Stripping Voltammetry Method Research Articles

Anodic stripping voltammetry coupled with design of experiments for simultaneous determination of Zn+2, Cu+2, Pb+2, and Cd+2 in gasoline

In this paper a rapid method of anodic stripping voltammetry (ASV) coupled with experimental design was developed for simultaneous determination of Zn2+, Cd2+, Pb2+, and Cu2+ in gasoline samples. A microwave assisted gasoline digestion procedure for sample preparation was also established. The determination limit was found to be 0.24μgL−1 for Zn2+; 8.58×10−4μgL−1 for Cd2+; 0.13μgL−1 for Pb2+, and 0.87μgL−1 for Cu2+. It was found that the interferences of concomitant metal ions were negligible. Gasoline samples collected in the city of São Luis (MA), Brazil were analyzed using this developed method, and the results demonstrated that this method was reliable and accurate. It is expected that this method can be used as a routine technique for metal ion determination in gasoline.

Ultrasensitive Electrochemical Analysis of Two Analytes by Using an Autonomous DNA Machine that Works in a Two‐Cycle Mode

We report a novel autonomous DNA machine for amplified electrochemical analysis of two DNAs. The DNA machine operates in a two-cycle working mode to amplify DNA recognition events; the working mode is assisted by two different nicking endonucleases (NEases). Two bio-barcode probes, a ZnS nanoparticle (NP)-DNA probe and a CdS NP-DNA probe, were used to trace two target DNAs. The detection system was based on a sensitive differential pulse anodic stripping voltammetry (DPASV) method for the simultaneous detection of Zn(II) and Cd(II) tracers, which were obtained by dissolving the two probes. Under the optimised conditions, detection limits as low as 5.6×10(-17) (3σ) and 4.1×10(-17) M (3σ) for the two target DNAs were achieved. It has been proven that the DNA machine system can simultaneously amplify two target DNAs by more than four orders of magnitude within 30 min at room temperature. In addition, in combination with an aptamer recognition strategy, the DNA machine was further used in the aptamer-based amplification analysis of adenosine triphosphate (ATP) and lysozyme. With the amplification of the DNA machine, detection limits as low as 5.6×10(-9) M (3σ) for ATP and 5.2×10(-13) M (3σ) for lysozyme were simultaneously obtained. The satisfactory determination of ATP and lysozyme in Ramos cells reveals the good selectivity and feasibility of this protocol. The DNA machine is a promising tool for ultrasensitive and simultaneous multianalysis because of its remarkable signal amplification and simple machine-like operation.

The Chemical and Electrochemical Activity of Citrate on Pt Electrodes

Citrate is widely used as a complexing agent in electrolytes for deposition of metals and alloys. While the chemistry of metal-citrate complexes is well known, the electrochemical behavior of the citrate ion, particularly on the cathode, was given little attention, although the participation of citrate in the cathodic processes could influence the mechanism of metal deposition and the stability of the plating bath and the properties of the deposits. In the present work, the behavior of on Pt cathodes is investigated by the methods of cyclic voltammetry, anodic stripping voltammetry, HR-XPS and ToF-SIMS. Blocking the Pt electrode surface in contact with solutions is shown by the methods of stripping voltammetry and HR-XPS, the composition of the blocking film being affected by the electrolysis potential. ToF-SIMS investigations show the presence on the cathode surface of species having a high molecular weight, following electrolysis of the solutions containing sodium citrate. The data obtained allow us to suggest a scenario of formation of a film on the electrode surface. Specific adsorption of citrate anions and catalytic transformation of citrate accompanied by decarboxylation and electron transfer to the electrode surface followed by further reduction of the adsorbed species has been observed.

Preparation of nano-sized Pb 2+ imprinted polymer and its application as the chemical interface of an electrochemical sensor for toxic lead determination in different real samples

In this work, a new nano-structured ion imprinted polymer (IIP) was synthesized by copolymerization of methacrylic acid–Pb 2+ complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Methacrylic acid acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. A carbon paste electrode modified with IIP-nanoparticles was used for fabrication of a Pb 2+ sensitive electrode. Differential pulse stripping voltammetry method was applied as the determination technique, after open circuit sorption of Pb 2+ on the electrode and its reduction to metallic form. The IIP modified electrode showed a considerably higher response, compared to the electrode embedded with non-imprinted polymer (NIP). This indicated that the suitable recognition sites were created in the IIP structure in the polymerization stage. Various factors, effective on the response behavior of the electrode, were investigated and optimized. The introduced sensor showed a linear range of 1.0 × 10 −9 to 8.1 × 10 −7 M and detection limit of 6.0 × 10 −10 M (S/N = 3). The sensor was successfully applied for the trace lead determination in different samples.

