A new approach to flow-batch titration. A monosegmented flow titrator with coulometric reagent generation and potentiometric or biamperometric detection

Monosegmented flow analysis (MSFA) has been used as a flow-batch system to produce a simple, robust, and mechanized titrator that enables true titrations to be performed without the use of standards. This paper also introduces the use of coulometry with monosegmented titration by proposing a versatile flow cell. Coulometric generation of the titrand is attractive for titrations performed in monosegmented systems, because the reagent can be added without increasing the volume of sample injected. Also, biamperomeric and potentiometric detection of titration end-points can increase the versatility of the monosegmented titrator. The cell integrates coulometric generation of the titrand with detection of end-point by potentiometry or biamperometry. The resulting titrator is a flow-batch system in which the liquid monosegment, constrained by the interfaces of the gaseous carrier stream, plays the role of a sample of known volume to be titrated. The system has been used for determination of ascorbic acid, by coulometric generation of I₂ with biamperometric detection, and for determination of Fe(II), by coulometric generation of Ce(IV) with potentiometric detection of the end-point, both in feed supplements.     

Thermometric titration in investigation of the formation of polyanions of molybdenum(VI), tungsten(VI), vanadium(V), and chromium (VI)-I: comparison of thermometric and potentiometric titration curves

A new twin-cell thermometric titrator has been devised and used for thermometric titration of solutions of sodium molybdate, sodium tungstate, sodium orthovanadate, ammonium metavanadate, and potassium chromate with perchloric acid. The thermometric titration curves were compared with corresponding pH-titration curves for elucidation of the reactions occurring in the titrations. Thermometric titrimetric methods have been developed for the determination of tungsten, vanadium and chromium.     

Oxidability Determination in Waste Waters Using an Automatic Titrator Based on a Multicommutated Unsegmented Flow System

Abstract

The automatic titrator based on a multicommutated unsegmented flow system was applied to redox titrations and used for oxidability determination in waters analysis. This automatic titrator allows the attainment of complete titration curves, being the determination of titrand concentration performed without requiring any prior calibration. After sample treatment (oxidation step), the oxidability determination in waste water samples was accomplished by the automatic flow titrator (titration step). Repeated determinations of standard solutions gave a 3.5% RSD (n=10, 0.010M) for repeatability and a 3.2% RSD (n=2, 0.057M) for reproducibility. Samples results (n=9) were in good agreement (t-test) with those obtained with a reference procedure.     

Kalman filter applied to setpoint control in continuous titrations

A state-space model is described for continuous titrations based on first-order dynamics. The Kalman filter allows on-line monitoring of an empirically established setpoint in the titration curve. The algorithm advocated is examined for potentiometric titrations of ca. 10^?3 M solutins of acids, silver(I) and copper(II). Only gross indications of the essential parameters such as the time constant and noise covariances are required. The computer-controlled titration system is compared with a conventional setpoint titrator. Especially in cases of slow response times and steep inflections, there are advantages in both accuracy and speed when the Kalman filter is applied.     

Controlled dynamic titrator

The controlled dynamic titrator described operates with constant titrant flow and time-proportional sample flow; sample and titrant are mixed in a microcell and the equivalence point is reached when the products of the normalities and flow rates of the titrant and the sample are equal. Titration times are measured and printed out. The concentration of the sample is inversely proportional to the titration time. The automatic titrator is discontinuous and suitable for on-line and off-line use. The cycle time of the motor-driven programmer is 2 min. Flow-through detectors for potentiometric, photometric or voltammetric indication can be used for a selection of acid—base and redox titrations. With this equipment, titration of large series of liquid samples with similar contents is simple.     

Potentiometric determination of octanol-water and liposome-water partition coefficients (log P) of ionizable organic compounds

The logarithm of the octanol-water partition coefficient, log P, is a key physicochemical property for both pharmaceutical drugs and agrochemicals. It is also required by legislation as part of the physicochemical properties profile for high volume production chemicals. This Letter describes a simple method for determining log P values (over a wide range from −0.8 to 5.3) for 12 organic weak acids and bases using potentiometric titrations, with octanol or phosphatidyl choline liposomes as the partitioning medium. Such titrations take comparatively little time (about 30-45 min per titration), are easy to implement, and can be carried out with an inexpensive laboratory titrator.     

Rapid and accurate titrations with a convenient and compact automatic derivative spectrophotometric titrator

A convenient and compact automatic derivative spectrophotometric titrator is described which is suitable for automatically performing a wide variety of the well known color indicator titrations without any procedure modifications and usually with few, if any, pretitration considerations and instrument adjustments The results for many acid-base and oxidation-reduction titrations are presented to illustrate the general applicability and important characteristics of the instrument     

全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量

采用全自动电位滴定法测定锂电池原料碳酸锂中主成分的含量,用盐酸标准溶液进行滴定,考虑自动电位滴定仪的灵敏性和准确度,通过多次对比实验,确定了仪器的最佳工作参数、滴定剂浓度和样品称样量等滴定条件;对两个不同品位试样分别进行了11次平行测定,相对标准偏差(RSD)均小于1%。在碳酸锂试样中加入基准物质无水碳酸钠进行碳酸根的加标回收实验,碳酸根的加标回收率在99.4%~100%。与传统的酸碱滴定法相比,全自动电位滴定法方便、快捷,同时方法测定结果准确、可靠、精密度高,适合大批量样品快速分析。     

