A sensitive and rapid method for determination of pyrophosphatase activity

A new, rapid and sensitive method of measuring the rate and amount of PPi hydrolysis is described. The method is based on registration of small pH changes, caused by decrease of hydrogen-ion concentration during the pyrophosphatase reaction. With this detected value of hydrogen-ion concentration change and the buffering capacity of each reaction mixture determined by titration, the rate and amount of PPi hydrolysis can be calculated. The results obtained by pH method are in good agreement with values determined by direct phosphate analysis. The described method can be applied to the continuous determination of pyrophosphatase activity in chromatophores, mitochondria, crude extracts or purified enzymes.     

Kinetic detection of the end-point in titrations involving slow reactions Direct titration of polyhydroxy-compounds with periodate

A new titration technique is described in which the end-point is determined by measuring the relative reaction rate of the titration reaction. This technique is adequate for rather slow reactions where conventional direct titrations are not applicable. The titrations are done automatically under microcomputer control. The efficiency of this technique is demonstrated with direct titrations of certain polyhydroxy-compounds with standard periodate solution. Ethylene glycol and propylene glycol (0.05-0.3 mmole), glycerol (0.06-0.17 mmole) and mannitol (0.01-0.03 mmole) were determined with average relative errors of 0.1-0.3%.     

热动力学的滴定量热发研究 I.一级反应的热动力学

用滴定量热法分别建立了滴定期和滴反应期一级反应热动力学的数学模型，根据这两种模型，均可由一次实验的滴定量热曲线同时解析出一级反应的速率常数和摩尔反应焓。用滴定量热法研究了去离子水溶剂中乙酸乙酯皂化反应的热动力学，实验结果验证了本文用滴定量热法研究一级反应热动力学的适用性。     

催化滴定(Ⅱ)——EDTA滴定金属离子

许多学者研究过金属离了的催化络合滴定,但都是间接滴定,即先加入过量的氨羧络合剂,然后用金属离子如锰、镍、钴、铜、铁等反滴定。Olson等研究下列交换反应:Ni-Trien+Cu-EDTA⇔Cu-Tricn+Ni-EDTA发现当无游离的EDTA或三亚乙基四胺(Trien)时交换反应进行得很慢,但当存在痕量的EDTA或Thien时交换反应大大加速,籍此可用动力学法测痕量的金属离子或配位     

Omega Chrome Fast Blue 2G: A new metal indicator for EDTA titrations

Summary Omega Chrome Fast Blue 2G was used as an indicator for the direct titration of calcium, magnesium, manganese and nickel. A displacement reaction was described for the titration of lead and cadmium. Fenugreek mucilage which is a colourless polysaccharide was used as medium for spot tests. The method is illustrated by spot tests for Ca, Mg, Mn, Ni, and Co. It has the advantage of sensitivity and simplicity.     

Behaviour of ferroin indicator in iron(ii)- dichromate titrations A Critical study

A critical evaluation has been made of the optimum conditions for a successful direct and reverse titration of iron(II) with dichromate, with ferroin as indicator, taking into account the influence of acidity, the catalytic effect of iron(III) and the induction effect of the iron(II)-dichromate reaction on the indicator oxidation reaction. The difference in the behaviour of the indicator in the direct and reverse titrations is believed to be due to the presence of a slow : step in the indicator oxidation mechanism ; this is however surmounted in the reverse titration, making it possible to use the indicator even in a 2N sulphuric add medium for this titration. The higher potentials recorded in the reverse titration are believed to be due to the oxide film on the platinum metal electrode. While iron(III) seems to help lower the kinetic barrier of the slow step sufficiently in the indicator oxidation mechanism, the ferriin-ferroin system seems to help m a similar way toe establishment of a more positive potential of the Ct(VI)/Cr(III) system at the platinum electrode in me direct titration; this value explains the feasibility of the direct visual titration in 2N sulphuric acid, although the colour change at the end-point is slow for other reasons.     

Titrimétrie des ions céreux par le permanganate

A direct titration method of cerous ions by means of permanganate in a nearly neutral pyrophosphate solution is described.The reaction has been studied both potentiometrically and amperometrically. The latter method yields the bcbt results and permits the use of a particularly simple and practical device.The only interfering clement is in fact manganese.     

An analytical study of the vanadium(IV)-chromium(VI) reaction

Experimental conditions for reduction of chromium(VI) by vanadiuin(IV) are described. An excess of vanadium(IV) is necessary. The evidence indicates that the direct titration fails for kinetic rather than thermodynamic reasons, but that the back-titration procedure is made quantitative by the slow rate of the reverse reaction between vanadium(V) and chromium(III).     

A new flow injection titration analysis

Summary A new type of flow injection titration method where a well-stirred mixing chamber is placed in the middle of the injection loop of a 6-way valve has been developed. With this method expensive or unstable reagents can be used for the titration. Moreover, it is potentially available for slow titration reactions. Its fundamental characteristics have been investigated using acid-base titration reaction with phenolphthaleine as the indicator. The sampling rate was 60–120 samples per hour and its reproducibility was also high (3%).

