Application Of Square Wave Voltammetry Research Articles

Design of a printed electrochemical strip towards miRNA-21 detection in urine samples: optimization of the experimental procedures for real sample application

MicroRNAs (miRNAs) are clinical biomarkers for various human diseases, including cancer. They have been found in liquid biopsy samples, including various bodily fluids. They often play an important role in the early diagnosis and prognosis of cancer, and the development of simple and effective analytical methods would be of pivotal importance for the entire community. The determination of these targets may be affected by the different physicochemical parameters of the specimen of interest. In this work, an electrochemical detection platform for miRNA based on a screen-printed gold electrode was developed. In the present study, miRNA-21 was selected as a model sequence, due to its role in prostate, breast, colon, pancreatic, and liver cancers. A DNA sequence modified with methylene blue (MB) was covalently bound to the electrochemical strip and used to detect the selected target miRNA-21. After optimization of selected parameters in standard solutions, including the study of the effect of pH, the presence of interferent species, and NaCl salt concentration in the background, the application of square-wave voltammetry (SWV) technique allowed the detection of miRNA-21 down to a limit in the order of 2 nM. The developed device was then applied to several urine samples. In this case too, the device showed high selectivity in the presence of the complex matrix, satisfactory repeatability, and a limit of detection in the order of magnitude of nM, similarly as what observed in standard solutions.

Determination of temporary dye Basic Red 51 in commercial hair dye, river water and wastewater from hairdressing salon using graphite-epoxy composite electrode modified with magnetic nanoparticles

The present work reports the development of a simple, fast and inexpensive method for the determination of Basic Red 51 (BR 51) dye, known to be widely employed in comercial formulations of temporary dyes. The method involved the use of graphite-epoxy magnetic composite electrode (GEMCE) modified by carboxyl-functionalyzed magnetic nanoparticles (CFMNs) for the pre-concentration of the dye aiming at increasing the electrode sensitivity through the application of square wave voltammetry. The pre-concentration of BR 51 occurs via strong interaction between charged imidazole group present in the dye and the carboxyl group in the magnetic nanoparticles. This reaction is the basis for BR 51 determination through a well-defined peak at +0.89 V vs. Ag/AgCl, which is attributed to the oxidation of tertiary amine after the transfer of one electron and one proton. Under optimized conditions, which consisted of 30 sec. exposure of the GEMCE/CFMNs to BR 51 dye immersed in phosphate buffer (pH 7.0), an analytical curve was constructed in the concentration range of 1.50 × 10−6 mol L−1 to 5.50 × 10−5 mol L−1 using square wave voltammetry (SWV). The limits of detection and quantification obtained were 1.19 × 10−7 and 3.97 × 10−7 mol L−1, respectively. The proposed method was successfully applied for the determination of BR 51 dye in samples of commercial hair dye, wastewater from hairdressing salon, and river water, and was validated using high performance chromatography coupled to diode array detector (HPLC-DAD).

The fabrication of carbon nanotubes array-based electrochemical chiral sensor by electrosynthesis

How to align the single-walled carbon nanotubes (SWCNTs) onto the electrode vertically and to control their density and orientation are still a major challenge. Theoretically, properly selected chiral SWCNTs can discriminate enantiomers through their different dielectric response to the adsorption of chiral species, few reports can confirm this theoretic model. Herein, we presented a new strategy to fabricate SWCNTs array-based electrochemical chiral sensor. Carboxylated chiral SWCNTs were vertically attached to the oxidized glass carbon electrode with ethylenediamine as a linker by electrosynthesis. The electrode surface was characterized with atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The practicability of the sensor was validated by chirally recognizing 3,4-dihydroxyphenylalanine as a model molecule. We found that both the highly ordered standing of SWCNTs and the application of square wave voltammetry (SWV) amplified the intrinsic chirality of chiral SWCNTs.

Enhanced Detection of Ponceau 4R Food Dye by Glassy Carbon Electrode Modified with Reduced Graphene Oxide

This paper reports the development of a glassy carbon electrode modified with a reduced graphene oxide (r-GO/GCE) for the determination of the food dye named Ponceau 4R (PNC). The modified sensor presented excellent signal gain in relation to the GCE and GCE modified with graphene oxide besides exhibiting well defined oxidation peaks for PNC at potential of 0.61 V. Through the application of square wave voltammetry using the medium of 0.1 mol L-1 Britton-Robinson (BR) buffer (pH 5.0), analytical curves were constructed under optimized conditions, where linear regions were found within the range of 0.200 to 20.0 μmol L-1. The limits of detection and quantification were 2.84 × 10-8 and 9.46 × 10-8mol L-1, respectively. The sensor was successfully applied towards the determination of PNC in instant juice sample. A comparison made between the result obtained through the application of this sensor and via the high-performance liquid chromatography (HPLC) technique showed no significant difference between the two methods.

