Paired Electrolysis of Aldoses in a Divided Flow Cell

Simultaneous anodic oxidation and cathodic reduction of aldoses in a divided flow cell were studied. The stream of the anolyte was an aqueous solution containing D-glucose, sodium bromide, and sodium bicarbonate. The stream of the catholyte was also an aqueous solution containing xylose and sodium sulfite. The factors which affected both the anodic and cathodic reactions were studied. The results indicate that the flow rates and temperatures of the anolyte and the catholyte, concentrations of the aldoses, pH values and the material of electrodes significantly affect both anodic and cathodic yields. The selectivities of gluconic acid in the anode and xylitol in the cathode were very high. The power consumption of paired electrolysis in the flow system was less than paired electrolysis in a batch system.     

Catecholamine release from cultured bovine adrenal medullary chromaffin cells in the presence of 60-Hz magnetic fields

Effects of powerline frequency (50/60 Hz) electric and magnetic fields on the central nervous system may involve altered neurotransmitter release. This possibility was addressed by determining whether 60-Hz linearly polarized sinusoidal magnetic fields (MFs) alter the release of catecholamines from cultured bovine adrenal chromaffin cells, a well-characterized model of neural-type cells. Dishes of cells were placed in the center of each of two four-coil Merritt exposure systems that were enclosed within mu-metal chambers in matched incubators for simultaneous sham and MF exposure. Following 15-min MF exposure of the cells to flux densities of 0.01, 0.1, 1.0 or 2 mT, norepinephrine and epinephrine release were quantified by high-performance liquid chromatography (HPLC) coupled with electrochemical detection. No significant differences in the release of either norepinephrine or epinephrine were detected between sham-exposed cells and cells exposed to MFs in either the absence or presence of Bay K-8644 (2 microM) or dimethylphenylpiperazinium (DMPP, 10 microM). Consistent with these null findings is the lack of effect of MF exposure on calcium influx. We conclude that catecholamine release from chromaffin cells is not sensitive to 60-Hz MFs at magnetic flux densities in the 0.01-2 mT range.     

醇脱氢酶电极的研制

通过化学交联法将醇脱氢酶(ADH)固定在玻碳电极表面(Φ=5mm),使用N-甲基吩嗪甲基疏酸盐(PMS)和铁氰化钾为介体、间接测定酶促反应中生成的还原辅酶Ⅰ(NADH)。工作电位+300mv(vs.SCE)乙醇测定的线性范围为0.05～1.0mmol/L,响应时间小于20s。如果电极每天测定30次,可以使用两周。并对电极的选择性进行了讨论。     

Electrocatalytic Oxidation of Amines on a Mediator‐Modified Electrode by Electrochemical Copolymerization of Nitroxyl Radical Precursor Containing Pyrrole Side Chain and Bithiophene

This paper describes the electrocatalytic oxidation of amines on TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl)‐modified electrodes prepared by electrochemical copolymerization of TEMPO precursor containing pyrrole side chain and 2,2′‐bithiophene. The modified electrode exhibits electrocatalytic activity for the oxidation of primary and secondary amines. Cyclic voltammetric studies showed that the peak current of the cyclic voltammogram increased linearly with increasing concentration of amine in the sample solution.     

Methylated Azopyridine as a New Electron Transfer Mediator for the Electrocatalytic Oxidation of NADH

Carbon ionic liquid electrode (CILE) has been modified with a new synthesized mediator i.e. N,N′‐dimethyl‐4,4′‐azopyridinium hexafluorophosphate (MAZPHP) via sol process and the electron transfer mediating characteristics of this mediator has been evaluated. 4,4′‐Azopyridine (AZP) did not show any electrocatalytic activity toward the selected probe, NADH, while its synthesized methylated derivative, MAZPHP, is a very efficient mediator for the electrocatalytic NADH oxidation. Cyclic voltammetry of MAZPHP/Sol/CILE exhibited a pair of reversible peaks corresponding to incorporated mediator with a formal potential of about 221 mV vs. Ag/AgCl. MAZPHP/Sol/CILE is free from fouling effects by the oxidation products of NADH which generally give hindrance to amperometric detection of NADH. Using amperometric technique, NADH can be determined in the range of 1.0×10^?5 M to 1.4×10^?3 M with a detection limit of 2.0×10^?6 M.     

