Differential Pulse Polarography Research Articles

Green synthesis of new ionic liquid and its electrochemical determination at some detergents and cosmetics samples using differential pulse polarography

The 1-propargylpyridazinium bromide (PDB) was synthesized by using ultrasound irradiation as an eco-friendly and efficient process. The structure of PDB was characterized by different analysis such FT-IR, 1H NMR, 13C NMR, LCMS and elemental analysis. One of the principal goals of the present study was the determination of the synthesized (PDB) in some detergent and cosmetic samples by using the differential pulse polarography (DPP) as an efficient method. Different supporting electrolytes, pH, pulse amplitude, pulse time and sweep rate were evaluated in order to record a high cathodic current and good peak. It turned out that Britton-Robinson (B-R) supporting electrolyte, pH 4, pulse amplitude 90 mV, pulse time 30 ms and sweep rate 20 mV s−1, have given the best cathodic current and they were chosen to complete the electrochemical studies for PDB determination. Furthermore, the DPP technique has been performed by monitoring the reproducibility, stability, recovery, calibration curve and detection limit.

Role of pre-corrosion of Fe0 on its efficiency in remediation systems: An electrochemical study

The duration of in-situ generation of iron corrosion products (FeCPs) prior the remediation process (so called “aging” of metallic iron (Fe0)), was found as the key parameter affecting the efficiency of Fe0 for water remediation. Batch experiments were performed in buffered solutions (pH 4.0, 4.7 and 5.5) and under oxic conditions (presence of dissolved oxygen) using Zn2+ as probe contaminant. The time-dependent (0–16 d) concentration changes of aqueous Fe2+ and Zn2+ were monitored using differential pulse polarography (DPP). During the time of pre-corrosion varying from 0 to 6 d, an “induction period” of the corrosion occurs in the first one – 2 h when no Fe2+ ion is released in the solution. After this period, Fe2+ was identified in solution and its concentration progressively increases up to 6 h, then starts to decrease and after 6 d nearly disappears. Experiments with Zn2+ reveal that the most efficient Fe0 remediation occurs after 6 h of pre-corrosion. This coherence thus proves that the presence, the amount and the age of FeCPs (“degree” of corrosion) significantly impact the removal efficiency of Zn2+ in Fe0/H2O systems. The present study severely refute the wording ‘reactivity loss’ and states that progress in designing sustainable Fe0/H2O systems will not be achieved before the role of “active” FeCPs is clarified.

Heavy metals and arsenic content in water along the southern Caspian coasts in Iran.

Due to the importance of pollution monitoring in marine ecosystems and lack of a coherent and systematic investigation of heavy metal ions along the southern shores of the Caspian Sea, in the present study, the amount of these metals and As ions in coastal waters along its 780-km-long coast in Iran have been studied. Heavy metals (cobalt, nickel, copper, zinc, cadmium, mercury, lead) and a poisonous metalloid (arsenic) were selected in 59 sampling stations and determined using differential pulse polarography method. The multivariate statistical tools were applied to describe and interpret the experimental data. The overall mean concentrations of studied metals (in microgram per liter; μgL-1) in the samples were found in the order Zn (10.9) > Ni (7.4) > Cu (5.5) > Pb (1.9) > Hg (1.4) > As (1.3) > Co (1.1) > Cd (0.2). The results when compared with reported international standards confirmed that the sampled waters do contain some of these elements above the suggested maximum permissible limits. Hg and Cu were detected in 54.2 and 72.9% of the samples, almost all above the permissible limits. Ni, Zn, Pb, and Co were detected in 100, 96.6, 93.2, and 88.1%, respectively, while 8.5, 22.0, 3.4, and 1.7% were above the permissible limits. Cd and As were present in 61 and 93% of the samples, and their concentrations were higher than the rate presented by Russian System of Management Chemicals (RSMC). In addition, spatial distribution of heavy metal concentrations showed that Gorgan Bay is an ecosystem serving as a filter, trapping natural and anthropogenic materials that are brought from industrial, commercial, and urbanized areas. The multivariate data analysis reveals that Caspian Sea is contaminated by both anthropogenic as well as pedo-geochemical sources.