Electrochemical ultra-micro sensors for the determination of synthetic and natural antioxidants in edible vegetable oils

We describe the application of square wave voltammetry at ultramicroelectrodes for the determination of natural antioxidants (α, δ, and γ tocopherols), and tert-butyl hydroxytoluene in edible vegetable oils.Tocopherol determinations were performed in benzene/ethanol (1:2)+0.1molL−1 H2SO4+oil samples at a carbon fiber disk ultramicroelectrode, and tert-butyl hydroxytoluene was determined in acetonitrile (ACN)+0.1molL−1 (C4H9)4NF6P at a Pt band ultramicroelectrode after performing its extraction from the oil sample with ACN.Recovery percentages determined by the standard additions method were in the range from 92% to 102%, with variation coefficients between 0.5% and 4%.Antioxidant concentrations calculated by this methodology were in good agreement with those values declared by the manufacturers.

Square-wave stripping voltammetry for direct determination of eight heavy metals in soil and indoor-airborne particulate matter

The application of square-wave voltammetry (SWV) for the determination of eight elements viz. Cd(II), Pb(II), Cu(II), Zn(II), Co(II), Ni(II), Cr(VI), and Mo(VI) in soil and indoor-airborne particulate matter has been examined and optimized. The cathodic and anodic types of the SWV technique were examined for the detection of these metal ions. It was found that the square-wave anodic stripping voltammetry is the conventional technique for the determination of Zn(II), Cd(II), Pb(II), and Cu(II), but square-wave adsorptive cathodic stripping voltammetric method is used for the determination of Co(II), Ni(II), Mo(VI) and Cr(VI). Various experimental parameters, which influenced the response of the mercury film electrode to these metal ions, were optimized. The detection limits of these metal ions were 0.03, 0.4, 0.04, 0.1, 0.15, 0.05, 0.2, and 3.2μg/kg for Cd(II), Pb(II), Cu(II), Zn(II), Co(II), Ni(II), Cr(VI), and Mo(VI), respectively, with very good accuracy (standard deviation is below 2%). Interference from coexisting ions was successfully investigated. A comparison of analytical data for analyzing real samples was carried out between the SWV method and the graphite furnace atomic absorption spectrophotometric (GFAAS) method. By the standard addition method, the recoveries were 96.6–104% with SD of 0.75–2.5%. The great advantage of SWV is the simplicity, selectivity, sensitivity, and shortening analysis time over the GFAAS method.

QUANTIFICAÇÃO DE PESTICIDAS UTILIZANDO TÉCNICAS ELETROANALÍTICAS

The aim of this work is to discuss some selected application of square wave voltammetry published in the last years. The application focused here cover several electroanalytical fields as the determination of pesticides, metals and others environmental pollutants. These new methodology are simple, fast and sensitivity when compared with the traditional ones such as chromatography and spectrophotometry.

Enhanced application of square wave voltammetry with glassy carbon electrode coupled to multivariate calibration tools for the determination of B 6 and B 12 vitamins in pharmaceutical preparations

Vitamins B 6 (VB 6) and B 12 (VB 12) were simultaneously determined in pharmaceutical preparations by using square wave voltametry (SWV) together with artificial neural networks (ANNs). Supporting electrolyte solution, pH and voltametric technique were optimised. The calibration set was built with several artificial samples containing both active ingredients and excipients. Deviations from linearity were observed for both analytes. It is probably due to interactions among the electro active components and competition by the electrode surface, fact that supports the use of ANNs. Recoveries when analysing a nine sample validation set, of 100.2 and 96.4 were calculated for VB 6 and VB 12, respectively. Commercial samples were analysed with reasonably good results considering the complexity of the mixture studied.