Voltammetry of naltrexone in commercial formulation and human body fluids: Quantification and pharmacokinetic studies

Naltrexone HCl (NAL.HCl) has been reduced at the mercury electrode in Britton–Robinson universal buffer of pH values 2–11 with a mechanism involving the quasi-reversible uptake of the first transferring electron followed by a rate-determining protonation step of its C = O double bond at position C-6. Simple, sensitive, selective and reliable linear-sweep and square-wave adsorptive cathodic stripping voltammetry methods have been described for trace quantitation of NAL.HCl in bulk form, commercial formulation and human body fluids without the necessity for sample pretreatment and/or time-consuming extraction steps prior to the analysis. Limits of quantitation of 6.0 × 10 −9 M and 8.0 × 10 −10 M NAL.HCl in bulk form or commercial formulation and of 9.0 × 10 −9 and 1.0 × 10 −9 M NAL.HCl in spiked human serum samples were achieved by the described linear and square-wave stripping voltammetry methods, respectively. Furthermore, pharmacokinetic parameters of the drug in human plasma samples of healthy volunteers following the administration of an oral single dose of 50 mg NAL.HCl (one Revia ® tablet) were estimated by means of the described square-wave stripping voltammetry method without interferences from the drug's metabolites and/or endogenous human plasma constituents. The estimated pharmacokinetic parameters were favorably compared with those reported in literature.

The determination of molybdenum in selected mushrooms by stripping voltammetry

Abstract The highly sensitive method of adsorptive stripping voltammetry (AdSV), with differential pulse steps, was performed at a mercury film electrode and has been applied here for the determination of trace molybdenum content in selected wild mushrooms. Fruiting body caps of 12 selected macrofungi species from Basidiomycetes have been investigated. Molybdenum content of investigated samples was determined in the range of 0.006 to 0.38 mg kg−1 of dry matter. The highest value of molybdenum content was found in Leccinum rufum and the lowest in Lactarius deliciosus.

Stripping voltammetric determination of silymarin in formulations and human blood utilizing bare and modified carbon paste electrodes

Silymarin is one of the most powerful natural substances that have the ability to protect and rebuild the liver cells damaged by alcohol and other toxic substances. Silymarin showed two irreversible anodic peaks in buffered solutions (pH 2.5–8.0) at either the bare carbon paste electrode or the montmorillonite-Ca modified carbon paste one. These two peaks have been attributed to oxidation of the two phenolic OH groups at positions C-20 and C-7 of silymarin molecule. A square-wave adsorptive anodic stripping voltammetry method was optimized for determination of silymarin utilizing the bare and the modified carbon paste electrodes. The method was fully validated and successfully applied for the determination of silymarin in commercial formulations and human serum without prior extraction utilizing both carbon paste electrodes. Limits of quantitation of 1 × 10 −7 and 7 × 10 −9 mol L −1 silymarin have been achieved in bulk form or in formulations while 2 × 10 −7 and 8 × 10 −9 mol L −1 silymarin were achieved in spiked human serum utilizing the bare carbon paste electrode and the modified one, respectively. The two electrodes exhibited excellent selectivity towards silymarin even in the presence of 10 2to 10 3-fold excess of its co-formulated drugs, common excipients, and common metal ions. The pharmacokinetic parameters of silymarin in plasma of healthy human volunteers were estimated following the administration of a single oral dose of 120 mg silymarin utilizing the modified carbon paste electrode. The estimated pharmacokinetic parameters were favorably compared with those reported in literature.

Comparison of voltammetric and AAS methods for As(III) quantification in presence of iron species in model water samples with a low mineral content

Voltammetry was adapted to quantify As(III) in model water samples with a low mineral content and compared to the Hydride Generation Atomic Absorption Spectrometry (HG-AAS) method. The specificity lies in the study of the influence of interfering species on the quantification of samples treated by coagulation/flocculation using iron salts. First, a Square Wave Cathodic Stripping Voltammetry method at a Hanging Mercury Drop Electrode (SW-CSV – HMDE) was optimised and compared with the HG-AAS method. Second, the influence of the presence of Fe(II), Fe(III) and As(V) was evaluated. No interferences from As(V) were observed, however for both methods, the As(III) signal decreased by 10% in presence of iron. Standard addition method was thus required to efficiently quantify As(III) in complex matrix and the SW-CSV (limit of quantification = 0.5 µg L−1) method was preferred to the HG-AAS technique to determine low As(III) levels ([As(III)] ≤ 2 µg L−1).

