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971.
Peter G. Kirira Masami Kuriyama Dr. Osamu Onomura Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(13):3970-3982
Electrochemical oxidation of α‐allylated and α‐benzylated N‐acylated cyclic amines by using a graphite anode easily affords the corresponding α‐methoxylated products with up to 76 % yield. Ease of oxidation was affected by the type of electrode, the size of cyclic amine, and the nature of the protecting group. This method was successfully applied to the synthesis of optically active N‐acylated α‐alkyl‐α‐amino acid esters with up to 99 % ee. 相似文献
972.
应用循环伏安法、线性扫描伏安法和微分脉冲伏安法研究头孢哌酮在玻碳电极上的电化学行为,建立了应用伏安法定量检测头孢哌酮的新方法。头孢哌酮的电极过程为受吸附控制的不可逆过程,电极反应转移电子数和转移质子数均为2。头孢哌酮在pH1.0的1mol/LH3PO4-NaOH介质中,在+0.13V(vs.Ag/AgCl)电位处产生一灵敏的氧化峰,应用微分脉冲伏安法进行测定,该峰电流值Ip与头孢哌酮质量浓度在5.05×10-7~1.01×10-4g/mL范围内有良好的线性关系(R=0.9996),检出限为4.95×10-9g/mL,样品测定平均加标回收率达99.50%,相对标准偏差(RSD)为3.17%。 相似文献
973.
纳米材料修饰电极在电化学分析中的应用研究进展 总被引:1,自引:0,他引:1
综述了纳米材料修饰电极在电化学分析中的应用研究.主要总结了国内外纳米金属材料、纳米金属氧化物材料、碳纳米管与碳纳米管复合物以及其他纳米材料在电化学分析中的应用研究,并指出了纳米材料修饰电极在电化学分析应用中存在的问题. 相似文献
974.
锂离子电池正极材料LiMn_(2-2x)Sm_xSr_xO_4的合成及电化学性能 总被引:1,自引:0,他引:1
采用高温固相反应合成了一系列的LiMn2-2xSmxSrxO4正极材料(0≤x≤0.1);采用X射线衍射仪分析了合成产物的晶体结构;利用充放电试验测定了产物的电化学性能,利用电化学阻抗谱分析了产物的电化学循环机理.结果表明,所合成的LiMn2-2xSmxSrxO4(x=0,0.01,0.02,0.03,0.04,0.05)样品均保持尖晶石相,属于Fd3m空间群.LiMn1.9Sm0.05Sr0.05O4的电化学性能最佳,首次放电容量为96.8 mAh/g,在3.0~4.4 V区间内50次循环后容量保持率超过96%.与此同时,LiMn2O4和LiMn1.90Sm0.05Sr0.05O4的电极阻抗变化不同,进而影响其电化学性能. 相似文献
975.
976.
Operation of the SECM in feedback mode over a coated metal allows changes in the state of the surface to be monitored using dissolved oxygen in the test environment as redox mediator. The system investigated consisted in mild steel samples coated with a polyurethane film in which a defect was deliberately introduced into it. Accurate approach curves under negative‐feedback condition were obtained using a platinum microelectrode over regions of the intact coating. Imaging experiments were also carried out over the artificial defect on the coating. Under these conditions, corrosion of the exposed metal substrate at the defects could be monitored. 相似文献
977.
