Cathodic Stripping Research Articles

Determination of heavy metal poisoning antidote 2,3-dimercapto-1-propanesulfonic acid using silver solid amalgam electrode

Voltammetric behavior of heavy metal poisoning antidote 2,3-dimercapto-1-propane-sulfonic acid (DMPS) was investigated using linear scan voltammetry (LSV), differential pulse cathodic stripping voltammetry (DPCSV), differential pulse anodic stripping voltammetry (DPASV), and elimination voltammetry with linear scan (EVLS) at a polished (p-AgSAE) and at a meniscus modified (m-AgSAE) silver solid amalgam electrode. It was confirmed that the mechanism of the electrode process involves two consecutive reductive desorptions with coupled proton/electron transfer preceded by a kinetic process prominent at higher scan rates as revealed by EVLS. Voltammetric and complexation behavior of DMPS in the presence of Pb2+ was further investigated by DPASV and DPCSV titrations confirming reductive desorption, complex formation, and transmetalation. Optimum conditions for DPCSV were as follows: Britton-Robinson buffer (BRB) of pH 10, Eacc = −200 mV and tacc = 30 s for p-AgSAE and BRB of pH 5, Eacc = 0 mV and tacc = 15 s for m-AgSAE. Limits of quantification (LOQs) and detection (LODs) were 0.3 and 0.1 μmol L−1 at m-AgSAE and 0.8 and 0.3 μmol L−1 at p-AgSAE, respectively. The practical applicability of the newly developed method was verified by determination of DMPS in commercial drug Dimaval and in human urine samples.

Electrochemical enzyme biosensor for carnitine detection based on cathodic stripping voltammetry

Recently, the amount of carnitine in saliva has been considered a biomarker for pancreatic cancer. Traditional analytical instrument such as liquid chromatography and mass-spectroscopy (MS) has been employed for carnitine detection. Only FET based biosensor was reported for carnitine, but the limit of detection was far above the required concentration. Here, we describe a highly sensitive and selective enzyme biosensor that we have developed for carnitine by using an enzyme-modified electrode combined with cathodic stripping voltammetry. The biosensor exhibits high sensitivity because of the preconcentration on the gold electrode of CoA, which was generated by the enzymatic reaction between carnitine and acetyl coenzyme A (acetyl-CoA) with carnitine acetyltransferase. Although both acetyl-CoA and CoA can adsorb on the gold electrode, the potential difference of reductive desorption detects CoA selectively. Under optimized conditions, the biosensor exhibited a linear range from 0.025 to 25 μM with a detection limit (S/N = 3) of 0.025 μM for carnitine determination. Moreover, the recovery experiments determination results show a stable range from 96.6 to 97.2 %. This developed carnitine biosensor has a potential in clinical detection due to the excellent performance.

The nature of the copper sulfide film grown on copper in aqueous sulfide and chloride solutions

AbstractIn this paper, the properties of copper sulfide films formed both anodically and naturally in deaerated/anoxic aqueous sulfide and chloride solutions were investigated using a series of electrochemical and surface analytical techniques. A combination of cyclic voltammetric, corrosion potential (Ecorr), and cathodic stripping voltammetric experiments showed that the sulfide film growth kinetics and film morphologies were controlled by the supply of SH− from the bulk solution to the copper surface. There was no passive barrier layer observed on the copper surface under either electrochemical or corrosion conditions. The film morphology was dependent on the type and concentration of anions (SH−, Cl−) present in the solution. Scanning electron microscopy on both surfaces and focused ion beam‐cut cross‐sections showed the growth of a thin, but porous, base layer of chalcocite (Cu2S) after short immersion periods (up to 2 hr) and the continuous growth of a much thicker crystalline outer deposit over longer immersion periods (≥36 hr), suggesting a solution species transport‐based film formation process and the formation of an ineffective thin “barrier‐type” layer on copper.

