RESUMO
Objective: To establish an electrochemical method for the determination of phenol. Methods: An electrochemical workstation with three electrodes system was used with glassy carbon electrode as working electrode, Ag/AgCl as reference electrode and Pt as counter electrode. Cyclic voltammetry and differential pulse voltammetry were used for the determination of phenol. Results:Under the condition of 4% Na2SO4as the supporting electrolyte, phenol showed an obvious oxidation peak on the glassy carbon elec-trode. The peak current increased linearly with the concentration of phenol within the range of 0. 8 μg·ml-1-10. 2 μg·ml-1( r=0. 997 5). The lower limit of detection was 0. 20 μg·ml-1. The average recovery was 101. 2% (RSD=2. 2% , n=6). Conclusion:The method is simple and accurate, and can be used for the determination of phenol.
RESUMO
Nanopore technique is a low-cost, ultrafast method for single-molecule level analysis without labels. Nanopore technique was first proposed more than 20 years ago and exhibited an excellent potential in DNA sequencing. So far, the commercial development of nanopore strand-sequencing as a portable device has been realized. Meanwhile, a remarkable number of studies have demonstrated that nanopore represents versatile single-molecule sensors for a wide range of molecule. Therefore, in this article we mainly review the use of nanopore technique based on the interface interactions between biological pore and the analytes such as protein/peptide to obtain kinetic and thermodynamic information at single-molecule level. And a large number of biological molecules and metal ions are quantitatively detected by nanopore analysis, allowing its development for the future biotechnologies and medicine applications. Besides, electrochemical detection system is crucial to nanopore technique. Therefore, we focus on advancements in relative software and ultralow current instrumentations with high-bandwidth.
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Based on the high solubility of azodicarbonamide (ADC) in hot solution and its electrostatic interaction with Nafion film,a new electroanalytical method was developed for the determination of ADC by using Nafion film electrode.The effect of temperature on the solubility of ADC and the mechanism of the reduction reaction of ADC on Nafion film electrode were investigated.Under the experimental conditions such as water bath at a constant temperature of 80 ℃,pH 6.0 and optimal test parameters,the differential pulse voltammetric response was proportional to the concentration of ADC in the range of 0.93-10.5 μg/L,and the detection limit was estimated to 0.58 μg/L.The relative standard deviation was less than 5.86 ％ and the recovery was 95.8％-104.0％ for the determination of the ADC in flour samples.The semicarbazide and nitrofurazone did not interfere with the determination of ADC.
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O processo da eletrorredução de benzodiazepinas, uma ferramenta, capaz de usar-se em pesquisa eletroanalítica, foi analisado dos pontos de vista mecanístico e matemático. O modelo correspondente veio sendo investigado por meio da teoria de estabilidade linear e análise de bifurcações e, por meio da sua análise, pôde-se obter o requisito da melhor eficiência do processo, investigar a pH-dependência do seu desempenho, bem como as condições das instabilidades oscilatória e monotónica. Faz-se uma tentativa de uma análise mecanística sistemática do desempenho de sensores eletroquímicos de benzodiazepinas.
The benzodiazepines' electrochemical reduction process, a tool, capable to be used in electroanalytic investigation, was anaylzed by mechanistic and mathematical means. The correspondent model was analyzed by means of linear stability theory and bifurcation analysis, and by its mean it was possible to get the requisite for the best process efficiency, the pH-dependence of its function, like also of oscillatory and monotonic instability. An effort is made fot the systematic mechanistic analysis of the work of benzodiazepine electrochemical sensors.
RESUMO
An ordered mesoporous silica ( OMS ) was synthesized through hydrothermal process. The synthesized material was characterized by different techniques such as X-ray diffraction, nitrogen adsorption-desorption and transmission electron microscope. The electrochemical characteristics of the OMS modified carbon paste electrode ( OMS/CPE ) were investigated by using cyclic voltammetry and electrochemical impedance spectroscopy. Compared with bare carbon paste electrode ( CPE ) , the OMS/CPE exhibited a larger electrode surface and a faster electron-transfer rate. Electrochemical behaviors and kinetic properties of L-tryptophan ( L-Trp) at the OMS/CPE in the presence of sodium dodecylsulphate ( SDS) were studied. The results showed that the voltammetric response of L-Trp at OMS/CPE was improved due to the synergistic effect of OMS and SDS. The electrochemical oxidation of L-Trp at OMS/CPE in the presence of SDS was an irreversible process involved two electrons and two protons, and the electrode process was controlled by the adsorption step. Some parameters such as SDS concentration, accumulation time, accumulation potential and pH were optimized. Under optimal conditions, the oxidation peak current was linearly proportional to L-Trp concentration in the range of 8. 0×10-8 to 4. 0×10-6 mol/L, with a detection limit of 7. 0×10-8 mol/L (S/N=3 ) . The proposed method was applied for the determination of L-Trp in oral liquid with the recoveries of 99 . 6%-102 . 6%.