Calcium and Magnesium Carbonates Tablets
»Calcium and Magnesium Carbonates Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amount of calcium carbonate (CaCO3)and not less than 85.0percent and not more than 115.0percent of the labeled amount of magnesium carbonate (MgCO3).
Packaging and storage— Preserve in well-closed containers.
Labeling— Tablets that are gelatin-coated are so labeled.
Identification—
A: The addition of 1Nhydrochloric acid to 1Tablet produces effervescence,and the resulting solution,after having been filtered,responds to the tests for Calcium á191ñ.
B: Heat 2Tablets in 20mLof 1Nsulfuric acid.Cool,add 20mLof alcohol,mix,and allow to stand for 30minutes.Filter this solution,and add 2mLof 1Nhydrochloric acid to the filtrate:this solution responds to the tests for Magnesium á191ñ.
Disintegration á701ñ: 10minutes,except that where Tablets are labeled as gelatin-coated the time is 30minutes,simulated gastric fluid TSbeing substituted for water in the test.
Uniformity of dosage units á905ñ: meet the requirements for Weight Variationwith respect to calcium carbonate and to magnesium carbonate.
Acid-neutralizing capacity á301ñ— Not less than 5mEq of acid is consumed by the minimum single dose recommended in the labeling,and not less than the number of mEq calculated by the formula:
0.8(0.024M)+0.9(0.02C),
in which 0.024and 0.02are the theoretical acid-neutralizing capacities,in mEq,of MgCO3and CaCO3,respectively;and Mand Care the respective quantities,in mg,of MgCO3and CaCO3in the specimen tested,based on the labeled quantities.
Assay for calcium carbonate— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 400mg of calcium carbonate,to a beaker with the aid of 25mLof water,and add 10mLof 1Nhydrochloric acid.Heat on a steam bath for 30minutes,allow to cool,transfer with the aid of water to a 100-mLvolumetric flask,dilute with water to volume,mix,and filter.Transfer 20.0mLof the filtrate to a suitable container,dilute with water to 100mL,add 15mLof 1Nsodium hydroxide,5mLof triethanolamine,and 100mg of hydroxy naphthol blue,and titrate with 0.05Medetate disodium VSuntil the solution is deep blue.Each mLof 0.05Medetate disodium is equivalent to 5.004mg of calcium carbonate (CaCO3).
Assay for magnesium carbonate— Transfer an accurately measured portion of the filtrate remaining from the Assay for calcium carbonate,equivalent to about 120mg of calcium carbonate and magnesium carbonate combined,to a suitable container,dilute with water to 100mL,add 10mLof ammonia–ammonium chloride buffer TS,5mLof triethanolamine,and 0.3mLof eriochrome black TS,and titrate with 0.05Medetate disodium VSto a blue endpoint.From the volume of 0.05Medetate disodium consumed,deduct the volume of 0.05Medetate disodium corresponding to the content of calcium carbonate in the volume of the filtrate taken for the assay.The difference is the volume of 0.05Medetate disodium equivalent to the amount of magnesium carbonate present.Each mLof 0.05Medetate disodium is equivalent to 4.216mg of MgCO3.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 323
Pharmacopeial Forum:Volume No.27(6)Page 3256
Phone Number:1-301-816-8251