Voltammetric and Quantum Investigation of Selected Succinimides

A series of succinimide derivatives were studied using the cyclic and square wave voltammetry. Density function theory was used in order to determinate which of the structural parameters influence the electrochemical activity. The quantum chemical calculations of the investigated succinimides were linked with the experimental electrochemical data and used to propose the oxidation mechanism. The most active among studied succinimides is 1,3-diphenylsuccinimide. The results obtained from the cyclic and square wave voltammetry and quantum chemical calculations indicate that the investigated compounds undergo oxidation by irreversible, diffusion controlled process including transfer of 1e(-) and 1 proton. The voltammetric and DFT results signify that the mechanism of electrochemical oxidation of all compounds involve the conversion of carbonyl-methyne-phenyl segment or methylene group in free radical. This conversion proceeds by the loss of one proton one electron process

Cancer Incidence in a Population Living Near a Petrochemical Facility and Oil Refinery

There is growing concern that pollution from petrochemical and oil refinery installations in Pan~evo (Serbia) has increased the incidence of various diseases including cancer. The aim of our study was to investigate cancer incidence in Pan~evo and to compare it with the region of central Serbia. Cancer incidence data were obtained from the corresponding Serbian Cancer Registries. Systematic local monitoring of benzene, toluene and methyl mercaptane in the atmosphere within Pan~evo’s industrial area indicated that the average monthly and yearly concentrations often exceeded permitted levels proposed by EU standards (5 mgm–3). Cancer incidence was lower in Pan~evo than in central Serbia (the standardised incidence for all types of cancers in Pan~evo was 218.3 and in central Serbia it was 241.7 per 100,000 inhabitants). The available data do not allow us to correlate air pollution in Pan~evo with increased cancer incidence

Investigation of forced and total degradation products of amlodipine besylate by liquid chromatography and liquid chromatography-mass spectrometry

An isocratic, reversed-phase liquid chromatographic method was applied for the investigation of the degradation products of amlodipine besylate under the stressed conditions in solution. Amlodipine besylate stock solutions were subjected to acid and alkali hydrolysis, chemical oxidation and photodegradation as well as to the electrochemical degradation by cyclic voltammetry in 0.05 mol/L NaHCO3 on gold electrode. The total degradation of amlodipine besylate was achieved in 5 mol/L NaOH at 80°C for 6 h and the compound with molecular formula C15H16NOCl was identified as a main degradation product. Under acidic (5 mol/L HCl at 80°C for 6 h) stress conditions 75.2% of amlodipine besylate degradation was recorded. Oxidative degradation in the solution of 3% H2O2-methanol 80:20 at 80°C for 6 h showed that amlodipine besylate degraded to 80.1%. After 14 days of expose in photostability chamber amlodipine besylate solution showed degradation of 32.2%. In electrochemical degradation after 9 hours of cyclization the beginning of amlodipine oxidation was shifted for 200 mV to more negative potentials, with the degradation of 66.5%. Mass spectrometry analysis confirmed the presence of dehydro amlodipine derivate with molecular formula C20H23N2O5Cl in oxidative and acidic conditions while in electrochemical degradation was detected in traces. [Projekat Ministarsva nauke Republike Srbije, br. 172013

A study of the electrochemical behaviour of methomyl on a gold electrode in a neutral electrolyte

A gold electrode was used for the qualitative and quantitative electrochemical determination of analytical methomyl in a neutral electrolyte (0.050 M NaHCO3) using cyclic linear sweep voltammetry. In the potential range from –800 mV vs. SCE to 1000 mV vs. SCE the analytical methomyl was quantitatively determined in the concentration range 4.0–16 mg L-1. In the potential range from ‑1300 mV vs. SCE to 1300 mV vs. SCE, methomyl was qualitatively determined by two anodic and four cathodic reactions. Cycling the potential in this range for 150 min caused the degradation of the molecule, which was confirmed by HPLC analysis. On the other hand, technical methomyl exhibited an inhibition of the gold electrode surface due to the impurities

Voltammetric and Square-Wave Anodic Stripping Determination of Amlodipine Besylate on Gold Electrode

The oxidative behaviour of amlodipine besylate was studied. The gold electrode and Au/o-MWCNT (oxidized multi-wall carbon nanotubes) were used for determination of amlodipine besylate standard and as a content of Alopres tablet, in 0.05 M NaHCO3 and in phosphate buffer (pH=11) by cyclic voltammetry and square-wave anodic stripping voltammetry. Electrode surfaces were characterized by AFM in the presence of amlodipine and the concentrations of drugs in electrolytes were simultaneously followed by HPLC. The linear dependency of the anodic currents of amlodipine besylate as standard and in Alopres tablet vs. concentration was observed in both electrolytes, but in phosphate buffer for the higher concentrations. The peak currents obtained in all experiments are more than fifty-fold higher comparing to all previously published results concerning the glassy carbon electrode and the carbon paste electrode. The gold electrode is better catalyst for anodic oxidation of amlodipine besylate than glassy carbone. The results obtained with Au/o-MWCNT show lower anodic activity comparing to previously published GC/o-MWCNT. GC/o-MWCNT is better catalyst than Au/o-MWCNT under similar experimental conditions

