萃取有机相中微乳液的稳定性研究

赊P507钾盐外，PSO7理、钠、按盐和P204的理、钠、钾、按以及有机接盐等与醇一油一水在一定条件下都能形成微乳液．因此，进一步搞清这些体系形成微乳液的结构、性质和稳定性，对革取化学研究是十分重要的．我们曾对PSO7（K）一醇一正庚烷一水四组分体系的结构参数［’j和物理化学性质［’］进行过研究，观察到辅助表面活性剂性质和含水量对微乳液结构有重要的影响·本文采用测定微乳液电导的变化，研究含有不同醇和不同量水时，P507（K）在革取有机相中形成微乳液颗粒的活化能（凸E），并用凸E的大小来描述和比较微乳液的界面膜强度…     

Separation of chlamydosporol epimers by reversed-phase HPLC using commercial solvent optimisation software

Summary Two epimers of the mycotoxin chlamydosporol were separated by HPLC on an RP-18 column using a quaternary mobile phase consisting of water (79.1%), methanol (10.0%), acetonitrile (10.4%) and tetrahydrofuran (0.5%), with a flow rate of 1 ml min^–1. This optimal composition of mobile phase, with which the resolution value for the two epimers (1 and2) was 2.73 with retention times of 5.88 and 7.12 min, respectively, was achieved by the application of Philips Solvent Optimisation Software PU 6100. The presence of free silanols on the stationary phase was shown to be an essential requirement for the separation of the chlamydosporol epimers.     

Polarisabilites moléculaires et effet diélectrique de milieu à l'état liquide. Étude théorique de la molécule d'eau et de ses diméres

The model of Onsager in which a polar molecule undergoes a reaction field due to the polarization of the molecular surroundings is used to evaluate by a S.C.F. calculation (CNDO/2 approximation) the modifications of a molecular structure in the liquid state.Application to water molecule and to three polar dimers for values of the dielectric constant varying between 3 and 78, shows that most of geometric parameters and dipoles moments vary of few per cent when the molecule is inserted in a liquid. In the liquid state dipole moments do not depend very much on the dielectric constant but energies and relative stabilities of isomers are strongly dependent on the medium.[/p]

     

芹菜中黄酮类物质的提取和测定

采用碱溶酸析法，成功地提取了芹菜中黄酮类物质。经HCl-镁粉反应和红外光谱鉴定，提取物为黄酮类物质。另外，利用分光光度法，以芦丁为标准对芹菜的叶和茎中的总黄酮分别进行了测定，其质量分数分别为10．19mg／g，3．064mg／g。同时讨论了时间及色素对测定方法的影响，结果表明，显色时间在40min内稳定，色素引起误差为5％。     

The effectiveness of solvents as hydrogen bond donors

Taft and Kamlet's -scale of solvent hydrogen bond donation ability is reexamined with regard to its correlations with three widely used polarity scales: Dimroth and Reichardt's E _T (30), Kosower's Z and Mayer's A _N , as well as with the _m values of the solvents when present as monomeric solutes. The correlation with E _T serves to extend the solvent -scale according to the expression:

Solubility Measurements of Surfactants and Dissolution of Cytochrome c in 1,1,1,2‐Tetrafluoroethane Modified with Organic Solvents

The solubilities of four surfactants, sodium bis‐2‐ethylhexyl sulfosuccinate (AOT), cetyltrimethylammonium chloride, didodecyldimethylammonium bromide, and n‐dodecyltrimethylammonium chloride in liquid refrigerant 1,1,1,2‐tetrafluoroethane (R134a) modified with methanol, ethanol, and 2‐propanol were measured. The measurements were performed under 25 and 50 bar at 25 °C. The solubility of AOT was as high as 92 mM in R134a with addition of 2% ethanol. Cytochrome c molecules were then verified to be soluble in the AOT‐containing and ethanol‐modified R134a solution. Accordingly, liquid R134a is suggested as a potential extraction solvent for hydrophilic compounds.     

Comparison of the analysis of corticosteroids using different techniques

In this work we have optimized the analysis of 18 human corticosteroids, some endogenous (tetrahydrocortisol, tetrahydrocortisone, cortisol, and cortisone) and others synthetic (betamethasone, budesonide, cortisone acetate, desonide, dexamethasone, dexamethasone acetate, flunisolide, fluocinolone acetonide, halcinonide, methylprednisolone, prednisolone, prednisone, triamcinolone, and triamcinolone acetonide). Three analytical techniques were developed: ELISA, gas chromatography coupled with mass spectrometry (GC–MS), and liquid chromatography coupled with mass spectrometry (LC–MS). Several sample-preparation methods were optimized for each technique and enabled compounds of interest to be extracted from small urine samples (several mL). The results enabled us to assess the possibilities and the sensitivity of each technique for application to doping tests.     

Determination of partition behavior of organic surrogates between paperboard packaging materials and air

The suitability of recycled paperboard packaging materials for direct food contact applications is a major area of investigation. Chemical contaminants (surrogates) partitioning between recycled paper packaging and foods may affect the safety and health of the consumer. The partition behavior of all possible organic compounds between cardboards and individual foodstuffs is difficult and too time consuming for being fully investigated. Therefore it may be more efficient to determine these partition coefficients indirectly through experimental determination of the partitioning behavior between cardboard samples and air. In this work, the behavior of organic pollutants present in a set of two paper and board samples intended to be in contact with foods was studied. Adsorption isotherms have been plotted and partition coefficients between paper and air have been calculated as a basis for the estimation of their migration potential into food. Values of partition coefficients (Kpaper/air) from 47 to 1207 were obtained at different temperatures. For the less volatile surrogates such as dibutyl phthalate and methyl stearate higher Kpaper/air values were obtained. The adsorption curves showed that the more volatile substances are partitioning mainly in air phase and increasing the temperature from 70 to 100 degrees C their concentrations in air (Cair) have almost doubled. The analysis of surrogates was performed with a method based on solvent extraction and gas chromatographic-flame ionization detection (GC-FID) quantification.     

Solvent-assisted catalysis mechanism on Keto–enol tautomerism of cyameluric acid

The keto–enol tautomerism of cyameluric acid, both in gas phase and in water and methanol solution, has been studied at the B3LYP/6-31++g(d,P) level of theory in this paper. The harmonic frequencies of all the structures are calculated. The results show that the transition states of the tautomerism are 4-membered ring conformations in gas phase, whereas 6-membered ring conformations in solution. In the first proton transfer, activation energy ΔE^# is 56.4 and 50.9 kJ/mol for water and methanol solution, respectively, which is much lower than that in gas phase (163.2 kJ/mol). Solvent molecules (water and methanol) produce an important catalytic effect in the tautomerism, especially for methanol-solvated system. NBO analysis shows that there is a strong interaction between cyameluric acid and solvent molecules in transition states. AIM charge analysis indicates that the keto–enol tautomerism shows a certain degree of proton transfer character. From the reaction enthalpy and reaction rate point of view, keto–enol tautomerism in water-solvated and methanol-solvated system is easier than that in gas phase. The keto–enol tautomerisms are endothermic both in gas phase and in solution, so the enol forms are less stable than the keto ones.     

Sodium bromide catalysed one-pot synthesis of tetrahydrobenzo[b]pyrans via a three-component cyclocondensation under microwave irradiation and solvent free conditions

Sodium bromide catalysed three-component cyclocondensation of aryl aldehydes, alkyl nitriles and dimedone proceeds under microwave irradiation in solvent free conditions to give highly functionalised tetrahydrobenzo[b]pyrans in excellent yields.