Anodic Stripping Peak Current Research Articles

Graphene and Au NPs co-mediated enzymatic silver deposition for the ultrasensitive electrochemical detection of cholesterol

Cholesterol is an essential ingredient in mammals, and serum cholesterol is a major component of atherosclerotic plaques. The level of cholesterol in human serum has become an important index for clinical diagnosis and prevention of cardiovascular disease. In this paper, a simple and ultrasensitive cholesterol biosensor based on graphene oxide (GO) and gold nanoparticles (Au NPs) co-mediated enzymatic silver deposition was designed by immobilizing cholesterol oxidase (CHOD), cholesterol esterase (CHER) and GO onto the surface of Au NPs modified screen-printed carbon electrode (SPE). Under the synergistic effect of CHER, CHOD and GO, the cholesterol was hydrolyzed to generate hydrogen peroxide, which can reduce the silver (Ag) ions in the solution to metallic Ag which deposited on the surface of Au NPs modified SPE. The ultrasensitive detection of cholesterol was achieved by anodic stripping voltammetry measurement of the enzymatically deposited Ag. Under optimal conditions, the anodic stripping peak current of Ag increased with the increasing cholesterol concentration in the range from 0.01μg/mL to 5000μg/mL with a limit of detection of 0.001μg/mL (S/N = 3). In addition, the ultrasensitive cholesterol biosensor exhibited higher specificity, acceptable reproducibility and excellent recoveries for cholesterol detection.

Ultrasensitive cholesterol biosensor based on enzymatic silver deposition on gold nanoparticles modified screen-printed carbon electrode

Cholesterol is one of the essential structural constituents of cell membranes. Determination of cholesterol is of great importance in clinical analysis because the level of cholesterol in serum is an indicator in the diagnosis and prevention of heart diseases. In this work, a simple and ultrasensitive cholesterol biosensor based on enzymatic silver deposition was designed by immobilizing cholesterol oxidase (CHOD) and cholesterol esterase (CHER) onto the surface of gold nanoparticles (Au NPs) modified screen-printed carbon electrode (SPE). By the catalytic action of CHER and CHOD, the cholesterol was hydrolyzed to generate hydrogen peroxide (H2O2) which can reduced the silver (Ag) ions in the solution for the deposition of metallic Ag on the surface of Au NPs modified SPE. The ultrasensitive detection of cholesterol was achieved by anodic stripping voltammetry (ASV) measurement of the enzymatically deposited Ag. The influence of relevant experimental variables was optimized. The anodic stripping peak current of Ag depended linearly on the concentration of cholesterol in the range of 5–5000μg/mL with the regression correlation coefficient of 0.9983. A detection limit of 3.0μg/mL was attained by 3 sigma-rule. In addition, the ultrasensitive cholesterol biosensor exhibited higher specificity, acceptable reproducibility and excellent recoveries for cholesterol detection.

Over‐Oxidized Poly (Phenol Red) Film Modified Glassy Carbon Electrode for Anodic Stripping Voltammetric Determination of Ultra‐Trace Antimony (III)

AbstractIn this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over‐oxidized poly(phenol red) modified glassy carbon electrode (PPhRedox/GCE) in 0.1 mol L‐1 HCl medium. The formation of both poly(phenol red) and over‐oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRedox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRedox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 ‐ 1.218 μg L−1 and 3.40 – 18.26 μg L−1 with a detection limit of 0.0075 μg L−1. The proposed over‐oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0–103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE‐EnviroMAT™ EP−L‐2).

Determination of mercury using a glassy carbon electrode modified with nano TiO2 and multi-walled carbon nanotubes composites dispersed in a novel cationic surfactant

A glassy carbon electrode modified with nano TiO2 and multi-walled carbon nanotubes composites dispersed in a novel cationic surfactant was described for the determination of trace mercury(II) by linear anodic stripping voltammetry. Under optimal experimental conditions, the linear sweep anodic stripping peak current was linear with the concentration of Hg(II) in the range of 0.1–100μmolL−1 with a detection limit of 0.025μmolL−1. The sensitivity was found to be 3.7014A/molL−1. The proposed electrode also showed a high selectivity for mercury in the presence of common potential interfering metal ions. Moreover, the proposed electrode revealed good reproducibility and stability. The proposed method was successfully applied for the determination of Hg(II) in river water and industrial wastewater samples.

