Recently, some users are reflecting that when using infrared or halogen moisture meter 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, and they doubt the accuracy of the instrument at the same time, they also doubt the rationality of the test moisture analysis method. After communication with our technical staff, the basic judgment of the problem and the crux of the problem is:
1, after different models of rapid moisture tester on the same sample test, the results are within the normal range of error, so basically ruled out the suspicion of the accuracy of the instrument.
2, careful inquiry and other users of moisture test results of the error, found that the other test method is used in the Karl Fischer volumetric method or coulometric test sample moisture. The results are often relatively low.
3, the user also can not determine whether the sample in addition to moisture, there are other volatile solvents.
In summary, the basic reason for the errors in the testing process of our samples to the user is the presence of other volatile solvents in addition to moisture in the user's sample, and at the same time, depending on the test temperature, other changes will occur.
We know that the testing principle of infrared or halogen rapid moisture meter is heating weight loss method, is by heating to a certain temperature, volatile sample moisture, so that according to the calculation function of the electronic balance, calculate the moisture percentage of the sample, the results and accuracy is based on the accuracy of the electronic balance, of course, the speed of the heating method, uniformity, but also must have affected the accuracy of the sample test moisture. At present, due to the halogen heater heating speed main and uniformity are preferred to infrared heating method, the price is not very different, halogen rapid moisture tester is gradually promoted.
If there are other volatile solvents in the sample, we heat and volatilize the water at the same time, also volatilize the volatile solvents in it, so the part of weight loss does not represent the accurate content of moisture, so this time, the use of rapid moisture tester to determine the moisture of the sample is inaccurate, the higher the content of volatile solvents, the greater the error.
If you encounter this situation, we suggest the user to use Karl Fischer volumetric method or coulometric method to test the moisture of the sample, because Karl Fischer reagent only produces chemical reaction to the moisture, thus avoiding the influence of other solvents on the moisture content in the test sample. The results obtained by this method should be accurate, but of course, depending on the properties of the solid sample, different methods can be used. If the sample is dissolved in methanol, then it is relatively convenient to use the volumetric method. If the solid sample is not dissolved in methanol, the coulometric method is used, in addition to the solid vaporizer used in conjunction with it.
Contact Person: Ms. Ivy Xie