Square-wave Adsorptive Cathodic Stripping Voltammetry Research Articles

How to overcome the difficulty in assaying Ni in biodiesel samples? Extraction induced by microemulsion breaking and square wave adsorptive stripping voltammetry could be the answer

Herein, a simple, green, and relatively inexpensive approach to determine nickel (Ni) in biodiesel samples by square wave adsorptive cathodic stripping voltammetry (SWAdCSV) is presented. A method based on the accumulation of Ni as Ni(II)-dimethylglyoxime (Ni(II)(HDMG)2) on the glassy carbon electrode was carried out in a solution containing the aqueous phase extract (APhEx) obtained from an extraction induced by microemulsion breaking (EIMB), which was achieved by adding a few microliters of ultrapure water to a microemulsion composed of biodiesel, n-propanol and a diluted HNO3 solution. The LOD and LOQ were 0.2 μg L−1 and 0.8 μg L−1, respectively, and the accuracy was evaluated by recovery assays of spiked samples and by analyzing a standard reference material. Results obtained from a comparative method (HR-CS GF AAS) were also used for this evaluation. The method was applied to biodiesel samples produced from different feedstocks. To the best of the authors knowledge, it is the first time that: 1) Ni in biodiesel is determined by a voltammetric method; 2) EIMB is applied to extract Ni from this matrix and 3) this type of sample preparation method is used with adsorptive stripping voltammetry.

Development of an Electroanalytical Method for Ronidazole Determination in Environmental and Food Matrices Using Boron-Doped Diamond Electrode

A novel electroanalytical approach is presented for the determination of ronidazole in environmental and food matrices by applying a cathodically pretreated boron-doped diamond electrode and the square-wave adsorptive cathodic stripping voltammetry technique. From the studies of cyclic voltammetry to investigate the electroactivity of the ronidazole molecule, the occurrence of an irreversible cathodic process was verified, which was more efficiently detected using the cathodically pretreated boron-doped diamond electrode compared to the anodically pretreated electrode. Still on the electrochemical response of ronidazole, the effects of pH and scan rate were studied and, its apparent diffusion coefficient was determined by chronoamperometry (8.20 × 10−6 cm2 s−1). Under optimal experimental conditions, the analytical curve obtained for ronidazole was linear in two concentration ranges (12.70 to 63.40 µmol L−1 and 76.04 to 126.2 µmol L−1), with a limit of detection of 2.55 µmol L−1. For intra- and inter-day repeatabilities, relative standard deviations of only 2.7 and 3.5% were verified, which demonstrated the stable analytical response of the electrode. Recovery percentages ranging from 96 to 100% were achieved in the analysis of natural water and whole milk samples. Therefore, the proposed electroanalytical method shows satisfactory analytical performance towards ronidazole determination in varied matrice samples.

A new sustainable approach using a composite material based on dimethylglyoxime and graphite immobilized on a 3D printed support for selective nickel detection

In this work, the development of a low-cost electrochemical device (U$ 0.02 per electrode) from the immobilization of a composite material (CM) based on graphite powder, dimethylglyoxime (DMG) and nail polish, on a 3D printed acrylonitrile butadiene styrene (ABS) support was proposed for direct, sensitive and selective determination of Ni(II) by square-wave cathodic adsorptive stripping voltammetry (SWCAdSV) in a reduction potential of −1.15 V (vs Ag|AgCl|KCl(sat)). The CM was properly characterized by X-ray diffraction (XRD) and Raman spectroscopy, additionally, the electrode surface of the proposed device (3Ds-CM/DMG) was morphologically characterized through images obtained by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrode was applied as a proof of concept for monitoring Ni(II) levels in spiked tap water and synthetic urine samples. Under optimal analysis conditions, the developed method showed a good linear working range with concentrations ranging from 5 to 100 µg L−1, detectability (limit of detection) of 1.693 µg L−1, and excellent precision with relative standard deviation (RSD) of 2.9%. The doped samples at three concentration levels presented recovery values from 93.8 to 103.1%, using as a sample preparation step a simple dilution in supporting electrolyte. Furthermore, the results were analytically validated by statistical comparison with results obtained by flame atomic absorption spectrometry (F AAS). Finally, the electrodes showed RSD of 6.1% for construction reproducibility, which allows inferring that the proposed electrode proves to be a promising analytical tool with wide applicability.