Disposable immunosensor for human cytomegalovirus glycoprotein B detection

Combining the advantages of the biosensor field with the problem of detecting Human Cytomegalovirus (HCMV) in human samples, an inexpensive, simple and disposable electrochemical immunosensor for glycoprotein B detection in urine is proposed. Glycoprotein B has been chosen once is the dominant antigen of HCMV. The approach is based on a sandwich-type immunoassay, with the HCMV glycoprotein B sandwiched between the Anti-HCMV antibody adsorbed onto the working electrode, and the Anti-HCMV labeled with gold nanoparticles. Glycoprotein B detection was carried out through electrochemical stripping analysis of silver nanoparticles quantitatively deposited on the immunosensor through catalysis by the nanogold labels. The influence of different steps in the immunosensor construction, namely the silver deposition time, silver enhancer concentration, antibody concentration, BSA concentration and glycoprotein B incubation time, were examined and optimized. The method showed a linear dependence between glycoprotein B concentration and the corresponding anodic stripping peak current, resulting in detection limits of 3.3±1.7ng/mL for samples prepared in buffer and 3.2±0.2ng/mL for urine samples, suggesting that the biological matrix does not interfere with the immunosensor detection capability. Given its mode of preparation, by physical adsorption of the capture antibody in the working electrode, the immunosensor also exhibited an acceptable reproducibility, with a residual standard deviation of 13.5% for samples prepared in buffer and 11.2% for urine samples, thereby presenting a promising development potential for clinical applications.

Indirect electrochemical determination of ciprofloxacin by anodic stripping voltammetry of Cd(II) on graphene-modified electrode

An indirect electrochemical determination method for ciprofloxacin (CIP) was developed based on the complexation of CIP with Cd2+. On graphene-modified electrode, Cd2+ showed a strong anodic stripping peak current response, which was efficiently prohibited in the presence of CIP. Thus, the anodic stripping peak current of Cd2+ was employed as the indicating signal for CIP determination, which was more sensitive than the direct electrochemical oxidation response of CIP. Some influence factors such as the modified volume of graphene, solution pH, accumulation time, complexation reaction time were systematically investigated. Under optimum conditions, the anodic stripping response of Cd2+ on the graphene-modified electrode was inversely proportional to CIP in the concentration range from 1.0×10−7 to 1.0×10−5molL−1 with a detection limit (3S/N) of 5.9×10−8molL−1. The method showed high selectivity, good reproducibility and was successfully applied to the determination of CIP in pharmaceutical formulation and human urine.

Electrochemical detection of blood lead based on the enhancement effect of copper

The anodic stripping peak current of lead on the glassy carbon electrode surface was greatly increased in the presence of high concentration of copper ion. The effects of supporting electrolyte, concentration of Cu2+, accumulation potential and accumulation time were studied on the stripping peak current of Pb2+. As a result, a sensitive, simple and rapid electrochemical method was developed for the detection of lead. In 0.01 M HNO3 solution containing 800 g,g L−1 Cu2+, the stripping peak current of Pb2+ increases linearly with its concentration over the range from 2 to 100 μg L−1. The detection limit is 1 μg L−1 after 4-min accumulation at −0.8 V. It was used to detect the concentration of lead in blood samples, and the results consisted with the values that obtained by atomic absorption spectrometry.

Determination of total antimony(III,V) by square-wave anodic stripping voltammetry with in situ plated bismuth-film electrode

A sensitive and reliable method is described for the determination of total Sb(III, V) at traces levels by Osteryoung square-wave anodic stripping voltammery (OSWASV). This method is based on the co-deposition of Sb(III, V) with Bi(III) onto an edge-plane pyrolytic graphite substrate at an accumulation step. OSWASV studies indicated that the co-deposited antimony was oxidised with anodic scans to give an enhanced anodic peak at about 450 mV vs. Ag/AgCl (sat. KCl). The anodic stripping peak current was directly proportional to the total concentration of antimony in the ranges of 0.01–0.10 µg L−1, 0.10–1.0 µg L−1 and 1.0–18.0 µg L−1 with correlation coefficient higher than 0.995 when 2.0 mol L−1 hydrochloric acid was used. The detection limits calculated as S/N = 3 was 5.0 ng L−1 in 2.0 mol L−1 hydrochloric acid at 180 s deposition time. The relative standard deviation was 5% (n = 6) at 0.10 µg L−1 level of antimony. The analytical results demonstrate that the proposed method is applicable to analyses of real water samples.