Panagiota Agrafiotou Sotiris Sotiropoulos Adriani Pappa‐Louisi 《Journal of separation science》2009,32(7):949-954
The combined use of a dual‐UV detector, a fluorimetric one and of a multiple electrochemical (EC) detector equipped with a dual electrode, consisting of a conventional size 3 mm diameter glassy carbon electrode (GCE) and of a pair of 30 μm thick carbon microfibers, is proposed for the determination of 15 amino acids, two dipeptides and creatinine. This online coupling of the above detection modes could partially replace amino acid analysis by derivatization methods, since it solves problems concerning the direct detection of selected underivatized amino acids. Additionally, it was proved that the use of multiple‐detection allows positive peak identification in a single chromatographic run, yields more information for free amino acids and solves in some cases the problem of chromatographic resolution. In order to optimize the detection conditions of the underivatized amino acids and related compounds by different detectors, their detection characteristics were determined by adequate preliminary experiments. The electro‐oxidation characteristics of the underivatized compounds of interest were determined by hydrodynamic voltammetry using a flow cell with a macrodisc GCE and by ex‐situ voltammetry using both a GCE of conventional size and a carbon fiber disk microelectrode. Important practical advantages of microfiber and microdisk electrodes with respect to macroelectrodes were demonstrated. 相似文献
978.
Two compounds, BaNd2Fe2O7(s) and BaNdFeO4(s) in the quaternary system BaNdFeO were prepared by citrate-nitrate gel combustion route and characterized by X-ray diffraction analysis. Heat capacities of these two oxides were measured in two different temperature ranges: (i) 130-325 K and (ii) 310-845 K, using a heat flux type differential scanning calorimeter. Two different types of solid-state electrochemical cells with CaF2(s) as the solid electrolyte were employed to measure the e.m.f. as a function of temperature. The standard molar Gibbs energies of formation of these quaternary oxides were calculated as a function of temperature from the e.m.f. data. The standard molar enthalpies of formation from elements at 298.15 K, ΔfHm° (298.15 K) and the standard entropies, Sm° (298.15 K) of these oxides were calculated by the second law method. The values of ΔfHm° (298.15 K) and Sm° (298.15 K) obtained for BaNd2Fe2O7(s) are: −2756.9 kJ mol−1 and 234.0 J K−1 mol−1 whereas those for BaNdFeO4(s) are: −2061.5 kJ mol−1 and 91.6 J K−1 mol−1, respectively. 相似文献
979.
Chmielewska A Konieczna L Plenis A Bieniecki M Lamparczyk H 《Biomedical chromatography : BMC》2006,20(1):119-124
A reversed-phase high-performance liquid chromatographic method with electrochemical detection for the quantitative determination of diclofenac potassium in plasma was developed. Naproxen was used as the internal standard. The drug and internal standard were isolated from plasma by extraction with dichloromethane and 2 M hydrochloric acid. Chromatographic separation was performed on a C18 column with methanol-water (68:32, v/v) adjusted to pH 3.2 with phosphoric acid as mobile phase. The oxidation potential for detection was established by constructing a voltammogram for diclofenac. The quantification limit for diclofenac in plasma was 5 ng mL(-1). Linearity of the method was confirmed in the range 5-2000 ng mL(-1), correlation coefficient 0.9998. Within-day relative standard deviations (RSDs) ranged from 0.66 to 14.00% and between-day RSDs from 0.59 to 15.78%. The method was successfully applied for the determination of pharmacokinetic parameters after ingestion of a 50 mg dose of diclofenac. Studies were performed on 18 healthy volunteers of both sexes. 相似文献
980.
The enzyme catechol-O-methyltransferase (COMT) plays an important role in the metabolism of catechol estrogens and degradation of the catecholamine neurotransmitters, such as epinephrine. Several analytical methods, mainly high-performance liquid chromatography with electrochemical amperometric detection, have been reported for the analysis of catecholamines and their metabolites in biological fluids. In this paper we report the relevance of controlling temperature in calibration procedures of metanephrine, an O-methylated product of catechol-O-methyltransferase, using epinephrine as substrate. The results at higher temperatures show shorter retention times of metanephrine, no undue band-broadening and increased electro signals. This study also showed that, despite different temperatures leading to similarly specific activities of recombinant human COMT as expected, there are additional advantages in flow analytical methods where good sensitivity, efficiency and selectivity is required, mainly in tissues with low levels of COMT activity. 相似文献