Electrical and morphological characterization of multiwalled carbon nanotubes functionalized via the Bingel reaction

Covalent sidewall functionalization of multiwalled carbon nanotubes (MWCNTs) has been performed using two approaches, direct and indirect cycloaddition through diethyl malonate, based on the Bingel reaction. The results revealed that functionalized MWCNTs demonstrated enhanced electrical properties and significantly lower sheet resistance, especially after electric field thermal assisted annealing at 80 degrees C was performed. The presence of 1,3-dicarbonyl compounds caused the surface of MWCNTs to be more hydrophilic, approachable for the electrolyte and improved the capacitance performance of Au/MWCNTs electrodes. The modified MWCNTs have been incorporated into nanocomposites by using solution mixing method with polyaniline and drop-casting resulting mixture on the paper substrate. The reduction in the sheet resistance with increasing the content of MWCNTs in the prepared nanocomposite films has been achieved

Cancer Incidence in a Population Living Near a Petrochemical Facility and Oil Refinery

There is growing concern that pollution from petrochemical and oil refinery installations in Pan~evo (Serbia) has increased the incidence of various diseases including cancer. The aim of our study was to investigate cancer incidence in Pan~evo and to compare it with the region of central Serbia. Cancer incidence data were obtained from the corresponding Serbian Cancer Registries. Systematic local monitoring of benzene, toluene and methyl mercaptane in the atmosphere within Pan~evo’s industrial area indicated that the average monthly and yearly concentrations often exceeded permitted levels proposed by EU standards (5 mgm–3). Cancer incidence was lower in Pan~evo than in central Serbia (the standardised incidence for all types of cancers in Pan~evo was 218.3 and in central Serbia it was 241.7 per 100,000 inhabitants). The available data do not allow us to correlate air pollution in Pan~evo with increased cancer incidence

The use of a gold electrode for the determination of amphetamine derivatives and application to their analysis in human urine

The catalytic abilities of gold electrode were tested for the quantitative determination of amphetamine (A) and 3,4-methylenedioxy-N-methylamphetamine (MDMA) standards by their oxidation using cyclic voltammetry (CV). The value of the oxidative currents of A and MDMA standards at 0.80 V vs. SCE in 0.05 M NaHCO3 at the scan rate of 50 mV/s is linear function of concentration in range of 110.9-258.9 mM and 38.7-229.2 mM, respectively. Square wave voltammetry (SWV) revealed linear increase of current with concentration of MDMA (range 30.9-91.6 mM) and thus quantitative determination of amphetamine derivates. SWV analysis is successfully performed in spiked urine samples as well. A and MDMA in the presence of sucrose and as a content in illegally produced tablets were also analyzed. The voltammetric determination of A and MDMA derivatives using CV and SWV at gold electrode is a rapid, selective and simple procedure and its accuracy was confirmed with reference method, high performance liquid chromatography (HPLC). The spiked urine samples analysis offers additional possibility for the rapid detection of A and MDMA in human urine

A STUDY OF THE CATALYTIC ROLE OF A GOLD ELECTRODE IN THE ELECTROCHE-

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Degradation of azithromycin using Ti/RuO2 anode as catalyst followed by DPV, HPLC-UV and MS analysis

The electrodegradation of azithromycin was studied by its indirect oxidation using dimensionally stable Ti/RuO2 anode as catalyst in the electrolyte containing methanol, 0.05 M NaHCO3, sodium chloride and deionized water. The optimal conditions for galvanostatic electrodegradation for the azithromycin concentration of 0.472 mg cm(-3) were found to be NaCl concentration of 7 mg cm(-3) and the applied current of 300 mA. The differential pulse voltammetry using glassy carbon electrode was performed for the first time in the above-mentioned content of electrolyte for the nine concentration of azithromycin (0.075-0.675 mg cm(-3)) giving the limits of azithromycin detection and of quantification as: LOD 0.044 mg cm(-3) and LOQ 0.145 mg cm(-3). The calibration curve was constructed enabling the electrolyte analysis during its electrodegradation process. The electrolyte was analyzed by high-performance liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The electrooxidation products were identified and after 180 min there was no azithromycin in the electrolyte while TOC analysis showed that 79% of azithromycin was mineralized. The proposed degradation scheme is presented