Differential Pulse Adsorptive Cathodic Stripping Research Articles

A simple, fast and inexpensive approach to quantify low concentrations of iron in biodiesel by voltammetry after extraction induced by microemulsion breaking.

An alternative approach to assay iron (Fe) in biodiesel by differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV) is presented herein. The sample treatment involved a simple, rapid, but effective extraction of Fe from biodiesel into an aqueous phase after microemulsion (ME) breaking. Then, Fe was determined as the complex Fe(III)-PAN (1-(2-pyridylazo)-2-naphthol) on a glassy carbon electrode (GCE) in the presence of bismuth (Bi(III)). The extraction induced by microemulsion breaking (EIMB) was achieved by adding 0.80 mL of ultrapure water into a water-in-oil ME containing 7.00 mL biodiesel, 2.70 mL n-propanol and 0.30 mL of 0.25 mol L-1 HNO3 solution. No deliberate addition of surfactant was necessary to form and maintain the ME. The EIMB resulted in a 1.30 mL lower aqueous phase extract (APhEx) and an upper oily phase. DP voltammograms were recorded with a portable potentiostat, showing the potentiality of carrying out the determination out of a central laboratory. Another feature was the non-necessity of deaerating the solution to eliminate the dissolved O2. The limits of detection (LOD) and quantification (LOQ) were 1.7 μg L-1 (140 mg kg-1) and 5.5 μg L-1 (455 mg kg-1), respectively. The accuracy of the method was evaluated by recovery assays of spiked samples, by analyzing a standard reference material and by comparisons with high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS).

Dopamine / Artesunate loaded polyhydroxybutyrate-g-cellulose- magnetite zinc oxide core shell nanocomposites: Synergistic antimicrobial and anticancer efficacy

In this study, polyhydroxybutyrate-g-cellulose - Fe3O4/ZnO (PHB-g-cell- Fe3O4/ZnO) nanocomposites (NCs) was synthesized and used as a delivery system for Dopamine (DO) /Artesunate (ART) drugs. Different types of cells (Ccell, Scell, Pcell) grafted with PHB were designed and mixed with different contents of Fe3O4/ZnO. Physical and chemical features of PHB-g-cell-Fe3O4/ZnO NCs were detected by FTIR, XRD, dynamic light scattering, transmission electron microscopy, and scanning electron microscopy. ART/DO drugs were loaded into PHB-g-cell- Fe3O4/ZnO NCs by single emulsion technique. The rate of drugs release was studied at different pHs (5.4, 7.4). Owing to the overlap between the absorption bands of both drugs, differential pulse adsorptive cathodic stripping voltammetry (DP-AdCSV) was used for the estimation of ART. To study the mechanism of ART and DO release, zero-order, first order, Hixon Crowell, Higuchi and Korsmeyer-Peppas models were applied to the experiment results. The results showed that Ic50 of ART @PHB-g-Ccell-10% DO@ Fe3O4/ZnO, ART @PHB-g-Pcell-10% DO@ Fe3O4/ZnO and ART @PHB-g-Scell-10% DO@ Fe3O4/ZnO were 21.22, 12.3, and 18.11 μg/mL, respectively. The results revealed that ART @PHB-g-Pcell-10% DO@ Fe3O4/ZnO was more effective against HCT-116 than the carriers loaded by a single drug. The antimicrobial efficacy of the nano-loaded drugs was considerably improved compared with free drugs.

Cyclic Voltammetric determination of an antidepressant drug (Duloxetine hydrochloride) by using glassy carbon electrodes in bulk form and human biological fluids

Duloxetine hydrochloride was measured by employing Differential Pulse Cathodic Adsorptive Stripping Voltammetry (DP-CAdSV) and Square Wave Cathodic Adsorptive Stripping Voltammetry at the glassy carbon electrode (GCE) in bulk form and human biological fluids. Duloxetine hydrochloride exhibited one distinct and well-defined cathodic peak in the potential range -0.80 to -0.85 V v/s Ag/AgCl/KCl reference electrode. Cyclic Voltammetry, DP-CAdSV and SW-CAdSV showed one reduction wave with peak potential -0.85 V at pH 7. The proposed method's excellent sensitivity was demonstrated by the obtained LOD of 2.233X10-8mol L-1and a LOQ of 7.445X10-8mol L-1bulk by applying DP-CAdSV). On the other hand, a LOD of 5.099X10-8mol L-1and a LOQ of 1.699X10-7mol L-1bulk Duloxetine hydrochloride were achieved by applying SW-CAdSV method. The described methods could be recommended for use in trace analysis, quality control and clinical laboratories.

