitivity and selectivity with a recovery of 95.08 – 100.5 %.     

Voltamperometric determination of kinetin with a carbon paste modified electrode

The electrochemical behaviour of kinetin (6-furfurylaminopurine) on a carbon paste modified with OV-17 silicone electrode, is studied. The determination of kinetin is possible working in square wave voltammetric techniques, reaching limits of determination of 38.7 ng ml⁻¹. The proposed method was successfully applied to determine the cytokinin in extracts of apples (previously spiked with kinetin) and the obtained results were in accordance with the results obtained with HPLC-UV.     

Voltammetric determination of catechol using a sonogel carbon electrode modified with nanostructured titanium dioxide

In this study, we investigate highly efficient sonogel carbon electrode (SGC/TiO₂) modified with nanostructured titanium dioxide synthesized via sol-gel method employing surfactant template for tailor-designing the structural properties of TiO₂. The stable SGC/TiO₂ electrode detects catechol, a neurotransmitter, in the presence of ascorbic acid, a common interferent, using cyclic voltammetry. A possible rationale for the stable catechol detection of SGC/TiO₂ electrode is attributed to most likely the adsorption of catechol onto highly porous TiO₂ (surface area of 147 m² g⁻¹ and porosity of 46.2%), and the formation of C₆H₄(OTi)₂ bond between catechol and TiO₂. The catechol absorbed onto TiO₂ rapidly reaches the SGC surface, then is oxidized, involving two electrons (e⁻) and two protons (H⁺). As a result, the surface of TiO₂ acts as an electron-transfer accelerator between the SGC electrode and catechol. In addition to the quantitative and qualitative detection of catechol, the SGC/TiO₂ electrode developed here meets the profitable features of electrode including mechanical stability, physical rigidity, and enhanced catalytic properties.     

Determination of thiourea using a carbon paste electrode decorated with copper oxide nanoparticles

We report on a novel sensor for the electrochemical determination of thiourea (TU). It is based on an active carbon paste electrode modified with copper oxide nanoparticles. The modified electrode and the electrochemical properties of thiourea on its surface were investigated using cyclic voltammetry and differential pulse voltammetry. Under optimized conditions, the detection limit is 20 μg?L^?1 of TU. The method was applied to the determination of thiourea in fruit juice, orange peel and industrial waste water.

Electrochemical behavior of nicotinamide using carbon paste electrode modified with macrocyclic compounds

The electrochemical behavior of nicotinamide was studied at a carbon paste electrode and the electrodes modified with macrocyclic compounds using voltammetric and impedance measurements. The electrodes so formed were able to bind nicotinamide ions chemically and gave better voltammetric responses than the unmodified ones. The macrocycles used as modifiers for the electrode preparation were 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, 7,16-dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane, 1,4,7,10,13,16-hexathiacyclooctadecane (Hexathia), 1,4,7,10-tetratosyl-1,4,7,10-tetraazacyclododecane, 1,4,8,11-tetraazacyclooctadecane, c-Methylcalix[4]resorcenarene and calix[8]arene. Among these macrocyclic modified electrodes, hexathia showed more affinity towards nicotinamide and a 2.3-fold increase in voltammetric signal was obtained. Impedance measurement was used to confirm this enhancement observed on modified electrode. This increase in anodic peak current was then used for finding linear working range, which was 0.1–500 μg mL⁻¹ with a detection limit of 0.03 μg mL⁻¹ by DPV. Interference from other vitamins like thiamine HCl (Vit. B₁), riboflavin (Vit. B₂), pyridoxine HCl (Vit. B₆) cynocobamine (Vit. B₁₂), para-aminobenzoic acid (PABA) and ascorbic acid (Vit. C) was also studied. The modified electrode could be used for the simultaneous determination of riboflavin, nicotinamide and pyridoxine HCl. It has also been utilized for the analysis of nicotinamide in pharmaceutical preparations.     

Determination of l-histidine by modified carbon paste electrode using tetra-3,4-pyridinoporphirazinatocopper(II)

This paper describes a potentiometric method for determination of l-histidine (l-his) in aqueous media, using a carbon paste electrode modified with tetra-3,4-pyridinoporphirazinatocopper(II) (Cu (3,4tppa)). The electrode exhibits linear response to the logarithm of the concentration of l-histidine from 2.4 × 10⁻⁵ to 1.0 × 10⁻² M, with a response slope of −49.5 ± 1 mV and response time of about 1.5 min. The detection limit according to IUPAC recommendation was 2.0 × 10⁻⁵ M. The proposed electrode shows a good selectivity for l-his over a wide variety of anions. This chemically modified carbon paste electrode was successfully used for the determination of l-his in a synthetic serum and RANDOX control serum solutions.     

Determination of captopril in patient human urine using ferrocenemonocarboxylic acid modified carbon nanotubes paste electrode

<正>In this work,we describe a new strategy for the electrochemical determination of captopril(CA) using ferrocenemonocarboxylic acid as a mediator and multiwall carbon nanotubes as sensors in aqueous solution at pH 7.0.The diffusion coefficient(D),and the kinetic parameters such as electron transfer coefficient(α).and heterogeneous rate constant(k_h),for CA were also determined using electrochemical approaches.Under the optimized conditions,the electrocatalytic oxidation peak current of captopril showed two linear dynamic ranges with a detection limit of 0.3×10~(-6) mol L~(-1) captopril.The linear calibration range was 0.8×10~(-6) to 65×10~(-6) mol L~(-1) using cyclic voltammetry.Finally,this modified electrode was also examined as a selective,simple and precise new electrochemical sensor for the determination of captopril in real samples such as drug and patient human urine.     

