Indirect Determination of Captopril with Sodium Nitrate and Thiocyanate by Floatation Separation of Copper

A new method for indirect determination of captopril (CPT) with NaNO₃ and NH₄SCN by floatation and separation of copper has been studied. In the weak acid, a small amount of Cu(II) can be reduced to Cu(I) by CPT, then Cu(I) reacted with the SCN, which can float on the surface of the liquid phase with NaNO₃. A good linear relationship is observed between the floatation yield (E%) of Cu(II) and the amount of captopril. The linear range is 2?32 mg/L. On the ground, captopril can be indirectly determined by determining E(%) of Cu(II). The method is simple, rapid, reliable and has good selectivity. The developed method can be applied to indirect determination of captopril with satisfactory results.     

我国锂资源及其开发技术进展

介绍了我国盐湖锂资源的现状及其开发技术的进展情况,讨论了各种提锂工艺的优缺点,并对现阶段我国盐湖锂资源的开发提出了建议。     

A 1H NMR study of 1,4-bis(N-hexadecyl-N, N-dimethylammonium)butane dibromide/sodium anthranilate system: spherical to rod-shaped transition

The effect of addition of sodium anthranilate to 5 mM micellar solutions of gemini surfactant 1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide is investigated by ¹H NMR. The solubilization site of anthranilate anion near the micellar surface is inferred. In the micelles, the An⁻ ions intercalate among the surfactant headgroups producing morphological changes.     

A Convenient Regiospecific Synthesis of New Conjugated Tetrazole Derivatives via the Reaction of Dienones with the Tetrachlorosilane-Sodium Azide Reagent and their NMR Structural Assignment

Summary. Several new 1-aryl-, aralkyl-, and heteroaryl-5-(4-phenylbuta-1,3-dienyl)tetrazole derivatives and annulated tetrazole derivatives were efficiently and regiospecifically prepared in nearly quantitative yield via a facile one step reaction of dienones with a combination of tetrachlorosilane and sodium azide in acetonitrile under mild conditions. A complete structure assignment of three representative examples of the tetrazoles was achieved by advanced 2D NMR measurements including COSY, TOCSY, HSQC, HMBC, NOESY, and ROESY experiments.Received March 17, 2003; accepted March 18, 2003 Published online July 28, 2003     

铋(Ⅲ)-8-羟基喹哪啶体系极谱行为——表面活性剂增敏机理和分析应用——Ⅱ.铋(Ⅲ)-8-羟基喹哪啶络合物电极反应和十二烷基苯磺酸钠增敏机理

试验表明,铋(Ⅲ)-8-羟基喹哪啶(8-OXQ)络合物(pHll,-0.60V)的峰电流(p)具吸附特性,为准可逆电极反应过程,其电子转移数(n),传递系数(α)及饱和吸附量(Γ_ο)分别为3,0.45,6.5×10~(-12) mol/cm~2。加入十二烷基苯磺酸钠(SDBS)未形成三元络合物,因SDBS的超载强烈吸附,引起诱导吸附,电双层结构激烈变化,而使电流峰形巨变,电流峰高(i_p)增大10余倍。讨论并指出SDBS对Bi(Ⅲ)与8-羟基喹啉(8-OX)及衍生物络合吸附电流增敏或抑制,与试剂组分、结构、解离态及络合物存在状态、电荷数、符号有关。     

The reaction of fluorine-containing compounds with conjugated dienoic acids initiated by sodium dithionite

The reaction of fluorine-containing halides and acetamides with conjugated dienoic acids initiated by sodium dithionite gave halide-free 1,4-adducts in 40-80% yields, with the E configuration as the major products.     

Die Kristallstruktur des Natriumorthogermanats,Na4GeO4

The crystal structure of the title compound has been determined from single crystal X-ray diffraction data and refined toR=0.125. The unit cell is triclinic, space group P, (No. 2),a=5.688(1),b=5.701(1),c=8.583(1) Å, =81.32(1), =71.50(1), =67.95(1)° andZ=2. The structure consists of isolated [GeO₄] tetrahedra linked together by four- and five-coordinate sodium atoms. Na₄GeO₄ is isostructural with Na₄CoO₄ (which has been described to be non-centrosymmetric and for which a centrosymmetric model is presented), K₄GeO₄, K₄SnO₄ and K₄PbO₄.

     

硫酸铈-亚硫酸钠流动注射化学发光法测定多贝斯

基于多贝斯对硫酸铈-亚硫酸钠化学发光体系的抑制作用,建立了流动注射-化学发光测定多贝斯的新方法,并且研究了各种实验条件的影响。在酸性介质中,发光强度的降低(ΔICL)与多贝斯浓度在4.0×10-6~6.0×10-5mol/L范围内呈良好线性关系,回归相关系数为0.9976,方法的检出限为2.0×10-6mol/L,相对标准偏差为1.2%(n=6)。     

Selective synthesis of isobutanol by means of the Guerbet reaction: Part 2. Reaction of methanol/ethanol and methanol/ethanol/n-propanol mixtures over copper based/MeONa catalytic systems

The synthesis of isobutanol via the Guerbet condensation between methanol and ethanol was studied by using sodium methoxide (MeONa) as soluble basic component and copper-based catalysts as heterogeneous dehydrogenating/hydrogenating metal species. The effect of the nature of the catalyst and the relative amount of its individual components with respect to the reacting alcohols as well as of temperature on productivity and selectivity of the process was investigated. The collected data indicated that the copper chromite/MeONa was more active than Cu-Raney/MeONa system. The reaction was shown to proceed with the formation only of n-propanol and isobutanol. Ethanol conversion up to 61% with selectivity to isobutanol up to 98.4% was obtained. The same catalytic systems were also employed in the reaction of the methanol/ethanol/n-propanol ternary mixture. Again copper chromite/MeONa resulted more active than the Cu-Raney/MeONa system. Finally, experiments were carried out on methanol/n-propanol mixtures in the presence of the copper chromite/MeONa catalytic system by recycling both the recovered solid copper component and the liquid reaction mixture for evidencing eventual copper leaching by MeONa. On the basis of the obtained results it was concluded that in the Guerbet reaction copper chromite works as heterogeneous catalyst.     

Comparison between the adsorption behaviors of an organic cation and an organic anion on several reversed-phase liquid chromatography adsorbents

Adsorption data of an organic cation (propranololium chloride) and an organic anion (sodium 1-naphthalene sulfonate) were measured by frontal analysis on two RPLC adsorbents, Symmetry-C18 and XTerra-C18, with aqueous solutions of methanol as the mobile phases. The influence of supporting neutral salts on the adsorption behavior of these two ions are compared. The Henry constants are close (H approximately 5). The four sets of isotherm data are all well accounted for using the bi-Moreau model. However, the isotherms of the two ions behave differently at high concentrations. The initial behaviors of all the isotherms are antilangmuirian but remain so in a much wider concentration range for the cation than for the anion, due to its stronger adsorbate-adsorbate interactions on the low-energy adsorption sites. The retention times of both ions increase with increasing concentration of neutral salt in the mobile phase, suggesting the formation of ion-pair complexes, with Cl- for the cation and with Na+ for the anion. The adsorbate-adsorbate interactions vanish in the presence of salt and the bi-Moreau isotherm model tends toward a bi-Langmuir model. Differences in adsorption behavior are also observed between the cation and the anion when bivalent inorganic anions and cations, respectively, are dissolved in the mobile phase. High concentration band profiles of 1-naphthalene sulfonic acid are langmuirian, except in the presence of a trivalent cation, while those of propranolol are antilangmuirian under certain conditions even with uni- or divalent cations.