Factors Controlling Stripping Voltammetry of Lead at Polycrystalline Boron Doped Diamond Electrodes: New Insights from High-Resolution Microscopy

We report wide-ranging studies to elucidate the factors and issues controlling stripping voltammetry of metal ions on solid electrodes using the well-known Pb/Pb(2+) couple on polycrystalline boron doped diamond (pBDD) as an exemplar system. Notably, high-resolution microscopy techniques have revealed new insights into the features observed in differential pulse anodic stripping voltammetry (DPV-ASV) which provide a deeper understanding of how best to utilize this technique. DPV-ASV was employed in an impinging wall-jet configuration to detect Pb(2+) in the nanomolar to micromolar concentration range at a pBDD macrodisk electrode. The deposition process was driven to produce a grain-independent homogeneous distribution of Pb nanoparticles (NPs) on the electrode surface; this resulted in the observation of narrow stripping peaks. Lower calibration gradients of current or charge versus concentration were found for the low concentrations, correlating with a lower than expected (from consideration of the simple convective-diffusive nature of the deposition process) amount of Pb deposited on the surface. This was attributed to the complex nature of nucleation and growth at solid surfaces in this concentration regime, complicating mass transport. Furthermore, a clear shift negative in the stripping peak potential with decreasing concentration was seen correlating with a change in the size of the deposited NP, suggesting an NP size-dependent redox potential for the Pb/Pb(2+) couple. At high concentrations a nonlinear response was observed, with less Pb detected than expected, in addition to the observation of a second stripping peak. Atomic force microscopy (AFM) and field emission scanning electron microscopy revealed the second peak to be due to a change in deposition morphology from isolated NPs to grain-independent heterogeneous structures comprising both thin films and NPs; the second peak is associated with stripping from the thin-film structures. AFM also revealed a substantial amount of Pb remaining on the surface after stripping at high concentration, explaining the nonlinear relationship between stripping peak current (or charge) and concentration. Finally, the use of an in situ cleaning procedure between each measurement was advocated to ensure a clean Pb-free surface (verified by AFM and X-ray photoelectron spectroscopy analysis) between each run. The studies herein highlight important and complex physicochemical processes involved in the electroanalysis of heavy metals at solid electrodes, such as pBDD, that need to be accounted for when using stripping voltammetry methods.

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

AbstractA 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 (Ip,c) at −0.39 V versus Ag/AgCl electrode. The plot of Ip,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.

Ultrasensitive Simultaneous Quantification of Nanomolar Level of Cd and Zn by Cathodic Adsorptive Stripping Voltammetry in Some Real Samples

AbstractA novel, simple and sensitive adsorptive stripping voltammetry method was developed for simultaneous determination of Cd and Zn using N‐Nitrozo‐N‐phenylhydroxylamine (Cupferron) as a selective complexing agent. Cadmium and zinc metals gave peaks that were distinctly separated by 450–1200 mV, allowing their determination over a wide range of concentrations. The influence of pH and the nature of supporting electrolytes, concentration of ligand, preconcentration time and applied potential were investigated. The detection limits were 0.058 ng/mL for Zn and 0.092 ng/mL for Cd, and the RSD at a concentration level of 50 ppb, were 1.8–2.1 % for both zinc and cadmium, respectively. The method was applied to the determination of cadmium and zinc in blood, drug, food and water samples with the satisfactory results.

Electrochemistry of the antibacterial and antifungal drug nitroxoline and its determination in bulk form, pharmaceutical formulation and human blood

Nitroxoline has been reduced at the mercury electrode in buffered solutions (pH 2−11) in two irreversible cathodic steps. The first step was attributed to reduction of –NO 2 group to the hydroxylamine stage and the second one to reduction-saturation of the C=N double bond. DC-polarographic and various adsorptive stripping voltammetric methods were developed for determination of nitroxoline in bulk form. Limits of quantitation of 1.02 × 10 −6, 3.05 × 10 −8, 9.01 × 10 −9, and 9.12 × 10 −10 M nitroxoline were achieved by means of the developed DC-polarography, differential-pulse-, linear-sweep-, and square-wave-adsorptive cathodic stripping voltammetric methods, respectively. All these electroanalytical methods were successfully applied for determination of nitroxoline in its Nibiol ® tablets. While only the developed adsorptive stripping voltammetry methods were successfully applied for determination of the drug in spiked human serum and for pharmacokinetic studies in real human plasma. The analysis was carried out without interference from common excipients and without the necessity for prior extraction or interaction with any reagent during the analysis.