Indium Tin Oxide for Sensitive Detection of Manganese in Environmentally and Biogically Relevant Samples

Indium tin oxide (ITO) has long been used as an optically transparent electrode for a variety of applications. For sensing, ITO is commonly seen as the working electrode for spectroelectrochemical measurements where spectroscopic measurements are made under electrochemical control. In this work, however, ITO was investigated for its ability to detect manganese (Mn) in both environmentally and biologically relevant samples using cathodic stripping voltammetry (CSV). ITO exhibited superior performance compared to traditionally-used electrode materials such as glassy carbon, platinum, and boron-doped diamond. The ITO physical vapor deposition (PVD) processes were optimized for Mn detection, including substrate heating during deposition and post-process annealing. Crystallographic changes were observed with the <400> orientation showing the most promise towards Mn detection. Characterization was achieved using multiple topographical and electrochemical methods. Charge-selective polymer films were deposited on the ITO surface to investigate increases in selectivity and/or sensitivity. Using various ITO electrode types, limits of detection (LODs) below 1 ppb were obtained in short measurement times (2-3 min) in environmental samples. In bovine whole-blood samples, ITO exhibited comparable results to those obtained with both graphite furnace- atomic absorption spectroscopy (GF-AAS) and inductively coupled plasma-mass spectrometry (ICP-MS). This work expands on the use of ITO and metal oxides as voltammetric electrodes/sensors; the results presented may be applicable to other analytes amenable to detection by CSV.

Electrochemical detection of Cr(VI) and Cr(III) ions present in aqueous solutions using bio-modified carbon paste electrode: a voltammetric study

ABSTRACTChromium is recognised as a potent water pollutant by the WHO and thus it becomes pertinent to continuously monitor chromium levels in the waterbodies. Voltammetry, an electroanalytical technique, has been utilised for the detection of hexavalent (Cr(VI)) and trivalent (Cr(III)) chromium in aqueous samples. Carbon Paste Electrode (CPE) modified using Sphingopyxis macrogoltabida SUK2c, an indigenous bacterial strain isolated from the water samples collected from Sukinda Valley, Odisha, India, was used as a working electrode in a typical three-electrode electrochemical cell. The developed biosensors were found to provide about 3.5 fold increase in cathodic peak current compared to the bare CPE for Cr(VI) ions. Using cyclic voltammetry (CV), the Lowest Limit of Detection (LLOD) of 1 × 10−4 M and 1 × 10−2 M for Cr(VI) and Cr(III) ions, respectively, were achieved with the biosensors. The LLOD was further improved to 1 × 10−9 M and 1 × 10−7 M for Cr(VI) and Cr(III) ions, respectively, adopting differential pulse cathodic stripping Vvoltammetry (DPCSV) technique employing the biosensors. The concentrations of Cr(VI) and Cr(III) ions present in water samples collected from Sukinda Valley, Odisha, India, could be determined using the biosensor. The plausible mechanisms involved in the detection of Cr(VI) and Cr(III) ions by the developed electrochemical biosensor are discussed.

Novel Electrochemical Sensor Based on Nylon 6,6-Modified Graphite HB Pencil Electrode for Chlorothalonil Determination by Differential Pulse Cathodic Stripping Voltammetry

Mercury-based electrode was the choice of electrode material for many years, and it has been extensively used in voltammetry studies. Nonetheless, alternative electrode materials are highly preferred in voltammetry studies due to the toxicity of mercury. This work introduces a novel green sensor, nylon 6,6-modified graphite HB pencil electrode (Nyl-MHBPE) as electrochemical method for chlorothalonil determination by differential pulse cathodic stripping voltammetry (DPCSV). The Nyl-MHBPE was significantly improved electroactivity towards the reduction of chlorothalonil, under the optimal conditions (at pH 8.0). It was clearly observed that nylon 6,6 revealed as an efficient modifier for enhancing stripping signal for voltammetric analysis. Moreover, the developed sensor showed great feature such as a remarkably low detection limit in nanomolar level (0.94 × 10−8 M) with a linear range from 1 to 26 × 10−7 M. It presented excellent repeatability with high sensitivity and selectivity. Besides, analysis of chlorothalonil in real water samples was successfully carried out with good recovery values (92.5–103%) and relative standard deviation (RSD) values < 2.2%. The performance of Nyl-MHBPE was also compared to bare pencil electrode (HBPE). Another significant feature of this work is that the conductivity properties of the Nyl-MHBPE were superior as compared to hanging mercury drop electrode (HMDE). The present study provides admirable merits that make the Nyl-MHBPE selected as a promising electrochemical sensor to perform routine analysis of chlorothalonil.

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.

