Showing papers on "Polarography published in 2018"

Voltammetric determination of copper in seawater at a glassy carbon disk electrode modified with Au@MnO2 core-shell microspheres

Abstract: Anodic stripping voltammetric determination of copper ions was accomplished at a glassy carbon disk electrode modified with core-shell microspheres of the gold@manganese dioxide (Au@MnO2) type. These were synthesized via electrochemical deposition. The gold nanoparticles (AuNPs) were electrochemically deposited and employed as an active support material for the growth of MnO2 to yield Au@MnO2 core-shell particles with unique and regular spherical morphology. The microspheres have a diameter of 200–250 nm and scrolled edges like a cactus. Due to the absorption capacity of MnO2 and the electrocatalytic ability of the AuNPs, an excellent anodic signal is obtained for copper ions. Response is linear in the 20 nM to 1 μM copper ion concentration range, with a 4.9 ± 0.2 nM (n = 3) detection limit under optimized conditions. The electrode is stable and excellently reproducible. It was successfully applied to the analysis of copper ions in spiked seawater samples.

A General Approach Based on Sampled-Current Voltammetry for Minimizing Electrode Fouling in Electroanalytical Detection

Abstract: Electrochemical analysis of species known to passivate electrode surfaces remains challenging. We previously proposed a new method dealing with sampled-current voltammetry performed on an electrode array to mimic polarography at a dropping mercury electrode for the detection of copper. In this work, we study the effectiveness of this method to circumvent electrode fouling with the analysis of phenol solutions at high concentrations (10-2 mol L-1), known to polymerize on electrode surface during its oxidation. Electrode arrays well-adapted to the analysis with such system are prepared by photolithography and characterized by X-Ray photoelectron spectroscopy, X-ray diffraction and voltammetry. While analyses performed in conventional linear voltammetry or sampled-current voltammetry on a single electrode are considerably affected by electrode fouling, a linear calibration plot was achievable using our method. Modelling of the electrochemical signal showed that the current depends only on the applied potential and a parameter characteristic of the passivation phenomenon. It also underlined that sampled-current voltammetry on electrode array can circumvent the problem of passivation by a judicious choice of the sampling time.

Catalytic Oxidation of Cyclohex-2-enol at Porous Iron Zeolite-like Material: Investigations by GC/MS, Polarography and X-ray Powder Diffraction

Abstract: The polymeric complexes of porous iron phosphates (NH4)4Fe3(OH)2F2[H3(PO4)4] (1), (C3H12N2) Fe6(H2O)4[B4P8O32(OH)8] (2), and {[Fe(H2PO4)2-(μ4,4'-bipy)(H2O)]·H2O·(4,4'-bipy)} (3) were successfully tested towards oxidation of cyclohex-2-enol. The resulting products have been monitored and characterized using gas chromatography/mass spectroscopy, IR spectroscopy, and elemental analysis. Structural properties of the polymeric complexes have been studied using powder X-ray diffraction and electrochemical measurements. The results indicate that these complexes display an irreversible redox process and have high thermal stability. The results also indicated that these complexes undergo a phase change as evidenced by the change of the state of oxidation of metal centres.

Dropping mercury period adjustment method and system for dropping mercury electrode in polarography

Abstract: The invention discloses a dropping mercury period adjustment method and system for a dropping mercury electrode in a polarography. The method comprises the following steps of analyzing the relation between a mercury surface height and mercury drop formation through theories at first, and constructing a second-degree parabola model by utilizing experimental data; calculating a specifically needed mercury surface height as required by a dropping mercury period by utilizing the model; then transmitting a PWM (pulse width modulation) driving signal to a lifting rod driving device by using a microcontroller according to a mercury surface height parameter obtained through calculation, and enabling a lifting rod to drive a dropping mercury cup to lift; meanwhile, measuring a relative height of the mercury surface in real time by using a distance measuring sensor and feeding back to the microcontroller in a pulse form so as to form closed-loop control of the mercury surface height. Specific todifferent detection requirements, the relative height of the mercury surface is accurately adjusted to achieve control of formation of mercury drops, the accuracy of polarogram measurement is improved accordingly, the usage amount of mercury is reduced, the degree of automation is improved, the manual intervention is reduced, and the detection accuracy and detection efficiency are improved.

