Differential Pulse Cathodic Stripping Voltammetry Research Articles

Microelectrode Voltammetric Analysis of Low Concentrations of Se(IV) Ions in Environmental Waters.

The current research is an attempt to analyze on-site selenium(IV) ions in environmental water samples using an eco-friendly miniaturized sensor developed by deposition of a very thin amount of metallic bismuth in a solid Bi electrode tightly closed in miniaturized housing. Numerous experimental variables are optimized, including the composition of the supporting electrolyte and its pH, as well as activation and accumulation conditions. Under optimized measurement conditions, the method shows high sensitivity, permitting a very low limit of detection equal to 7 × 10-10 mol L-1 to be achieved in a short accumulation time of 50 s. The performance of this microsensor was investigated against numerous interference factors and its good anti-interference capability was demonstrated. A series of voltammetric experiments by differential pulse cathodic stripping voltammetry (DPCSV) were carried out and they proved that the miniaturized sensor is characterized by very good accuracy and precision as well as long-term stability. The solid bismuth microelectrode displays a good voltammetric response in the analysis of diverse samples with a complex matrix and demonstrates a good recovery rate.

Electro-kinetic investigations and voltammetric detection of anti-ulcer drug cinitapride at low-cost pencil graphite electrode

Herein, we proposed a cost-effective, eco-friendly, fast and sensitive square wave cathodic stripping voltammetry (SWCSV) and differential pulse cathodic stripping voltammetry (DPCSV) methods for the quantification of anti-ulcer drug cinitapride in pharmaceuticals. Cinitapride electrochemically reduced at pencil graphite electrode and gave an irreversible well-defined cathodic peak in cyclic, square wave, and differential pulse voltammograms. The effect of pH of buffer, scan rates, and drug concentration on peak current and peak potential were studied. The reduction of cinitapride at pencil graphite electrode was diffusion controlled and occurred via participation of two electrons and two protons (2e−/2H+). The various electro-kinetic parameters such as diffusion coefficient(Do), surface coverage (T o)and electron transfer coefficient (α) were calculated, additionally, the mechanism of reduction of cinitapride at pencil graphite electrode was also proposed. The peak currents vary linearly in the concentration range 2.48 μmolL−1 to 17.39 μmolL−1 for all the voltammetric techniques. The obtained value of LOD for SWCSV and DPCSV techniques were2.48 μmolL−1 and 3.19 μmolL−1, respectively, which proved higher sensitivity of the proposed methods.

Voltammetric Determination of Copper by Biosorption‐based Mesorhizobium Opportonistum Modified Microbial Biosensor

In this study, Cu (II) was determined with a carbon paste electrode modified with Mesorhizobium opportonistum bacteria species used for the first time in the production of a microbial biosensor (MOMB). Cu (II) ions were first accumulated on an electrode surface via open circuit, then electrochemical determination was conducted with cyclic and differential pulse cathodic stripping voltammetry techniques. Experimental conditions such as pH, scan rate etc. were optimized. The MOMB exhibited linearity in the range of 5.0×10−8 M to 2.0×10−6 M for Cu (II) (correlation coefficients: 0.9914) with detection limit (LOD) of 2.0×10−8 M, a limit of quantification (LOQ) 6.64×10−8 M and a detection sensitivity (10.34 μA/μM), for Cu (II). The electrode-to electrode reproducibility of the MOMB was found to be 2.41 % (n=6) coefficient of variation. The MOMB has advantages for Cu (II) determination, including good sensitivity and reproducibility, easy preparation, low cost, applicability to sample and not having a need for additional chemical processes.

A Highly Sensitive Modified Glassy Carbon Electrode with a Carboxylated Multi-walled Carbon Nanotubes/Nafion Nano Composite for Voltammetric Sensing of Dianabol in Biological Fluid.

