Study on flow ratiometry for fully automated high-throughput titration

流动比率法是由首席研究员于2000年开发的，用于高通量滴定。在所开发的系统中，滴定剂流量根据来自计算机的控制信号线性增加/减少，而总流量（滴定剂+被滴定物）保持恒定。新编写了一个程序，使系统控制、分析信号采集和数据分析完全自动化。该算法由两种操作模式组成。采用基于反馈的变三角波控制方式定位等值点。在检测到等效点的瞬间，控制信号的扫描方向从向上变为向下，反之亦然。随后的固定三角波控制模式被用于进一步限制扫描范围仅在等效点附近。因此，可以避免在不必要的范围内的扫描，并实现前所未有的高吞吐率（最大34滴定每分钟）。该方法已成功地应用于光度法或电位法检测的酸滴定和螯合滴定。然而，使用光度和电位传感器同时滴定钙和镁离子仍然有一个问题需要解决：分析结果的精度不是很高。该方法也可用于各种条件下酸、碱的电解解离常数的自动快速测定。

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.