共振光散射方法研究钙存在下十二烷基苯磺酸钠的聚集行为

利用共振光散射技术在不引入探针的条件下,建立了室温下直接测定十二烷基苯磺酸钠(SDBS)的临界胶束浓度(CMC)的方法.研究发现:在室温下,SDBS水溶液的共振光散射强度(RLS)随SDBS浓度的增加而增强;且当SDBS接近其临界胶束浓度时,RLS强度增强显著,共振光散射峰分别位于330和396 nm.396 nm处的RLS强度与SDBS浓度关系曲线呈S型曲线,本文将曲线突升起点处两条切线的交点对应的SDBS浓度,确定为SDBS的临界胶束浓度(CMC),这与荧光芘探针和电导率等方法测定结果基本一致.并利用此方法分别研究了Ca2+浓度对SDBS及其SDBS-聚乙二醇辛基苯基醚(OP)复配体系聚集行为的影响.结果表明,SDBS与OP以1∶ 3复配时,增强了体系的抗钙能力.     

共振瑞利散射光谱法对盐酸异丙嗪与盐酸氯丙嗪的同时测定

钼酸铵(AM)与盐酸氯丙嗪(CPZ)及盐酸异丙嗪(PZ)均能反应形成离子缔合物,引起共振瑞利散射(RRS)的显著增强,并出现新RRS光谱。2种反应产物具有相似的RRS光谱特征,其最大散射峰均在365nm处,且在一定范围内散射增强(ΔIRRS)与药物的质量浓度成正比,但RRS强度随药物质量浓度的线性增幅存在显著差异。结合两组分RRS光谱强度的加和性,可建立双组分信号响应的两条同原射线的计量分析法。方法对CPZ和PZ的检出限分别为4.5、7.7μg/L,线性范围均为0.03².4mg/L。将该方法用于血清、尿样和非那根止咳糖浆中CPZ和PZ的同时测定,取得满意结果。     

Determination of Arsenic in Hair by Resonance Rayleigh Scattering Method with Iodine Green–Molybdate System

Abstract

A simple and fast resonance Rayleigh scattering (RRS) method for the determination of arsenic was developed. The method is based on the formation of ion-association complexes {(IG)₃·[As₂(Mo₂O₇)₁₂]H₅}_m of iodine green (IG) and heteropoly acid anion [As₂(Mo₂O₇)₁₂]^14? formed as As (V) reacts with molybdate in H₂SO₄ solution. The ion-association complexes can lead to distinct enhancement of RRS. The enhanced RRS intensity is proportional to the concentration of As (V) in the range of 0.008–0.40 µg ml^?1. The optimum conditions, the influence factors for the reaction, and the effects of coexisting substances have been investigated. The method has high sensitivity and good selectivity; the detection limit for As (V) (3 S ₀/S) is 1.50 ng ml^?1. The method can be applied to the determination of As (V) in hair samples. Furthermore, the mechanism of the reaction and the reasons for RRS enhancement is discussed.     

Saponification of ethyl acetate in 2,6-lutidine + water near its critical point

We have measured the rate of saponification of ethyl acetate (CH₃COOC₂H₅) in 2,6-lutidine (2,6-DMP)?+?water (H₂O) near and far away from its critical point by electrical conductivity experiment. We found that the rate of saponification slowed in the one-phase region at temperatures near the critical point. This behaviour is evidence in support of critical slowing down. Moreover, the experimental results were compared with those of the same reaction in a different critical mixture of 2-butoxyethanol?+?H₂O [Y.W. Kim, Int. J. Thermophys. 25, 1025 (2004)].     

乙二醇对烷基三甲基溴化铵胶团化行为的影响

利用电导法研究了烷基三甲基溴化铵表面活性剂(CnTAB,n=12,14,16),即十二烷基三甲基溴化铵(DTAB),十四烷基三甲基溴化铵(TTAB)和十六烷基三甲基溴化铵(CTAB),在混合极性溶剂乙二醇/水(体积分数0～40%)中的胶团化行为。考察了温度对胶团形成的影响,应用相分离模型估算了三个表面活性剂的胶团热力学参数。结果表明临界胶团浓度(cmc)和反离子解离度(α)都随乙二醇组分的增加而增大。在乙二醇/水混合溶剂中胶团形成的标准吉布斯自由能相差很小,混合焓都是负值,而混合熵都为正值,说明焓-熵补偿效应在胶团形成中起主导作用。     

Thermosensitive gels incorporating polythioether units for the selective extraction of class b metal ions

Novel temperature-responsive copolymers of N-isopropylacrylamide and monoaza-tetrathioether derivative, were synthesized for the selective extraction of soft metal ions such as silver(I), copper(I), gold(III) and palladium(II) ion. The ratio between N-isopropylacrylamide group and monoaza-tetrathioether group in the copolymer was determined. The ratio between N-isopropylacrylamide group and monoaza-tetrathioether group varied in the range of 66:1–187:1. Each lower critical solution temperature (LCST) of the polymer solution was determined spectrophotometrically by the relative absorbance change at 750 nm via temperature of the polymer solution. Metal ion extraction using the copolymer with appropriate counter anions such as picrate ion, nitrate or perchlorate ion was examined. Soft metal ions such as silver(I), copper(I), gold(III) and palladium(II) ion were extracted selectively into the solid polymer phase. The extraction efficiency of a metal ion such as silver ion increased as the increase of the ratio of the monoaza-tetrathioether group to N-isopropylacrylamide group in the polymer. The quantitative extraction of class b metal ions as well as the liquid–liquid extraction of metal ions with monoaza-tetrathioether molecule was performed.     

Gutmann's Donor Numbers Correctly Assess the Effect of the Solvent on the Kinetics of SNAr Reactions in Ionic Liquids

We report an experimental study on the effect of solvents on the model S_NAr reaction between 1‐chloro‐2,4‐dinitrobenzene and morpholine in a series of pure ionic liquids (IL). A significant catalytic effect is observed with reference to the same reaction run in water, acetonitrile, and other conventional solvents. The series of IL considered include the anions, NTf₂^?, DCN^?, SCN^?, CF₃SO₃^?, PF₆^?, and FAP^? with the series of cations 1‐butyl‐3‐methyl‐imidazolium ([BMIM]⁺), 1‐ethyl‐3‐methyl‐imidazolium ([EMIM]⁺), 1‐butyl‐2,3‐dimethyl‐imidazolium ([BM₂IM]⁺), and 1‐butyl‐1‐methyl‐pyrrolidinium ([BMPyr]⁺). The observed solvent effects can be attributed to an “anion effect”. The anion effect appears related to the anion size (polarizability) and their hydrogen‐bonding (HB) abilities to the substrate. These results have been confirmed by performing a comparison of the rate constants with Gutmann's donicity numbers (DNs). The good correlation between rate constants and DN emphasizes the major role of charge transfer from the anion to the substrate.