Differential Pulse Anodic Stripping Research Articles

Electrochemical determination of sorafenib by chronopotentiometry and ASDPV based on novel molecularly imprinted polymer and their applications in oncology patients

A promising selective and sensitive biosensor was fabricated for the first time to monitor trace amounts of sorafenib (SORF), a multi-target kinase inhibitor, based on the electropolymerization of pyrrole on a carbon paste electrode (CPE). To prepare a modified CPE, the prepared metal organic framework (NH2-MIL-101(Fe)) was mixed with graphite powder in the presence of an appropriate amount of paraffin oil before it was packed into a plastic tube containing a copper wire. Computational studies appreciate the use of pyrrole as the functional monomer for electropolymerization at the CPE surface using chronopotentiometry in the presence of SORF as a template. After the leaching of SORF, the imprinted sensor was characterized using FT-IR, SEM, and AFM, while NH2-MIL-101(Fe) was investigated by XRD, XPS, and SEM analysis. Under optimum conditions, SORF was detected using anodic stripping differential pulse voltammetric and chronopotentiometric techniques. High sensitivity (6.40 × 10−12 mol/L), excellent selectivity, and a wide linear range (4.20 × 10−11–7.10 × 10−3 mol/L) were recorded. Furthermore, the proposed sensor exhibited good repeatability (RSD = 2.40 % for n = 7) and high lifetime stability (∼7 weeks). Based on the above-mentioned merits, the designed electrochemical sensor was properly utilized for SORF determination in different oncology patients with satisfactory results (recovery = 94.40–99.90 %).

Fabrication of an Organofunctionalized Talc-like Magnesium Phyllosilicate for the Electrochemical Sensing of Lead Ions in Water Samples.

A talc-like magnesium phyllosilicate functionalized with amine groups (TalcNH2), useful as sensor material in voltammetry stripping analysis, was synthesized by a sol–gel-based processing method. The characterizations of the resulting synthetic organoclay by scanning electron microscopy (SEM), X-ray diffraction, N2 sorption isotherms (BET method), Fourier transform infrared spectroscopy (FTIR), CHN elemental analysis and UV–Vis diffuse reflectance spectroscopy (UV–Vis-DRS) demonstrated the effectiveness of the process used for grafting of amine functionality in the interlamellar clay. The results indicate the presence of organic moieties covalently bonded to the inorganic lattice of talc-like magnesium phyllosilicate silicon sheet, with interlayer distances of 1568.4 pm. In an effort to use a talc-like material as an electrode material without the addition of a dispersing agent and/or molecular glue, the TalcNH2 material was successfully dispersed in distilled water in contrast to natural talc. Then, it was used to modify a glassy carbon electrode (GCE) by drop coating. The characterization of the resulting modified electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed its charge selectivity ability. In addition, EIS results showed low charge transfer resistance (0.32 Ω) during the electro-oxidation of [Fe(CN)6]3−. Kinetics studies were also performed by EIS, which revealed that the standard heterogeneous electron transfer rate constant was (0.019 ± 0.001) cm.s−1, indicating a fast direct electron transfer rate of [Fe(CN)6]3− to the electrode. Using anodic adsorptive stripping differential pulse voltammetry (DPV), fast and highly sensitive determination of Pb(II) ions was achieved. The peak current of Pb2+ ions on TalcNH2/GCE was about three-fold more important than that obtained on bare GCE. The calculated detection and quantification limits were respectively 7.45 × 10−8 M (S/N = 3) and 24.84 × 10−8 M (S/N 10), for the determination of Pb2+ under optimized conditions. The method was successfully used to tap water with satisfactory results. The results highlight the efficient chelation of Pb2+ ions by the grafted NH2 groups and the potential of talc-like amino-functionalized magnesium phyllosilicate for application in electrochemical sensors.