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

Abstract: The differential pulse polarographic behavior and determination of simvastatin (SMV) in pure and pharmaceutical dosage forms were investigated on dropping mercury electrode (DME). The method involves the reduction behavior of SMV has been studied in different supporting electrolytes within the pH range 3–9 at DME by differential pulse polarographic analysis (DPPA). The best definition of the analytical signals was found in sodium acetate buffer at pH 7.5 at -1378 to -1384 mV (vs. Ag/AgCl). Under optimized conditions the peak current (Ip) is linear over the range 0.1256- 8.731 µg.mL-1. The DPPA was used successfully for the determination of SMV in pure form. The relative standard deviation did not exceed 4.6% for the concentration of SMV 0.12556 µg.mL-1. Regression analysis showed a good correlation coefficient (R2=0.9997) between Ip and concentration over the mentioned range. The limit of detection (LOD) and the limit of quantification (LOQ) were to be 0.015 µg.mL-1 and 0.045 µg.mL-1, respectively. The proposed method was validated for linearity, precision and accuracy, repeatability, sensitivity (LOD and LOQ), robustness and specificity with average recovery of 99.7-100.7%. The developed method is applicable for the determination of SMV in pure and different dosage forms with assay 99.0-103.0% and the results are in good agreement with those obtained by the HPLC reference method.

Device and method for measuring residual chlorine

Abstract: PROBLEM TO BE SOLVED: To provide a device and a method for measuring residual chlorine capable of obtaining a free residual chlorine concentration without using a reagent, hardly affected by combined residual chlorine even if a sample solution is sea-water, and capable of being used over a long period of time.SOLUTION: A residual chlorine measurement device by a double-electrode type polarography method includes: a metallic detection electrode 13 soaked in a sample solution S and a platinum counter electrode 15; a voltage application mechanism 22 for applying a voltage selected from a range of 500 to 800 mV between the detection electrode 13 and the counter electrode 15; an ammeter 23 for measuring an oxidation-reduction current flowing between the detection electrode 13 and the counter electrode 15 when the voltage application mechanism 22 applies the voltage; and a mechanism for automatically cleaning the detection electrode and the counter electrode.SELECTED DRAWING: Figure 1

Electrochemical Stripping Studies Of Felodipine

Abstract: Research on increasing sensitivity of electroanalytical methods has led to the development of the techniques of stripping voltammetry. The concentration step is carried out for a definite time under reproducible conditions and the stripping process in most cases is performed in some voltammetric scanning procedure. The resulting “stripping voltammogram” shows peaks, the heights of which are generally proportional to the concentration of the corresponding electroactive species and the potentials of which have the same qualitative meaning as their half-wave potentials in polarography. Dilute solutions in the range 10-6 to 10-9 M/dm3 and less, are analysed with excellent precision and selectivity. Thus this technique extends the range of classical polarography by three to four times making possibly the analysis in nano range. The important characteristics of stripping voltammetric peaks are its height, width and peak potential. They are affected by the type of electrodes and scan rate. The same electrode is used both in the concentration and stripping processes. The process is not disturbed by the presence of organic substances other than analyte, provided they are not adsorbed on the electrode surface.Compared with other highly sensitive electroanalytical methods such as linear-sweep oscillographic polarography and square wave or pulse polarography, stripping voltammetry gives the same performance at lower cost.

Differential Pulse Polarographic Behavior and Quantification of the Flucloxacillin in Pure and Pharmaceutical Dosage Forms Using a Static Mercury Drop Electrode

Abstract: Differential pulse polarographic analysis (DPPA) by using static mercury drop electrode (SMDE) for quantification of flucloxacillin (FLUX) in pure and pharmaceutical dosage forms was studied. The optimum conditions for the polarographic signal were determined and a study was made of the different parameters affecting the electrochemical process. The best definition of the analytical signals was found in Britton–Robinson buffer (0.06 M) at pH 4.0 . Under the optimum conditions, liner calibration graph, Ip=f(CFLUX) was obtained in the concentration ranges of 0.1 mM (0.0494 ?g.mL-1) to 26 mM (12.8414 ?g.mL-1) at -940 to -1000 mV (versus Ag/AgCl) with relative standard deviations (RSD) did not exceed 2.4% for the concentrations of FLUX (0.0494 ?g.mL-1). Regression analysis showed a good correlation coefficient (R2=9998) between Ip and concentration over the mentioned range. The limit of detection (LOD) and the limit of quantification (LOQ) were to be 0.0040 and 0.0120 ?g.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 99.4 to 102.2 % and the results are in good agreement with those obtained by the HPLC reference method.