---

Neues Verfahren zur Fließinjektions-Volumetrie

     

The use of Metomega Chrome Blue BBL as a metal indicator and its application for the determination of calcium and magnesium in serum

Summary Metomega Chrome Blue BBL was used as a metal indicator for the detection and titration of calcium, magnesium, manganese, nickel and manganese. A displacement reaction was described for the titration of cadmium using Mn-EDTA. A stepwise titration was conducted for the direct titration of both calcium and magnesium in blood serum.Fenugreek mucilage was used as a media for increasing the sensitivity limits of detection of barium, cadmium, cerous, calcium, copper, cobalt, magnesium, manganese, nickel, lead and zinc.     

催化滴定 III: 影响EDTA滴定金属离子时突跃的因素

本文探讨以催化反应指示终点直接用EDTA滴定金属离子时影响突跃的因素. 采用滴定曲线突跃部分的斜率, tanθ, 作为指示反应速率的表征. 通过实验探讨了PH、CuEDTA和NiTrien用量以及滴定速率对tanθ的影响, 并从理论上导出tanθ的近似表达式, 它是NiTrien的起始浓度、加入EDTA的速率以及EDTA与NiTrien的反应速率常数三个变量的线性函数, 利用这一表达式可对实验结果作出较为满意的解释.     

An automatic back titration method for microchemical analysis

An automatic back titration method for microchemical analysis is introduced, which is based on conventional volumetric analysis's principle and the use of flow injection analysis apparatus for the automation and microminiaturization of the process. The sample and a known, but excess amount of a calibrated reagent solution are injected and propelled into a titration cell, where their reaction takes place. The excess of the reagent is then titrated with a titrant containing an indicator and the end point is monitored photometrically. Since homogeneous mixing in the titration cell is obtained magnetically in the whole process, there is a linear relationship between the analyte's concentration and the volume of the titrant consumed. Nickel in the range of 10-70 g 1(-1) is determined by the above method, in which 30 microl of sample and 500 microl of EDTA are injected and the excess of EDTA is titrated with a standard zinc salt solution containing xylenol orange which could be blocked by nickel ion in a direct titration. This method is characteristic of low sample and reagent consumption, high sampling rate as high as 45 samples h(-1), negligible effect of sample's viscosity, small carry-over effect (lower than 0.14%), and very good precision, whose relative standard deviations are as small as 0.24%.     

直接滴定法测定葡萄酒中糖含量操作条件的探讨

通过分析滴定温度、滴定碱度、热源温度、沸腾时间和滴定速度等操作条件,探讨了操作条件对直接滴定法测定葡萄酒中糖含量的影响,确定了最佳操作条件,提高了测定结果的准确度。     

Study of intermolecular interaction of Mg-5,15-Di(o-methoxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphin with o-xylene organic peroxides. Effect of imidazole on the reaction kinetics

Using the method of spectrophotometric titration a reaction of magnesium porphyrinate with the o-xylene organic peroxides was investigated, the reaction mechanism and kinetic parameters were determined. The effect of imidazole on the rate of the reaction under investigation was demonstrated. The presence of steric strain in the magnesium porphyrinate macrocycle and its increase in the course of formation of intermediates was observed.     

Selective determination of thiamine (vitamin B(1)) in pharmaceutical preparations by direct potentiometric argentometric titration with use of the silver-silver sulphide ion-selective electrode

A simple and selective argentometric titration method is described for determination of thiamine (vitamin B(1)), based on direct potentiometric titration in alkaline media (0.5M) in which a chemical transformation takes place, creating two acidic groups, the protons of which are replaceable by silver ions. The acidimetric and argentometric potentiometric titration curves display two consecutive potential breaks specific for thiamine. The second break is reproducible and corresponds to a 2:1 reaction ratio of silver to thiamine. No interference is caused by other vitamins, active ingredients and inactive excipients normally present in multivitamin preparations. The results obtained for determination of thiamine in pure powders, pharmaceutical tablets and ampoules showed an average recovery of 98.2% of the nominal values and a mean standard deviation of 0.5%, and agreed fairly well with data obtained by the British Pharmacopoeia procedure.     

