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971.
Shao‐Hua Wu Jian‐Jun Sun Zhi‐Bin Lin Ai‐Hong Wu Yong‐Ming Zeng Liang Guo De‐Feng Zhang Hui‐Ming Dai Guo‐Nan Chen 《Electroanalysis》2007,19(21):2251-2257
Electrically heated graphite cylindrical electrodes (HGCEs) made from ground pencil leads have been used to perform adsorptive stripping square wave voltammetry (SWV) measurements of trace riboflavin (RF). The SWV stripping peak current was significantly enhanced with increasing the electrode temperature only during preconcentration step. This enhancement was due to the forced thermal convection induced by heating the electrode rather than the bulk solution. It is the thermal convection that has the ability to improve mass transfer and facilitate adsorption thus enhance stripping responses. It was found that the detection limit of 5×10?9 M (S/N=3) could be obtained at an electrode temperature of 72 °C during 5 min accumulation, more than one magnitude lower than that at 22 °C (room temperature), the sensitivity could be enhanced ca. eight or four folds for two different RF concentration ranges. So it is possible to develop a new highly sensitive method to determine riboflavin at HGCEs. Such HGCEs were also successfully used to determine RF in multivitamin tablets. 相似文献
972.
佝偻病儿童血微量元素测定 总被引:6,自引:2,他引:6
对 10 3例婴幼儿佝偻病进行了血中锌、铁、铜、钙、锰、铅含量测定 ,并与健康儿童比较。结果表明 ,佝偻病组不仅是钙缺乏 (P <0 0 5) ,锌、铁缺乏较健康组儿童更为显著 (P <0 0 1) ,提示佝偻病儿不仅要重视钙的补充 ,锌、铁的补充也很必要。 相似文献
973.
Ai Bing Chen Wei Ping Zhang Yong Liu Xiu Wen Han Xin He Bao 《中国化学快报》2007,18(8):1017-1020
An in situ reduction method has been developed to fabricate metallic Ag nanoparticles inside the channels of mesoporous carbon CMK-3.This approach combines function of the CMK-3 surface by oxidation using HNO_3 with the subsequent absorption of Ag~ . The resultant nanocomposite materials were characterized by nitrogen adsorption,X-ray diffraction,Auger electron spectroscopy and transmission electron microscopy.Compared with the conventional impregnation method,our approach shows that Ag nanoparticles of 2-4 nm can be uniformly incorporated into CMK-3. 相似文献
974.
电流反馈倒数示波计时电位滴定法 总被引:4,自引:0,他引:4
经典的示波计时电位滴定法是利用用dE/dt-E曲线上去极剂切口的出现或消失指示滴定终点,其优点是仪器简单、终点直观、准确快速,不足之处是有些去极剂在示波计时电位图上的切口不敏锐,当被测物含量较低,或用较低浓度的滴定剂进行滴定时,终点变化更不 相似文献
975.
Ai Qun JIA Ning Hua TAN Jun ZHOU 《中国化学快报》2006,17(4):477-480
New minor cyclic peptides, named arenariphilin C 1 and arenariphilin D 2, were isolated from the whole plants of Arenaria oreophila (Caryophyllaceae). Their structures were determined as cyclo(Pro1-Pro2-Leu1-Leu2-Phe-Ser-Gly-Thr) and cyclo (Ser-Cys) on the basis of spectroscopic data, especially by two-dimension NMR (2D NMR) technologies. 相似文献
976.
Base on the enhancement of Rayleigh light scattering signals of molecular "light switches" by DNA under acidic condition, a sensitive and convenient method for DNA determination was proposed. The experiments indicated that, under optimum conditions, good linear relationships were obtained between the Rayleigh light scattering intensity and the concentration of nucleic acids. The detect limits of calf thymus DNA (ctDNA) were 13.0 ng ml(-1), 4.2 ng ml(-1), 51.5 ng ml(-1) and 3.0 ng ml(-1) with four "light switches", respectively. Plasmid DNA extracted from Bacillus subtilis were determined by the proposed method with satisfactory results, and the recovery rates of calf thymus DNA were in the range of 94.6-110.7%. 相似文献
977.
