Discussion on the Test Error of Moisture Analyzer
Recently, some users have reflected that when using infrared or halogen moisture meters to test the moisture content in solid samples, there is a certain error with the results of the moisture test report provided by the user or supplier. While doubting the accuracy of the instrument, Also skeptical about the rationale for testing moisture analysis methods. After communicating with our company's technical staff, the basic judgment of the problem and the crux of the problem:
1. After testing the same sample with different types of rapid moisture analyzers, the results are within the normal error range, which basically eliminates doubts about the accuracy of the instrument.
2. Inquire carefully about the error in the moisture test results with other users, and find that the other party's test method is to use the Karl Fischer volumetric method or the Coulomb method to test the moisture content of the sample. The result is often lower.
3. The user cannot judge whether there are other volatile solvents in the sample besides water.
To sum up, the basic reason for the errors in our testing of user samples is that in addition to water, there are other volatile solvents in user samples. At the same time, according to different test temperatures, other changes will occur. .
We know that the testing principle of the infrared or halogen fast moisture analyzer is the heating and weight loss method, which is to evaporate the moisture of the sample by heating to a certain temperature, and then calculate the moisture percentage of the sample according to the calculation function of the electronic balance. The results and accuracy are determined by the accuracy of the electronic balance. Of course, the speed and uniformity of the heating method must also affect the accuracy of the sample moisture test. At present, because the heating speed and uniformity of the halogen heater are superior to the infrared heating method, and there is no big difference in price, the halogen fast moisture analyzer is gradually promoted.
If there are other volatile solvents in the sample, we will also volatilize the volatile solvents while heating the volatile water, so the part of weight loss does not represent the accurate content of water, so at this time, use rapid moisture determination The meter is inaccurate in determining the moisture content of the sample, and the higher the volatile solvent content, the greater the error.
If you encounter this situation, we recommend that users use the Karl Fischer volumetric method or coulometric method to test the water content of the sample. Since the Karl Fischer reagent only reacts with water, it avoids the influence of other solvents on the water content of the test sample. The results tested by this method should be accurate. Of course, different methods can be adopted according to the different properties of the solid sample. If the sample is dissolved in methanol, it is relatively convenient to use the volumetric method. If the solid sample does not dissolve in methanol, use the coulometric method and install a solid gasifier in conjunction with it.
Of course, infrared or halogen moisture analyzers are widely used in various industries, and are recognized by everyone because of their speed, convenience and high accuracy. However, due to the sample requirements, it has certain limitations. Therefore, when users choose a moisture analyzer, they can understand the physical and chemical properties of the samples they want to test, and whether there are any impurities, so as to reduce unnecessary troubles caused by purchasing instruments.