A novel electrochemical method for determination of cis-jasmone based on enhancement effect of cetyltrimethylammonium bromide

A novel electrochemical system for the sensitive determination of cis-jasmone on an electrodeposited Nafion film modified glassy carbon electrode (e-Nafion/GCE) in the presence of cetyltrimethylammonium bromide (CTAB) was described. The redox mechanism of cis-jasmone on e-Nafion/GCE was studied by voltammetry, chronocoulometry and infrared spectroscopy. The property and interface behavior of the e-Nafion film were characterized by electrochemical impedance spectrometry. The standard rate constant k 0, the diffusion coefficient D and the surface coverage Γ were calculated and discussed. Under optimal working conditions, the anodic stripping peak current of cis-jasmone linearly increased with its concentration in the range of 6.0 × 10 −7 to 1.0 × 10 −4 mol/L, with a detection limit of 4.0 × 10 −7 mol/L. The proposed method was applied to the determination of cis-jasmone in spikelet samples of rice and the good recoveries showed that it may have potentially valuable applications.

Sensitive voltammetric determination of tryptophan using an acetylene black paste electrode modified with a Schiff's base derivative of chitosan

Chitosan was modified by salicylaldehyde via Schiff's base reaction and the resulting product was modified on the surface of an acetylene black paste electrode (ABPE) by the drop-coating method. In 0.5 mol L(-1) acetate buffer (pH 4.2), a substantial increase in the anodic stripping peak current of tryptophan (Trp) (compared to conventional bare carbon paste electrode (CPE) and bare ABPE) is observed at the Schiff's base chitosan-modified electrode. The parameters influencing voltammetric determination of Trp have been optimized. Under the selected conditions, the linearity between the anodic peak currents and concentrations of Trp demonstrated a wide range of 6.0 × 10(-8) mol L(-1) to 2.0 × 10(-6) mol L(-1), 2.0 × 10(-6) mol L(-1) to 4.0 × 10(-5) mol L(-1) and 4.0 × 10(-5) mol L(-1) to 1.0 × 10(-4) mol L(-1), a low detection limit of 2.0 × 10(-9) mol L(-1) was obtained after a 60 s accumulation. In addition, the developed electrochemical sensor has been successfully applied for the determination of Trp in pharmaceutical and biological samples with satisfactory assay results.

An electrochemical immunosensor based on enzyme-encapsulated liposomes and biocatalytic metal deposition

A novel electrochemical immunosensor based on double signal amplification of enzyme-encapsulated liposomes and biocatalytic metal deposition was developed for the detection of human prostate specific antigen (PSA). Alkaline phosphatase (ALP)-encapsulated and detection antibody-functionalized liposomes were first prepared and used as the detection reagent. In the sandwich immunoassay, the model analyte PSA was first captured by anti-PSA capture antibody immobilized on the electrode and then sandwiched with the functionalized liposomes. The bound liposomes were then lysed with surfactant to release the encapsulated ALP, which served as secondary signal amplification means. ALP on the electrode surface initiated the hydrolysis of ascorbic acid 2-phosphate (AA-p) to produce ascorbic acid. The latter, in turn, reduced silver ions on the electrode surface, leading to deposition of the metal silver on the electrode surface. Linear sweep voltammetry (LSV) was chosen to detect the amount of the deposited silver. The results showed that the anodic stripping peak current was linearly dependent on the PSA concentration in the range of 0.01-100 ng mL(-1), and a detection limit as low as 0.007 ng mL(-1) can be obtained. Since the cut-off value of human PSA is 4 ng mL(-1), the proposed electrochemical immunosensor would be expected to gain widespread applications for the detection of PSA in clinical diagnosis.

Ultrasensitive electrochemical detection of DNA based on PbS nanoparticle tags and nanoporous gold electrode

An electrochemical stripping assay for ultrasensitive detection of target DNA was reported in this work. The protocol involved nanoporous gold (NPG) electrode modified with single-stranded DNA (ssDNA) and Au nanoparticles (Au-NPs) co-loaded with two kinds of ssDNA, one was reporter DNA which was complementary to the target DNA, the other modified with PbS nanoparticles (PbS-NPs) was signal DNA which was non-complemented, reducing the cross-reaction between the targets and reporter DNA on the same Au-NP. The amount of target DNA was determined by indirect determination of the amount of lead ions through differential pulse anodic stripping voltammetry (DPASV). This protocol could detect target DNA of as low as femtomolar and exhibited excellent selectivity against one-base mismatched DNA and non-complementary DNA. Under the optimum conditions, the anodic stripping peak current of lead demonstrated a good linear relationship with the target DNA concentration in the range of 9.0 × 10 −16 to 7.0 × 10 −14 M. A detection limit of 2.6 × 10 −16 M of target DNA was achieved.

