How to Detect Moisture of New Trinder’s reagent
The new Trinder's reagent is a commonly used as chromogen substrate in the enzymatic photometric biochemical detection. It belongs to the peroxidase system. After the substrate is oxidized, it has a specific detection wavelength, which is highly sensitive and easy to operate. There are more than ten kinds of reagents, including TOOS, ADPS, MAOS, etc.All of them are stable in the form of hydrates, and the moisture content of them can be measured by Karl Fischer Technology.
Characteristic of new Trinder’s reagent
This type of reagent is a derivative of highly water-soluble aniline sulfonic acid sodium salt.Modified with functional groups on the basis of traditional phenol or aniline,the water solubility and stability of new Trinder’s reagents are significantly improved. It should be noted, however, that the new Trinder’s reagents still can be oxidized slowly in air. Such reagents is relatively existing stably in the form of crystal water .In order to increase the stability, it is generally stored in a low temperature and dark place. Such as TOOS, TOPS, ADPS and other chromogen substrate reagents, some of the molecules will carry crystal water. After they are formulated into a solution for a long time, the color of solution will change with slowly oxidized by the oxygen in the air, so it is generally configured before used.
Karl Fischer Technology for Moisture detection for New Trinder’s reagent
If the new Trinder’s reagent need to be stored stably, its moisture content should be neither too low nor too high, usually 3%-8% is suitable.So it needs to measure the moisture. Karl Fischer is the authoritative and commonly used method for moisture determination, which has been improved over the years to increase the accuracy and expand the measurement range. It is the standard method for moisture determination of various reagents including Trinder’s reagent.
Principle of Moisture Determination
Karl Fischer method belongs to iodometric method, and its basic principle is that when using iodine to oxidize sulfur dioxide, a quantitative amount of water is required to participate in the reaction:I2+S02+2H2O=2HI+H2SO4
The above reaction is reversible. In order to move the reaction in a positive direction and proceed quantitatively, an alkaline substance must be added. Experiments show that pyridine is the most suitable reagent, and pyridine also has the effect of combining with iodine and sulfur dioxide to reduce their vapor pressure. Therefore, methanol or another solvent containing an active hydroxyl group must be added to convert pyridine sulfate anhydride into stable methyl hydrogen sulfate pyridine.
The above briefly introduces the moisture detection method of the new Trinder's reagent.In addition to TOOS, TOPS and MAOS, the other biological buffers such as Tris and Bicine produced by Desheng Biochemical can also use Karl Fischer for moisture determination.
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