Complexation Study of Humic Acids Extracted from Forest and Sahara Soils with Zinc (II) and Cadmium (II) by Differential Pulse Anodic Stripping Voltammetry (DPASV) and Conductimetric Methods

The complexation of heavy metals, present in their dissolved state at relevant trace levels, with new humic acids (HAs) isolated from Yakouren forest (YHA) and Sahara (Tamenrasset: THA) soils has been studied by differential pulse anodic stripping voltammetry (DPASV) at a hanging mercury drop electrode and conductimetry methods. After extraction and purification, humic acids were characterized by elemental analyses, atomic absorption spectroscopy, FT-IR, and solution state 13C-NMR. Taking Zn(II) and Cd(II) as examples, the aim of this study was to gain direct information on the general level of importance of humic acids for the speciation of certain heavy metals in soil to determine the complexing capacities of AHs and stability constant of the complexes formed with these metal ions and to compare the complexation capacity of forest and Sahara soils with the commercial humic acid and other published AHs. The results determined by conductimetry method are interpreted using an excess function (∆k) which related the conductivity of the mixture and of the separated components. A positive value of this function is obtained. It indicates the complexation of humic acids with metallic ions. The DPASV method was used for determining metal ion complexing capacities and stability constants of metal ion complexes of HAs in solution at pH 7. In both types of soils, the commercial humic acid (CHA) is less efficient in complexing Zn(II) and Cd(II) than THA and YHA and the complexing capacity (CCM) decreases in the order: THA > YHA > CHA. In general, the results of complexing capacity for all humic acids and stability constants of Zn(II) and Cd(II) complexes found by DPASV method showed good correlation with those of conductimetry method. CCM of THA and YHA calculated by DPASV were higher than those of CHA and the other natural HAs published in the literature at pH 7 basing on these results.

Simultaneous voltammetric analysis of tetracycline antibiotics in foods

The new simple, cost effective and well performing differential pulse stripping voltammetry method for the simultaneous determination of antibiotics – oxytetracycline, tetracycline and chlorotetracycline was researched and developed. It depends on the reduction of these compounds at a hanging mercury drop electrode. The samples were extracted from (i) spiked animal feed, and (ii) fresh fish muscle dosed with the drugs. The voltammograms from the drug mixture produced complex, overlapping profiles, and chemometrics methods were applied for calibration modelling. The analytical linear ranges were within 0.02–0.18 μg mL −1 and the corresponding LODs were 3–5 μg L −1 for the three analytes. These values compare well with those from the HPLC and fluorescence methods in the literature. The % relative prediction errors from the verification trials were between 4% and 9% with % Recoveries being 103–107. Also, the % Recoveries of the antibiotics from animal feeds as measured by the new method were comparable with those from the HPLC analysis (85%), i.e. the method is highly competitive, especially as a screening approach.

DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY FOR DETERMINATION OF SOME HEAVY METALS IN URANIUM

The direct determination of some metals impurity in uranium by using differential pulse anodic stripping voltammetry (DPASV) method at a hanging mercury drop electrode and in a carbonate buffer media was developed. It was found that the carbonate buffer show the strongest affinity for uranium and gives the best separation between the DPASV peaks of heavy metals impurities. The carbonate concentration markedly affects the oxidation and reduction the major and the minor constituents of the uranium samples. In 0.1 M carbonate buffer solution pH 10, copper, bismuth, thalium, lead, cadmium, zinc, could be determined without the removal of the uranium matrix. Recovery and relative standard deviation (RSD) of this method was in the range of 174% - 85.2% for recovery and 36.8% - 1.2% for RSD. The larger error of analytical result was obtained for Zn at low concentration. In general, the analytic results error and RSD decreased with increasing metals concentration. Keywords: heavy metal determination, differential pulse anodic stripping voltammetry, uranium