The extraordinary prerequisite for the analysis of an anabolic steroid, namely dianabol (DB), has inspired towards the development of a cost-effective and high-performance sensing probe. Thus, a simple and robust electrochemical sensor (c-MWCNTs-Nafion®lGCE) for dianabol (DB), a widely used steroid, was developed using a glassy carbon electrode (GCE) modified with functionalized carboxylated multi-walled carbon nanotubes (c-MWCNT) and Nafion®. At pH 7 - 8, differential pulse-cathodic stripping voltammetry (DP-CSV) displayed two cathodic peaks at -0.85 and -1.35 V that varied linearly over a wide range (9.0 × 10-9 (2.7 μg L-1) - 9.0 × 10-6 (2.7 × 103 μg L-1) mol L-1) and 2.9 × 10-6 (8.7 × 102 μg L-1) - 8.0 × 10-5 (2.4 × 104 μg L-1) mol L-1) of DB concentrations, respectively. The low limits of detection and quantification at peak I (-0.85 V) were 2.7 × 10-9 (8.1 × 10-1 ng mL-1) and 9.0 × 10-9 (2.7 ng mL-1) mol L-1, respectively. The repeatability and reproducibility displayed relative standard deviations lower than 5%. The method was applied for DB analysis in human urine and subsequently compared with the standard HPLC method. Interference of common metabolites in biological fluids samples to DB sensing was insignificant. This method has distinctive advantages e.g. precise, short analytical time, sensitive, economical, reproducible and miniaturized sample preparation for DB analysis in biological samples of human origin.

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.

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.

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).

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.

2,2-Hydroxyphenylbenzoxazole as a selective chelating agent for complexation with Tin and Zinc: a voltammetry study

A highly selective and sensitive adsorptive stripping procedure for simultaneous determination of trace tin and zinc is presented. The method is based on adsorptive accumulation of the complexes of Sn (II) and Zn (II) ions with 2, 2-hydroxyphenylbenzoxazole (HBO) onto a hanging mercury drop electrode, followed by the reduction of the adsorbed species by differential pulse cathodic stripping voltammetry. The optimal experimental conditions include the use of 0.1 M acetate buffer (pH 5.0), 2.0×10-5 M HBO, an accumulation potential of -0.35 V (versus Ag/AgCl), an accumulation time of 90 s and a scan rate of 100 mV/s. Under optimised conditions, linear calibration curves were established for the concentration of Sn(II) and Zn(II) in the range of 0.2 -100 µg/L and 0.1- 120 µg/L, respectively, while the detection limit is 0.009 µg/L for tin and 0.01µg/L for zinc for a 90 s adsorption time. The method was applied to the determination of tin and zinc in biological samples with satisfactory results.

Doxorubicin determination using two novel voltammetric approaches: A comparative study

Doxorubicin (DOX) represents an anthracycline-based antitumor and antibiotic medication. DOX determination in body fluids is relevant for treatment, monitoring, and individual dosage optimization. Two novel methods of DOX determination have been compared in this manuscript: i) differential pulse cathodic stripping voltammetry (DPCSV) on a polished silver solid amalgam electrode (p-AgSAE) in a specially designed micro-volume voltammetric cell (MVVC) and ii) differential pulse voltammetry (DPV) on a polarized liquid/liquid interface represented by a supported membrane prepared by impregnating a polyvinylidenfluoride microporous filter with a room-temperature ionic liquid (RTIL) tridodecylmethylammonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TDMA-TFPB). Moreover, elimination voltammetry with linear scan (EVLS) has been applied for elucidation of controlling reaction processes observed at the p-AgSAE.DPCSV method on the p-AgSAE is applicable for the determination of DOX in the linear dynamic range (LDR) from 0.6 to 10 μmol L−1, with the limit of detection (LOD) of 0.44 μmol L−1. Applicability of this method was verified on analysis of spiked samples of tap water (recovery 100.6 ± 6.6%, relative standard deviation (RSD) 5.9%, on the DOX level of 1.0 μmol L−1) and human urine (recovery 100.7 ± 6.6%, RSD 4.3%, on the DOX level of 1.0 μmol L−1).Using the above-mentioned innovative liquid/liquid interface method, similar results have been achieved (LOD of 0.84 μmol L−1, LDR from 1 to 40 μmol L−1). Nevertheless, due to the presence of some interfering compounds and of charged lipophilic compounds, this method must be preceded by a separation step in the case of body fluids analysis.

Electrochemical Evaluation of Selenium (IV) Removal from Its Aqueous Solutions by Unmodified and Modified Graphene Oxide.

The removal of selenium from superficial and waste water is a worldwide problem. The maximum limit according to the World Health Organization (WHO) for the selenium in the water is set at a concentration of 10 μg/L. Carbon based adsorbents have attracted much attention and recently demonstrated promising performance in removal of selenium. In this work, several materials (iron oxide based microparticles and graphene oxides materials) and their composites were prepared to remove Se(IV) from water. The graphene oxides were prepared according to the simplified Hummer’s method. In addition, the effect of pH, contact time and initial Se(IV) concentration was tested. An electrochemical method such as the differential pulse cathodic stripping voltammetry was used to determine the residual selenium concentration. From the experimental data, Langmuir adsorption model was used to calculate the maximum adsorption capacity. Graphene oxide particles modified by iron oxide based microparticles was the most promising material for the removal of Se(IV) from its aqueous solution at pH 2.0. Its adsorption efficiency reached more than 90% for a solution with given Se(IV) concentration, meanwhile its maximal recorded adsorption capacity was 18.69 mg/g.

