毛细管电泳-激光干涉检测法测定饮料中蔗糖含量

本文将毛细管电泳-激光干涉检测法用于饮料中蔗糖的定量测定.结果表明,在样品浓度低于10mg/mL时,检测信号与样品浓度成正比.样品不需衍生化处理直接进行测定,分析结果较为满意.     

茜素荷移分光光度法测定泛酸钙

泛酸又名遍多酸，是人和动物所必需的一种B族维生素，作为辅酶A的一个重要组成部分参与体内新陈代谢，特别是对脂肪的合成与代谢起着十分重要的作用，近年来作为营养增补剂，广泛应用于医药、食品和饲料工业。商品泛酸通常制成钙盐即泛酸钙，目前已报道的分析方法主要有微生物测定法、酶联免疫法和高效液相色谱法以及以测定泛酸水解后的产物β-丙氨酸为基础建立起来的离子交换层析分光光度法和茚三酮分光光度法等，     

Stabilization and characterization of colloidal gas aphron dispersions

Colloidal gas aphrons (CGAs) are finding increasing application in water processing, bioseparation, bubble-entrained floc flotation, separation of oil from sand, etc. This article proposes an effective method of encapsulation to stabilize the CGA bubbles with silicic sol solution for their characterization. The stabilized CGA bubbles can keep shapes and sizes for at least 12 h; even the bubbles smaller than 25 mum can also be stabilized and exist for very long times. Effects of concentration and pH of silicic sol solution on CGA stabilization were studied. The optimal ranges of concentration and pH of silicic sol solution are 0.15-0.25 mol/dm(3) and 7-10, respectively. The bubble distortion behavior in disturbance and size distribution of CGAs were examined by using the stabilization method and photographic techniques.     

Black fungus derived aerogel with double faced properties

Black fungus aerogel (BFA) exhibited interesting double-faced properties. Weexplored the diverse properties of each side of the black fungus in three aspects:water contact angle measurements, liquid selective absorption capacity and air pollutant adsorption abilities.     

Selective effect of guest molecule length and hydrogen bonding on the supramolecular host structure

A host supramolecular structure consisting of bis-(2,2':6',2' '-terpyridine)-4'-oxyhexadecane (BT-O-C16) is shown to respond to guest molecules in dramatic ways, as observed by using scanning tunneling microscopy (STM) on a highly oriented pyrolytic graphite surface under ambient conditions. It is observed that small linear molecules can be encapsulated within the host supramolecular lattice. The characteristics of the host structure were nearly unaffected by the encapsulated guest molecules of terphthalic acid (TPA) dimers, whereas appreciable changes in cavity dimension can be observed with azobenzene-4,4'-dicarboxylic acid. The STM study and density functional theory (DFT) analysis reveal that intermolecular hydrogen bonding interaction plays an essential role in forming the assembling structures. The difference in guest molecule length is considered the important cause for the different guest-host complexes.     

Reactions of magnesium formate on supports

Thermal decomposition of supported magnesium formate has been studied by gas chro-matography.The reaction paths of decomposition of supported magnesium formate depend on thenature of the supports.For Mg(HCO_2)_2/HZSM-5,the zeolite behaves as a dehydration catalyst togive CO and H_2O at lower temperatures;when the zeolite is modified by phosphorus,the methanationreaction will be partly restrained.In the case of Mg(HCO_2)_2/AC,strong adsorption of CO_2 leadsto the formation of the shoulder peak of CO_2 at higher temperatures,however,CH_4 disappears aftermodified by phosphorus.For Mg(HCO_2)_2/Al_2O_3,the dehydrogenation of HCO_2~- takes place on thesurface of Al_2O_3.The decomposition of Mg(HCO_2)_2 on SiO_2 in hydrogen yields two peaks of COand only one appears after modified by phosphorus.When Mg(HCO_2)_2 decomposes on MgO,the firstpeak of CO_2 arises from the reaction of surface Mg~(2+) with HCO_2~- from dissociated Mg(HCO_2)_2.     

Adsorption voltammetry of the scandium-alizarin red S complex onto a carbon paste electrode

For the first time, a new method is described for the determination of scandium based on the cathodic adsorptive stripping of the scandium-alizarin red S complex onto a carbon paste electrode. The second-order derivative linear scan voltammograms of the complex are recorded by use of model JP-303 polarographic analyzer from 0.0 to -1.0 V (versus SCE). Optimum conditions are found to be: an acetic acid (0.36 mol l(-1))-potassium biphthalate (0.064 mol l(-1)) buffer solution (pH 4.0) containing 2.0x10(-5) mol l(-1) alizarin red S, a preconcentration potential of 0.0 V, a preconcentration time of 60 s, a rest time of 10 s and a scan rate of 100 mV s(-1). The results show that the complex can be adsorbed on the surface of a carbon paste electrode, yielding one peak at -0.58 V, corresponding to the reduction of alizarin red S in the complex at the electrode. The detection limit is found to be 6.0x10(-10) mol l(-1) for 3 min of preconcentration time. The linear range is 1.0x10(-9) to 4.0x10(-7) mol l(-1). Application of the procedure to the determination of scandium in the ore samples gave good results.     

Preparation and Characterization of Nanoscopic Organic Semiconductor of Oxovanadium Phthalocyanine

Nanoscopic particles of oxovanadium phthalocyanine (VOPc, phase-II) with different particle sizes are prepared by aggregation of VOPc molecules in the presence of surfactants for the first time. A size effect in the region of nanoscale was observed in the UV-visible spectra. The photoconductivity of the nanoscopic VOPc is much higher than that of bulk VOPc. Copyright 1999 Academic Press.     

Organolithium-mediated diversification of peptide thiazoles

[Reaction: see text] We report a one-step, racemization-free method for the diversification of peptide thiazoles via direct lithiation of the thiazole ring. The method is compatible with N-Boc, N-trityl, carboxylic ester, and carboxamide protecting groups and has been used to directly functionalize the thiazole ring of cyclopeptide natural products.     

利用电荷迁移反应测定头孢羟氨苄

提出一种基于电荷迁移反应简便可靠地测定头孢羟氨苄的分光光度法。在甲醇－乙醇介质中，头孢羟氨苄与氯冉酸于５０℃反应１５ｍｉｎ能够形成稳定的１：１络合物，其λｍａｘ＝５２８ｎｍ，线性范围为２０￣４００ｍｇ／Ｌ。用拟定的方法测定原粉和胶囊，结果与药典法一致。对浓度１００ｍｇ／Ｌ的药物１０次测定相对标准偏差为１．４％，样品的标准加入回收率为９９．０％￣１００．８％。