Stripping Voltammetry Method Research Articles

Optimization of stripping voltammetric sensor by mixture design-artificial neural network-genetic algorithm for determination of trace copper(II) based on iodoquinol-carbon nanotube modified carbon paste electrode

In this work, differential pulse cathodic stripping voltammetry method has been developed for determination of Cu (II) ions in aqueous solutions using a carbon paste electrode (CPE) modified with iodoquinol and multi-walled carbon nanotubes. The factors affecting the performance of the modified carbon paste electrode (MCPE) including the electrode composition and pH were optimized. The optimization process was performed using experimental design, artificial neural network (ANN) and genetic algorithm (GA). At first, experiments were performed using mixture design with pH factor as the process variable. The data from mixture design including experimental conditions and results were used to train the ANN using Bayesian regularization. The ANN was trained over 211 iterations with mean square error (MSE) of 1.60 and regression ocoefficient of r=0.9328. The predicted model obtained from the trained ANN was introduced to GA as the fitness function to be optimized. GA optimized the fitness function using the defined constraints. Under optimal conditions a linear calibration graph in the range 0.01–5μM was obtained. The square of regression coefficient was obtained 0.9880. The limit of detection (3S/N) was obtained 0.005μM. The real samples analysis was performed to determine trace copper (II) in some oil and water specimens. The repeatability and reproducibility of method (n=3) were obtained 3.31 and 4.12%, respectively. The shelf life of the sensor was obtained at least 4 months.

Metal speciation from stream to open ocean: modelling v. measurement

Environmental contextThe chemical speciation of metals strongly influences their transport, fate and bioavailability in natural waters. Analytical measurement and modelling both play important roles in understanding speciation, while modelling is also needed for prediction. Here, we analyse a large set of data for fresh waters, estuarine and coastal waters, and open ocean water, to examine how well measurements and modelling predictions agree. AbstractWe compiled a data set of ~2000 published metal speciation measurements made on samples of fresh waters, estuarine and coastal waters, and open ocean waters. For each sample, we applied the chemical speciation model WHAM7 to calculate the equilibrium free metal ion concentrations, [M] (molL–1), amounts of metal bound by dissolved organic matter (DOM), ν (molg–1), and their ratio ν/[M] (L g–1), which is a kind of ‘local’ partition coefficient. Comparison of the measured and predicted speciation variables for the whole data set showed that agreements are best for fresh waters, followed by estuarine and coastal waters, then open-ocean waters. Predicted values of ν/[M], averaged over all results for each metal, closely follow the trend in average measured values, confirming that metal reactivity, and consequent complexation by DOM, in natural waters accord with the expectations of the speciation model. Comparison of model predictions with measurements by different analytical techniques suggests that competitive ligand–stripping voltammetry methods overestimate metal complexation by DOM, and therefore underestimate [M]. When measurements by other methods are compared with predictions, for all metals, reasonable agreement with little bias is obtained at values of ν>10–6molg–1 DOM, but at lower values of ν, the model predictions of [M] are mostly higher than the measured values, and the predictions of ν and ν/[M] are mostly lower. Research is needed to establish whether this reflects analytical error or the failure of the model to represent natural high-affinity ligands.

Metal-Polymer Sensors for Voltammetric Analysis

The way of the graphite electrodes production, modified by polymeric composition, containing nanoparticles of gold or mercury, for determination of metals’ ions by the method of stripping voltammetry is offered. The influence of copolymer’s structure, nature of solvent, concentration of metal-modifier, viscosity of composition, film’s thickness and conditions of its formation on electrochemical and mechanical characteristics of sensor systems was studied. The approbation of electrodes was carried out using the certified techniques with help of the method of stripping voltammetry during determination of zinc, cadmium, lead, copper, mercury, arsenic, selenium.

