酸碱指示剂的发展方向

介绍了酸碱指示剂的基础知识和选择依据,重点介绍了目前天然植物色素在酸碱指示剂和酸碱滴定中的应用。同时,由于新技术的快速发展,基于纳米技术和DNA结构转变的无污染环保指示剂更加值得关注。     

基于多元外在表征理论的酸碱中和滴定概念教学设计

在多元外在表征教学理论的基础上,提出了酸碱中和滴定的教学设计,主要包括创设酸碱中和滴定实验情境、引入酸碱中和滴定概念与原理、介绍滴定管、选择指示剂、演示实验、使用Netlogo解释酸碱中和滴定等内容。研究结果表明该教学设计能帮助高职生更好地理解“酸碱中和滴定”知识。     

氯化十六烷基吡啶对酸碱指示剂离解平衡及变色范围的影响

探讨了表面活性剂氯化十六烷基吡啶形成的胶束对溴百里香酚蓝、甲酚红、邻甲苯酚酞和百里香酚蓝离解反应的离解常数的影响,同时,也研究了该表面活性剂对上述四种酸碱指示剂变色范围的影响。实验结果表明,表面活性剂存在时,酸碱指示剂的离解平衡及其变色范围将发生改变,选择适当的胶束溶液作为滴定介质,可以扩大酸碱指示剂的应用范围,同时也可以提高滴定的准确度。     

利用自制花汁指示剂标定氢氧化钠溶液

为了加深学生对酸碱指示剂和酸碱滴定的认识与了解,进一步培养学生的探究兴趣和科学素养,将自制酸碱指示剂与商品酚酞指示剂标定氢氧化钠的结果进行了比较,由F检验和t检验证明,两者测定数据的准确度和精密度无显著性差异,同时探究了有机酸碱指示剂的自制方法及其在不同pH范围内的显色情况,为探究性实验提供了有益的参考。     

甲基橙在酸性溶液中的变色机理

早在18世纪80年代,甲基橙就作为指示剂而用于酸碱滴定,现在已成为酸碱滴定中最常应用的三种指示剂(酚酞、甲基橙、甲基红)之一。甲基橙是对氨基偶氮苯的衍生物,其结构式为:     

新西佛碱3.5—二溴水杨醛缩氨基硫脲的合成及其在荧光滴定中的应用

本文研究了新西佛碱３．５－二溴水杨醛缩氨基硫脲（简称３．５－ＤＢＳＴＳ）的合成，及基为一种新荧光滴定指示剂，应用于有色溶液中酸碱滴定的条件，建立了一种简便，准确，快速测定有色溶液中酸碱浓度的新方法，用于有色饮料中酸含量的测定，结果满意，指示剂发光的ｐＨ突跃范围为７．４８－９．７２，λｅｘ＝５００ｎｍ。     

基于光纤折射率传感原理的新颖酸碱滴定法

首次提出并研究了一种基于光纤折射率传感原理的新颖的化学酸碱滴定分析方法, 为光纤传感技术在化学滴定分析的新应用作出了有意义的尝试. 实验结果表明: 此方法适应于酸碱互滴, 只需少量样品; 在待测样品浓度较低时, 采用浓度高的滴定剂效果更佳, 可测量浓度低至0.001 mol/L 的溶液; 与传统的pH滴定方法等比较, 本方法无需添加终点指示剂, 可实现实时监控; 在二元酸碱的滴定中, 化学计量点指示更明确, 精度更高; 稳定性和准确性测试效果良好, 对HNO₃, NaOH进行测定RSD分别为0.23%和0.28%.     

