基于Karl Fischer电位滴定原理的超微量液体容积精密测量方法

摘要

为克服静力称重法受蒸发量影响大的不足,同时适应在线测量的需要,根据法拉第定律和Karl Fischer 电化学分析原理,研究了超微量液体电位滴定测量法.通过测量电解过程中所消耗电量进行微量液体水含量的计算,并结合液体密度测量可以计算出超微量液体容积.设计了这种非静力称重方法的测量系统,采用与静力称重测量系统比对试验的方式对这2种方法进行了验证,试验数据表明超微量液体电位滴定测量法和静力称重法测量结果具有良好的一致性,均符合ISO 8655的技术要求,但测量值偏大.与静力称重法相比,对测量环境要求低,易于实现在线测量,而且可以有效减少液体蒸发对测量结果的影响.%In order to overcome the shortcoming of significant influence of evaporation capacity on gravimetric method,and meet the requirements of online measurement,one non-gravimetric method was introduced for measuring micro liquid volume.According to Faraday law and Karl Fischer electrochemical principle,the Karl Fischer potentiometric titration method (KFCT method) is also investigated for micro liquid volume measurement,which calculates micro water content by measuring consumed electric quantity in electrolytic process,and obtains the micro liquid volume by combining liquid density.Comparing to gravimetric method,experimental systems for the non-gravimetric method was designed.The experiment indicates that the test result by using KFCT method is in good conformance with that by using gravimetric method,and meet the technical requirement of ISO 8655,but the measured value of KFCT method is a little bigger.Comparing with gravimetric method,which is low in requirement of measurement environment,easy to realize the online calibration and capable of effectively reducing the influence of liquid evaporation.