Differential Pulse Adsorptive Cathodic Stripping Voltammetry for the Simultaneous Determination of Pb and Zn in Seawater Using Calcon

Differential Pulse Adsorptive Cathodic Stripping Voltammetry for the Simultaneous Determination of Pb and Zn in Seawater Using Calcon

Voltammetric sensing of fenitrothion in natural water and orange juice samples using a single-walled carbon nanohorns and zein modified sensor

A glassy carbon electrode (GCE) modified with single-walled carbon nanohorns (SWCNH) and zein (ZE), a prolamin type-protein find in maize, for the differential pulse adsorptive cathodic stripping voltammetric determination of fenitrothion (FT) is proposed. The proposed film was characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Regarding the electrochemical characterization, comparing the results obtained by cyclic voltammetry and electrochemical impedance spectroscopy, the modified electrode (SWCNH-ZE/GCE) showed an electroactive surface area 3 times higher and faster electron transfer kinetic than bare GCE. By using differential pulse adsorptive cathodic stripping voltammetry and SWCNH-ZE/GCE the analytical curve exhibited a linear response ranging of 9.9 × 10−7 to 1.2 × 10−5 mol L−1, with a limit of detection of 1.2×10−8 molL−1. The proposed sensor was successfully applied for the determination of FT pesticide in natural water and orange juice samples. Moreover, the electrochemical sensor showed good repeatability and reproducibility arising from the excellent film stability, suggesting that the proposed architecture has broad potential for applications in sensing and biosensing.

Electrochemical Determination of Anesthetic Drug Ropivacaine in Pharmaceutical Formulations by Differential Pulse Cathodic Adsorptive Stripping Voltammetry

Electrochemical Determination of Anesthetic Drug Ropivacaine in Pharmaceutical Formulations by Differential Pulse Cathodic Adsorptive Stripping Voltammetry

Electrochemical Behaviour and Differential Pulse Cathodic Adsorptive Stripping Voltammetric Determination of Carmustine

Electrochemical Behaviour and Differential Pulse Cathodic Adsorptive Stripping Voltammetric Determination of Carmustine

Determination of Diazepam and Clonazepam in Natural Water – a Voltammetric Study

AbstractThe differential pulse adsorptive cathodic stripping voltammetry (DP‐AdsCSV) employing the hanging mercury drop electrode (HMDE) was used towards the determination of two psychotropic drugs in environmental samples. Voltammetric and experimental conditions to Clonazepam (CLO) and diazepam (DIAZ) were optimized and the methods were in‐house validated. Accumulation potentials were −0.3 V to CLO and −0.6 V to DIAZ at 120 s of accumulation time. Pulse amplitude, pulse time and scan rate were 80 mV, 20 ms and 25 mV s−1 to CLO and 100 mV, 20 ms and 40 mV s−1 to DIAZ, respectively. Recovery tests were done in three different concentrations to evaluate methods’ accuracy and the results were from 88±6 to 120±13 %. In precision tests, standard deviations were lower than 15 % for both methods. Goods limits of quantification 0.65 and 0.27 μg L−1 to CLO and DIAZ respectively were achieved without pre‐concentration steps such as SPE, etc. Voltammetry employing HMDE was first used for the determination of CLO and DIAZ in natural water. Natural samples were spiked and recovery tests confirmed the applicability of the methods developed. Nine samples from Parana state, Brazil, were analyzed and CLO and DIAZ values were below the limits of detection in all samples.

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.

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.

Differential Pulse-Adsorptive Cathodic Stripping Voltammetric Determination of Sulfadiazine Drug in Pharmaceutical Formulations and Drug Residue in Wastewater at a Hanging Mercury Dropping Electrode

An adsorptive differential pulse cathodic stripping voltammetry method has been developed for determining the presence of sulfadiazine drugs. The method is based upon the adsorptive collection of the drug on a hanging mercury dropping electrode at −1.0 V versus Ag/AgCl reference electrode. Factors affecting the stripping performance such as, pH, accumulation time and potential, sweep rate were critically studied. The optimum conditions were achieved in a Britton–Robinson buffer of pH 5–6. At the optimal conditions, the cathodic stripping current of the drug at −1.0 V versus concentrations was linear in the concentration range \({3.7 \times 10^{-9}}\) –\({1.0 \times 10^{-7}\;{\rm mol L}^{-1}}\). The lower limit of detection and quantification of the drug were \({1.1 \times 10^{-9}}\) and \({3.7 \times 10^{-9} {\rm mol L}^{-1}}\), respectively. The method was successfully applied for the determination of industrial wastewater, pure form (\({98.2 \pm 3.1}\) %) and drug formulations (\({98.3 \pm 2.9}\) %). The method was validated by comparison with the standard HPLC and the reported methods. The method offers a simple system, coupled with good reproducibility, accuracy, ruggedness, and cost-effectiveness.