Bismuth-Chitosan Nanocomposite Sensors for Trace Level Detection of Ni(II) and Co(II) in Water Samples

Trace minerals play an essential role in methane production via anaerobic digestion (AD). It is important to monitor Ni(II) and Co(II) concentrations and the Ni/Co concentration ratio for the rapid diagnosis of the ecological status or activity of methanogens in AD. Electrochemical detection of Ni(II) and Co(II) was investigated by coating the Bi-chitosan nanocomposite on a glassy carbon electrode (GCE) via the electrodeposition technique. A square-wave adsorptive cathodic stripping voltammetry technique (SWAdCSV) was applied and optimized when dimethylglyoxime (DMG) was used as the chelating agent for Ni(II) and Co(II) measurements. The SWAdCSV results showed that the current peaks for Co(II) detection are 6.1 times greater than the current peaks for Ni(II) measurements, probably due to the different affinity of DMG molecules between Ni(II) and Co(II). DMG molecules demonstrated higher selectivity toward Co(II) cations compared to Ni(II). The modified Bi-chitosan GCE developed in this study showed a relatively wide range of the Ni(II) and Co(II) concentrations (2–100 µg L−1) with a limit of detection of 3.6 µg L−1 for Ni(II) and 2.4 µg L−1 for Co(II), respectively. The developed sensor was applied to Ni(II) and Co(II) spiked natural water samples and showed good performance of detection with 12 consecutive measurements. Overall, the fabricated sensor showed excellent sensitivity toward Ni(II) and Co(II) in natural water samples.

Simultaneous Adsorptive Stripping Voltammetric Analysis of Heavy Metals at Graphenated Cupferron Pencil Rods

Electroanalysis of heavy metal ions in the presence of cupferron ligands has been extensively studied due to its ability to form stable metallic coordination complexes. Herein, electrochemically reduced graphene oxide (ERGO) sheets were for the first time employed in conjunction with low-cost, disposable pencil graphite rods and in situ plated thin mercury films (HgF) for the simultaneous detection of Cd2+, Cu2+, Pb2+, and Zn2+ in the presence of cupferron as a chelating agent by square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV). The technique is based on the catalytic reduction of adsorbed cupferron-metal ion complexes at the surface of the ERGO-HgF-PGE at 0.1 V for 60 s in 0.1 M acetate buffer solution (pH 4.6). Owing to the improved electronic and surface effects associated with ERGO inclusion, improved sensitivity was further achieved. Under optimized conditions, the ERGO-HgF-PGE showed a linear relationship from 20 to 200 μg.l−1 with detection limits below the US-EPA of 0.17 μg.l−1, 0.02 μg.l−1, 0.17 μg.l−1 and 0.14 μg.l−1 for Cd2+, Cu2+, Pb2+ and Zn2+, respectively at a deposition time of 60 s. The ERGO-HgF-PGE exhibited highly reproducible results with negligible intermetallic interferences and applied successfully to the determination of trace metals in tap water with satisfactory results.

Ultrasensitive determination of selenium in foodstuffs and beverages using an electroanalytical approach

This work describes the development of an electroanalytical methodology to the determination of nanomolar levels of selenium, which is sensitivity, selectivity, simple, low cost, quickness, and robustness. Therefore, it was employed a silver solid amalgam electrode modified by a thin and stable mercury film (f-AgSAE) allied to square-wave cathodic adsorptive stripping voltammetry (SWCASV). Besides this, the adsorptive and square-wave voltammetry parameters were previously optimized following the built of analytical curves in the linear range from 1.00 × 10−7 to 8.00 × 10−6 mol L−1, that resulted in a correlation coefficient of 0.9989, repeatability of 1.64%, reproducibility of 4.90%, detection limit of 1.01 × 10−9 mol L−1 and quantification of 3.36 × 10−9 mol L−1. This methodology proposed can be compared with similar data obtained by sophisticated spectroscopic techniques and other electroanalytical techniques. The procedure proposed was applied to selenium determination in in natura food (apple, orange, potato, spinach and tomato) and beverage (coconut water, soy juice and soy milk) samples. These samples were digested using a simple procedure that resulted in very satisfactory recovery percentages, confirming suitable robustness of the proposed methodology.