Fast iron speciation in seawater by catalytic Competitive Ligand Equilibration-Cathodic Stripping Voltammetry with tenfold sample size reduction

Iron speciation analysis in seawater is a fundamental step to understand the cycling of this element in oceanic waters, in view of its central role in regulating primary productivity and its connection to global planetary cycles. At present, analytical procedures are the bottleneck for speciation analysis, in term of both time and sample size requirement. Here we present a novel instrumental configuration for the speciation analysis of iron by the Competitive Ligand Equilibration - Cathodic Stripping Voltammetry (CLE-CSV) procedure. The new system features a 1 mL microcell and a silver wire pseudoreference enabling a tenfold reduction of the sample volume. 2,3-dihydroxynaphthalene was used as the complexing ligand and atmospheric oxygen as the catalytic enhancer because they ensured the best analytical performances in terms of detection capabilities. The side reaction coefficient for the FeDHN complex αFe’DHN was calibrated against EDTA and an average value of 9.25 for logK’Fe’DHN was calculated. The method was successfully validated in UV digested seawater using diethylenetriaminepentaacetic acid (DTPA), which has known stability constant for iron. The method was lastly applied to six samples from the Ross Sea water column (Antarctica), demonstrating its fit for purpose for the detection of trace amounts of iron ligands in seawater. Thanks to the employed instrumental configuration and the high sensitivity, the proposed method achieved a tenfold reduction in sample size, a tenfold increase in sensitivity compared with other methods employing DHN and halved the analysis time with respect to the fastest method reported in the literature. Half an hour is enough to measure a 12 point titration, making the analysis of at least three titrations per day feasible. It is expected that the application of this procedure will foster the sample throughput, thanks to the reduced analysis time, and make possible the analysis of limitedly available and challenging samples, like porewater and vent fluids via the tenfold reduction in sample size.

Development of the TIP-HOLE gas avalanche structure for nuclear physics/astrophysics applications with radioactive isotope beams: preliminary results.

We discuss the operational principle and performance of new micro-pattern gaseous detectors based on the multi-layer Thick Gaseous Electron Multiplier (M-THGEM) concept coupled to a needle-like anode. The new gas avalanche structure aims at high-gain operation in nuclear physics and nuclear astrophysics applications with radioactive isotope beams. It is thereafter named TIP-HOLE gas amplifier, and consists of a THGEM or a two-layers M-THGEM mounted in a WELL configuration. The avalanche electrodes are collected by thin conductive needles (with up to a few ten μm radius and a height of 100 μm), located at the center of the hole and acting as a point-like anode. The bottom area of the needle could be surrounded by a cylindrical cathode strip in order to increase the electron collection efficiency. The electric field lines from the drift region above the M-THGEM are focused into the holes, and then forced to converge on the needle tip. An extremely high field is reached at the top of the needle, creating a point-like avalanche process. Stable, high-gain operations in a wide range of pressures can be achieved at relatively low operational voltage, even in pure quencher gas at atmospheric pressure (e.g. pure isobutene). The TIP-HOLE structure may be produced by the innovative scalable additive manufacturing technology for large-area, multiple-layer printed circuit boards, recently developed by the UHV technology company (USA) and discussed for the first time in this work.

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.

ОПРЕДЕЛЕНИЕ ПОЛИСУЛЬФИД-ИОНОВ В ЩЕЛОЧНОЙ СРЕДЕ В УСЛОВИЯХ КАТОДНОЙ ИНВЕРСИОННОЙ ВОЛЬТАМПЕРОМЕТРИИ С РТУТНО-ПЛЕНОЧНЫМ ЭЛЕКТРОДОМ

Актуальность. Полисульфиды щелочных, щелочноземельных металлов и аммония являются компонентами технологических сред в крупнотоннажных производствах (щёлоки в технологии целлюлозы; растворы чернения и воронения; реагенты для производства полисульфидных эластомеров), используются для получения новых функциональных материалов (герметики), играют определяющую роль при функционировании химических источников тока нового поколения. В связи с этим изучение закономерностей протекания электродных процессов с участием полисульфидов является актуальным. Цель: установить условия определения полисульфид-ионов в щелочных растворах с использованием катодной инверсионной вольтамперометрии с ртутно-пленочным электродом. Объекты: растворы полисульфидов натрия Na2S2 и Na2S3, растворы гидроксида натрия. Методы: постоянно- и переменнотоковая катодная инверсионная вольтамперометрия, циклическая вольтамперометрия, накопительный электролиз. Результаты. Предложены эмпирические уравнения для расчета изменения энергии Гиббса образования Sn2–-ионов в водных растворах и их стандартных потенциалов в зависимости от степени полисульфидности в интервале n=1…8. Проведены расчеты равновесных активностей ионно-молекулярных форм в системе Hg–S–H2O при различных значениях рН и потенциалов. Установлены оптимальные условия определения полисульфид-ионов S22– и S32– в щелочной среде (0,1 М NaOH) на ртутно-пленочном электроде с использованием постоянно- и переменнотоковой катодной инверсионной вольтамперометрии: потенциал предэлектролиза –0,5 В (х. с. э.); продолжительность предэлектролиза 1…2 мин; последующая катодная поляризация до Екон= –1,0 В; предварительное деаэрирование растворов азотом. В этих условиях концентрационная зависимость величины максимума катодного тока Iк при Еmax= –0,8…–0,9 В линейна в интервале концентраций полисульфидов 1×10–7…1×10–3 М. Метод может быть использован для определения общего содержания полисульфидов в растворе и для расчета средней степени полисульфидности в ионах Sn2–.