一种新型气压式滴定仪的研制

介绍一种新型气压式滴定仪的结构、性能、特点及使用方法。该仪器能迅速、准确地加液调零,使用方便,克服了旧式滴定管漏液、取液时易玷污、加液调零较麻烦等缺点,在适当的情况下还可以作为移液管使用。     

一种新型自动数字滴定管的研制

本文报道一种新型自动数字滴定管，采用马利奥特恒流器和石英数字计时器设计而成，液流无脉动、无滞后，滴定剂用量（或滴定度）用时间计量和数字显示，避免了使用容量滴定管产生的问题和困难，这种自动数字滴定管电路简单，造价低廉、操作简便，可简便地与计算机连接以实现自动化，实际应用结果令人满意。     

Microcomputer-controlled automatic titrator with analysis of results by means of spline functions

A method of controlling an automatic titrator by means of a microcomputer is described. Experimental titration data have been analysed by the use of approximative or rational spline functions.     

A simple automatic titrator based on a digital balance

A computer-controlled automatic titrator incorporating a weight burette is described. The titration vessel is mounted on the pan of a zero-displacement digital balance which records the weight of added sample as well as the weight of titrant added during the titration.     

Titrations using an apparatus for recording the antilogarithm of pH or pM

A titration apparatus plotting either the concentration of sample ion or the concentration of titrant ion has been tested. An antilog apparatus, converting measured e.m.f. values into concentrations is connected to ordinary titration equipment. The instrument has been tested by means of acid—base titrations (titrations of mixtures of weak acids and of a weak and a strong acid), precipitation titrations (determination of the chloride concentration in tap-water, titration of mixtures of halides), titrations with ion-selective electrodes (determination of the fluoride content of toothpaste) and complexometric titrations (determination of copper with EDTA, using mercuric ion as indicator ion and amalgamated silver rod as indicator electrode, or using a copper-selective indicator electrode). The method considerably simplifies the evaluation of the results as compared to conventional potentiometric titrations.     

Stepwise photometric titrations

Stepwise titrations of several metals with photometric end-point detection are described. The equivalence points when 2 metal ions are titrated compleximetrically, can be detected if the conditional stability constants are sufficiently high in value even if there are only slight differences between the colours of the different species of the indicator compounds.The following systems were analysed by stepwise photometric titration using either metalphthalein or eriochrome black T as indicator: manganese-calcium; manganese-magnesium; calcium-magnesium; manganese-calcium-magnesium; zinc-magnesium, EDTA, DTPA and EGTA were used as titrants. A satisfactory accuracy was attained in each case. The results agreed with conclusions drawn from the theory of stepwise photometric titrations based on equilibrium calculations and absorbance values.     

离子选择电极电位法中结果计算方法(Ⅱ)——电位滴定三参数拟合法

提出了离子选择电极电位法中用于计算结果的三参数拟合法。该法可用于各种类型的电位滴定。本法的优点是精度较高,同时可确定C_x,E′_o、S。法特别适用于自动滴定分析。     

Rapid automatic potentiometric method for analytical control in the manufacture of extraction phosphoric acid

A rapid automatic method for determination of free sulphuric acid in the manufacture of extraction phosphoric acid from apatite has been developed. It is based on potentiometric titration combined with the Gran approach for linearization of the titration curve. The analysis is done with an automatic potentiometric titrator controlled by an HP-85 microcomputer. BASIC software activates the system to perform the data acquisition and calculations, and the whole operation takes only 7-8 min.     

The systematic error in photometric set-point titrations of submicromolar amounts of calcium and zinc

Although reproducible results can be obtained in photometric set-point titrations of submicromolar amounts (5·10^?5 M and higher) of calcium(II) and zinc(II) by using an automatic titrator, the systematic error can be considerable. This error is partly intrinsic in nature, but there is an additional error caused by dilution in successive titrations. Accurate values can be obtained only when standardization and actual titrations are performed under the same conditions of dilution, set-point, indicator concentrations, etc.     

A new automatic recording titrator and its applications

A new type of automatic recording titrator has been developed. The titrant is added intermittently and the titration curve is recorded stepwise, potential changes being registered in the intervals between deliveries of titrant. The increments of titrant and the intervals can be pre-set, but give the best results if controlled automatically during the titration. The end-point and the volume of titrant consumed are read from the recorded titration curve.     

芥子气纯度测定不确定度分析与评定

采用酸碱滴定法测定芥子气纯度,对测量结果的不确定度进行评定。分析了测定过程中不确定度来源,包括滴定剂的标定、消耗滴定剂体积、样品称量等引入的不确定度及其计算方法,最后合成得到标准不确定度。当芥子气纯度测定结果为94.78%时,扩展不确定度为0.34%(k=2)。实验结果表明,样品称量引入的不确定度对测量结果的影响最大。     

Spektralphotometrische Analyse und relative pK-Wertbestimmung von dreistufigen Protolyse-Gleichgewichten

Spectrophotometric titrations of three-step, unbranched protolyse equilibria are analyzed with the absorbance tetrahedron in a three-dimensional absorbance diagram. The titration system is divided up into its individual equilibria in the absorbance tetrahedron by means of special planes. These separated equilibria are then treated as one-step systems. — A new method is discussed for the determination of relative pK-values in the absorbance tetrahedron without using pH-values. The new methods are demonstrated using the titration of benzenetricarboxylic acid-(1,2,4).