Electrooxidation and Development of a Highly Sensitive Electrochemical Probe for Trace Determination of the Steroid 11-Desoxycorticosterone Drug Residues in Water

Anabolic-androgenic steroids (AASs), a class of compounds frequently misused by competitors and unfortunately by the general population, have lately attracted international attention. Thus, extraordinary demands for developing low cost, precise, rapid, and facile protocols for detection and/or determination of AAS have arisen. Hence, the current strategy explores for the first time the redox features of 21-hydroxypregn-4-ene-3, 20-dione, namely, 11-desoxycorticosterone (DCS) AA drug steroid at a glassy-carbon electrode (GCE) in a wide pH range (pH 2.0–10.0) by adsorptive differential pulse-anodic stripping voltammetry (DP- ASV) and cyclic voltammetry (CV). At pH 2, DP-ASV and CV at the optimized pH 2–3 displayed an irreversible anodic peak at 0.4 V versus Ag/AgCl electrode. The dependency of the anodic peak current of the CV at 0.4 V at various concentrations and scan rate of the DCS drug was characteristic of an electrode-coupled electron transfer of EE type mechanism. At the optimized parameters, the proposed strategy allowed quantification of DCS in the concentration range 2.5 -13.19 nM (0.83-4.36 ng mL−1) with satisfactory limits of detection (LOD) and quantization (LOQ) of 9.3 × 10−1 nM (3.1 × 10−1 ng mL−1) and 3.1 nM (1.02 ng mL−1), respectively. A relative standard deviation (RSD) of ±3.93% (n = 5) at 4.0 ng mL−1 DCS was achieved. The established probe was fruitfully employed and validated for trace determination of DCS residues in environmental water. The interference of several common diverse species on DCS sensing was insignificant revealing good selectivity. The established probe exhibited good sensitivity, selectivity, precision, and accuracy, short analytical time, and low cost compared with the reported methods, for DCS determination.

Electrochemical Behaviour of Gold Thin Film Glassy Carbon Electrode for Determination of Chromium(VI)

A modified glassy carbon electrode (Aufilm/GCE) using a gold film was constructed for determination of chromium(VI) in real water samples. A GCE was immersed in HAuCl4 solution (10-3 M) and the thin layer of gold was electrodeposited for 10 min at −0.4 V (vs. Ag/AgCl). Compared with only GCE, a strong affinity between chromium and gold species was observed with an increase in Cr(VI) signal. The type of supporting electrolytes, electrodeposition time, scan rate, pH, modulation time and the modulation amplitude were optimized through differential pulse-anodic stripping voltammetry (DP-ASV). A calibration graph acquired using the accumulation time of 120 s with a sensitivity of 1.3 × 10-2 μA/μgL-1 was linear in the range of 10-120 μg L-1. A low detection limit of 5.5 μg/L Cr(VI) and a strong correlation coefficient R2 = 0.9971 were obtained under the optimal experimental conditions. Signals were reproducible and exhibited a relative standard deviation of ±4.5%. A modified sensor was employed to determine the Cr(VI) content in the sewage water samples.

Lead ion selective electrodes from dibenzo-18-crown-6 derivatives: An exploratory study

Dibenzo-18-crown-6 (DB18C6) and three of its derivatives (-COCH3, -Br, -NO2), are investigated via Density Functional Theoretical (DFT) modelling, Fourier Transform Infrared (FT-IR) and absorption spectroscopies, Differential Pulse Anodic Stripping (DPASV), Cyclic (CV) and Square Wave (SWV) voltammetries, as possible materials for preparing plasticiser free lead(II) ion selective electrodes. The spontaneous, entropy driven, interactions between lead(II) ions and DB18C6 derivatives are such that they form 1:1 complexes via coordination with the high electron density open ether cavity, except for the brominated derivative where the metal: ligand stoichiometry is 2:1 due to exo-cavity coordination via the high electron density bromine atoms. Monolayers resulting from electropolymerization of some derivatives (-H, -COCH3, -Br) and chemisorption of the -NO2 derivative, allows quantification of lead(II) ions at concentrations below 10 mg L−1 with minimal interference from other metal ions except Hg2+ and Al3+.