Reduced Graphene Oxide Impregnated Antimony Nanoparticle Sensor for Electroanalysis of Platinum Group Metals

AbstractA very sensitive electrochemical sensor based on a reduced graphene oxide film impregnated with antimony nanoparticles was prepared and applied to the electroanalysis of platinum group metal ions of Pd(II), Pt(II) and Rh(III). The electrochemical behavior of platinum group metals at the modified electrode was studied by adsorptive differential pulse cathodic stripping voltammetry in the presence of dimethylglyoxime as chelating agent. Several operational parameters were optimised to enhance the electroanalytical performance of the modified glassy carbon electrode sensor. The results showed sharp stripping peaks and a relatively constant peak potential with a good linear behaviour in the examined concentration range from 40 to 400 pg L−1 for all metal ions investigated. The detection limit was found to be 0.45, 0.49 and 0.49 pg L−1 (S/N=3) for Pd(II), Pt(II) and Rh(III), respectively. The developed electrochemical sensor also exhibited good precision with a relative standard deviation of 4.2 %, 2.55 % and 2.67 % for 5 successive measurements for Pd(II), Pt(II) and Rh(III), respectively. The proposed nanostructure showed good sensitivity and stability, which has promising potential applications in electrochemical sensors.

Rapid Screening Method for Detecting Ethinyl Estradiol in Natural Water Employing Voltammetry

17α-Ethinyl estradiol (EE2), which is used worldwide in the treatment of some cancers and as a contraceptive, is often found in aquatic systems and is considered a pharmaceutically active compound (PhACs) in the environment. Current methods for the determination of this compound, such as chromatography, are expensive and lengthy and require large amounts of toxic organic solvents. In this work, a voltammetric procedure is developed and validated as a screening tool for detecting EE2 in water samples without prior extraction, clean-up, or derivatization steps. Application of the method we elaborate here to EE2 analysis is unprecedented. EE2 detection was carried out using differential pulse adsorptive cathodic stripping voltammetry (DP AdCSV) with a hanging mercury drop electrode (HMDE) in pH 7.0 Britton-Robinson buffer. The electrochemical process of EE2 reduction was investigated by cyclic voltammetry at different scan rates. Electroreduction of the hormone on a mercury electrode exhibited a peak at −1.16 ± 0.02 V versus Ag/AgCl. The experimental parameters were as follows: −0.7 V accumulation potential, 150 s accumulation time, and 60 mV s−1 scan rate. The limit of detection was 0.49 μg L−1 for a preconcentration time of 150 s. Relative standard deviations were less than 13%. The method was applied to the detection of EE2 in water samples with recoveries ranging from 93.7 to 102.5%.

Selective and Sensitive Determination of Uranyl Ions in Complex Matrices by Ion Imprinted Polymers‐Based Electrochemical Sensor

AbstractWe report on the design of a UO22+‐selective electrode based on the use of UO22+ imprinted polymer nanoparticles (IP‐NPs), and its application for the differential pulse adsorptive cathodic stripping voltammetry determination of uranyl ions. A carbon paste electrode was modified with the IP‐NPs, and differential pulse adsorptive cathodic stripping voltammetry was applied as the detection technique after open‐circuit sorption of UO22+ ions. The modified electrode responses to UO22+ was linear in the 0.1 µg L−1 to 10 µg L−1 and in the 0.01 mg L−1 to 10 mg L−1. The method detection limit of the sensor was 0.03 µg L−1.

Organic complexation of iron in the West Atlantic Ocean

The characteristics of the dissolved iron (DFe) binding organic ligands were determined during 3 Dutch GEOTRACES cruises covering the length of the West Atlantic Ocean. Adsorptive Differential Pulse Cathodic Stripping Voltammetry (AdDPCSV) with TAC as competing ligand was used to measure Fe binding organic ligands. Although the distribution of DFe is related to its sources, sinks and vertical processes, ultimately it is the solubility of Fe in seawater that determines its concentrations in the oceans. The Fe binding organic ligands increase the solubility of Fe. The total ligand concentration and the excess ligand over Fe concentration showed a decreasing trend from north to south in the surface ocean as well as in the North Atlantic Deep Water (NADW). This trend could be extended further north to the Arctic Ocean, where ligand concentrations were even higher. The Arctic might be a source of ligands to the northern West Atlantic Ocean. We calculated a residence time of 779 to 1039years for dissolved organic ligands in the NADW. This is 2.5 to 4 times larger than the estimated residence time of DFe in the NADW.The highest concentrations of excess ligands were found in the surface where the dissolved Fe concentrations were the lowest. This resulted in high ratios of [Lt]/DFe in the surface decreasing with depth to a value close to 2 below 500m, where more ligands were saturated. Dissolved organic ligands were saturated with Fe in a large part of the southern West Atlantic at mid-depth, where DFe concentrations increased due to hydrothermal activity.The inorganic Fe concentrations, [Fe′], were surprisingly uniform for the western Atlantic Ocean. Values ranged between 0.2 and 1pM in the deep Atlantic as well as in the surface, where ligands were unsaturated with Fe. However, in the hydrothermal influenced region, where ligands were (nearly) saturated, [Fe′] was high, possibly larger than the solubility product of the Fe(oxy)hydroxides and thus suggesting either high concentrations of colloidal Fe or particulate Fe. Our results showed that the dissolved Fe concentrations were strictly regulated by a steady state between complexation by ligands and adsorption/precipitation of particles, the extensive hydrothermal influenced area seemed to be an exception.

