Hydroxypropyl methyl cellulose manufacturers analyze and test hydroxypropyl methyl cellulose
The analysis items of hydroxypropyl methylcellulose include methoxy content, hydroxypropyl content, viscosity, moisture, ash, chloride, alkalinity, iron content, heavy metal content, PH value, solid content and relative density, etc. . The determination of methoxy content and hydroxypropyl content is much more complicated than that of methyl cellulose and hydroxypropyl cellulose, because hydroxypropyl methyl cellulose is a mixed ether. After the measurement results of the 2 items are corrected, the correct results of the 2 items can be obtained. For the specific analytical procedures of these items, please refer to the standard method of hydroxypropyl methylcellulose test in the American Society for Testing and Materials (ASTM) published in 1976.
For example, according to the requirements of different applications, there are some specific test items, such as the determination of the salting-out point and the determination of the fiber rate.
(1) The determination of hydroxypropyl content uses chromic acid oxidizing property to oxidize it to acetic acid. Then the uncorrected hydroxypropyl content (%) is obtained by alkali titration according to the standard method, and then the methyl fiber must be measured in the same way The corrected hydroxypropyl content is derived from the hydroxypropyl value of the blank sample.
(2) The determination of the methoxy content uses hydroiodic acid to make alkylsulfonates, which are taken away with a stream of carbon dioxide, passed through a condenser, and finally absorbed with bromine, acetic acid and sodium acetate. After the alkyl iodide is absorbed, it is oxidized to alkyl iodate. The excess iodine is reduced with formic acid; the iodate is determined by the iodometric method of potassium iodide and standard thiosulfate