Green Adsorptive Stripping Electrochemical Methods for Determination of Vortioxetine Hydrobromide at Graphite Pencil Electrode

Vortioxetine hydrobromide is a recently developed antidepressant drug which is associated with a great concern of suicide attempts. Herein, eco-friendly, inexpensive and sensitive electrochemical methods were developed to help control vortioxetine hydrobromide (VOR) at clinical safe level. The methods are based on anodic stripping differential Pulse (ASDPV), square wave (ASSWV) and linear sweep (ASLSV) voltammetry utilizing the high adsorption affinity of VOR on a graphite pencil lead. Several experimental parameters affecting the electrochemical oxidation process including pH, supporting electrolyte, scan rate and accumulation time were investigated. Calibration curves exhibited linear responses with detection limits of $2.0\times 10^{-8}$ M for the ASDPV and ASSWV, and $1.4\times 10^{-8}$ for the ASLSW. Evaluation of within-day repeatability and day to day precision using two different concentrations of the drug substance showed satisfactory accuracy and precision. The three methods were used successfully for the assay of VOR in the finished product. Furthermore, the ASSWV method was employed for the selective measurement of VOR in human plasma and urine samples.

A novel electrochemical method for the detection of oxymetazoline drug based on MWCNTs and TiO2 nanoparticles

Oxymetazoline, a nasal decongestant drug was investigated by a sensitive, simple and reproducible electrochemical method using Titania (TiO2) nanoparticles and carboxyl group functionalized multi-walled carbon nanotubes fabricated on glassy carbon electrode using cyclic voltammetry and differential pulse voltammetry. The possible electro-oxidation mechanism of this drug was also studied in detail. The performance of designed method was determined by electrochemical impedance spectroscopy, cyclic voltammetry and anodic stripping differential pulse voltammetry. The obtained results revealed enhanced electrochemical behavior of oxymetazoline as compared to bare glassy carbon electrode. Under optimum conditions i.e. buffer pH; pH7.0 phosphate buffer solution, accumulation potential; 0V, and accumulation time; 180s, the differential pulse voltammetric response of oxymetazoline was probed between the linear concentration range of 0.12μM to 1.5μM in aqueous medium containing pH7.0 PBS and 20% methanol. The limit of detection of oxymetazoline was evaluated as 4.40nM. Moreover, the developed sensing method was validated for its practical application in nasal spray with excellent recovery.

Determination of Ultra Trace Copper in Water Samples by Differential Pulse Polarography after Solid Phase Extraction

A high selective and sensitive anodic stripping differential pulse polarographic method for determination of ultra-trace amounts of Cu 2+ ion in water samples is proposed. The method is based on the separation and preconcentration of Cu 2+ on an octadecyl bonded silica (ODBS) membrane disk modified by a recently synthesized triazene ligand, ([1-(ortoacyl benzene)3-(3,4-dichlorobenzene)triazene]). Various parameters such as, pH of aqueous solution (7-8), flow rates (10 mL min -1 ), the amount of ligand (6.0 mg) and the type of stripping solvent (0.1M nitric acid) have optimized. The breakthrough volume was greater than 500 mL with an enrichment factor of more than 100 and 3.88µg L -1 detection limit. The capacity of the modified disks is 220µg of copper per 6mg of the ligand. The effects of various cationic interferences on the percent recovery of copper ion were studied. The method was successfully applied to the determination of copper ion in different samples. DOI: http://dx.doi.org/10.17807/orbital.v9i5.1093

Adsorptive anodic stripping differential pulse voltammetric determination of CellCept at Fe3O4 nanoparticles decorated multi-walled carbon nanotubes modified glassy carbon electrode

