Temperature requirements for samples when using a Karl Fischer titrator to determine moisture content
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The Mettler Karl Fischer moisture meter was used today in the production workshop; 60°C dichloroethane was brought in in order to determine its moisture content. However, it seemed inappropriate to use such a high temperature for this purpose, so the sample was allowed to cool down for 20 minutes before testing again. I would like to ask whether there are any requirements regarding the sample temperature when using the Karl Fischer method to determine moisture content in samples
This post was last edited by qugd on 2016-7-7 at 13:07. The temperature of the sample should not be more than 10 degrees higher than that of the titration system. If the sample temperature is too high and the water content is low, a relatively large amount of sample will be added. High temperatures can cause the low-boiling components in the system to evaporate, and they can also cause iodine to vaporize into the gas phase, thereby introducing significant errors into the titration process. If samples with high temperatures are frequently measured, it is recommended to use titration solvents with higher boiling points as alternatives to methanol and chloroform. If the sample temperature is high, it is advisable to collect as much sample as possible and fill the sample bottle to the brim; this way, as the sample cools down, it will not absorb too much moisture from the surrounding environment. Additionally, the sample should not be shaken vigorously.
Hello, Professor Academician. After reading your answer, I have two questions. 1. If samples with high temperatures are frequently measured, it is recommended to use titration solvents with higher boiling points as alternatives to methanol and chloroform. Is it a solvent with a high boiling point? 2. For Karl Fischer moisture meters, are there any requirements regarding the operating temperature of the electrodes? Thank you.
1. Use a solvent with a higher boiling point. 2. The indicator electrode is not significantly affected by temperature (but in the case of the coulometric method, very high temperatures can have some unpredictable effects on the electrochemical reaction)