Alumina,Magnesium Carbonate,and Magnesium Oxide Tablets
»Alumina,Magnesium Carbonate,and Magnesium Oxide Tablets contain the equivalent of not less than 90.0percent and not more than 110.0percent of the labeled amounts of aluminum hydroxide [Al(OH)3]and magnesium carbonate (MgCO3),and not less than 85.0percent and not more than 115.0percent of the labeled amount of magnesium oxide (MgO).
Packaging and storage— Preserve in tight containers.
Identification—
A: Place about 3g of finely powdered Tablets in a flask equipped with a stopper and glass tubing,the tip of which is immersed in calcium hydroxide TSin a test tube.Add 5mLof 3Nhydrochloric acid to the flask,and immediately insert the stopper:gas evolves in the flask and a precipitate is formed in the test tube.
B: To the solution in the flask obtained in Identificationtest Aadd 5drops of methyl red TS,and heat to boiling.Add 6Nammonium hydroxide until the color of the solution changes to deep yellow,continue boiling for 2minutes,and filter through hardened filter paper.(Retain the filtrate for Identificationtest C.)Wash the precipitate with 350mLof a hot ammonium chloride solution (1in 50),discarding the washings:the precipitate so obtained,dissolved in 3Nhydrochloric acid,responds to the tests for Aluminum á191ñ.
C: The filtrate obtained in Identificationtest Bresponds to the tests for Magnesium á191ñ.
Disintegration á701ñ: 10minutes,simulated gastric fluid TSbeing substituted for water in the test.
Uniformity of dosage units á905ñ: meet the requirements for Weight Variationwith respect to alumina,to magnesium carbonate,and to magnesium oxide.
Acid-neutralizing capacity á301ñ— Not less than 5mEq of acid is consumed by the minimum single dose recommended in the labeling.
Assay for aluminum hydroxide—
Edetate disodium titrant— Prepare and standardize as directed in the Assayunder Ammonium Alum.
Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 1200mg of aluminum hydroxide,to a 150-mLbeaker,add 20mLof water,stir,and slowly add 30mL3Nhydrochloric acid.Heat gently,if necessary,to aid solution,cool,and filter into a 200-mLvolumetric flask.Wash the filter with water into the flask,add water to volume,and mix.
Procedure— Pipet 10mLof the Assay preparationinto a 250-mLbeaker,add 20mLof water,then add,in the order named and with continuous stirring,25.0mLof Edetate disodium titrantand 20mLof acetic acid–ammonium acetate buffer TS,and heat near the boiling point for 5minutes.Cool,add 50mLof alcohol and 2mLof dithizone TS,and mix.Titrate with 0.05Mzinc sulfate VSuntil the color changes from green-violet to rose-pink.Perform a blank determination,substituting 10mLof water for the Assay preparation,and make any necessary correction.Each mLof 0.05MEdetate disodium titrantconsumed is equivalent to 3.900mg of Al(OH)3.
Assay for magnesium carbonate— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 750mg of magnesium carbonate,to a 250-mLconical flask fitted with a two-hole stopper.Fill the lower transverse section of a U-shaped drying tube of about 15-mm internal diameter and 15-cm height with loosely packed glass wool.Place in one arm of the tube about 5g of anhydrous calcium chloride,and accurately weigh the tube and the contents.Into the other arm of the tube place 9.5g to 10.5g of soda lime,and again weigh accurately.Insert stoppers in the open arms of the U-tube,and connect the side tube of the arm filled with soda lime to a calcium chloride drying tube,which in turn is connected to one of the holes in the stopper of the 250-mLconical flask.Attach a dropping funnel to the other hole in the stopper of the 250-mLconical flask.Add 100mLof water and 10mLof a mixture of hydrochloric acid and nitric acid (4:1)to the 250-mLconical flask through the dropping funnel,and close the dropping funnel.Heat the 250-mLconical flask at 95for 1hour,and allow the evolved carbon dioxide to pass through the U-tube.Replace the dropping funnel with a source of carbon dioxide-free air,and pass the carbon dioxide-free air through the apparatus at a rate of about 75mLper minute for 30minutes.Disconnect the U-tube,cool to room temperature,remove the stoppers,and weigh.The increase in weight corresponds to the quantity of carbon dioxide evolved.Calculate the quantity,in mg,of magnesium carbonate in each Tablet taken by the formula:
(84.31/44.01)(I)(WA/WP),
in which 84.31and 44.01are the molecular weights of magnesium carbonate and carbon dioxide,respectively;Iis the quantity,in mg,of carbon dioxide evolved from the portion of Tablets taken;WAis the average weight,in g,of 1Tablet;and WPis the weight,in g,of the portion of Tablets taken.
Assay for magnesium oxide— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 1000mg of magnesium carbonate and magnesium oxide combined,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 1.216mg of Mg.Calculate the quantity,in mg,of magnesium equivalent in each Tablet taken by the formula:
10T(WA/WP),
in which Tis the magnesium equivalent obtained in the titration;WAis the average weight,in g,of 1Tablet;and WPis the weight,in g,of the portion of Tablets taken.Calculate the quantity,in mg,of magnesium oxide in each Tablet taken by the formula:
(40.30/24.31)(A-0.2883B),
in which 40.30and 24.31are the molecular weight of magnesium oxide and the atomic weight of magnesium,respectively;Ais the quantity,in mg,of magnesium equivalent in each Tablet;and Bis the quantity,in mg,of magnesium carbonate in each Tablet,as determined in the Assay for magnesium carbonate.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 85
Phone Number:1-301-816-8251