Native biofilm cultured under controllable condition and used in mediated method for BOD measurement

In this article, we developed a native biofilm (NBF) bioreactor used for biochemical oxygen demand mediated method (BOD_Med). There were two innovations differed from previous BOD_Med assay. Firstly, the immobilization of microorganisms was adopted in BOD_Med. Secondly, the NBF was introduced for BOD measurement. The NBF bioreactor has been characterized by optical microscopy. A culture condition of NBF with 24 h, 35 °C and pH 7 was optimized. Furthermore, a measuring condition with 35 °C, pH 7 and 55 mM ferricyanide in 1 h incubation were optimized. Based on the optimized condition, the real wastewater samples from local sewage treatment plant had been measured. Performances of the NBFs proposed at different culture conditions were recorded for 110 d, and the results indicated that long-term storage stability was obtained. With the proposed method, an uncontaminated native microbial source solution can be obtained from a wastewater treatment plant. In this way, we can ensure that the microbial species of all in the NBF are same as that in the target to be measured.     

Electrocatalytic Oxidation of Carbohydrates Mediated by Nitroxyl Radical‐modified Electrodes in Aqueous Solution

The electrocatalytic activity of a 2,2,6,6‐tetramethylpipridine‐N‐oxyl (TEMPO)‐modified electrode toward the oxidation of carbohydrates in phosphate buffer solution was investigated under neutral aqueous solution conditions at 25 °C. The modified electrode was prepared on the surface of a glassy carbon electrode by the electrochemical polymerization of a TEMPO precursor containing a pyrrole side chain. Cyclic voltammetric studies showed that the anodic peak current increased with the concentration of carbohydrates in a dose‐dependent manner.     

Electricity generation by an enriched phototrophic consortium in a microbial fuel cell

Microbial fuel cell (MFC) technology is a novel electricity generation process catalyzed by microorganisms. Much progress is made in the design and construction of MFCs, however the diversity of the electrochemically active microorganisms and the electricity generation mechanisms remain a black box. As sun is a predominantly unused energy resource, here we present a highly enriched phototrophic consortium that can produce electricity in an “H” typed MFC at a high power density (2650 mW m⁻², normalized to membrane area) in light, which was eightfold of that produced by non-enriched consortium in the same reactor. Light–dark shift experiments showed that light contributed to the electricity generation. A microbial excreted mediator assisted the electron transfer to the electrode. During the experiment, the accumulation of the mediator over time enhanced the electron transfer rate. The excitation–emission matrix fluorescence spectroscopy results indicated indole group containing compound representing the dominant mediator component.     

测酚用的酪氨酸酶媒体玻碳电极的研制

通过聚乙烯亚胺(PEI)包埋和外覆Nafion膜 ,将酪氨酸酶固定在以天青—双氰胺 -甲醛聚合物修饰的玻碳电极表面。工作电位 -100mV(vs.SCE),电极对多种酚有响应 ,对苯酚测定的线性范围为0.20～96μmol/L,响应时间t95 小于50s ,用于测标样和炼焦废水样 ,精密度、准确度好。     

On-line removal of redox-active interferents by a porous electrode before amperometric blood glucose determination

A porous reticulated vitreous carbon (RVC) electrode and a disk electrode coupled in tandem in an electrochemical flow cell has been used for electrolytic removal of interferents before amperometric glucose detection. The electrolytic efficiency at the upstream RVC electrode is 100% at a flow rate of 0.1 mL min⁻¹ or lower. Potential interferents such as acetaminophen, ascorbic acid, and uric acid can be completely eliminated by electrolysis at the RVC electrode. A mixed monolayer comprising glucose oxidase (GOD) and ferrocenyl-1-undecanethiol preformed at the downstream gold disk electrode was used as a mediator-based amperometric glucose sensor. The dependence of the amperometric current on the glucose concentration exhibits good linearity across over three orders of magnitude. The glucose measurements were also found to be reproducible (RSD < 3.5%) and accurate. Unlike the chemiluminescence method, this device obviates the use of carcinogenic substrates and the glucose sensor performance is independent of the oxygen present in sample. On the basis that the RVC electrode requires minimal cleanup and the GOD-modified electrode remains stable for a week, the electrochemical flow cell should be amenable for automated on-line removal of redox interferents for other types of enzyme-based biosensors.