Ultra micro liquid volume measurement system based on potentiometrie titration principle

Abstract

In order to overcome the shortcoming that influences of evaporation capacity on the gravimetric method, and meet the requirement of online measurement, a non-gravimetric method is introduced for measuring micro liquid volume. According to Faraday's 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. Due to pressure variation the correction is used for micro liquid volume calculation. Comparing with gravimetric method, experimental systems for non-gravimetric method is designed. The experiment indicated that the test result obtained by using KFCT method is in good agreement with that the test result obtained by using gravimetric method, and meets the technical requirements of ISO 8655, but the measured result of KFCT method is slightly higher. Comparing with gravimetric method, the non-gravimetric method provides a better solution for micro liquid volume measurement, which has lower requirements on the measurement environment, is easier to implement on-line calibration, and effectively reduce the impact of the liquid evaporation.