Polarographic determination of benzotriazoles and their sorption behavior on granular activated carbon

Because of their persistence and unknown environmental risks, the widespread occurrence of benzotriazoles has been gaining increased attention. A highly selective, rapid, and economical method—differential pulse polarography—was developed and applied for the quantitation of commercially significant methylbenzotriazole isomers in environmental samples of relevance to wastewater treatment, non-point source pollution and acid mine drainage. Differential pulse polarography was able to accurately measure aqueous methylbenzotriazole, as well as the methylbenzotriazole fraction that sorbed to activated sludge biomass, subsurface sediments, and activated carbon. Granular activated carbons were characterized for their ability to sequester benzotriazoles from aqueous environments using differential pulse polarography and high-performance liquid chromatography. Langmuir, Freundlich, Toth and Redlich–Peterson isotherm models were compared for their ability to describe benzotriazole partitioning to granular activated carbons under a relatively wide range of water quality conditions. Sorption behavior of 5-methylbenzotriazole was best-described by a Redlich–Peterson isotherm model, where water quality parameters were varied in the following range pH (1 < pH < 5), temperature (5 °C < T < 25 °C), and in the following ranges of an ionic strength (0.005 < M < 0.02). 4- and 5-methylbenzotriazole concentrations determined by differential pulse polarography correlated well with those concentrations measured by high-performance liquid chromatography through an environmentally significant range (0.4–30 mg/L). Using a static mercury drop electrode, the method detection limit was 50 and 40 μg/L for 4- and 5-methylbenzotriazole, respectively. The developed DPP polarographic method was found to be simple, rapid, and it can be applied directly to environmental samples without filtration, extraction, and centrifugation.

Anticancer Drug 5-Fluorouracil in Aqueous Solution by Differential Pulse Polarography: An Assessment of Optimum Conditions

Anticancer Drug 5-Fluorouracil in Aqueous Solution by Differential Pulse Polarography: An Assessment of Optimum Conditions

Coordination behavior of 3-amino-5,5′-dimethylhydantoin towards Ni(II) and Zn(II) ions: Synthesis, spectral characterization and DFT calculations

The interaction of 3-amino-5,5′-dimethylhydantoin with nickel and zinc ions was investigated at different conditions by means of UV–Vis, FTIR spectroscopy and electrochemical methods as well as DFT quantum chemical calculations. Through calculated DFT frequencies and experimental FTIR spectra of the complexes the correlation analysis has been made. NBO analysis of the ligand and complexes provides the information about intramolecular resonance stabilization energy and charge transfer between ligand and metal ions. First derivative UV–Vis spectra were done in order to resolve the π→π* and n→π* carbonyl electron transitions of the ligand and complexes. We have shown that complexes with 1:2 stoichiometry were formed at pH closed to physiological. The stability constant was determined for 3-amino-5,5′-dimethylhydantoin (L) and Ni(II) ions using differential pulse polarography data. The existence of one complex (n¯ = 2) is proved in the presence of high ligand concentration (CL = 2 × 10−3 ÷ 6 × 10−3 mol L−1) and the values of the total constant is: lgβNI(II)-L=9.5±0.4 (I = 0.1). The UV–Vis spectroscopy and DFT calculations confirm the stoichiometry of the complexes. The results of the study are useful for incorporation with chemical equilibrium models for evaluation of the speciation and the reactions of metals with hydantoin derivatives in order to develop methods for determination of these metals in different milieu.