Speciation analysis of Pt and Rh in urban road dust leachates

Road dust is a major reservoir of anthropogenic Pt and Rh. However, information about how these elements are released to the aquatic systems under environmentally relevant conditions is scarce. In this work, an innovative combination of analytical strategies is used to provide insight into the speciation analysis of those elements. A composite sample of road dust thoroughly characterized was incubated over 7 days in synthetic rainwater and seawater. In the filtered (<0.45 μm) solutions, truly dissolved Pt and Rh concentrations were measured by adsorptive cathodic stripping voltammetry, while total concentrations were determined by inductively coupled plasma mass spectrometry. Truly dissolved species corresponded to a small fraction of total Pt and Rh in the road dust; accordingly, values of 0.01% and 0.1% were obtained in both media for Pt and Rh, respectively, which remained constant over time. The concentration of total filter-passing species predominates for both elements by a factor of 10 and 2–3 for Pt and Rh, respectively, evidencing that particulate species coexist with truly dissolved forms. Temporal variations were observed for Pt, as opposed to Rh. These findings contribute to the gap in knowledge regarding Pt and Rh mobility in aquatic systems.

A highly selective electrochemical sensor for trace determination and speciation of antimony (III &amp; V) in water and soil samples using 2-thenoyltrifluoroacetone

The current works extend the utility of 2-thenoyltrifluoroacetone reagent (HTTA) towards the least explored antimony (III & V) ions in complex matrices. The redox characteristics and the excellent surface coverage (Γ) of the electroactive antimony (III)-HTTA chelate onto the hanging mercury dropping electrode suggested establishing a differential pulse cathodic stripping voltammetric (DP–CSV) analysis for chemical speciation of antimony (III & V) in environmental water samples. Under the optimized conditions of pH, deposition time, potential, sweep rate, and HTTA concentration, the cathodic peak current at − 0.18 V linearly increased on growing antimony (III) concentration in a wide working range from 2.46 × 10−9 to 1.07 × 10−7 mol L−1, with an obtained detection and quantification limits 7.38 × 10−10 and 2.46 × 10−9 mol L−1, respectively. The figure of merits were compared successfully with some reported electrochemical, chromatographic, and spectrochemical methods. The established DP–CSV method has a unique advantages (rapid response, short analytical time, sensitive, selective, and reproducible) to be quantitatively applied for trace analysis of antimony (III & V) species in fresh and marine water (the Atlantic Ocean and the Red Sea) samples. The settled method was also validated (Student’s t and F tests at P = 0.05) by comparison with the official inductively coupled plasma-mass spectrometry (ICP-MS) method.

Upgrades to the CMS Cathode Strip Chambers for the HL-LHC

The Large Hadron Collider (LHC) will be upgraded in several phases to significantly expand its physics program, and these upgrades present major challenges to the operations of the CMS Cathode Strip Chamber muon system. After the current long shutdown during 2018–2021 (LS2), the accelerator luminosity will have increased, exceeding the design value of 1034 cm−2s−1 and allowing the CMS experiment to collect approximately 100 fb−1/year. A subsequent upgrade in 2023–2024 will increase the luminosity up to 5 × 1034 cm−2s−1. The CMS muon system must be able to sustain a physics program after the LS2 shutdown that maintains and enhances sensitivity to electroweak scale physics and for TeV scale searches similar to what was achieved up to now. For the Cathode Strip Chamber (CSC) muon detectors, the electronics will be upgraded to handle the expected higher data rates. The design of the upgraded CSC electronics is discussed in this report. In addition, accelerated irradiation tests are being performed to study the behaviour of the CSC electronics under conditions that are nearly an order of magnitude beyond the original design values. Studies have also been performed of chamber gas mixtures to reduce greenhouse-gas impacts. The status of this irradiation campaign and results are presented.