A simple and sensitive method based on adsorptive anodic stripping differential pulse voltammetry (AASDPV) for the determination of cellcept, using a magnetic Fe3O4 nanoparticles and functionalized (carboxylated) multi-walled carbon nanotubes modified glassy carbon electrode (f-MWCNs/Fe3O4/GCE) was developed. In phosphate buffer solution (pH = 5), the voltammogram of cellcept exhibited tow anodic peaks and the well-defined peak at about 0.611 V vs SCE was used for its monitoring. The modified electrode was characterized by different methods such as electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The experimental parameters, such as pH, deposition potential and time, as well as scan rate were optimized. Under the optimized conditions, Ip (μA) was proportional to the cellcept concentration in the range of 0.05–200 μM (R2 = 0.9989) with a detection limit of 9.0 nM and limit of quantification of 30.2 nM. The recovery was >98%. The practical analytical utilities of the modified electrode were demonstrated by the determination of cellcept in human urine and blood serum samples. Modified electrode showed an adequate sensitivity and stability for evaluated samples.

Sensitive stripping voltammetry detection of Pb(II) at a glassy carbon electrode modified with an amino-functionalized attapulgite

The electroanalysis of Pb2+ ions using an organoclay modified electrode is reported herein. The amine functionalized attapulgite used as electrode modifier was prepared by the covalent grafting of [3-(2-Aminoethylamino)propyl]trimethoxysilane (AEPTMS). The properties of the obtained hybrid material were studied by various physico-chemical techniques, including infrared spectroscopy, X-ray diffraction and CHN elemental analysis that together confirmed the effectiveness of the grafting process. The modified clay was then coated as thin film onto the active surface of a glassy carbon electrode (GCE) and the resulting modified electrode was evaluated for the electrochemical determination of Pb2+. A two-step analytical procedure was used: the accumulation at open circuit of Pb2+ and its detection by anodic stripping differential pulse voltammetry. Various experimental parameters that can influence i-E curves of Pb2+ at the GCE modified electrode were fully investigated and optimized. A linear response for Pb2+ was obtained in the concentration range from 4×10−12M to 4×10−11M, with a detection limit estimated at 0.88×10−12M (S/N=3). The interfering effect of some ions likely to influence the stripping determination of Pb2+ was evaluated and the proposed method was successfully applied to the analysis of laboratory tap water.

Electrochemical oxidation behavior of itraconazole at different electrodes and its anodic stripping determination in pharmaceuticals and biological fluids

The oxidation of itraconazole at three different electrodes; ultra-trace graphite (UTGE), pencil graphite (PGE) and carbon paste (CPE) electrodes were studied voltammetrically. After the optimization of solution pH, accumulation potential and accumulation time, anodic stripping differential pulse and anodic stripping square wave voltammetric peaks were obtained. The oxidation mechanism was proposed. Based on these findings, a simple and not time-consuming procedure was successfully applied for the determination of itraconazole in pharmaceutics and biological fluids.

Voltammetric determination of tannic acid in beverages using pencil graphite electrode

Vu D.L., Ertek B., Dilgin Y., Cervenka L. (2015): Voltammetric determination of tannic acid in beverages using pencil graphite electrode. Czech J. Food Sci., 33: 72-76. The pretreated pencil graphite electrode (Pre-PGE) prepared by a chronoamperometry technique was applied for the determination of tannic acid using anodic stripping differential pulse voltammetry. The currents obtained from voltammetry measurements at optimum conditions were linearly correlated with the concentration of tannic acid. Calibration curve was obtained for tannic acid in the concentration range of 5.0-500 × 10 -9 mol/l. The limit of detec - tion was found to be 1.5 × 10 -9 mol/l. The content of tannic acid in beverage samples determined with Pre-PGE was in good agreement with that obtained by the standard spectrophotometric method.

Sensitive Voltammetric Determination of Natural Flavonoid Quercetin on a Disposable Graphite Lead.