Stability of Benzotriazole Derivatives with Free Cu, Zn, Co and Metal-Containing Enzymes: Binding and Interaction of Methylbenzotriazoles with Superoxide Dismutase and Vitamin B12

Benzotriazole derivatives form very strong bonds with transition metals, and are the most widely used type of industrial corrosion inhibitor. Some benzotriazole derivatives have been implicated as hormone regulators which also carry the ability to induce uncoupling responses or otherwise inhibit respiration processes in some microorganisms. However, the mechanisms associated with benzotriazole toxicity and inhibition are unknown. Using Differential Pulse Polarography, the stability constants of commercially significant corrosion inhibitors, 4-and 5-methylbenzotriazole, coordinated with free Cu (II) and Co (III), were determined to be 1015 and 108, respectively. Polarographic analyses were extended to confirm that methylbenzotriazole also binds the copper center(s) in the ubiquitous enzyme superoxide dismutase, and the Corrin site in the coenzyme cobalamin (vitamin B12). These results suggest that the metal-chelating ability of this unique class of compounds may confer inhibition to certain enzyme systems.

Differential Pulse Polarography Procedure for the Estimation of Deferoxamine in Pharmaceuticals

Differential Pulse Polarography Procedure for the Estimation of Deferoxamine in Pharmaceuticals

Electrochemical Behavior and Differential Pulse Polarographic Determination of Flucloxacillin in Pure and Pharmaceutical Dosage Forms Using Dropping Mercury Electrode

Electrochemical behavior and differential pulse polarographic determination of flucloxacillin (FLUX) in pure and pharmaceutical dosage forms using drop mercury electrode (DME) has been studied. The method involves the electrochemical behavior of flucloxacillin at DME by differential pulse polarographic analysis (DPPA). Various parameters (electrolyte, pulse time, pulse amplitude, etc.) affecting the FLUX determination were examined. Different buffer solutions were used over a wide pH range (2.5–10.0). The best definition of the analytical signals was found in Britton–Robinson buffer (0.04 M) at pH 4.0. Under the optimum conditions, liner calibration graph, Ip=f(CFLUX) was obtained in the concentration ranges of 1x10-7 M (0.0494 µg.mL-1) to 2x10-5 M (9.8780 µg.mL-1), at -975 to -1000 mV (versus Ag/AgCl) with relative standard deviations (RSD) did not exceed 2.1% for the concentrations of FLUX (0.0494 µg.mL-1). Regression analysis showed a good correlation coefficient (R2=9997) between Ip and concentration over the mentioned range. The limit of detection (LOD) and the limit of quantification (LOQ) were to be 0.0034 and 0.0102 µg.mL-1, respectively. The proposed method was validated for linearity, precision and accuracy, repeatability, sensitivity (LOD and LOQ), robustness and specificity. The developed method is applicable for the determination of FLUX in pure and different dosage forms in presence a same amount of amoxicillin (AMOX) with average recovery of 99.8 to 101.2% and the results are in good agreement with those obtained by the HPLC reference method.

Rapid and Sensitive Determination of Hg(II) Using Polarographic Technique and Application to Chlorophytum comosum

A differential pulse polarographic (DPP) method has been used for the indirect determination of Hg(II). With a known amount of cyanuric acid (CA) in polarography cell (B–R buffer, pH 10.5) was added an unknown Hg(II) sample and the Hg(II) concentration is calculated simply from the decrease in the CA peak after reaction with Hg(II). The linear concentration range was between 20 and 120 μM and limit of detection was calculated to be 6.7 μM. The proposed method was successfully applied to the dried leave samples belong to C. comosum plant. The method was extended to the indirect determination of mercury(II) in C. comosum plant and results were in agreement with that obtained by a spectrometric comparison method (ICP-MS). The sufficiently good recoveries and low standard deviations reflect the high accuracy of developed method.

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

Binding of vanadium to human serum transferrin - voltammetric and spectrometric studies