Salmonella typhi determination using voltammetric amplification of nanoparticles: A highly sensitive strategy for metalloimmunoassay based on a copper-enhanced gold label

A highly sensitive electrochemical amplification immunoassay for Salmonella typhi ( S. typhi) determination has been developed for the first time by using a copper-enhanced gold nanoparticle label coupled with anodic stripping voltammetry. Monoclonal antibodies for S. typhi were first immobilized on polystyrene microwells and then captured by S. typhi bacteria. After an immunoreaction occurred, a polyclonal, antibody–colloidal gold conjugate was added to bind to the S. typhi bacteria. Next, a copper-enhancer solution containing ascorbic acid and copper (II) sulfate was added into the polystyrene microwells. The ascorbic acid was employed to reduce the copper (II) ions to copper (0), which was subsequently deposited onto the gold nanoparticle tags. After the copper was dissolved in nitric acid, the released copper ions were detected by anodic stripping voltammetry. The amount of deposited copper was related to the amount of gold nanoparticle tag present, which was controlled by the amount S. typhi attached to the polyclonal antibody–colloidal gold conjugate. Therefore, the anodic stripping peak current was linearly dependent on the S. typhi concentration over concentration range of 1.30 × 10 2 cfu/mL to 2.6 × 10 3 cfu/mL in a logarithmic plot, with a detection limit as low as 98.9 cfu/mL. The influences of the relevant experimental variables, such as the concentration of copper and the reaction time of S. typhi with antibody, were investigated. We also successfully applied this method to determine the presence of S. typhi in human serum. Our results are a step towards developing more sensitive and reliable nanoparticle immunoassays.

Successively amplified electrochemical immunoassay based on biocatalytic deposition of silver nanoparticles and silver enhancement

A successively signal-amplified electrochemical immunoassay has been reported on the basis of the biocatalytic deposition of silver nanoparticles with their subsequent enlargement by nanoparticle-promoted catalytic precipitation of silver from the silver-enhancer solution. The immunoassay was carried out based on a heterogeneous sandwich procedure using polystyrene microwells to immobilize antibody. After all the processes comprising the formation of immunocomplex, biocatalytic deposition of silver nanoparticles and following silver enhancement were completed, the silver on polystyrene microwells was dissolved and quantified by anodic stripping voltammetry (ASV). The effect of relevant experimental conditions, including the concentration of ascorbic acid 2-phosphate (AA-p) substrate and Ag(I) ions, the biocatalytic deposition time, and of crucial importance, the silver enhancement time, were investigated and optimized. The anodic stripping peak current was proportional to the concentration of human IgG in a dynamic range of 0.1–10 ng ml −1 with a detection limit of 0.03 ng ml −1. Scanning electron microscope (SEM) was applied to characterize the silver nanoparticles before and after silver enhancement on the surface of polystyrene microplates. By coupling the highly catalytic effect of enzyme and nanoparticles to successively amplify the analytical signal, the sensitivity of immunoassay was enhanced so dramatically that this approach would be a promising strategy to achieve a lower detection limit for bioassays.

Microwave-enhanced electro-deposition and stripping of palladium at boron-doped diamond electrodes

In situ microwave activation has been applied to the electro-deposition and stripping of palladium metal (which is widely used as a catalyst) at cavitation resistant boron-doped diamond electrodes. Focused microwave radiation leading to heating, boiling, and cavitation is explored as an option to improve the speed and sensitivity of the analytical detection procedure. The deposition and anodic stripping of palladium by linear sweep voltammetry in 0.1M KCl (pH 2) solution and at boron-doped diamond electrodes is shown to be strongly enhanced by microwave activation due to both (i) the increase in mass transport and (ii) the increase in the kinetic rate of deposition and stripping. The temperature at the electrode surface is calibrated with the reversible redox couple Fe(CN)(6)(4-)/Fe(CN)(6)(3-) and found to be reach 380K. In the presence of microwave radiation, the potential of onset of the deposition of palladium is strongly shifted positive from -0.4 to +0.1V versus SCE. The optimum potential for deposition in the presence of microwaves is -0.4V versus SCE and the anodic stripping peak current is shown to increase linearly with deposition time. Under these conditions, the stripping peak current varies linearly with the palladium concentration down to ca. 2muM. At concentration lower than this a logarithmic variation of the stripping peak current with concentration is observed down to ca. 0.1muM (for 5min pre-concentration in presence of microwave radiation).