Absorption of iodotyrosine from iodized milk protein in animals

Introduction. One of the ways to the solve iodine deficiency problem is the addition of iodine to farm animal feed. It allows producing iodized livestock products. Promising sources of organic iodine are iodotyrosine-containing iodized milk proteins. Organic iodine accumulation in organs and tissues has not been sufficiently studied.&#x0D; Study objects and methods. We determined iodotyrosine content in rat blood plasma and in pig muscle tissue. For this purpose, high performance liquid chromatography with mass spectrometric detection and cathodic stripping voltammetry were used.&#x0D; Results and discussion. At the first stage of the study, we examined iodotyrosines in rat blood plasma after a single administration of iodized milk protein or potassium iodide (30 μg I/kg weight) at specific time intervals. A significant increase in the concentration of monoiodotyrosine and diiodotyrosine was recorded 4 and 24 h after the administration. At the second stage, we studied the accumulation of iodotyrosines in the muscle tissue of pigs during their fattening period (104 days). The diet of the control animal group included potassium iodide (0.6 mg I/kg of feed). The experimental groups A and B got iodized milk protein (0.3 and 0.6 mg I/kg of feed, respectively). Monoiodotyrosin content in the muscle tissue of pigs of the experimental groups was 3.0 and 5.2 times higher than that in the control group. Diiodotyrosine content was 4.9 and 8.2 times higher. In the experimental group A, iodine content in muscle tissues was 26% higher than that in the control group, in the experimental group B it was 72% higher. Calculations of iodine intake balance and its accumulation in muscle tissues showed that in animals whose diet included iodized milk protein, the iodine assimilation was much higher (0.70 and 0.53%) than in the control group (0.21%).&#x0D; Conclusion. Iodotyrosines from iodized milk protein are absorbed by the gastrointestinal tract in an unchanged form and accumulate in muscle tissues. The findings give more clear understanding of physiological and biochemical mechanisms of organic iodine absorption in animals.

A metal-catex composite electrode for determination of paraquat in various samples by Ad-differential pulse cathodic stripping voltammetry

In this work, a novel kind of metal-catex composite electrode for determination of paraquat (PQ) by adsorptive differential pulse voltammetry is introduced. The metal-catex composite electrode was fabricated by cathodic electropolymerization of p-nitrophenol and p-nitrobenzoic acid in the presence of tin (II) chloride as a scaffold for composite structure on prepared glassy carbon electrode. Electropolymerization was carried out in sodium acetate medium. The surface of the fabricated electrode was characterized with field emission scanning electron microscope and energy-dispersive X-ray spectrometry. The obtained results show that there are Sn nanoparticles in the structure of the catex-composite. Chemical structure of metal-catex composite electrode was investigated using FTIR (ATR), 13C NMR, H NMR and a suitable mechanism for electropolymerization has been proposed. This metal-catex composite electrode was applied for determinations of PQ using sodium acetate buffer solutions at pH = 6.5 as an electrolyte solution. All parameters influencing the performance of the fabricated electrode were studied and optimized. The proposed electrode exhibits good linearity versus PQ concentration in the range of 3.8 × 10−8 to 7.7 × 10−7 mol L−1 and shows a manifold increase in sensitivity (more than 30 times) as compared to the glassy carbon electrode. The LOQ of this electrode was 7.78 × 10−9 mol L−1, which is comparable with that of other electrochemical methods. The mean, standard deviation and relative standard deviation for seven repetitive determinations of paraquat (7.78 × 10−8 mol L−1) were measured to be 7.75 × 10−8 mol L−1, ±0.29 × 10−8 mol L−1, and 3.75% respectively. This electrode was applied for the determination of paraquat in natural water, natural juice, potatoes and onions. The introduced electrode shows good stability with repeated use and over long periods (about 20 days). There is a good agreement between the results for water analysis by this method and the standard method.

An estimation of sulfur concentrations released by three algae (Chlorella vulgaris, Chlamydomonas reinhardtii, Scenedesmus obliquus) in response to variable growth photoperiods.

