Cartridge micro-drop titrator
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When measuring trace water, the water content obtained varies depending on the amount of sample injected; generally, the greater the amount of sample injected, the higher the measured water content. Why is that? How should it be handled?
This post was last edited by qugd on 2010-8-2 09:19. Regarding the determination of trace water content using the Karl Fischer method, the phenomenon mentioned by the original poster is common; its main cause is the diluting effect of the sample on the titration system. Imagine that for a sample with a water content of 1000 ppm, it is possible to obtain accurate results using 100 milliliters of titration medium, with an injection volume of just 0.1 milliliters; in this case, the dilution rate of the sample in the titration medium is only 0.1%. On the other hand, when the water content is 10 ppm, at least 10 milliliters of sample must be injected to achieve accurate results, resulting in a dilution rate of 10%. This additional 10% in the volume of the titration medium represents a background effect, and a certain amount of titrant is still required to reach the endpoint. However, in calculations, it is not possible to account for the additional titrant consumed due to this dilution effect; as a result, the analytical results appear to be slightly high. However, this slight increase should not have a significant impact on the reliability of the measurement results.
It should depend on the nature of the product; whenever the solubility of the sample permits, a larger sample weight should be used to minimize errors!
Is the dilution rate directly related to the measured absolute water content?
This post was last edited by pecker on 2010-8-8 19:45. In the context of license analysis: 1. Conduct multiple parallel analysis experiments； II. Try to select high doses for analysis.
This post was last edited by zbx on 2010-8-9 at 20:47. It seems that in my unit, tests are conducted using a sample volume of 1 milliliter; multiple parallel tests should be carried out
Actually, you need to consider the volume of your burette; generally, it is required that this volume be between 1/2 and 2/3 of the total volume. Within this range for the titration volume, it’s sufficient to conduct several duplicate tests
The sample volume is selected based on the approximate water content; there is very detailed information on microwater determination on the website of a company in Tianjin that produces cartridge reagents! !
Our department uses Mettler machines, but they don’t seem to be very stable; however, they work okay. The sample volume is 1 milliliter.