In this paper, a pencil graphite electrode was pretreated using chronoamperometry technique in phosphate buffer solution (pH=7.0) for sensitive determination of quercetin. Oxidation of quercetin was investigated using pretreated pencil graphite electrode and anodic stripping differential pulse voltammetry. Under optimal conditions, the anodic current of quercetin exhibited linear response to its concentration in the range from 0.001 to 1.5 µmol/L with the limit of detection of 0.3·10-3 µmol/L. The proposed method was successfully applied for the determination of quercetin in cranberry and blackcurrant juices with recovery rate from 93.2 to 94.7%. Solid-phase extraction was found to be necessary prior to voltammetric determination of quercetin in fruit juice samples using pretreated pencil graphite electrode.

Boehmite nanoparticle modified carbon paste electrode for determination of piroxicam

The voltammetric oxidation of piroxicam was studied at a carbon paste (CP) and boehmite nanoparticles modified carbon paste (BNP–CP) electrodes by cyclic voltammetry and its determination were carried out by anodic stripping differential pulse voltammetry. The experimental parameters, such as electrode composition, pH, scan rate, accumulation time and accumulation potential, were optimized. Under the optimal conditions at BNP–CP electrode, a linear relationship was realized between the anodic peak currents and piroxicam concentrations in the range of 0.5 to 100.0nM, with the detection limit of 0.11nM. The proposed method was applied to the determination of piroxicam in serum and pharmaceutical samples with the desirable results. Comparison of these results with that obtained by UV spectrophotometric method shows a good agreement between two methods.

On-line detection of Cu (II) in bioleaching system by anodic stripping differential pulse voltammetry

On-line Cu (II) ion concentration detection in bioleaching system was achieved by anodic stripping differential pulse voltammetry (ASDPV). Good linearity between Cu (II) concentration and oxidation peak current was obtained when Cu (II) existed in 0K media in the concentration range of 1 μmol/L (64 μg/L) to 1 mmol/L (64 mg/L). Moreover, when 0.2 mol/L KCl was added into this media, the linear detection range could be extended from 1 mmol/L to 100 mmol/L (6.4 g/L). The reduction of Cu (II) to metallic copper was shown to proceed as two successive single-electron transfer reactions involving an intermediate chemical step where the cuprous ion (Cu+) was complexed by chloride to form the dichlorocuprous anion (CuCl−). In addition, interference effect was also investigated when Fe3+ existed in the media, which was the common situation in the copper bioleaching system. The results showed no interference effect once the concentration of Fe3+ was less than 100 mmol/L (5.6 g/L).

DETERMINATION OF ANTI-CANCER DRUG EMODIN USING A SILICA-GEL-MODIFIED CARBON PASTE ELECTRODE

In this paper, a silica-gel-modified carbon paste electrode (Si-gel/CPE) was used to determine the anti-cancer drug emodin by anodic stripping differential pulse voltammetry (ASDPV). The effects of the silica-gel content, the pH of the supporting electrolyte, and the scan rate on the oxidation current of emodin were investigated. The oxidation currents of emodin obtained from ASDPV measurements were linearly correlated with the concentration in the range of 5.0 × 10-9 to 300.0 × 10-9 mol L-1. The limit of detection was determined to be 1.5 × 10-9 mol L-1. The current method was successfully applied to determine emodin in a knotweed root sample, with recovery rate of 92.5% to 98.3%.

Dendrimer-encapsulated copper as a novel oligonucleotides label for sensitive electrochemical stripping detection of DNA hybridization