Previous studies generally agree that in the blood serum vanadium is transported mainly by human serum transferrin (hTF). In this work through the combined use of electrochemical techniques, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry and small-angle X-ray scattering (SAXS) data it is confirmed that both VIV and VV bind to apo-hTF and holo-hTF. The electrochemical behavior of solutions containing vanadate(V) solutions at pH=7.0, analyzed by using two different voltammetric techniques, with different time windows, at a mercury electrode, Differential Pulse Polarography (DPP) and Cyclic Voltammetry (CV), is consistent with a stepwise reduction of VV→VIV and VIV→VII. Globally the voltammetric data are consistent with the formation of 2:1 complexes in the case of the system VV-apo-hTF and both 1:1 and 2:1 complexes in the case of VV-holo-hTF; the corresponding conditional formation constants were estimated. MALDI-TOF mass spectrometric data carried out with samples of VIVOSO4 and apo-hTF and of NH4VVO3 with both apo-hTF and holo-hTF with V:hTF ratios of 3:1 are consistent with the binding of vanadium to the proteins. Additionally the SAXS data suggest that both VIVOSO4 and NaVVO3 can effectively interact with human apo-transferrin, but for holo-hTF no clear evidence was obtained supporting the existence or the absence of protein-ligand interactions. This latter data suggest that the conformation of holo-hTF does not change in the presence of either VIVOSO4 or NH4VVO3. Therefore, it is anticipated that VIV or VV bound to holo-hTF may be efficiently up-taken by the cells through receptor-mediated endocytosis of hTF.

Monitoring of nickel(II) in biological samples using 4-(2-hydroxy-phenylethamino)benzene-1,3-diol by extractive differential pulse polarography

&lt;p class="PaperAbstract"&gt;&lt;span lang="EN-US"&gt;A novel analytical reagent, 4-(2-hydroxyphenylethamino)benzene-1,3-diol was synthesized for determination of nickel(II) in biological samples and plant materials by extractive differential pulse polarography. The analysis of nickel(II) was carried out by extracting the nickel(II)-(4-(2-hydroxyphenylethamino)benzene-1,3-diol) complex from chloroform prior to injecting into the instrument. The electrochemical behavior of nickel(II) complex was studied under optimum parameters like effect of pH, pulse amplitude, scan rate and choice of solvent. The calibration curve was constructed in the concentration range of 0.05-42 µg mL&lt;sup&gt;-1&lt;/sup&gt; at pH 4.0 (acetate buffer) with a correlation coefficient of 0.992, respectively. Interference of diverse ions was also investigated during the analysis of nickel(II) to optimize the conditions. The accuracy and validity of the proposed method were checked by the analysis of Certified Reference Materials which is distributed by the National Institute of Standard Technology&lt;/span&gt;&lt;/p&gt;

Redox properties of alkyl-substituted 4-aryl-2,4-dioxobutanoic acids

Redox properties of a set of aryldiketo acids (ADKs), small organic molecules that comprise 2,4-dioxobutanoic acid moiety, were studied. Along with well-known HIV-1 integrase (IN) inhibition, ADKs exert widespread biological activities. The aim of this work was to evaluate the effects of aryl substitutions on the properties of the dioxobutanoic moiety that is involved in key interactions with metal ions within the active sites of target enzymes. The effect of pH on the electronic properties of nine congeners was examined using cyclic voltammetry and differential pulse polarography. The compounds were chosen as a simple set of congeners bearing Me-groups on the phenyl ring, which should not be involved in electrochemical reactions, leaving the diketo moiety as the sole electrophore. The substitution pattern was systematically varied, yielding a set having different torsion between the phenyl ring and the aryl keto group (Ar?C(O)). The protonation state of the ADKs at different pH values was determined from the experimentally obtained pKa values. The results showed that an equal number of protons and electrons were involved in the oxidation and reduction reactions at the surface of the electrode. Quantitative linear correlations were found between the reduction potentials and the energies of the frontier orbitals, calculated for neutral, mono-anionic and the corresponding radical anionic species, and the steric parameter as two independent variables.

English

English

Influences of size-fractionated humic acids on arsenite and arsenate complexation and toxicity to Daphnia magna

The intrinsic physicochemical properties of dissolved organic matter (DOM) may affect the mobility and toxicity of arsenic in aquatic environments. In the present study, the humic acid (HA) was ultra-filtered into five fractions according to molecular weight, and their physicochemical properties were characterized. Complexation of HA fractions with arsenite and arsenate was first determined by differential pulse polarography (DPP). The influences of HA fractions on arsenic toxicity were then examined using Daphnia magna as a model organism. As(V) had a higher affinity with HA than As(III), and their complexation was dependent on the total acidity and fluorescence characteristics of DOM. We demonstrated that the acidity and fluorescence also better explained the As toxicity to daphnids than UV absorbance and hydraulic diameter. Arsenic speciation determined by DPP significantly affected the toxicity of arsenite and arsenate. The results extended the free-ion activity model application to the case of arsenic. The present study clearly indicated that DOM with different molecular weights has distinct physicochemical properties, and could influence the speciation and toxicity of As to different extent.

