Magnesium stearate is a white loose fine powder with a smooth feel. It is insoluble in water, ethanol and ether, but is soluble in hot water and ether. It decomposes into stearin when exposed to acid. Acids and corresponding magnesium salts. It has a slight odor and a greasy feel.
1. Identification of magnesium stearate:
(1) Take 5_0g of this product, place it in a round-bottomed flask, and add peroxide-free ether 50ml, 20ml of dilute nitric acid and 20ml of water, heat and reflux until completely dissolved, let cool, transfer to a separatory funnel, shake, place to separate layers, transfer the water layer to another separatory funnel; extract the ether layer twice with water , 4ml each time. After combining the water layers, wash the water layer with 15ml of peroxide-free ether. Transfer the water layer to a 50ml measuring bottle, add water to dilute to the mark, shake well, and use it as the test solution. The identification of magnesium salts should be shown. reaction.
(2) In the chromatogram recorded under the relative content check of stearic acid and palmitic acid, the retention time of the two main peaks in the chromatogram of the test solution should be the same as the retention time of the two main peaks of the reference solution. consistent.
2. Determination of magnesium stearate content:
Take about 0.2g of this product, weigh it accurately, and add n-butanol-absolute ethanol (1:1) solution 50ml, add 5tnl concentrated ammonia solution and 3ml ammonia-gasified ammonium buffer (pHlO.O), then accurately add disodium ethylenediaminetetraacetate titrant (0.05mol/U25ml) and chrome black A little T indicator, mix well, heat on a 40-50 drop: water bath until the solution is clear, titrate with zinc titrant (0.05md/L) until the solution changes from blue to purple, and correct the titration results with a blank test .Each 1ml of disodium ethylenediaminetetraacetate titrant (0.05mol/L) is equivalent to 1.215mg of Mg.
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