新西佛碱3．5－二溴水杨醛缩氨基硫脲的合成及其在荧光滴定中的应用

本文研究了新西佛碱３．５－二溴水杨醛缩氨基硫脲（简称３．５－ＤＢＳＴＳ）的合成，及其作为一种新型荧光滴定指示剂，应用于有色溶液中酸碱滴定的条件，建立了一种简便、准确、快速测定有色溶液中酸碱浓度的新方法，用于有色饮料中殴含量的测定，结果满意，指示剂发荧光的ｐＨ突跃范围为７．４８～９．７２，λ＿（ｅｘ）＝３８５ｎｍ，λ＿（ｅｍ）＝５００ｎｍ。     

弱酸的滴定终点及其离解常数的微机直接计算法

在酸碱滴定中,确定滴定终点一般采用指示剂法、“S”形曲线法和直线图解法。前两种方法作为常用的方法,简便易行,但仅适用于具有pH突跃的各种酸碱滴定;而直线图解法虽然适用于极弱酸的滴定,但又需要经过比较复杂的计算和作图,才能求得结果,同样也不便于实际应用。我们采用了微机直接计算法,测算结果无论在准确、快速和简便等方面均取得了较为满意的效果。     

GB及ISO中酸碱指示剂法测定食品中总酸的指示剂研究

在实际分析检测工作中 ,发现 GB或 ISO的酸碱滴定指示剂法 ,以酚酞为指示剂无法克服样品底液颜色深或浊度大而干扰终点观察 ,尤其是果汁饮料系列产品色彩缤纷 ,终点观测不方便 ,甚至无法观测 ,实验重现性差 ,严重影响测定结果的准确度与精密度。本文选择百里酚蓝为酸碱滴定指示剂 ,可克服原法缺点与局限。应用于果汁饮料系列产品柠檬酸含量测定 ,结果满意。     

The effect of surfactant micelles on the dissociation constants and transition points and transition intervals of acid-base indicators

The effects of cetyltrimethylammonium (CTAB), sodiumdodecylsulfate (SDS) and pol(oxyethylene)(9.5)p-(1,1,3,3-tetramethyl; Triton X-100) on the dissociation constants, transition points and transition intervals of thymol blue and bromothymol blue were studied. The experimental results indicated that surfactant micelles remarkably affected dissociation constants, transition points and transition intervals of the acid-base indicators, and the application ranges of acid-base indicators became wider and the titration accuracy increased when an appropriate surfactant micellar solution was chosen as a titration medium.     

Investigation of the Role of Ionic Liquids in Tuning the p<Emphasis Type="Italic">K</Emphasis><Subscript>a</Subscript> Values of Some Anionic Indicators

The effect of imidazolium-based ionic liquids, ([C₁₂mim][Cl] and [C₈mim][Cl]), on the acid-base equilibria of two sulfonated indicators has been studied. The presence of ILs leads to decreased pK _a values because of the stronger electrostatic interaction of cationic ILs with the basic forms of the indicators with more negative charge. The longer alkyl side chain of [C₁₂mim][Cl] compared to [C₈mim][Cl] results in stronger hydrophobic interaction of this IL with the basic forms of the dyes leading to a more effective decrease in the pK _a values. Also, the transition points and transition intervals of the acid-base titration curves of the indicators were affected by the presence of ILs. It was found that the IL interaction with acid-base indicators also results in sharpening the acid-base titration curves of the indicators. From these observations, it is concluded that the presence of ILs can tune the pK _a values of indicators. All the experiments were performed spectrophotometrically and the results were obtained using curve fitting methods.     

Acid-base equilibria in ethylene glycol--III: selection of titration conditions in ethylene glycol medium, protolysis constants of alkaloids in ethylene glycol and its mixtures

Theoretical titration curves are used for the selection of appropriate conditions for the acid-base volumetric determination of weak bases in ethylene glycol medium. The theoretical curves for titration of some alkaloids are deduced graphically on the basis of the logarithmic concentration diagram. The acid-base constants used for the construction of the theoretical titration curves were determined by potentiometric titration in a cell without liquid junction, equipped with a glass and a silver-silver chloride electrode. It is shown that the alkaloids investigated can be determined accurately by visual or potentiometric titration. The same approach for the selection of titration conditions seems to be applicable to other non-aqueous amphiprotic solvents.     

