Study on flow ratiometry for fully automated high-throughput titration

流ratiometry,已开发的研究员在2000年,用于滴定分析和高吞吐率。在开发的系统中，滴定液流量根据计算机控制信号线性增加/减少，而总流量（滴定液+滴定液）保持恒定。为实现系统控制、分析信号采集和数据分析的全自动化，自行编写了程序。该算法由两种运行模式组成。基于反馈变量三角波控制模式是用来定位等当点。扫描方向的控制信号改变了从上升到下降,反之亦然,在即时检测的等当点。随后采用固定三角波控制方式，进一步将扫描范围限制在等当点附近。因此，可以避免不必要的扫描范围，并实现前所未有的高吞吐率（每分钟最多34次滴定）。该方法成功地应用于抗酸和螯合滴定与光度或potentlometric检测。然而,同时使用光度滴定钙和镁离子和电位传感器仍有一个问题需要解决:分析结果的精度不是很高。方法也应用于自动和快速的电离常数测定酸和碱在不同的条件。

Flow ratiometry, which had been developed by the head investigator in 2000, was applied to titrimetry with high throughput rate. In the developed system, titrant flow rate is linearly increased/decreased in accordance with control signal from a computer, while total (titrant + titrand) flow rate was hold constant. A program was newly written in house for full automation of controlling the system, acquiring analytical signal and analyzing the data. The algorithm was constituted of two operation modes. Feedback-based variable triangular wave control mode was used for locating the equivalence point. Scan direction of the control signal was changed from upward to downward, and vice versa, at an instant of the detection of the equivalence point. Subsequent fixed triangular wave control mode was used for further limiting the scan range just around the equivalence point. Thus, the scan in needless range can be avoided and unprecedented high throughput rate (maximally 34 titrations per minute) was realized. The method was successfully applied to acid-based and chelatometric titrations with photometric or potentlometric detection. However, simultaneous titration of calcium and magnesium ions using both photometric and potentiometric sensors still has a problem to be solved : precision of the analytical results is not so high. The method was also applied to the automatic and rapid determination of the electrolytic dissociation constants of acids and bases at various conditions.