Evaluation of metal content in perch of the Ob River basin

The geochemical features of river perch in the River Ob basin have been studied (the upper and middle reaches of the Ob River and the lower reach of the Tom River). The contents of Ag, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sn, W, Zn, Hg in perch's soft tissue are defined by the methods of ICP AES and stripping voltammetry, that of mercury in bones - by the atomic absorption method using mercury analyzer PA-915+. The distribution series of metal absolute concentrations in perch's soft tissue from the Ob River basin are plotted: Fe > Zn > Cu > Mn, typical for uncontaminated or slightly metal contaminated water bodies. In soft tissue of the studied samples the metal content does not exceed the permissible values. The mercury content in bones of studied samples is in the range 0,036-0,556 mg/kg. The mercury concentration is higher in bones in comparison with soft tissue in all samples.

Determination of Platinum Metals in Carbonaceous Mineral Raw Materials by Stripping Voltammetry

The paper considers the possibility of determining platinum metals in mineral raw materials by stripping voltammetry on a graphite electrode modified by metals. Stripping voltammetry method is characterized by low determination limit, wide intervals of determined content and high sensitivity. As a result of the research the conditions for the determination of gold, platinum and palladium by stripping voltammetry have been selected. The comparison of the results of gold, palladium and platinum determination by stripping voltammetry and atomic absorption is presented.

Electrodeposited Bi-Au nanocomposite modified carbon paste electrode for the simultaneous determination of copper and mercury

An analytical anodic stripping voltammetry method has been developed for the simultaneous determination of copper and mercury at ultratrace levels using the Bi–AuNP modified CPE.

Determination of Ag+ and Cu2+ ions in mixture samples obtained in the microwave assisted polyol process by differential pulse anodic stripping voltammetry (DPASV) method

Abstract A simple and selective differential pulse anodic stripping voltammetry (DPASV) method for the determination of Ag+ and Cu2+ ions in mixture samples obtained in the microwave assisted polyol process was developed and validated. Analytical methods for the preparation of the reaction mixture for voltammetric analysis (dilute samples in the supporting electrolyte) were worked out and optimized. All measurements were conducted in three-electrode cell system equipped with glassy carbon electrode (GCE) as a working electrode, silver/silver chloride (Ag|AgCl|KCl(sat.)) as a reference and platinum wire as a auxiliary electrode. The optimal conditions for quantitative determination were obtained in an mixture Britton–Robinson buffer at pH 4.1 / ethylene glycol (100/1; v/v). The calibration curves of analysed compounds are linear within the range of concentration: 0.032 − 0.420 μg mL-1 and 0.075 − 0.960 μg mL-1 for Ag+ and Cu2+, respectively. Good linear behaviour over the investigated concentration ranges were observed with the values of r2 higher than 0.996 for the silver and cooper ions. The accuracy of analytical determinations ranged from 0.4 to 3.6%. The levels of analysed ions in the reaction mixture can be successfully determined using this developed method with no matrix effect.

Three-dimensional mono-6-thio-β-cyclodextrin covalently functionalized gold nanoparticle/single-wall carbon nanotube hybrids for highly sensitive and selective electrochemical determination of methyl parathion

This work described the fabrication of a gold nanoparticles/single-walled carbon nanotubes/glassy carbon electrode containing mono-6-thio-β-cyclodextrin (SH-β-CD) self-assembled monolayer (SH-β-CD/AuNPs/SWCNTs/GCE) and its application for electrochemical determination of methyl parathion (MP) pesticide in solution using square wave anodic stripping voltammetry (SWV) method. The SH-β-CD/AuNPs/SWCNTs nanohybrids had a three-dimensional porous nanostructure with large active surface area, and the SH-β-CD monolayer on AuNPs/SWCNTs surface could greatly enhance the sensitivity and selectivity in detecting MP pesticides. The SWV response of the MP on the SH-β-CD/AuNPs/SWCNTs/GCE was ca. 3.9 and 5.1 times that of MP on the SH-β-CD/AuNPs/GCE and AuNPs/SWCNTs/GCE, respectively. The sensor demonstrated a wide linear response range from 2.0–80.0nM, with a lower detection limit of 0.1nM (S/N=3) using 180s of preconcentration time. The interference experiments showed that other aromatic insecticide, such as, chlorpyrifos, 2,4-dDichlorophenoxy acetic acid, methamidophos, triazophos, parathion had little influence on the MP signal. The proposed sensor was further employed for detection of MP in the real environmental water sample.