Method for avoiding the interference of formamide with the Karl Fischer titration

 The Karl Fischer titration is based on a specific chemical reaction. Several measures exist to make all the water of insoluble samples accessible for the chemical reactants. The most efficient are the titration at elevated temperatures, the use of a homogenizer in the titration vessel and the modification of the polarity of the working medium (essentially methanol) by the addition of appropriate solvents like chloroform or formamide. It is known however that formamide interferes with the Karl Fischer reaction and so causes more or less false results. This effect increases with higher temperatures. A method is therefore presented to avoid this interference, even when working at the boiling point of the working medium. It takes advantage of the fact that the side reaction has a practically constant velocity, at least as long as usual titrations last. Thus, a constant additional consumption of Karl Fischer reagent is observed. This can be accounted for by measuring this effect before the start of the determination and by deducting the additional reagent consumption, which is proportional to the duration of the titration, from the totally added volume. With certain modern titrators this can even be carried out automatically. They can continuously measure the so-called drift, the titration rate necessary to keep the titration cell dry, and have the capability to use this drift as stop criterion for the titration. This means that the analysis is terminated when the drift existing before the titration is reached again. The additional consumption of reagent, to be deducted from the total volume, can (automatically) be calculated from the drift rate and the titration time. The proposed procedure allows the use of formamide as additional solvent, even at high temperatures, in order to shorten determination times considerably. It avoids false results due to the interference, which has so far prevented its use when exact results were desired and when the duration of the analysis was long. Received: 30 May 1996 / Revised: 26 July 1996/Accepted: 30 July 1996     

电位滴定分析方法在地质样品主量元素检测中的应用

对电化学分析法与电位滴定法的发展进行了简要介绍。电位滴定法是将电位分析与传统滴定法进行结合的新型分析方法,其反应类型包括酸碱滴定、沉淀滴定、氧化还原滴定与络合滴定,因其仪器操作简单,终点判断更加明确且节省人力的特点而得到广泛关注,因此就近年来电位滴定在地质样品中主量元素检测的应用进行了总结,分别对石灰石、白云石、硅酸盐、铬矿石、铁矿石、锰矿石、铜矿石与水等地质样品的电位滴定检测方法进行了阐述,电位滴定的应用将随着技术发展得以提升。     

The oxidation of organic substances with compounds of trivalent manganese: XXVII. The oxidation of 4,4′-dihydroxyazobenzene with the diphosphate complex of trivalent manganese

The oxidation of 4,4′-dihydroxyazobenzene with the diphosphate complex of trivalent manganese was studied. The reaction stoichiometry was found and a procedure for a direct potentiometric titration of the test substance has been proposed.     

A rapid method for the determination of some antihypertensive and antipyretic drugs by thermometric titrimetry

A simple and rapid method is described for the direct thermometric determination of milligram amounts of methyl dopa, propranolol hydrochloride, 1-phenyl-3-methylpyrazolone (MPP) and 2,3-dimethyl-1-phenylpyrazol-5-one (phenazone) in the presence of excipients. The compounds are reacted with N'-bromosuccinimide and the heat of reaction is used to determine the end-point of the titration. The time required is approximately 2 min, and the accuracy is analytically acceptable.     

The Art of Titration. From Classical End Points to Modern Differential and Dynamic Analysis

Titration represents the quantitative determination of a chemical change in response to the variation in concentration of a standrad. Information on reaction parameters is usually obtained from an analysis of the shape of the titration curve. In this paper the derivatives of titration functions with respect to concentration variables and with respect to equilibrium parameters are compared with one another. The latter can be determined directly from amplitudes and time constants of the dynamic responses to equilibrium perturbations, brought about by fast alterations of temperature, pressure or electirc field. Three general situations have to be distinguished: 1. If the interaction is very strong (i.e. the complex stability is high: K → ∞), the (average) number of sample praticles can be counted directly by means of their reaction with a calibrated number of standard particles.—2. If, on the contrary, the interaction is weak (i.e. the complex stability is low), the sample will react quantitatively only in the presence of a large excess of standard; the half-way point of which provides a direct measure of the binding constant.—3. Only for moderate interactions can individual curves characteristic of the binding strength be observed. The limiting cases 1 and 2 yield titration curves which reflect only the general class to which the system belongs. The dynamical procedures are fairly insensitive in case 1, which represents the classical end-point situation and is most suitable for quantitative anlaysis, i.e. for a determination of sample concentrations. For case 2, the classical and dynamical techniques yield comparable information: mass-action parameters are obtained from the extrema of the curves, which occur only in the presence of an excess of the standard. In case 3 the dynamical treatment provides a more direct access to the equilibrium constants, and also to the enthalpies or volumes of reaction as well as to the rate constants. The advantage of the dynamic method is due to the fact that in the two derivatives of the titration function d T_i/d ln q and d T_i/d ln p (where q is the titration variable, i.e. the ratio of standard and sample concentration, and p the mass-action parameter, i.e. a reduced binding constant) the terms resulting from a differentiation with respect to p are more closely related to the reaction parameters than those following from a variation of q. The dynamic analysis is generalized for applications to multiple-step titration processes, where it allows for the measurement fo equilibrium and rate parameters of individual steps. A uniform representation utilizing trigonometric functions was chosen which expresses clearly the singualr character of the end-point. The relations are summarized intabular form. They provide in conjunction with the illustrations the basis for a comparative discussion.