Simulation of differential pulse polarography of irreversible EC mechanism

A reversible electrode reaction that is followed by totally irreversible chemical reaction is investigated theoretically. The influence of chemical reaction on two components of the net response of differential pulse polarogram is analyzed. It is demonstrated that this EC mechanism depends on two kinetic parameters and that their critical values can be used for the measurement of the rate constant of chemical reaction.

A new and direct method for the determination of trace elements in spinach using differential pulse polarography

For the trace determination of elements in spinach a new differential pulse polarographic (DPP) method is established. The polarograms were taken in various electrolytes and pH values in the presence of digested spinach sample. Trace element determinations were made in acetate and ammonia electrolytes at various pH values, with or without EDTA. Fe and Cu peaks could be separated and determined at pH7, acetic acid electrolyte in the presence of EDTA. Ni and Zn peaks could be separated and determined in ammonia buffer at pH10. Lead could be determined at pH2 acetic acid and Mo (VI) was determined at pH4 acetate buffer, EDTA medium. Selenite was determined from its hydrogen catalytic peak. The trace element in spinach was found as Fe 15μg/g, Cu 17μg/g, Ni 8μg/g, Zn 27μg/g, Pb 47μg/g, Mo 43μg/g, and Se 762μg/g.

A new, fast and sensitive method for the determination of trace amounts of nitrite using differential pulse polarography

Nitrite salts of sodium or potassium are being used for the protection of meat products. They provide color and taste of meat and they protect against clostridia. On the other hand, nitrite ions can interact with amines to form nitrosamines which are known as carcinogenic substances. They may also react with hemoglobin and reduce its oxygen carrying capacity. Thus, its concentration in food-stuff has to be controlled carefully by highly sensitive methods.A new DP polarographic method is established for the determination of nitrite. Nitrite cannot be determined directly with any analytical methods. Long and tedious procedures are necessary for many of them. In this polarographic method arsenite, As(III), ion is used for the reduction of nitrite. The nitrite is determined from the As(III) quantity left over after the reaction with nitrite. The peak of arsenite has been used since it is sharp and responds well for the standard addition of arsenite.The optimum conditions for the quantitative reaction between nitrite and arsenite have been studied. It was found that the pH for the reaction medium has to be 5–7, since nitrite is decomposed at lower pH values. The reaction medium has to be stirred for about 5 min with nitrogen gas in order to expel the NO gas formed and thus to shift the equilibrium to products side. The limit of detection, LOD, was found to be as 2 × 10−7 M. No interference was observed from most common ions.

Electroanalytical procedure and sorption studies for imazaquin in different soils

ABSTRACTThe objective of the present work is to determine sorption coefficients of the herbicide imazaquin using the differential pulse polarography in the major soil classes occurring in the State of São Paulo, Brazil. This study contributes to the predictions of pesticide fate and transport mechanisms in the environment as well as its exposure and interactions with different soil materials. Imazaquin was analysed directly in soil samples (scan rate 2 mV s–1, mercury drop size 0.37 mm, and pulse height 50 mV) and the detection limits varied from 42 to 58 g L–1 for different soils. Imazaquin showed the KF values varying from 0.8 (for the sandy soil) to 35.5 L kg–1 (for the medium textured soil), with a significant dependence on the soil pH, organic matter content, and clay minerals. The study demonstrates the practical utilisation of the electroanalytical methodology to determine the imazaquin adsorption in soil and consequently assess the impact of this herbicide in the environment, especially for the evaluation of the potential risk of surface and groundwater contamination.