Chitosan coated magnetite nanoparticle as a working electrode for determination of Cr(VI) using square wave adsorptive cathodic stripping voltammetry

The application of chitosan coated magnetite nanoparticle modified carbon paste electrode as a working electrode (chitosan@Fe3O4/CPE) for Cr(VI) analysis is presented. The electrochemical detection mode of square wave adsorptive cathodic stripping voltammetry (SWAdCSV) was selected for determination of Cr(VI) due to the high sensitivity and selectivity. The optimal conditions for electrode preparation and the electrode behavior including parameters affecting the SWAdCSV signal were investigated. Two linear ranges of Cr(VI) determination were observed 0.01–0.3 μg L−1 and 0.5–30 μg L−1 with limits of detection of 0.0061 and 0.078 μg L−1, respectively. The precision of the electrode output in terms of %RSD was 11.4% (n = 30). The method was successfully applied to determine Cr(VI) in drinking water and sea water samples with recovery percentages in range 87–110%. Moreover, the results obtained agree with a paired t-test at the 95% confidence level which were comparable to the standard UV–visible spectrophotometric method.

Cathodic stripping voltammetric determination of β-cyfluthrin, a pyrethroid insecticide, using polished silver solid amalgam electrode

This work describes an electroanalytical procedure for determination of beta-cyfluthrin (βCF), a pyrethroid insecticide, using polished silver solid amalgam electrode (p-AgSAE) allied to a square-wave cathodic adsorptive stripping voltammetry (SWCASV). Although βCF is non-electroactive in the conventional electrodes, it was accumulated at the p-AgSAE surface as adsorbed mercury salt, allowing their indirect determination using the well-defined reduction peak of mercury complex at − 0.94 V, obtained after adequate experimental and voltammetric optimization. Analytical curves were constructed for βCF, and all analytical parameters were properly evaluated. The proposed methodology was applied in the βCF determination in natural water and tea samples, which were previously filtrated before voltammetric analysis, already the same analysis performed using gas chromatography with mass spectroscopy detection technique employed the solid-phase extraction step. Analytical parameters obtained using both techniques indicated no significant difference at 95% confidence, confirming that the electroanalytical procedure had high robustness, good stability and suitable sensitivity to determination of βCF in complex samples.

Enhanced Specificity and Sensitivity for the Determination of Nickel(II) by Square-wave Adsorptive Cathodic Stripping Voltammetry at Disposable Graphene-modified Pencil Graphite Electrodes

Chemical sensors relying on graphene-based materials have been widely used for electrochemical determination of metal ions and have demonstrated excellent signal amplification. This study reports an electrochemically reduced graphene oxide (ERGO)/mercury film (HgF) nanocomposite-modified pencil graphite electrode (PGE) prepared through successive electrochemical reduction of graphene oxide (GO) sheets and an in situ plated HgF. The ERGO-PG-HgFE, in combination with dimethylglyoxime (DMG) and square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV), was evaluated for the determination of Ni2+ in tap and natural river water samples. A single-step electrode pre-concentration approach was employed for the in situ Hg-film electroplating, metal-chelate complex formation, and non-electrolytic adsorption at –0.7 V. The current response due to nickel-dimethylglyoxime [Ni(II)-DMG2] complex reduction was studied as a function of experimental paratmeters including the accumulation potential, accumulation time, rotation speed, frequency and amplitude, and carefully optimized for the determination of Ni2+ at low concentration levels (μg L−1) in pH 9.4 of 0.1 M NH3–NH4Cl buffer. The reduction peak currents were linear with the Ni2+ concentration between 2 and 16 μg L−1. The limits of detection and quantitation were 0.120 ± 0.002 µg L−1 and 0.401 ± 0.007 µg L−1 respectively, for the determination of Ni2+ at an accumulation time of 120 s. The ERGO-PG-HgFE further demonstrated a highly selective stripping response toward Ni2+ determination compared to Co2+. The electrode was found to be sufficiently sensitive to determine metal ions in water samples at 0.1 µg L−1, well below the World Health Organization standards.

Optimization and Validation of a Methodology for the Quantification of Streptomycin Using Square Wave Voltammetry

The quantification of pharmaceuticals drugs is typically accomplished using chromatography, which requires several pretreatment steps of the sample, demanding time and supplies. Thus, the present work proposed the development and validation of a voltammetric method to quantify the antibiotic streptomycin (STP), in aqueous samples. Initially, the parameters of the technique were optimized applying square wave adsorptive cathodic stripping voltammetry (SW-AdsCSV), using the hanging mercury drop electrode (HMDE) as the working electrode. Then, the adequacy of the analytical method was evaluated using validation criteria, such as precision, selectivity, linearity, limits of detection and quantification. The linearity was evaluated by a standard addition curve from STP 8.09 to 210.4 µg L -1 . The limits of detection (LOD) and quantification (LOQ) were 0.18 and 0.60 µg L -1 , respectively. The accuracy and precision of each method were expressed as percentage of STP recovery in fortified solutions, resulting in deviation below 20%, acceptable for analytes at the trace level, indicating accuracy and precision of the methods. The voltammetric methods have advantages over others described in literature, since they do not require steps of pre-treatment of the samples, being, this way, fast and low cost analyzes. The method was applied in natural and effluent water; however, STP was not detected in a real sample, in three samplings. DOI: http://dx.doi.org/10.17807/orbital.v10i3.1091