Liang JG Zhang SS Ai XP Ji XH He ZK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):2974-2978
The interaction of some diamines (ethylenediamine (EDA), 1,6-hexanediamine (HDA), o-phenylenediamine (OPD)) with CdSe quantum dots (QDs) is reported. With increasing concentration of EDA from 0 to 2.0 x 10(-6) mol l(-1), slight fluorescence enhancement is observed. However, the CdSe QDs fluorescence quenching is seen at relatively higher concentration of EDA. There is a red-shift of 0-7 nm in fluorescence emission spectra of CdSe QDs when the concentration of EDA is changed from 2.0 x 10(-6) to 8.0 x 10(-6) mol l(-1). The resonance light scattering (RLS) spectra of CdSe QDs have little change when the concentration of EDA is less than 5.0 x 10(-6) mol l(-1). It indicates there are little large particles formed in the solution. However, a significant increase of the RLS is observed in the 300-500 nm wavelength range after adding higher concentration than 5.0 x 10(-6) mol l(-1) EDA, which could be attributed to the large particles formed. The interaction between HDA and CdSe QDs is similar to that of EDA. However, with the OPD, it is found that the interaction is much different from those of EDA, HDA, and that the quenching, even at low concentration, is effective for CdSe QDs emission. The quenching phenomenon could be explained by a surface bound complexation equilibrium model. 相似文献
978.
银微盘电极上碘离子的示差脉冲溶出伏安法 总被引:6,自引:0,他引:6
基于I能与Ag生成难溶出化合物特性,在银微盘电极上研究了I的示差脉冲溶出伏安法(DPSV)。该法不需镀汞,不要搅拌,可在较稀稀的支持电解质溶液中实施。于0.08mol/LHAc-NaC及0.01mol/LEDTA介质中,能检出1.00×10^-8mol/L的I,I的浓度为5.00×10^-6--1.20×10^-8mol/L范围与峰电流有良好的线性关系。该法用于自来水中I的测定,相对偏差为4.3% 相似文献
979.
Narrowly distributed polystyrene-g-p(N-isopropylacrylamide) (PSt-g-PNIPAM) was prepared by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide using the brominated polystyrene as macroinitiator and CuCl combined with hexamethyltriethylenetetramine
as catalyst. Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy confirmed the
structure of PSt-g-PNIPAM. The gel permeation chromatography (GPC) showed that the graft copolymer had a single distribution
peak with molecular weight, M
n (g/mol) of 19815 g/mol (using polystyrene as the standard). Differential scanning calorimetry (DSC) revealed that due to
both effects of hydrophobic isopropyl groups and hydrogen bonds in the amide group, the glass transition temperature (T
g) of PSt-g-PNIPAM enhanced 16.0°C compared to the T
g of the polystyrene. 相似文献
980.
Xuefeng Guo Deqing Zhang Huijuan ZhangQinghua Fan Wei XuXicheng Ai Louzheng FanDaoben Zhu 《Tetrahedron》2003,59(26):4843-4850
Three donor-acceptor-donor triads 1-3 consisting of tetrathiafulvalene units attached to perylene diimides by flexible and rigid spacers were synthesized and characterized. UV/vis spectroscopic and cyclic voltammetric results indicate that they all show negligible intramolecular charge transfer interaction in their ground states. As compared to the reference compound 21, triads 1-3 display reduced fluorescence and their fluorescence lifetimes are shortened, which is probably owing to the photoinduced electron transfer interactions between the PI units and TTF units. The different photophysical behaviors between 1 and 2 (and 3) might be due to their difference in the spatial separation of TTF and PI units. It is preliminarily found that the steric hindrance of the groups attached to TTF units can affect their photostability. 相似文献