Magnesium Carbonate and Sodium Bicarbonate for Oral Suspension
»Magnesium Carbonate and Sodium Bicarbonate for Oral Suspension contains not less than 90.0percent and not more than 110.0percent of the labeled amounts of MgCO3and NaHCO3.It may contain suitable flavors.
Packaging and storage— Preserve in tight containers.
Identification—
A: Place about 1g 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: The solution remaining in the flask responds to the tests for Magnesium á191ñand for Sodium á191ñ.
Minimum fill á755ñ: meets the requirements.
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)+0.8(0.0119S),
in which 0.024and 0.0119are the theoretical acid-neutralizing capacities,in mEq,of MgCO3and NaHCO3,respectively;andMand Sare the quantities,in mg,of MgCO3and NaHCO3in the specimen tested,based on the labeled quantities.
Assay for magnesium carbonate— Transfer an accurately weighed portion of Magnesium Carbonate and Sodium Bicarbonate for Oral Suspension,equivalent to about 4.2g of MgCO3,to a 500-mLvolumetric flask.Add 200mLof 1Nhydrochloric acid,and mix.When dissolved,dilute with water to volume,and mix.Transfer 10.0mLof this stock solution 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.Each mLof 0.05Medetate disodium consumed is equivalent to 4.216mg of MgCO3.
Assay for sodium bicarbonate—
Standard preparations— Dissolve a suitable quantity of sodium chloride,previously dried at 125for 30minutes and accurately weighed,in water,and dilute quantitatively with water to obtain a solution having a known concentration of about 600µg per mL.On the day of use,further dilute this solution quantitatively with water to obtain three solutions containing 6.0,12.0,and 18.0µg of sodium chloride per mL,respectively.
Assay preparation— Transfer an accurately measured volume of the stock solution remaining from the Assay for magnesium carbonate,equivalent to about 180mg of NaHCO3,to a 100-mLvolumetric flask,dilute with water to volume,and mix.Transfer 10.0mLof the resulting solution to a 1000-mLvolumetric flask,dilute with water to volume,and mix.
Procedure— Concomitantly determine the absorbances of the Standard preparationsand the Assay preparationat the sodium emission line at about 589.0nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-scattering á851ñ)equipped with a sodium hollow-cathode lamp and an air–acetylene flame,using water as the blank.Plot the absorbances of the Standard preparationsversus concentration,in µg of sodium chloride per mL,and draw the straight line best fitting the three plotted points.From the graph so obtained,determine the concentration,in µg per mL,of sodium chloride equivalent in the Assay preparation.Calculate the quantity,in g,of NaHCO3in the portion of Magnesium Carbonate and Sodium Bicarbonate for Oral Suspension taken by the formula:
(84.01/58.44)(5C/V),
in which 84.01and 58.44are the molecular weights of sodium bicarbonate and sodium chloride,respectively;Cis the concentration,in µg per mL,of sodium chloride equivalent in the Assay preparation;and Vis the volume,in mL,of the stock solution remaining from the Assay for magnesium carbonatetaken.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 1168
Phone Number:1-301-816-8251