Voltammetric determination of copper with proton pump inhibitor drug omeprazole

The electrochemical behavior of copper(II)-omeprazole complex was studied by differential pulse and cyclic voltammetry at a hanging mercury drop electrode. A well-defined voltammetric peak was obtained at −0.6 V (vs. Ag/AgCl sat’d KCl) in phosphate buffer (pH 7). The experimental results show that the reduction of the copper(II)-omeprazole complex is irreversible. The stoichiometry and stability constant of the Cu(II)-omeprazole complex were evaluated using differential pulse cathodic adsorptive stripping voltammetry and found to be 1 : 2 and 1.39 × 1011 M−1. The limits of detection and quantitation were found to be 3 × 10−9 and 1 × 10−8 M, respectively. The proposed procedure was successfully applied for the determination of trace level of copper in bottled natural drinking water samples.

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.

Determination of ppt Level Chromium(VI) Using the Gold Nano-Flakes Electrodeposited on Platinum Rotating Disk Electrode and Modified with 4-Thiopyridinium

The nano-gold layer formed on the platinum rotating disk electrode (nano-Au/Pt-RD) inherited the catalytic property for Cr(VI) reduction from platinum surface and owned the good features of nano-gold such as insensitivity with hydrogen ion, high surface area, augmenting diffusion of Cr(VI) and ability for self-assembling with 4-pyridine-ethanethiol (PET) through Au←S linkages, to form PET/nano-Au/Pt-RD electrode capable of accumulating Cr(VI) from sample. The obtained PET/ nano-Au/Pt-RD electrode showed an extreme sensitivity to Cr(VI). By using this electrode, 1.09 ng·L﹣1 was the detection limit of differential pulse adsorptive cathodic stripping voltammetry for Cr(VI) with the accumulation time of only 2 min. Moreover, this electrode was reproducible with 3.5% RSD for 30 times of Cr(VI) accumulating and stripping. In addition, this electrode was also selective for Cr(VI) determination, which was not almost interfered by other inorganic ions.

A new biomimetic sensor based on molecularly imprinted polymers for highly sensitive and selective determination of hexazinone herbicide

A new selective sensor based on molecularly imprinted polymers (MIPs) was developed for the determination of hexazinone (HXZ) in environmental samples. MIPs were synthesized using a non-covalent approach, and selection of the monomers employed in the polymerization reaction was carried out by molecular modeling. Three functional monomers with high (2-vinylpyridine (MP17)) and intermediate (methacrylic acid (MP12) and acrylamide (MP5)) energies of binding to the template (HXZ) were selected for preparation of the MIPs, in order to conduct comparative studies and validate the theoretical data. For sensor construction, carbon pastes were modified with each MIP or NIP (non-imprinted polymer), and HXZ determination was performed using differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV). All parameters affecting the sensor response were optimized. In HCl at pH 2.5, the sensor prepared with MP17 (5% w/w in the paste) showed a dynamic linear range between 1.9×10−11 and 1.1×10−10molL−1, and a detection limit of 2.6×10−12molL−1, under the following conditions: accumulation time of 200s at a potential of −0.5V, scan rate of 50mVs−1, pulse amplitude of 60mV, and pulse width of 50ms. The sensor was selective in the presence of other similar compounds, and was successfully applied to the analysis of HXZ in river water samples.

Application of Nitrilotriacetic Acid Modified Gold Electrode for Determination of Lead in Natural Waters with Differential Pulse Adsorptive Cathodic Stripping Voltammetry

Application of Nitrilotriacetic Acid Modified Gold Electrode for Determination of Lead in Natural Waters with Differential Pulse Adsorptive Cathodic Stripping Voltammetry