Nylon 6,6 modified screen printed carbon electrodes as electrochemical sensors for rapid chlorothalonil determination in water samples using differential pulse cathodic stripping voltammetry

A newly developed electrochemical sensor for chlorothalonil based on nylon 6,6 film deposited onto screen printed electrode (SPE) with electrochemical modulation of pH at the electrode/solution interface was studied for the first time. Differential pulse cathodic stripping voltammetry (DPCSV) was used to carry out the electrochemical and analytical studies. Experimental parameters such as accumulation potential, initial potential, accumulation time and pH of Britton-Robinson buffer have been optimized. Chlorothalonil gave optimum analytical signal in a medium of 0.04 M Britton-Robinson buffer at pH 6.0. A well-defined reduction peak was observed, at Ep= −0.851 and −0.938 V vs. Ag/AgCl (3.0 M KCl) for both bare SPE and modified SPE, respectively. The peak currents of modified SPE were significantly increased as compared to bare SPE. At the modified SPE, a linear relationship between the peak current and chlorothalonil concentration was obtained in the range from 0.1 to 2.8 × 10−6 M with a detection limit of 1.53 × 10−8 M (S/N= 3). The practical applicability of the newly developed method has been demonstrated on analyses of real water samples. The newly developed sensor shows good reproducibility with RSD of 3.92%. The nylon 6,6 modified SPE showed itself as promising sensor with good selectivity for chlorothalonil determination.

Green sensors for voltammetric determination of lindane in water samples using bare and nylon 6,6 modified pencil electrodes

Lindane, an insecticide, was determined using the differential pulse cathodic stripping voltammetry technique on bare and nylon 6,6 modified pencil electrodes.

Determination of Paraquat Dichloride from Water Samples Using Differential Pulse Cathodic Stripping Voltammetry

Paraquat dichloride commonly used as herbicide was determined by differential pulse cathodic stripping voltammetry technique. Experimental parameters, such as pH, accumulation time, accumulation potential and initial potential were optimized. In this analysis, paraquat dichloride exhibited a well-defined tworeduction peaks at −0.35 and −0.90 V in the pH range from 2.0 to 12.0. The 0.04 mol L–1 BR buffer at pH 2.0 was found a suitable medium for electroanalytical determination of the paraquat dichloride. Interfering ions effect was not significant. Linear calibration plots for standard solutions of paraquat dichloride were obtained in the range of 0.25 to 1.75 × 10–6 mol L–1. Detection limit was 3.66 × 10–8 mol L–1. The optimized parameters were effectively applied for the determination of commercial paraquat dichloride and in artificial samples. Artificial samples were prepared by spiking paraquat dichloride into tap water and drinking water dispenser samples. The recovery value was 90.5% in drinking water dispenser samples and 91.7% in tap water samples at the concentration range of 1.00 × 10–6 to 1.75 × 10–6 mol L–1.

Selective determination of niobium in natural waters at the low ng L− 1 level by differential pulse cathodic stripping voltammetry in the presence of pyrogallol red

A completely selective method for electrochemical determination of very low concentrations (ngL−1) of niobium is presented. The method relies on the cathodic reduction of the pyrogallol red‑niobium complex at pH3. Virtually no sample preparation (apart from cation exchange) is required. The method is both free from interferences (particularly from Ta) and affordable. Time consuming preconcentration and separation procedures as well as the use of hydrofluoric acid, fluorides or problematic solvents are avoided. The applicability of the method is illustrated through analysis of mineral waters containing niobium concentrations ranging from 1 to several hundred ngL−1.

A simple voltammetric determination of metsulfuron-methyl in water samples using differential pulse cathodic stripping voltammetry.