Adsorptive Stripping Measurements of Iron Accumulation in Mice Kidney Using Microelectrodes and Histological Features

The toxic effects caused by iron in kidney was performed on experimental studies with mice following administration of a metallic solution of this species to simulate the iron corrosion products of a metallic implant. To quantify the total levels of iron present in this organ, an electrochemical method was chosen based on the application of square wave voltammetry using adsorptive collection of iron-catechol on a mercury film microelectrode (MFM). The optimal working conditions to produce a very stable and reproducible iron peak in the digested kidney samples were found to be pH = 7.2 provided by 8.0 mmol/L PIPES buffer, catechol concentration of 3.0 x 10(-4) mol/L, deposition potential -1.80 V and deposition time 20 s. These results were compared with those obtained by atomic absorption spectrometry (AAS) indicating a good performance of the electrochemical method used. The analytical results show an increase of iron concentration with treatment time, which indicates that this metal ion is partially accumulated in the kidney. This accumulation induces with time some morphological alterations as evidenced by the histological analysis.

Application of square wave voltammetry to strongly adsorbed quasireversible redox molecules

The theory and application of square wave voltammetry to surface-confined quasi-reversible redox molecules (Ox+ne - =Red) is described. Theoretical voltammograms were calculated based on the following assumptions: (1) stable redox states ; (2) monolayer or less surface coverage; (3) equivalent surface sites and adsorbates; (4) non adsorbate-adsorbate interactions; (5) no diffusional contributions to the current; and (6) Bulter-Volmer electrode kinetics. A working curve strategy based on peak separation between positive-scan and negative-scan net current voltammograms was developed to facilitate the semiquantative determination of electron-transfer rate constants

Application of Square Wave Voltammetry for Electrochemical Detection in Gradient Elution HPLC

Abstract The utility of square-wave voltammetry with a conventionally sized indicator electrode for use in the detection of gradient elution HPLC applications is demonstrated. A redesigned electrochemical detector cell, based upon a type of wall-jet design, provides more efficient potential control and allows the voltammetric detection. The minimum detectable quantity and linear dynamic range for the new detector design were found to be 13pg and 5 orders of magnitude, respectively, comparable to other electrochemical detectors. In the separation of a test mixture containing hydroquinone. bromohydroquinone, catechol, resorcinol, and phenylhydroquinone baseline resolution of all five components is obtained in 12 minutes using a nonlinear solvent gradient. Importantly, no change in the chromatographic baseline is observed during the course of the separation. Gradient separations of the extracts of fennel seeds and mainstream cigarette smoke are also demonstrated with no apparent change in the baseline.

ChemInform Abstract: Square Wave Voltammetry ‐ A Rapid and Reliable Determination Method of Zn, Cd, Pb, Cu, Ni, and Co in Biological and Environmental Samples.

AbstractThe application of square wave voltammetry (SWV) for the simultaneous routine determination of the title elements has been examined and optimized.

Square wave voltammetry - a rapid and reliable determination method of Zn, Cd, Pb, Cu, Ni and Co in biological and environmental samples

The application of square wave voltammetry (SWV) for the routine determination of six elements has been examined and optimized. Square wave voltammetry is more sensitive for the determination of Zn, Ni and Co in comparison with differential pulse anodic stripping voltammetry (DPASV). For Cd and Pb, no significant improvement in sensitivity was observed. At Cu concentrations < 1 μg 1 −1, only DPASV can lead to satisfactory results. The great advantage of SWV is the shortening of the determination time for Zn, Cd, Pb and Cu, which is only half the time needed by DPASV and similar to the time needed for the determination of one element by ET AAS.

Theoretical considerations on square wave and differential pulse voltammetry applied in anodic stripping with use of mercury film electrodes

Simple theoretical approximate equations describing the peak height, peak width and peak position in square wave anodic stripping voltammetry have been proposed. The use of mercury film electrodes of various film thicknesses was considered. Under all conditions the application of square wave voltammetry leads to a higher analytical signal in comparison to fast or slow DP voltammetry. The finite element method was used in the calculatioins.

Analytical application of square wave voltammetry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAnalytical application of square wave voltammetryMatthew S. Krause and Louis. RamaleyCite this: Anal. Chem. 1969, 41, 11, 1365–1369Publication Date (Print):September 1, 1969Publication History Published online1 May 2002Published inissue 1 September 1969https://doi.org/10.1021/ac60280a008RIGHTS & PERMISSIONSArticle Views1245Altmetric-Citations87LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (551 KB) Get e-Alerts Get e-Alerts