MCM-41 mesoporous material modified carbon paste electrode for the determination of cardiac troponin I by anodic stripping voltammetry

An anodic stripping voltammetric method for the determination of cardiac troponin I (cTnI) at a MCM-41 mesoporous material modified carbon paste electrode (MCM-MCPE) was investigated. The test was based on the dual monoclonal antibody “sandwich” principle using colloidal gold as a labeled substrate. Four main steps were carried out to obtain the analytical signal, i.e. electrode preparation, immunoreaction, silver enhancement, and anodic stripping voltammetric detection. The anodic stripping peak current increased linearly with the concentration of cTnI over the range of 0.8–5.0 ng/ml. A detection limit of 0.5 ng/ml was obtained. The established method was applied to detect cTnI in acute myocardial infarction (AMI) samples using routine enzyme-linked immunoadsorbent assay (ELISA) for comparison analysis, and good results were obtained.

Electrochemical study and detection of perphenazine using a gold electrode modified with decanethiol SAM

A novel method for the determination of perphenazine has been developed. The method is based on the accumulation of perphenazine at a gold electrode modified with decanethiol (DEC) self-assembled monolayer (SAM) and its oxidation at about 0.6 V (vs. saturated calomel electrode (SCE)). Because some coexistent electroactives were blocked and perphenazine was selectively accumulated by the SAM, the electrode exhibited good selectivity and sensitivity. Various conditions were optimized for practical application. Under the selected conditions (i.e. 0.05 M pH 10 sodium borate buffer, accumulation time: 120 s, accumulation potential: −0.4 V, scan rate: 100 mV s −1), the anodic stripping peak current was linear to perphenazine concentration in the ranges of 6×10 −9–5×l0 −7 and 5×10 −7–5×10 −6 M with correlation coefficients of 0.998 and 0.995, respectively. For a 1.0×10 −6 M perphenazine solution, the relative standard deviation of peak height was 2.3% ( n=8). This method was applied to the determination of perphenazine in some drugs and the recovery was 92–101%. In addition, it was found that in the presence of perphenazine, the SAM structure changed a little and more needle holes appeared. However, the SAM could recover the original form when perphenazine and its redox product were removed from the monolayer by repeatedly cycling the electrode in a blank solution for a minute. The modified electrode was characterized by alternating current impedance and electrochemical probe.

Anodic stripping voltammetry of lead using a copper-mercury film electrode

The presence of copper increases the anodic stripping peak current of lead at bare glassy carbon and mercury film electrodes. Based on this, a preplated copper-mercury film electrode, prepared by the in situ plating of copper and mercury, can be employed to enhance the sensitivity for the determination of lead. When the molar concentration ratio of copper to mercury is high, a tenfold increase in sensitivity can be achieved compared with a pure mercury film electrode having the same film thickness. If the copper-mercury film is preplated freshly before each analysis, high precision is achievable, making it suitable for the routine monitoring of lead. The application of the copper-mercury film electrode to flow analysis is described.

Analytical Studies Using the Convection Electrode. XII. Anodic-stripping Voltammetry of Cadmium and Thallous Ions with the Pushed-out Mercury Drop Convection Electrode

Abstract The investigation of the anodic-stripping voltammetry of cadmium or thallous ions in a 0.1 m potassium nitrate solution was carried out by using the pushed-out mercury Drop Convection Electrode (cf. J. Suzuki and T. Ozaki, This Bulletin, 37, 230 (1964)). The metals were deposited on the mercury electrode by rotating the disk at 600—1200 rpm, and the stripping was performed by a linearly-varying potential method. The anodic-stripping peak current was proportional to the square roots of the rotating rate of the disk and of the voltage scanning rate, and to the bulk concentration of cadmium or thallous ions. Using the present stripping procedure, it was possible to determine thallous and cadmium ions at concentrations as low as 1×107 m with a mean error of about ±2%.