Determination of genotoxic effects of methidathion alkaline hydrolysis in human lymphocytes using the micronucleus assay and square-wave voltammetry

The interaction of pesticides with environmental factors, such as pH, may result in alterations of their physicochemical properties and should be taken into consideration in regard to their classification. This study investigates the genotoxicity of methidathion and its alkaline hydrolysis by-products in cultured human lymphocytes, using the square-wave voltammetry (square wave-adsorptive cathodic stripping voltammetry (SW-AdCSV) technique) and the cytokinesis block micronucleus assay (CBMN assay). According to the SW-AdCSV data the alkaline hydrolysis of methidathion results in two new molecules, one non-electro-active and a second electro-active which is more genotoxic than methidathion itself in cultured human lymphocytes, inducing higher micronuclei frequencies. The present study confirms the SW-AdCSV technique as a voltammetric method which can successfully simulates the electrodynamics of the cellular membrane.

Electrocatalytic Quantification of Pantaprazole

A polyaniline-zinc oxide-modified glassy carbon electrode (PANI-ZnO/GCE) has been developed for the determination of pantaprazole. The morphology of fabricated PANI-ZnO/GCE was characterized by scanning electron microscopy. The electrochemical behavior of pantaprazole on PANI-ZnO/GCE was investigated using square-wave cathodic adsorptive stripping voltammetry (SWCAdSV). Results showed that PANI-ZnO/GCE modified sensor exhibited excellent electrocatalytic activity to pantaprazole with a detection limit of 45.59 ng/mL, a reproducibility of 2.07% relative standard deviation, and a recovery from 99.76% to 99.81%. The ease of fabrication, high electroactive surface area and excellent electrochemical performance are the promising feature of the sensor.

Adsorptive stripping voltammetric determination of anticancer drug lomustine in biological fluids using in situ mercury film coated graphite pencil electrode

Abstract In situ mercury film coated graphite pencil electrode (MF/GPE) was prepared and applied for selective and sensitive electrochemical determination of anticancer drug lomustine (LMT). Parameter optimization for the preparation of MF/GPE was examined. The bare and modified GPEs were characterized by scanning electron microscopy (SEM), cyclic voltammetry and square wave voltammetry. With pH 5.0, Britton–Robinson (BR) buffer and in the presence of 0.5 M sulfate ions as indifferent supporting electrolyte, LMT yields a well defined and sensitive reduction peak at the MF/GPE. The electrochemical parameters such as the charge value (Q), surface concentration (Γ), electron transfer coefficient (α) and the standard rate constant (ks) for the reduction of LMT at the MF/GPE were calculated. The achieved limits of detection and quantification were 8.13 × 10− 8 M and 2.71 × 10− 7 M by square wave cathodic adsorptive stripping voltammetry (SWCASV), respectively. The modified MF/GPE was used as a sensor for the detection of LMT in human blood and urine samples with good accuracy and precision.

Square Wave Cathodic Adsorptive Stripping Voltammetric Determination of the Anticancer Drugs Flutamide and Irinotecan in Biological Fluids Using Renewable Pencil Graphite Electrodes

AbstractA sensitive electrochemical method based on square wave cathodic adsorptive stripping voltammetry (SWCASV) using pencil graphite electrodes (PGE) was developed for the individual and simultaneous determination of the anticancer drugs flutamide (Flu) and irinotecan (Irino) in biological fluids. Calibration curves showed an excellent linear response with limits of detection of 1.68×10−9 and 1.55×10−8 M Irino and Flu, respectively. The statistical evaluation of within‐day repeatability (n=5) and day to day precision (n=5) showed satisfactory accuracy and precision. SWCASV using a PGE for individual and simultaneous determination of both drugs in bulk form, human urine and serum samples was demonstrated.