Determination of cadmium in Bentonite clay mineral using a carbon paste electrode

Sodium activated Bentonite, a sodium modified Montmorillonite, was submitted to cadmium sorption from nitrate solutions in order to simulate a cadmium polluted clay mineral. The remaining cadmium concentration in solution was analyzed at equilibrium by means of Differential Pulse Polarography (DPP) in order to calculate the cadmium concentration sorbed by the clay. The cadmium distribution between clay mineral and solution was observed for different concentrations, showing a Freundlich sorption profile. The clay mineral, previously submitted to the cadmium sorption procedure, was included in a carbon paste in order to investigate the cadmium content by voltammetric determination. For cadmium detection in Bentonite, a linear response of the carbon paste electrode (CPE) was observed in the 5 · 10^–5– 1.8 · 10^–4 mol/g range with good reproducibility. Received: 23 July 1998 / Revised: 19 November 1998 / Accepted: 26 November 1998     

Sensitive determination of ATP using a carbon paste electrode modified with a carboxyl functionalized ionic liquid

We report on a new electrode for the determination of adenosine-5??-triphosphate (ATP). It is based on modified carbon paste electrode that contains an ionic liquid (IL) as the binder. The electrode shows strong electrocatalytic oxidative activity towards ATP at pH 4.5 in giving a well-defined single oxidation peak. The oxidation reaction is adsorption-controlled and due to the presence of the highly conductive IL. The electron transfer rate constant was calculated to be 2.04×10^?C3 s^?C1, and the surface coverage is 1.11×10^?C10 mol cm^?C2. Under the selected conditions, the oxidation peak current changes linearly with the concentration of ATP in the range from 5.0 to 1000???mol L^?1 and a detection limit of 1.67???mol L^?1 (3???) as determined by differential pulse voltammetry. The method displays good selectivity and was applied to the determination of ATP injection samples with satisfactory results.

Determination of cadmium in Bentonite clay mineral using a carbon paste electrode

Sodium activated Bentonite, a sodium modified Montmorillonite, was submitted to cadmium sorption from nitrate solutions in order to simulate a cadmium polluted clay mineral. The remaining cadmium concentration in solution was analyzed at equilibrium by means of Differential Pulse Polarography (DPP) in order to calculate the cadmium concentration sorbed by the clay. The cadmium distribution between clay mineral and solution was observed for different concentrations, showing a Freundlich sorption profile. The clay mineral, previously submitted to the cadmium sorption procedure, was included in a carbon paste in order to investigate the cadmium content by voltammetric determination. For cadmium detection in Bentonite, a linear response of the carbon paste electrode (CPE) was observed in the 5 · 10^–5– 1.8 · 10^–4 mol/g range with good reproducibility. Received: 23 July 1998 / Revised: 19 November 1998 / Accepted: 26 November 1998     

Determination of nitrite based on mediated oxidation at a carbon paste electrode modified with a ruthenium polymer

The use of carbon paste electrodes modified with [Ru(bpy)(2)(PVP)(10)Cl]Cl for the mediated detection of nitrite is described. This surface modifier substantially lowers the overpotential for nitrite oxidation, hence permitting its determination at a lower potential. Various electrode characteristics were optimized, including the modifier loading and the monitoring potential, using batch amperometry. Standard calibration curves yielded slopes of 0.30 microA/microM over the linear range 5 x 10(-8)-5 x 10(-4)M nitrite with a detection limit of 3 x 10(-8)M (1.38 ppb) nitrite. The modified electrode response was shown to be relatively stable over a period of 5 days with a signal diminution of 8%. Electrode-to-electrode precision was measured as 11.4%. Flow-injection studies indicated the suitability of this electrode as a detector in flowing streams.     

Voltammetric determination of trace amounts of gold(III) with a carbon paste electrode modified with chelating resin

A carbon paste electrode modified with chelating resin (ammino-isopropylmercaptan-type cross-linked chelating resins) for the voltammetric determination of gold(III) was characterized by cyclic voltammetry. The gold(III) ion is accumulated on the surface of the modified electrode only by the chelating effect of the modifier in the carbon paste, without application of a potential. After exchange of the medium the accumulated amount of gold(III) is determined by voltammetry in a blank electrolyte solution. The response depends on both the concentration of gold and the accumulation time. For a 5-min preconcentration time, a linear calibration graph was obtained in the range 3 × 10^?8-1 × 10^?6 M and the detection limit was about 1 × 10^?8 M. A combination of chemical and electrochemical renewal allows the use of a single modified electrode in multiple analytical determinations over several days. For ten preconcentration—determination—renewal cycles [2 × 10^?7 M Au(III)], the response could be reproduced with 4.7% relative standard deviation. Many parameters such as the composition of the paste and pH influence the response of the measurement. Many other metal ions have no or little effect on the determination of gold. The procedure was applied to the determination of gold in minerals, copper and anode mud, with good results.