SQUARE WAVE CATHODIC STRIPPING VOLTAMMETRY ADSORPTIVE FOR NICKEL AND COBALT ANALYSIS

The adsorptive stripping voltammetric determination of Ni and Co based on adsorption of the Ni/Co and dimethylglioxime (DMG) complex on a hanging mercury drop electrode is studied. The reduction current of the adsorbed DMG complex is measured by square wave cathodic stripping voltammetry method. The effect of various parameters such as ligand concentration, pH of supporting electrolytic, adsorption potential and adsorption time on the current peak of Ni and Co voltammogram were studied. Optimum condition of this method are supporting electrolyte pH 9, DMG concentration 5×10 -4 M, adsorption potential -0.7 V vs Ag/AgCl and adsorption time 180 second. A linier relationship between the current peak and Ni or Co concentration was obtained in the range 5 - 30 ng/mL and the detection limit 0.6 ng/ml for both Ni and Co. The recovery of Ni and Co were 98.11-104.17% using standard biological materials with RSD 2.59 - 10.37%. Based on ";t"; test can be conclude that the result are nearly equal to the standard reference material. Keywords: adsorptive stripping voltammetric, dimethylglioxime complex, nickel, cobalt

Simultaneous determination of Mn(II), Cu(II) and Fe(III) as 2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol complexes by adsorptive cathodic stripping voltammetry at a carbon paste electrode

A simple and precise square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV) method has been described for simultaneous determination of Mn(II), Cu(II) and Fe(III) in water samples using a carbon paste electrode. In 0.1 mol L(-1) acetate buffer (pH 5) containing 50 micromol L(-1) of 2-(5'-bromo-2'-pyridylazo)-5-diethylaminophenol (5-Br-PADAP), Mn(II), Cu(II) and Fe(III) were simultaneously determined as metal-complexes with 5-Br-PADAP following preconcentration onto the carbon paste electrode by adsorptive accumulation at +1.0V (vs. Ag/AgCl/3M KCl). Insignificant interference from various cations (K(+), Na(+), Mg(2+), Ca(2+), Al(3+), Bi(3+), Sb(3+), Se(4+), Zn(2+), Ni(2+), Co(2+), Cd(2+), Pb(2+), V(5+), Ti(4+) and NH(4)(+)), anions (HCO(3)(-), Cl(-), NO(3-), SO(4)(2-) and PO(4)(3-)) and ascorbic acid was noticed. Limits of detection of 0.066, 0.108 and 0.093 microg L(-1) and limits of quantitation of 0.22, 0.36 and 0.31 microg L(-1) Mn(II), Cu(II) and Fe(III), respectively, were achieved by the described method. The described stripping voltammetry method was successfully applied for simultaneous determination of Mn(II), Cu(II) and Fe(III) in ground, tap and bottled natural water samples.

Identification of alkaloids using the stripping voltammetry method

The possibility in principle is shown of using the stripping voltammetry method for identification of alkaloids with the help of a test system in the form of an electrolyte solution containing a set of cations of different metals.

Characteristics of Voltammetric Determination and Speciation of Chromium – A Review

AbstractThis article reviews the voltammetric methods of chromium determination, including adsorptive and catalytic adsorptive stripping voltammetry at liquid mercury, metallic films, and modified carbon paste electrodes. The principle applications of the catalytic adsorptive stripping voltammetric method of chromium(VI) determination in the presence of DTPA and nitrate, most useful in the analysis of chromium traces and its speciation, is presented in detail. Special emphasis is put on the presentation and characterization of the voltammetric procedures which make it possible to conduction speciation studies of chromium(VI) in the presence of a great excess of chromium(III) and surfactants. This survey is based on 173 articles.

The effect of CeO2 on Pt/CeO2/CNT catalyst for CO electrooxidation

AbstractPt/CeO2/CNT catalysts were prepared by adsorbing Pt nanoparticles on the supports of CNTs coated with CeO2. The electrocatalytic performances in respect to the electrooxidation of chemisorbed CO were tested using potential step and stripping voltammetry methods under variable sweep rate and temperature conditions. At 10 mV s–1, the CO stripping voltammogram exhibited the peak splitting phenomenon. The oxidation charge and the peak potential of the two voltammetric peaks changed regularly with the number of Pt and CeO2 neighbours, the sweep rate, and the temperature. We considered that the low potential peak originated from the reaction of COads with hydroxyl groups on CeO2 adjacent to Pt sites, while the high potential peak came from the reaction of COads with hydroxyl groups produced on pure Pt. Furthermore, the experimental results of the peak potential against the logarithm of the sweep rate and the logarithm of the current maximum time against the step potential were plotted and intersecting lines with different slopes in high and low potential regions in the plot were observed. The lines intersected at lower potentials on the Pt/CeO2/CNT electrode than on the Pt/CNT electrode, which was attributed to the contribution of hydroxyl groups on CeO2.