Adsorptive Stripping Analysis of Riboflavin at Electrically Heated Graphite Cylindrical Electrodes

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.     

佝偻病儿童血微量元素测定

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。     

In situ introduction of dispersed metallic Ag nanoparticles into the channels of mesoporous carbon CMK-3

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.     

电流反馈倒数示波计时电位滴定法

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     

New Minor Cyclopeptides from Arenaria oreophila （Caryophyllaceae）

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.     

Determination of DNA by Rayleigh light scattering enhancement of molecular "light switches"

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%.     

The interaction between some diamines and CdSe quantum dots

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.     

STUDIES ON COMPLEXES OF RARE EARTHS WITH CROWN ETHERS(Ⅳ)SYNTHESIS AND CHARACTERIZATION OF THE COMPLEXES OF RARE EARTH NITRATES WITH 4''''-BROMO-5''''-NITROBENZO-15-CROWN-5

Six new solid complexes of macrocyclic polyether ligand 4′-bromo-5′-nitrobenzo-15-crown-5(L)withUivalent rare earth nitrates having composition of RE(NO_3)_3·L·mCH_3CN·nH_2O(RE=L_a--Nd,m=n=0,RE=Sm,Bu,m=0.1,n=1,4)have been synthesized in acetonitrile or acetone.All the isolated complexes have been char-acterized by elementary analysis,IR and UV spectra,differential thermal and thermogravimetric analysis,X-ray powderdiffraction analysis,molar conductance and measurementa of solubility in some general solventa.It shows thatcoordination number of the rare earth cation in the complexes of La,Ce,Pr and Nd nitrate is eleven.     

银微盘电极上碘离子的示差脉冲溶出伏安法

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％     

A CONVENIENT SYNTHESIS OF β-CYCLODEXTRIN 2-AND 3-O-MONOBENZOATE

ＡＣＯＮＶＥＮＩＥＮＴＳＹＮＴＨＥＳＩＳＯＦβ－ＣＹＣＬＯＤＥＸＴＲＩＮ２－ＡＮＤ３－Ｏ－ＭＯＮＯＢＥＮＺＯＡＴＥ￥ＡｉＹｏｕＨＡＯ；ＬｉｎＨｕｉＴＯＮＧ；ＦｕＳｈｅｎｇＺＨＡＮＧ；ＤａｏＳｅｎＪＩＮ（ＬａｎｚｈｏｕＩｎｓｔｉｔｕｔｅｏｆＣｈｅｍｉｃ...