计算机联用的电位测定仪在Ca2+,Mg2+电位连续滴定法中的应用

A NEW APPROACH OF CONSECUTIVE TITRATION TO ANALYSE THE MIXTURE OF Ca2+ AND Mg2+——APPLICATION OF THE COMPUTER-ASSISTED POTENTIOMETER

本文提出了一种分析Ca^(2+),Mg^(2+)混合物的新方法。该方法系在常温,于pH=9的硼酸缓冲溶液存在下,先用EGTA滴定Ca^(2+),然后用EDTA滴定Mg^(2+)的连续滴定;并由与计算机联用的电位测定仪系统控制、显示滴定终点和处理分析结果,简称连续法。研究结果表明,连续法具有如下的特点:连续法适用的Ca^(2+),Mg^(2+)浓度范围在10^(-2)～10^(-4)mol/L左右;Ca^(2+),Mg^(2+)浓度比(Ca^(2+)/Mg^(2+))在10/1～1/100,测量误差<5%;分析结果经SDM(二阶微商)法和Gran图解法处理,与常用法具有同样的正确性和精密度;在一份试液中直接测定Ca^(2+)和Mg^(2+)的浓度,操作简便、快速;具有自动采样、显示、数据处理、作图和打印等多种功能,有助于实现Ca^(2+),Mg^(2+)分析仪器的自动化和计算机化。

A new approach to analyse the mixture of Ca^(2+) and Mg^(2+) is developed. In this method, at room temperature, in the presence of pH=9 boric acid buffer, Ca^(2+) is first titrated by EGTA and then Mg^(2+) is continuously titrated by EDTA. In this consecutive titration procedure, the displaying of end-point and the processing of analytical results are controlled by a system of computer-assisted potentiometer. The experimental results showy that in the consecutive method, the applicablemeasuring ranges of Ca^(2+) and Mg^(2+) concentrations are about 10^(-2)～10^(-4) mol/L, the applicable concentration ratios (Ca^(2+)/Mg^(2+)) are between 10/1～1/100, and the attainable relative errors of determination are within 5%. The analytical results show that in the consecutive method they are as accurate and precise as in the common method when the experimental data are processed with SDM(Second Derivative Method)and Gran methods. Ca^(2+) and Mg^(2+) concentrations may be determined directly with an aliquot of the sample solution. The whole analytical system characterizes simple operations, rapid analyses, automatic sampling and displaying, data-processing, drawing and result-printing. These functions can be used in realizing the automatization and computerization for determining Ca^(2+) and Mg^(2+).