Electrochemical determination of pipazethate hydrochloride on Na-montmorillonite modified carbon paste electrode in formulation and human blood

The electrochemical and interfacial adsorptive behavior of pipazethate HCl (PZ.HCl) onto the developed carbon paste electrode surface modified with sodium-montmorillonite clay (Na-MMT CPE) were investigated using cyclic voltammetry. Two validated adsorptive anodic stripping voltammetry methods have also been developed for its determination using 7 % (w/w) Na-MMT-modified CPE. Langmuir isotherm can describe the experimental data well, indicating monolayer adsorption. Limits of detection of 2.4 × 10−7 and 3.0 × 10−8 mol L−1 PZ.HCl were achieved in the bulk form using linear-sweep and square-wave adsorptive anodic stripping voltammetric methods, respectively. The developed methods were also successfully applied for determination of PZ.HCl in pharmaceutical formulation and in spiked human serum without time-consuming extraction steps prior to the analysis. Statistical comparison of the results of the proposed methods with that of official and reported spectrophotometric methods indicates no significant difference in precision and accuracy between the proposed and reference methods.

Dual channel sensitive detection of hsa-miR-21 based on rolling circle amplification and quantum dots tagging.

An isothermal, highly sensitive and specific assay for the detection of hsa-miR-21 with the integration of QDs tagging and rolling circle amplification was offered. In addition, a dual channel strategy for miRNA detection was proposed: anodic stripping voltammetry (ASV) and fluorescent method were both performed for the final Cd2+ signal readout. The designed strategy exhibited good specificity to hsa-miR-21 and presented comparable detection results by detection methods.

Cathodic Stripping Determination of Water in Organic Solvents

AbstractA cathodic stripping voltammetry (CSV) method has been developed to determine water content in organic solvents based on electrooxidation of a gold electrode in the presence of water to form gold oxides upon anodic polarizations. Following cathodic potential scan, a sharp reductive stripping peak of gold oxides is generated and the magnitude of the peak current is related to the water content in the organic solvents. The method has been applied for determination of water in four commonly used water miscible organic solvents, acetonitrile, tetrahydrofuran, acetone and glacial acetic acid, with limits of detection of 60, 10, 40 and 10 ppm, respectively.

Electrochemical Reduction and Stripping Voltammetric Determination of the Anti-Glaucoma Drug Levobunolol HCl in Formulation and Human Serum at the Mercury Electrode

Levobunolol HCl is a potent non-selective s-adrenoceptor blocking agent used for the topical treatment of increased intraocular pressure in patients with chronic open angle glaucoma or ocular hypertension. Precise, rapid and extraction-free square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV) method has been described for trace quantitation of levobunolol HCl in bulk form, commercial formulation (ophthalmologic drops) and human serum. Limits of quantification (LOQ) of 1.0 × 10-10 mol L-1 (in bulk form) and 2.5 × 10-10 mol L-1 levobunolol HCl (in spiked human serum) were achieved by the described method. Insignificant interferences from excipients associated with formulation of levobunolol HCl and from some common metal ions, co-administrated drugs, some other s-blocker agents and its metabolite dihydrolevobunolol that are likely to be present in the biological fluids were obtained. The described SW-AdCSV method is sensitive enough to assay the drug in human serum compared to most of the reported methods.