Voltammetric Quantification of Antispasmodic Drug Drotaverine Hydrochloride in Human Serum

Drotaverine hydrochloride is an antispasmodic drug used to relieve cramps or spasms of the stomach, intestines and bladder. The electro reductive behaviour of drotaverine has been investigated and one irreversible well-defined cathodic peak was observed at -1.04 V vs. Ag/AgCl ((3.0 M) KCl). A validated, sensitive and reproducible cathodic adsorptive stripping voltammetric procedure for the trace determination of the bulk drug in human serum has been developed. The peak current showed a linear dependence with the drug concentration over the range 50 ng/mL to 25.6 μg/mL for Square-Wave Cathodic Adsorptive Stripping Voltammetry (SWCAdSV) and 0.2 μg/mL to 51.8 μg/mL for Differential Pulse Cathodic Adsorptive Stripping Voltammetry (DPCAdSV). Applicability to assay the drug in serum samples was illustrated and minimum detectability was found to be 49.83 ng/mL.

Lead determination in canned food by square-wave adsorptive cathodic stripping voltammetry

A sensitive and rapid method to analyse Pb(II) in canned fish samples was developed using square-wave adsorptive cathodic stripping voltammetry based on the adsorptive accumulation of 8-hydroxyquinoline complexes of Pb(II) onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan with square wave pulse modulation. The optimum conditions were found to be 0.1 M CH3COONH4 as a supporting electrolyte, pH 7.5, 8-hydroxyquinoline concentration of 15 µM, accumulation potential 0.70 V (versus Ag/AgCl), accumulation time 120 s, scan rate 0.3 V/s, and pulse amplitude 20 mV. Under the optimum conditions a linear calibration graph was obtained in the concentration range of 0.5-90.0 µg/l with correlation coefficient 0.9973, a limit of detection of 0.108 µg/l, and a limit of quantification of 0.360 µg/l. The recovery values were obtained in the range 93.7-95.1%. The relative standard deviations (n = 10) at lead concentration 5.0 µg/l was 2%. The method was successfully applied to the determination of lead content in canned fish samples. The concentration of Pb(II) in canned fish samples (wet weight) was found to be in the range of 0.121-0.285 µg/g, which is lower than the limit (1.00 µg/g) issued by the Ministry of Public Health of Thailand.

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.

Determination of Trace Antimony by Square-Wave Adsorptive Cathodic Stripping Voltammetry at an Ex Situ Prepared Bismuth Film Electrode

A square-wave adsorptive cathodic stripping voltammetric protocol to determine trace antimony(III) in the presence of gallic acid (GA) at an ex situ prepared bismuth film electrode (BiFE) has been investigated. A well-defined and sensitive stripping peak of the Sb(III)-gallic acid complex was observed at −0.53 V (vs. SCE) in a 0.1M acetate buffer solution (pH 4.8) at a deposition potential of −0.38 V (120 s). The experimental variables as well as potential interferences were studied. Compared with the ex situ mercury film electrode (MFE), the ex situ prepared BiFE displayed a better electroanalytical performance for the determination of antimony(III). Under the optimized conditions, the linear range was obtained between 2–25 μg/L, the limit of detection for antimony(III) was 60 ng/L and the relative standard deviation was 3.37% at the 10 μg/L level (n = 10). This method was applied to determine trace amounts of antimony in several environmental samples with the satisfactory results.

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.

Simultaneous Determination of Nickel and Cobalt Using a Solid Bismuth Vibrating Electrode by Adsorptive Cathodic Stripping Voltammetry

AbstractA simple, fast, sensitive and greener voltammetric procedure for simultaneous analysis of nickel (Ni) and cobalt (Co) by square wave adsorptive cathodic stripping voltammetry (SW‐AdCSV) using a solid bismuth vibrating electrode is presented for the first time. The procedure enables to determine Ni together with Co, in ammonia buffer 0.1 M (pH 9.2) and in the presence of oxygen, and involves an adsorptive accumulation of metal‐dimethylglyoxime (Ni‐DMG and Co‐DMG) complexes on the electrode surface. For Ni and Co, the detection limits, obtained with 30 s of accumulation time, were 0.6 and 1.0 µg L−1, respectively. The method was free of metals (Cd2+, Cr3+, Cr6+, Cu2+, Fe3+ and Pb2+ up to 50 µg L−1, Al3+ and Mn2+ up to 500 µg L−1; Zn2+ up to 300 µg L−1) interferences up to the concentrations mentioned in brackets. The proposed method was validated for simultaneous determination of Ni and Co in a certified reference surface and river waters with good results.