基于移动中和界面电泳酸碱滴定的新原理及装置

基于移动中和界面(MNB)概念,研制了一种基于电泳酸碱滴定(EABT)的新装置.其核心技术是在电泳管中建立MNB,通过对电泳管中的MNB在一定时间内迁移距离的测定,推测酸或碱的浓度.EABT实验表明:HCl浓度的对数值与MNB移动距离存在线性关系.此关系可用于检测未知酸的浓度；不同酸碱指示剂对EABT方法没有明显影响,这能有效避免在容量分析法中不同指示剂对判定终点断滴所造成的误差；EABT具有良好的精密性和稳定性,日内差和日间差的RSD值分别小于1.6％和3.8％.     

Low-Selective GaAs and GaSb Semiconductor Sensors for Potentiometric Analysis of Liquid Media

The possibility of using low-selective sensors based on gallium arsenide and gallium antimonide semiconductor compounds as indicators in acid-base, precipitating, and complexometric titration in model multicomponent systems and natural water was studied.     

Equivalence-point electromigration acid-base titration via moving neutralization boundary electrophoresis

In this paper, we developed a novel method of acid-base titration, viz. the electromigration acid-base titration (EABT), via a moving neutralization boundary (MNR). With HCl and NaOH as the model strong acid and base, respectively, we conducted the experiments on the EABT via the method of moving neutralization boundary for the first time. The experiments revealed that (i) the concentration of agarose gel, the voltage used and the content of background electrolyte (KCl) had evident influence on the boundary movement; (ii) the movement length was a function of the running time under the constant acid and base concentrations; and (iii) there was a good linearity between the length and natural logarithmic concentration of HCl under the optimized conditions, and the linearity could be used to detect the concentration of acid. The experiments further manifested that (i) the RSD values of intra-day and inter-day runs were less than 1.59 and 3.76%, respectively, indicating similar precision and stability in capillary electrophoresis or HPLC; (ii) the indicators with different pK(a) values had no obvious effect on EABT, distinguishing strong influence on the judgment of equivalence-point titration in the classic one; and (iii) the constant equivalence-point titration always existed in the EABT, rather than the classic volumetric analysis. Additionally, the EABT could be put to good use for the determination of actual acid concentrations. The experimental results achieved herein showed a new general guidance for the development of classic volumetric analysis and element (e.g. nitrogen) content analysis in protein chemistry.     

Sulpholane as a solvent for titration of barbiturates and sulpha drugs

Sulpholane (tetramethylenesulphone) has been used as the medium for non-aqueous potentiometric titration of barbiturates and sulpha drugs with tetrabutylammonium hydroxide. Recoveries for 0.1-0.3 mmole of barbituric acid, phenobarbital, amobarbital, barbital, secobarbital, sulphapyridine, sulphadiazine and sulphamerazine were generally in the range 99-101%. A glass-calomel electrode system was used: common acid-base indicators give no colour change in the medium used.     

Comparative acid-base properties of the surface of components of the CdTe-ZnS system in series of substitutional solid solutions and their analogs

The acid-base properties of the surface of solid solutions and binary components of the CdTe-ZnS system are studied by hydrolytic adsorption, nonaqueous conductometric titration, mechanochemistry, IR spectroscopy, and Raman scattering spectroscopy. The strength, nature, and concentration of acid centers on the original surface and that exposed to CO are determined. The changes in acid-base properties in dependence on the composition of the system under investigation in the series of CdB₆, ZnB₆ analogs are studied.     

Recognition of the Protonation Model of a Double-Stranded Polyribonucleic Acid by Spectrometry Data

Simulated and experimental multivariate dependences observed on spectrometric acid-base titration of polyribonucleic acid were examined. Examination of the simulated data revealed the possibility for differentiating distribution diagrams of polymer species produced by complex formation with single- and double-stranded infinite polymers under conditions of incomplete concentration and spectral selectivity. The protonation constants of polycytidylic polyribonucleic acid were calculated from experimental data by using the developed chemometric procedure.     

滴定分析的终点误差随待测物浓度及反应平衡常数单调变化之商榷

为了获得滴定分析的终点误差随待测物浓度、反应平衡常数这两个因素变化的准确规律,推导了有别于林邦终点误差公式的终点误差计算式,根据该式可以判断每个因素对计算结果的影响,结合在配位滴定分析和酸碱滴定分析的具体应用,结果发现：这两个因素其大小的变化不会一定导致终点误差绝对值的单调变化。