In this study, we estimated extracellular concentrations of algal-derived sulfur species in response to changing photoperiods. Cultures from three algal species (Chlorella vulgaris, Chlamydomonas reinhardtii, Scenedesmus obliquus) were subjected to five different light:dark cycles (12:12, 14:10, 16:8, 18:6, 20:4h) for a period of 3days. Sulfur compounds including total reactive thiol concentrations, electroactive reduced sulfur species (RSS), and thiol isomers were measured using qBBr fluorescence, differential pulse cathodic stripping voltammetry (DP-CSV), and high-resolution mass spectrometry (HRMS), respectively. Total reactive thiol concentrations were greater in Scenedesmus than in Chlamydomonas and Chlorella at low light regimes (i.e., 12:12h) whereas Chlamydomonas produced more RSS than the other two species (p < 0.05) at any light regime. Scenedesmus was the only responsive species to produce maximal electroactive RSS, and HRMS equivalent thiol compounds under low light regime, congruent with previous studies. Principal component analysis revealed relationships between qBBr-equivalent thiol and GSH-equivalent RSS concentrations for Scenedesmus and Chlamydomonas (p < 0.05) suggesting that thiols were the dominant species in the pool of electroactive RSS for these two algal species. Overall, these results showed that the light growth conditions greatly influenced the production of S-rich compounds by algae, affecting the complexation of metals such as mercury and cadmium, especially during planktonic blooms.

Phaeophyceae and rhodophyceae macroalgae from the Antarctic: A source of selenium

This study reports the development of a voltammetric method applied for Se determination in Phaeophyceae (A. utricularis, C. jacquinotii, A. mirabilis, D. anceps, H. grandifolius) and Rhodophyceae (G. confluens, C. racovitzae, I. cordata) macroalgae from the Antarctic. Evaluation of the instrumental parameters showed the square wave cathodic stripping voltammetry provided greater sensitivity (deposition potential, -0.4 V; deposition time, 420 s; amplitude, 0.08 V; frequency, 60 Hz) than influence of differential pulse cathodic stripping voltammetry. The matrix effect and the influence of Cu concentration on the determinations were also assessed. After microwave-assisted digestion of the samples, the quantification limit was from 5.21 × 10−3 (G.confluens) to 9.85 × 10−3 mg kg-1 (I. cordata). The quantification of Se was carried out over the concentration range from 0.23 (C. jacquinotii) to 1.22 mg kg-1 (A. mirabilis). The method accuracy was by analysing the reference material of peach leaves (SRM 1547).

Chemically modified electrode based on dihexadecyl hydrogen phosphate and carbonaceous materials: improvement of analytical and electrochemical features applied to uranium determination

This work deals about the evaluation and improvement of analytical and electrochemical features of chemically modified electrode based on dihexadecyl hydrogen phosphate (DPH) and carbonaceous materials. The electrochemical features of films obtained were evaluated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Between the modifications evaluated, the glassy carbon electrode (GCE) modified with CB and DPH (DHP-CB/GCE) showed lower resistance to charge transfer and higher electron transfer rate. Additionally, the highest current of U(VI) was obtained with DHP-CB/GCE in a very stable way, the process present quasi-reversible behavior and it is controlled by a mixture of diffusion and absorption. The best instrumental conditions for U(VI) determination were obtained applying frequency of 15 Hz, amplitude of 100 mV, and deposition potential of − 0.1 V (by square wave cathodic stripping voltammetry). Among the electrolyte compositions (acetate and citrate buffers), ionic strength (from 0.10, 0.15, to 0.20 mol L−1), and pH (from 3.6 to 5.6) evaluated, the highest current of U(VI) were obtained in 0.15 mol L−1 of acetate buffer, pH 5.6. The method was accurate, linear, and sensitive (detection limit of 0.088 μg L−1 using 300 s of deposition).

Development of a sequential injection analysis device and its application for the determination of Mn(II) in water

A sequential injection analysis device has been developed and applied for the automated determination of Mn(II) in environmental water samples. Differential pulse cathodic stripping voltammetry is selected as the electrochemical detection method. The device consists of several electronic equipment. The electrochemical flow cell was designed for replacing the traditional three-electrode system and introducing high reproducibility. An electrochemical analyzer saddled with laboratory-programmed software written by Embarcadero Delphi 10.2. For higher current response, various determination parameters such as the flow rate, the medium pH, the deposition potential and the thickness of gasket in the electrochemical flow cell have been optimized. Under the optimal conditions, the detection limit (3σ/slope) of 0.63 μg L−1 and a calibration curve (R2 = 0.9987) of current response and Mn(II) concentration from 2.5 μg L−1 to 200 μg L−1 could be achieved. The device was successfully applied to the determination of trace Mn(II) in environmental water samples, and in continuous real-time monitoring of Mn(II) variations in tap water for 14 days. The results are consistent with the reference method and the average recovery is found to be 95.2%–101.4%. The device shows high sensitivity and reproducibility in the determination of Mn(II), and presents a great potential for on-site and real-time detection of metal ions where rapid, low-cost and low-volume analysis is required.