络合滴定法测定钙含量微型实验研究

利用微型滴定法测定含钙制品中的Ca2 含量,并对微型滴定法与常量滴定法的平行测定结果进行了比较。结果两种方法无显著性差异,F检验t检验结果均在允许范围内,相对偏差均小于2.0%,微型滴定法的精度达到常量滴定法测定水平,能满足化学分析要求。     

固定pH滴定法测定弱酸弱碱性药物

报道一种水溶液吕测定弱酸弱碱性药物的新型滴定分析方法－固定ｐＨ滴定法，其理论基础是弱酸弱碱在水溶液中各种存在形式的分布系数在ｐＨ值固定时为常数，对甲硝唑，盐酸美西律等离散常数在１０＾－８至１０＾－１１范围内的７种弱酸弱碱性药物进行测定。结果与药典法吻合，回收率在９９．４％～１００．６％，方法简便，快速，准确，制剂中的赋形剂及色物不影响测定。     

Approaching supramolecular functionality

Functional molecules require a high degree of complexity which is difficult to achieve by covalent synthesis. This article discusses supramolecular approaches to the creation of larger architectures through noncovalent bonds, self-assembly, and template strategies. It highlights selected examples for the structural and conformational control of function and attempts to identify difficulties and challenges which may arise in future.     

Approximation of titration curves and other sigmoidal functions by proportionally spaced cubic B-splines

Proportionally spaced cubicB-splines are an appropriate function system for the approximation of titration curves and other sigmoidal functions. They give a smooth weighted leastsquares fit without instability problems. The degree of smoothing depends only on the number of spline function which can be chosen by the user. The equivalence points of titration curves can be estimated with high accuracy from the zeros of the second derivative.The method gives good approximation curves even in the case of empty data regions, i. e. there are no artefacts in subranges where no data points exist. The routine has been tested successfully with large series of simulated and experimental data.     

Compatibility and stability tests of risperidone with soft-drinks by isothermal titration microcalorimetry

Isothermal titration microcalorimetry has been applied to investigate the compatibility testing of risperidone oral solution with soft-drinks and the interaction with tea tannin such as (–)-epigallocatechin, (–)-epicatechin, theaflavin and their gallates. In aqueous solution, risperidone was exothermically bound to tea tannin with binding affinity (10³–10⁴ M^–1), small enthalpy and entropy changes reflecting van der Waal’s interaction to form an insoluble complex at 1:1 molar ratio. The heat effect of risperidone titrated into soft-drinks containing tannin was exothermic and proportional to the quantity of the complex. While, no significant heat effect was found for risperidone titrated into a pet-bottled water and an infusion of parched barley without tea tannin. These results were agreed with stability testing of risperidone in some soft-drinks by HPLC method.     

Spectrophotometric and titrimetric determination of gallium in minerals and ores using semimethylthymol blue

The composition, overall stability constant and molar absorptivity of the chelate of gallium(III) ion with semimethylthymol blue, SMTB, were determined spectrophotometrically in acetate buffer (pH 4.5–5). A violet Ga(SMTB) chelate was formed with logarithmic overall stability constant of 18.0±0.1 (I=0.1) and molar absorptivity of 4.25×10⁴l mol^–1cm^–1 (_max 580 nm). SMTB is proposed as a new reagent for the spectrophotometric determination of micro-molar amounts of gallium(III). The colour development depends on time, temperature, pH and buffer species. The interference of different cations, anions and organic acids on gallium(III) determination was also investigated. Beer's law was obeyed for 3.5–31.3 gGa(III)/25ml (0.14–1.25 g ml^–1). SMTB was used for the spectrophotometric determination of gallium in different grade minerals and ores and the results were of acceptable error and relative standard deviation. Comparison between the two suggested methods and atomic absorption spectrometry for Ga(III) determination was carried out.     

数据校正法与条件滴定度法提高络合滴定准确度

对于1gK＇_(My)C_M或1gK＇_(MY)C_M -1gK＇_(NY)C_N较小的络合滴定,可以使用单一参比溶液,使全部试样的pMeq均大于或小于该参比溶液的PM值,并使用数据校正法或条件滴定度法校正结果。实验证明,即使1gK＇_(MY)C_M或1gK＇_(MY)C_M -1gK＇_(NY)C_N小至4,仍能得精确结果。     

平菇多糖稀溶液行为的研究

平菇多糖属生物高分子, 文章对平菇多糖稀溶液性质进行了研究。实验系采用Elias浊点滴定法测定平菇多糖溶液的θ组成, 用快速动态膜渗透计和粘度法测定平菇多糖的数均分子量、维利系数与分子链的构型参数。探讨其在θ条件下的分子形态及用Tung函数法等处理分级数据, 从而获得平菇多糖的分子量分布。     

Ga3(HPO3)4F4(H3DETA) (DETA=diethylenetriamine): A new open-framework fluorinated gallium phosphite with pentameric building unit

Ga₃(HPO₃)₄F₄(H₃DETA) is a new open-framework fluorinated gallium phosphite obtained by mild hydrothermal synthesis using diethylenetriamine as templated agent and characterized by single crystal X-ray diffraction, the powder X-ray diffraction, IR spectroscopy, TGA, ICP and elemental analyses. It crystallizes in the monoclinic space group C2/c, a=12.741(6) Å, b=12.068(6) Å, c=11.988(5) Å, β=94.902(8)^o, V=1836.6(15) Å³, Z=4. The construction of 3D open-framework structure in the title compound may be viewed as the assembly of pentameric building units and HPO₃ groups. The pentameric building unit is the first to be found, which lead to form the three types of channels along a-, b- and c-axes, respectively, in gallium phosphite. The triprotonated DETA cations are inserted within the 10-membered ring channels and interact with anions of the framework via hydrogen bonds.     

Thermodynamic Data for the Complex Formation of Alkylamines and Their Hydrochlorides with α-Cyclodextrin in Aqueous Solution

The formation of complexes between α-cyclodextrin and n-alkylamines and their hydrochlorides has been studied in aqueous solution using calorimetric titrations. All alkylamines form stronger complexes than the corresponding hydrochlorides. The values of the reaction enthalpies are smaller for the alkylamine hydrochlorides compared with the alkylamines. By increasing the number of methylene groups, these differences become smaller. In addition, the reaction enthalpies for protonation of the alkylamines and their complexes with α-cyclodextrin have been measured. The heat of protonation of these complexes is always smaller compared with the alkylamines. Due to the protonation and the formation of a strong solvation shell around the ammonium group the interactions with α-cyclodextrins are weakened. From a thermodynamic cycle using all measured reactions, it can be concluded that the aggregation of the alkylamines with long alkyl chains (heptyl-, octyl-, and nonylamine) has an influence on the values of the reaction enthalpies and entropies for the protonated form only.This revised version was published online in July 2005 with a corrected issue number.