The voltammetric determination of metsulfuron-methyl, a type of pesticide, was investigated on a hanging mercury drop electrode using a differential pulse cathodic stripping voltammetry technique. The experimental parameters, such as the pH of the Britton-Robinson buffer, accumulation time, accumulation potential and initial potential were optimized for the metsulfuron-methyl determination. A well-defined reduction peak was observed at pH 2.0 to 4.0 in the potential range of -0.75 to -1.0 V. The pH of 2.0 was chosen as the optimum pH due to a good stripping signal of the reduction peak. There were no significant interfering ion effects on the electroanalysis of metsulfuron-methyl. The optimized parameters were then used to determine metsulfuron-methyl in the commercial pesticide Ally. The proposed method was highly sensitive due to the lower limit of determination (0.04 mg/L), being relatively selective, and consisting of good precision. The recovery values achieved were about 93% in water samples for this analysis.

A novel Pb-poly aminophenol glassy carbon electrode for determination of tetracycline by adsorptive differential pulse cathodic stripping voltammetry

A novel type of Pb-polyaminophenol filmed glassy carbon electrode for adsorptive cathodic stripping analysis of trace amounts of tetracycline was developed. The Pb-polymer electrode was fabricated in situ by simultaneous electrodeposition of Pb and cathodic electropolymerization of 4-nitrophenol in a sodium acetate medium at −1.5volt. The prepared Pb-polymeric film was characterized by CV, FT-IR (ATR), H-NMR, SEM, EDS and a suitable mechanism for the electrode-reaction was proposed. The outputs of some experiments showed that tetracycline can be adsorbed on the surface of this Pb-polymer filmed electrode in an open circuit condition. Therefore it was used in adsorptive cathodic stripping analysis of tetracycline. The response of the electrode was enhanced in the presence of cetyltrimethylammonium bromide. Some parameters affecting the performance of the electrode were studied and optimized. The response of the electrode was linear in the range of 5×10−8−1×10−5molL−1 of tetracycline with a correlation coefficient of 0.9981. The relative standard deviation for 5×10−7molL−1 of tetracycline was 1.8% (n=5). The L.O.D and L.O.Q were 4×10−9 and 1.3×10−8molL−1 of tetracycline, respectively. The introduced electrode was used for determination of tetracycline residues in some samples and the obtained results were in good agreement with the results of HPLC.

Seasonal variation and mixing behaviour of glutathione, thioacetamide and fulvic acids in a temperate macrotidal estuary (Aulne, NW France)

Fulvic acids and two dissolved reduced sulphur substances (RSS) were analysed for one year along the whole salinity gradient in the Aulne estuary (north-western France) using differential pulse cathodic stripping voltammetry. Concentrations of glutathione-like (GSH-like), thioacetamide-like (TA-like) and fulvic acid-like (FA-like) compounds ranged from 0.2 to 38 nmol L−1, from 0.02 to 6.6 μmol L−1 and from 0.1 to 4 mgC L−1, respectively. Our results indicated primarily allochthonous-continental sources for all three compounds. The behaviour of GSH-like compounds along the salinity gradient was globally conservative, with minor losses (<25%), possibly limited due to metal complexation. TA-like compounds generally displayed non-conservative behaviour with important removals. In terms of the TA-like budget, losses were counterbalanced by exceptional inputs occurring in the flood period (February). FA-like compounds were intensely degraded (∼50%) in the last section of the river and then behaved conservatively in the estuary. The annual flux of FA-like compounds to coastal waters was 2800 ± 600 tC. This flux was mainly (74%) delivered during the high discharge period, in accordance with its known pedogenic origin.

A Sensitive Reduced Graphene Oxide-Antimony Nanofilm Sensor for Simultaneous Determination of PGMs

Electrochemical kinetics of Platinum Group Metals was studied by cyclic voltammetry and the concentration of these metal ions was successfully detected by adsorptive differential pulse cathodic stripping voltammetry using a GCE/rGO-SbNPs sensor. The sensor constructed in this work consisted of a reduced graphene oxide film that was impregnated with antimony nanoparticles. The constructed nanosensor provided an excellent platform for the simultaneous determination of Pd (II), Pt (II) and Rh (III) metal ions. The analytical curve was linear in the concentration range from 0 - 0.40 ng L-1, and 0 - 0.56 ng L-1 for Pd (II)-Rh (III) and Pt (II)-Rh (III), respectively. The detection limits of Pd (II) and Rh (III) were found to be 0.46 ng L-1and 0.55 ng L-1, respectively while for Pt (II) and Rh (III) it was 0.52 ng L-1and 0.48 ng L-1, respectively. The relative standard deviation from 5 measurements for 0.4 ng L-1 Pd (II)-Rh (III) and Pt (II)-Rh (III) by using the GCE/rGO-SbNPs sensor was found to be 6.21% and 3.96%, respectively. Interferences by other metal ions were also studied.