Measuring Principle of Micro Moisture Tester
Generally we use trace moisture tester using Karl Fischer coulometric titration detection principle, Karl Fischer method, referred to as Fischer method, is the determination of moisture capacity splitting method. The following is a detailed introduction.
1, Fischer-Hugh method is the iodine volume method, the basic principle is the use of iodine oxidation of sulphur dioxide, the need for quantitative water to participate in the reaction: I2SO22H2O-2HIH2SO4, this reaction is reversible, in the system by adding pyridine, so that the reaction can be carried out to the right. Pyridine is the more effective reagent in the process of determination and also has the ability to bind to iodine and sulphur dioxide to reduce the vapour pressure of both. Therefore, the reagent needs to be added to methanol or another solvent containing active OH group.
2, Karl Fischer Moisture Determination is a method of measuring the moisture of the sample with methanol as the medium and Karl's solution as the titrant. This method is simple to operate, high accuracy, widely used in petroleum, chemical, pesticides, dyes, food and other fields. It is especially suitable for samples that are easily destroyed by heat, and can measure not only free water but also bound water, and is often used as a standard analysis method for moisture, especially trace moisture. However, it is not suitable for samples containing strong reducing substances such as VC.
3, Karl Fischer reagent is a determination of trace water in certain substances with the reagent, its composition: methanol, pyridine, iodine, sulfur dioxide. The endpoint determination method has two kinds of visual method and potential method.
The main components are I2, SO2, C5H5N, CH3OH Karl Fischer method is the basic principle of I2 oxidation of SO2, the need for quantitative H2OI2SO22H2O = 2HIH2SO4 this reaction is reversible, to make the reaction proceed positively, the need to add appropriate alkaline substances and the reaction of the acid produced, pyridine (C5H5N) can meet this requirement, add methanol can avoid the The addition of methanol can avoid side reactions. Karl Fischer's reagent shows brown colour due to iodine, when I2, SO2, H2O react, the iodine brown colour fades away, and this method takes the appearance of brown colour as the end point of titration.
4, Karl Fischer method is a non-aqueous titration, all containers need to be dry, 1L Karl Fischer reagent in the preparation and preservation process, if mixed with 6g of water, the reagent will be invalid. Karl Fischer reagent is a reagent for the determination of trace water in organic matter, so it is also known as water reagent, also known as Karl's reagent.