Electrochemical Immunochromatographic Strip Test for Melamine Biosensor in Milk Products Using Silver Nanoparticles as Probe

A quantitative and sensitive immunochromatographic strip test is developed to detect of melamine in milk products. The strip test based on antigen-antibody (melamine-anti melamine) complex reaction. As label to antibody is used silver nanoparticles to form antibody-silver nanoparticles (AgNP-Ab). The strip test consists of sample pad, conjugated pad (AgNP-Ab), nitrocelloluse membrane, test zone (Ab), and absorbant pad. When melamine is found in the sample, then antibody-melamine-antibody-silver nanoparticles complex was made. Silver nanoparticles have good electrochemical properties. Electrochemical measurement of silver nanoparticles is using anodic stripping voltammetry method. The strip test electrode device is using Ag/AgCl as reference electrode, glassy carbon (GC) as working electrode and platinum (Pt) wire as counter electrode. The quantity of silver nanoparticles is involved in the system is equivalent to the concentration of melamine. Therefore, quantitative detection of melamine could be done using the immunochromatographic strip test.

Determination of Sunset Yellow in Soft Drinks at Attapulgite Modified Expanded Graphite Paste Electrode

An expanded graphite paste electrode (EGPE) modified with attapulgite (ATP) was used for the determination of Sunset yellow (SY) in soft drinks using square-wave stripping voltammetry (SWSV) method. The experimental results suggest that ATP/EGPE exhibited higher electroanalytic activity toward the SY compared to bare EGPE. The fabricated electrode revealed some advantages such as convenient preparation, good stability and high sensitivity toward the SY determination. Under optimal experimental conditions, the ATP/EGPE revealed broad linear ranges of 2.5 × 10−9 M to 1.5 × 10−6 M with the detection limits of 1.0 nM. The analysis of drinks was also attempted and the obtained results were satisfactory. It can be predicted that many more analogs could be monitored using this electrode with high sensitivity.

Fabrication of Gold Nanoparticles by Laser Ablation in Liquid and Their Application for Simultaneous Electrochemical Detection of Cd2+, Pb2+, Cu2+, Hg2+

In this paper, we demonstrated the fabrication of high active and high sensitive Au nanoparticles by laser ablation in liquid (LAL) method, and their application in electrochemical detection of heavy metal ions. First, LAL method are used to fabricate Au nanoparticles in water in a clean way. Second, the Au nanoparticles were assembled onto the surface of the glassy carbon (GC) electrode by an electrophoretic deposition method to form an AuNPs/GC electrode for electrochemical characterization and detection. Through differential pulse anodic stripping voltammetry method, it shows that the AuNPs/GC electrode could be used for the simultaneous and selective electrochemical detection of Cd(2+), Pb(2+), Cu(2+), and Hg(2+). By studying the influence of test conditions to optimize the electrochemical detection, we can detect Cd(2+), Pb(2+), Cu(2+), and Hg(2+) simultaneously with a low concentration of 3 × 10(-7) M in the experiments.

Sensitive quantification of trace zinc in water samples by adsorptive stripping voltammetry

A simple and sensitive adsorptive stripping voltammetry method was developed for determination of Zn using N-nitrozo-N-phenylhydroxylamine (cupferron) as a selective complexing agent. This complex absorbed on the hanging mercury drop electrode and created a sensitive peak current. The peak current and concentration of zinc accorded with a linear relationship in the range of 0.85-320 ng mL(-1). The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The relative standard deviation at a concentration level of 50 ng mL(-1) was 1.8%. The method was applied to the determination of zinc in city, river and mineral water samples, with satisfactory results.

