Discussion on Test Error of Rapid Moisture Analyzer

Recently, some users have reported certain errors in the moisture content of the test samples provided by the user or supplier when using infrared or halogen moisture meters to test the moisture content of solid samples. They doubt the accuracy of the instruments. It is also suspected that the test water analysis method is reasonable. After communicating with the technical personnel of our company, we basically judge the problem and the crux:

1. After testing the same sample with different types of rapid moisture analyzers, the results are within the normal error range, which basically excludes the suspicion of the accuracy of the instrument.

2. Carefully inquire about the error with other users' moisture test results and find that the other party's test method is to use the Karl Fischer volumetric method or Coulomb method to test the moisture of the sample. The result is often relatively low.

3, the user can not determine whether the sample in addition to water, there are other volatile solvents.

In summary, the basic reason for the error in the user's sample testing process is that the user's sample contains other volatile solvents in addition to moisture. At the same time, other changes will occur depending on the test temperature. .

We know that the test principle of infrared or halogen fast moisture analyzer is heating weight reduction method, which is to heat the sample to a certain temperature and volatilize the moisture of the sample, so as to calculate the percentage of water content of the sample according to the calculation function of the electronic balance. The results and accuracy are based on the accuracy of the electronic balance. Of course, the speed and uniformity of the heating method will also affect the accuracy of the test sample moisture. At present, due to the fact that the heating rate of the halogen heater is superior to the infrared heating method in terms of both the main and uniformity of the heating rate, there is no great difference in price. The halogen fast moisture analyzer is gradually promoted.

If there are other volatile solvents in the sample, we will volatilize the water and volatilize the volatile solvents. Therefore, the weight loss part does not represent the exact content of moisture. Therefore, at this time, rapid moisture determination is used. The moisture content of the sample is not accurate, and the higher the volatile solvent content, the greater the error.

If this is the case, we advise the user to test the moisture content of the sample using the Karl Fischer volumetric method or the Coulomb method. Since the Karl Fischer reagent only reacts chemically to moisture, the effect of other solvents on the moisture content of the test sample is avoided. The results of testing by this method should be accurate, of course, depending on the performance of the solid sample, different methods can be taken. If the sample is dissolved in methanol, the volumetric method is relatively convenient. If the solid sample does not dissolve in methanol, coulometric method is used, and solid gasifier is additionally used in combination.

Of course, infrared or halogen moisture analyzers are widely used in various industries. Because of their fast, convenient and high accuracy, they are recognized by everyone. However, due to the requirements of the sample, it has certain limitations. Therefore, when the user selects a moisture analyzer, it is better to be able to understand the physical and chemical properties of the sample to be tested, whether or not there are impurities, so as to reduce the unnecessary trouble caused by purchasing the instrument.