This paper describes the synthesis and characterization of a novel electrochemical label for sensitive electrochemical stripping detection of DNA hybridization based on dendrimer-encapsulated copper. The generation 4.5 (G 4.5) carboxyl-terminated poly(amidoamine) dendrimer with a trimesyl core was used as a template for synthesis of Cu2+/dendrimer nanocomposites (Cu-DNCs). Ratios of Cu2+/dendrimer were optimized in order to obtain stable nanocomposites with maximal copper loading in the interior of a polymeric shell. Cu-DNCs labeled DNA probe was employed for determining a target ssDNA immobilized on multi-walled carbon nanotubes-modified glassy carbon electrode (GCE) based on a specific hybridization reaction. The hybridization events were monitored by electrochemical detection of Cu anchored on the hybrids after the release in a diluted nitric acid by anodic stripping differential pulse voltammetry (ASDPV). The results showed that only a complementary sequence could form a dsDNA with the Cu-DNCs DNA probe and give an obvious electrochemical signal. The non-complementary sequence exhibited negligible signal change compared with the blank measurement (means: the electrode containing no target DNA incubating in hybridization buffer solution containing Cu-DNCs DNA probe for a certain time). The use of Cu encapsulated-dendrimer as tags and ASDPV for the detection of the released Cu ions could enhance the hybridization signal, and result in the increase of the sensitivity for the target DNA. Under the conditions employed here, the detection limit for measuring the full complementary sequence is down to pM level.

Estimation of the Serum and the Salivary Trace Elements in OSMF Patients

Gutkha packets contain trace elements like copper, zinc, iron and magnesium. This study compared the levels of the trace elements in patients with gutkha eating habits with or without oral submucous fibrosis and in healthy patients. A total of 75 patients were included in this study and they were divided into three groups; the individuals with a history of gutkha intake with OSMF, the individuals with a history of gutkha intake without OSMF and apparently healthy individuals without OSMF and without any habits. Blood and saliva was collected and they were subjected for analysis by using atomic absorption spectrometry and a differential pulse anodic stripping voltmeter. The results were tabulated and they were subjected to a statistical analysis. There was a significant difference in the serum Mg and Fe levels between the patients with habits and the normal healthy individuals. A significant difference was observed in the serum zinc levels in the patients with habits with and without OSMF. Altered serum trace element levels are documented in malignant cases and they are considered to be good biomarkers for malignancies. The serum copper and Zn levels and the Cu/Zn ratio in OSMF patients can be considered as the markers which show a susceptibility towards cancer.

Self-assembled monolayer as a pre-concentrating receptor for selective serotonin sensing

We describe a novel medium, a captopril/thiophenol (Capt/TP) mixed self-assembled monolayer (SAM) formed on gold, for selectively pre-concentrating serotonin (5-hydroxytryptamine, 5-HT). The 5-HT molecules were shown to be selectively captured via formation of a strong complex, providing anodic stripping currents upon anodic scan or drastic increases in charge-transfer resistances for a redox probe, Fe(CN) 6 3−/4− pair, due to their blocking effects. The 5-HT molecules thus collected were subsequently detected by anodic stripping differential pulse voltammetry (ASDPV) or electrochemical impedance spectroscopy (EIS). The detection limit was 1.2 when detected by EIS and 28 nM with ASDPV. 5-HT was shown to be determined in physiological matrices containing ascorbic acid, dopamine, and other commonly encountered neurotransmitters.

1-Furoylthiourea-Sonogel-Carbon electrodes: Structural and electrochemical characterization

A new type of sensor based on Sonogel-Carbon materials modified with 1-(2-furoyl)-3-(1-naphthyl)thiourea is presented to be used as an amperometric sensor for metals. Different percentages of modifier were tested in order to optimise the structural and mechanical properties, as well as the electrochemical behaviour. Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Fourier transform-infrared spectroscopy (FTIR), single crystal X-ray diffraction (XRD) and powder XRD were used for the structural characterization of these electrodes. The 1-(2-furoyl)-3-(1-naphthyl)thiourea did not modify significantly the structural and mechanical properties of the Sonogel-Carbon electrodes, being similar to other modifications carried out previously in these materials. For the study of the electrochemical response, anodic stripping differential pulse voltammetry (ASDPV) was employed, optimising other parameters of measurement such as pH of the buffer, potential and accumulation time and pulse amplitude. The electrochemical response of the modified electrodes improved significantly with respect to the non-modified electrode, giving good signals and acceptable detection limit.