Determination of Ultra Trace Levels of Copper in Whole Blood by Adsorptive Stripping Voltammetry

A selective and sensitive method for simultaneous determination of copper in blood by adsorptive differential pulse cathodic stripping voltammetry is presented. The procedure involves an adsorptive accumulation of Cu(II)-ETSC (4- ethyl-3-thiosemicarbazide) on a hanging mercury drop electrode, followed by a stripping voltammetry measurement of reduc- tion current of adsorbed complex at about −715 mV. The optimum conditions for the analysis of copper (II) ion are : pH 10.3, concentration of 4-ethyl-3-thiosemicarbazide 3.25×10 �6 M and an accumulation potential of −100 mV. The peak current is proportional to the concentration of copper over the range 0.003−125 ng/mL with a detection limit of 0.001 ng/mL and an accumulation time of 60 s. Moreover, with the use of the proposed method, there is a considerable improvement in the detec- tion limit, the linear dynamic range and the deposition time, compared with the methods of adsorptive stripping voltammetry for the determination of copper. The developed method was validated by analysis of whole blood certified reference materials.

Removal of Antimony(III) from Aqueous Solution by Using Grey and Red Erzurum Clay and Application to the Gediz River Sample

The removal of Sb(III) from waste water is achieved in batch system by using grey and red Erzurum (Oltu) clay which are cheap and natural adsorbents. Adsorption experiments were studied. For this purpose, various important parameters such as contact time, pH, and temperature were examined on the adsorption of Sb(III) ions onto grey and red Erzurum (Oltu) clay. Decreasing amount of Sb(III) ions in the solutions by adsorption was determined with differential pulse anodic stripping voltammetry (DPASV) method. Langmuir and Freundlich isotherms for the adsorption processes were drawn. The adsorption was demonstrated in similarity with Langmuir model. The maximum adsorption capacity of red Erzurum clay for Sb(III) was found to be 9.15 mg/g. Also, surface of the adsorbent was characterized by using FTIR spectroscopy. Red Erzurum clay was applied on real sample (Gediz River), and 72.6% adsorption was obtained.

A novel quantum dot nanocluster as versatile probe for electrochemiluminescence and electrochemical assays of DNA and cancer cells

A novel dendritic quantum dot (QD) nanocluster was constructed and used as versatile electrochemiluminescence (ECL) and electrochemical probe for the detection of DNA and cancer cells. Owing to the many functional groups present in the nanoclusters, a large number of QDs were assembled on the nanoclusters, which could greatly amplify both the ECL and electrochemical signals of QDs. Carbon nanotubes (CNTs)/gold nanoparticles’ (NPs) hybrids were used as amplified platform for assembling large numbers of DNA on the electrode, which also improve the bioactivity and stability of the electrode. After the QD-DNA signal probe was recognized with target DNA (t-DNA), the amplified ECL signal for the detection of target DNA was obtained. Furthermore, magnetic nanoparticles were employed for cell aptamers immobilization, the same QD nanocluster-DNA probe was also extended for electrochemical detection of cancer cells using sensitive anodic stripping voltammetry (ASV) method, which simplified the separation procedures and improved the sensitivity. It is anticipated that the assays could provide promising and cost effective approach for the early and accurate detection of DNA and cancer cells.

Stripping voltammetry method for determination of manganese as complex with oxine at the carbon paste electrode with and without modification with montmorillonite clay

Oxine (8-hydroxyquinoline) was used as an efficient and selective ligand for stripping voltammetry trace determination of Mn(II). A validated square-wave adsorptive cathodic stripping voltammetry method has been developed for determination of Mn(II) selectively as oxine complex using both the bare carbon paste electrode (CPE) and the modified CPE with 7 % (w/w) montmorillonite-Na clay. Modification of carbon paste with montmorillonite clay was found to greatly enhance its adsorption capacity. Limits of detection of 45 ng l−1 (8.19 × 10−10 mol L−1) and 1.8 ng l−1 (3.28 × 10−11 mol L−1) Mn(II) were achieved using the bare and modified CP electrodes, respectively. The achieved limits of detection of Mn(II) as oxine complex using the modified CPE are much sensitive than the detection limits obtained by most of the reported electrochemical methods. The developed stripping voltammetry method using both electrodes was successfully applied for trace determination of Mn(II) in various water samples without interferences from various organic and inorganic species.