Magnesium Trisilicate Tablets
»Magnesium Trisilicate Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amount of Mg2Si3O8.
Packaging and storage— Preserve in well-closed containers.
Identification—
A: Powder 1Tablet,add 10mLof 3Nhydrochloric acid and 5drops of methyl red TS,heat to boiling,add 6Nammonium hydroxide until the color of the solution changes to deep yellow,then continue boiling for 2minutes,and filter:the filtrate so obtained responds to the tests for Magnesium á191ñ.
B: Wash the solids on the filter obtained in Identificationtest Awith hot ammonium chloride solution (1in 50),add 10mLof 3Nhydrochloric acid,and filter.Transfer the filter paper and contents to a small platinum dish,ignite,cool in a desiccator,and weigh.Moisten the residue with water,and add 6mLof hydrofluoric acid.Evaporate to dryness,ignite for 5minutes,cool in a desiccator,and weigh:a loss of more than 10%in relation to the weight of the residue from the initial ignition indicates SiO2.
Disintegration á701ñ: 10minutes,simulated gastric fluid TSbeing substituted for water in the test.
Uniformity of dosage units á905ñ: meet the requirements.
Acid-neutralizing capacity á301ñ— Not less than 5mEq of acid is consumed by the minimum single dose recommended in the labeling.
Assay— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 1g of magnesium trisilicate,to a beaker,add 20mLof water,and slowly add 40mLof 3Nhydrochloric acid,with mixing.Heat the mixture to boiling,cool,and filter into a 200-mLvolumetric flask.Wash the beaker with water,adding the washings to the filter.Add water to volume,and mix.Transfer 20.0mLof this solution to a 400-mLbeaker,add 180mLof water and 20mLof triethanolamine,and stir.Add 10mLof ammonia–ammonium chloride buffer TSand 3drops of an eriochrome black indicator solution prepared by dissolving 200mg of eriochrome black Tin a mixture of 15mLof triethanolamine and 5mLof dehydrated alcohol,and mix.Cool the solution to between 3and 4by immersion of the beaker in an ice bath,then remove,and titrate with 0.05Medetate disodium VSto a blue endpoint.Perform a blank determination,substituting 20mLof water for the assay solution,and make any necessary correction.Each mLof 0.05Medetate disodium consumed is equivalent to 6.521mg of Mg2Si3O8.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 1176
Phone Number:1-301-816-8251