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221.
222.
In the present paper, we describe a microfluidics-based sensing system for nonelectroactive anions under negative separation electric field by mounting a single carbon fiber disk working electrode (WE) in the end part of a poly(dimethylsiloxane) microchannel. In contrast to work in a positive separation electric field described in our previous paper (Anal. Chem. 2004, 76, 6902-6907), here the electrochemical reduction reaction at the WE is not coupled with the separation high-voltage (HV) system, whereas the electrochemical oxidation reaction at the WE is coupled with the separation HV system. The electroactive indicator is the carbon fiber WE itself but not dissolved oxygen. This provides a convenient and sensitive means for the determination of nonelectroactive anions by amperometry. The influences of separation voltage, detection potential, and the distance between the WE and the separation channel outlet on the response of the detector have been investigated. The present detection mode is successfully used to electrochemically detect F-, Cl-, SO4(2-), CH3COO-, H2PO4-. Based on the preliminary results, a detection limit of 2 microM and a dynamic range up to three orders of magnitude for Cl- could be achieved. 相似文献
223.
Hai-Bin Tian Duan-Zhi Yin Lan Zhang Li-Hua Wang Chun-Fu Zhang Jun-Ling Li Wei Zhou Chun-Ying Wu Yong-Xian Wang 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):383-389
The compound 3-{[4-(4-[18F]fluorophenyl)methyl]piperazin-1-yl}-methyl-1H-pyrrolo[2,3-b]pyridine ([18F]3), which is an analogue of L-745,870 binding D4
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
224.
225.
Protein tyrosine phosphatase 1B (PTP1B) functions by removing the phosphoryl group from tyrosinephosphorylated proteins in
insulin signaling and metabolism. The regeneration of the active site involves a sulphenylamide intermediate derived from
the intrastrand cross-linking between the catalytic serine and the neighboring backbone nitrogen. Two mechanisms have been
proposed for the formation of the sulphenylamide intermediate and the subsequent reactivation of the catalytic site. In the
current work, the proposed mechanisms have been investigated by the use of density functional theory calculations. Our results
suggest that these two mechanisms have similar overall energy barriers and that the preferred route will be determined by
the availability of hydrogen peroxide or other oxidizing reagents. 相似文献
226.
杯芳烃的分子设计(Ⅵ)--一种新的杯[4]磺胺衍生物的合成及晶体结构 总被引:2,自引:0,他引:2
杯芳烃是由酚单体通过亚甲基在羟基邻位桥连而成的环状低聚物, 它具有可调的杯状疏水空腔, 结构柔性较大, 构象可变, 并对中性分子和有机、无机离子具有选择性配位能力. 因此, 在其上下缘进行化学修饰所得到的杯芳烃衍生物可广泛应用于萃取分离、离子选择性电极、色谱分析、功能材料、催化及模拟酶等研究领域[1~4]. 相似文献
227.
Simple and sensitive electrochemical method for the determination of metronidazole, based on a nanostructured film coated glassy carbon electrode (GCE), is described. Multi-walled carbon nanotubes (MWNT) was dispersed into water in the presence of a hydrophobic surfactant to give very stable and homogeneous MWNT suspension, and a MWNT-film coated GCE was achieved via evaporating solvent. Metronidazole yields a well-defined reduction peak whose potential is −0.71 V at the MWNT-film coated GCE in pH 9.0 Britton-Robinson buffer. Compared with bare GCE, the MWNT-film modified GCE significantly enhances the reduction peak current of metronidazole. All the experimental parameters were optimized for the determination of metronidazole. The detection limit is 6×10−9 mol/l at 2 min accumulation. This method has been successfully used to determine metronidazole in the drugs. Furthermore, results obtained by the proposed method have been compared with spectrophotometric method. 相似文献
228.
Based on gaseous compound introduction as 1-phenyl-3-methyl-4-benzoylpyrazolone[5](PMBP) chelate of aluminum by electrothermal vaporization in ICP-AES, a method for determination of trace aluminum was developed. Trace aluminum was vaporized at temperature of 1000 degrees C, and the vaporization behavior of aluminum chelate was detailedly investigated. Under the optimum conditions, the detection limit of aluminum was 0.6 ng ml(-1), and the relative standard deviation for 0.1 mug ml(-1) aluminum was 4.7% (n=8). The proposed method was applied to the determination of trace aluminum in rice flour reference materials, and the results well agreed with the reference values. 相似文献
229.
镉—溴化物—罗丹明B高灵敏显色反应的研究:离心光度法测定镉 总被引:10,自引:0,他引:10
本研究了一个高灵敏的测定镉的方法,离心光度法,该体系络合物λmax=560nm,表观摩尔吸系数ε560=5.06×10^8L.mol^-1.cm^-1,Cd^2+浓度0.10×10^-2-1.0×10^-2μg/10mL呈线性关系,本法已用于血清和水中痕量镉的测定,探讨了高灵敏的显色反应机理。 相似文献
230.