Calcium Carbonate Tablets
»Calcium Carbonate Tablets contain not less than 90.0percent and not more than 110.0percent of the labeled amount of calcium carbonate (CaCO3).For Tablets labeled for any indication other than,or in addition to,antacid use the Tablets contain not less than 90.0percent and not more than 115.0percent of the labeled amount of calcium carbonate.
Packaging and storage— Preserve in well-closed containers.
Labeling— Label it to indicate whether it is for use as an antacid,or as a dietary supplement,or both.
Identification— The addition of 6Nacetic acid to the Tablets produces effervescence,and the resulting solution,after being boiled to expel carbon dioxide and neutralized with 6Nammonium hydroxide,meets the requirements of the tests for Calcium á191ñ.
Dissolution á711ñ— For Tablets labeled for any indication other than,or in addition to,antacid use.
Medium: 0.1Nhydrochloric acid;900mL.
Apparatus 2: 75rpm.
Time: 30minutes.
Determine the amount of CaCO3dissolved by employing the following method.
Lanthanum chloride solution,5%— Prepare a solution of lanthanum chloride in 0.1Nhydrochloric acid having a concentration of about 50mg per mL.
Blank— Pipet 25mLof Lanthanum chloride solution,5%into a 250-mLvolumetric flask,dilute with 0.1Nhydrochloric acid to volume,and mix.
Standard stock solution— Dissolve an accurately weighed quantity of calcium carbonate in 0.1Nhydrochloric acid,and dilute quantitatively,and stepwise if necessary,with 0.1Nhydrochloric acid to obtain a solution having a known concentration of about 100µg of calcium per mL.
Standard solutions— Into four 100-mLvolumetric flasks,each containing 10.0mLof Lanthanum chloride solution,5%,separately pipet 3-,4-,5-,and 6-mLportions of Standard stock solution.Dilute each with 0.1Nhydrochloric acid to volume,and mix to obtain Standard solutionshaving known concentrations of about 3,4,5,and 6µg of calcium per mL,respectively.
Test solution— Filter a portion of the solution under test.Pipet a volume of the filtrate,estimated to contain 1mg of calcium,into a 250-mLvolumetric flask,add 25.0mLof Lanthanum chloride solution,5%,dilute with 0.1Nhydrochloric acid to volume,and mix.
Procedure— Concomitantly determine the absorbances of the Standard solutionsand the Test solutionat the calcium emission wavelength of 422.8nm,with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering á851ñ),equipped with a calcium hollow-cathode lamp and an air–acetylene flame,against the Blank.Construct a standard curve by plotting absorbances versus calcium concentrations of the Standard solutions,then from it obtain the concentration,C,in µg of calcium per mL,of the Test solution,and calculate the quantity,in mg,of CaCO3dissolved by the formula:
(100.09/40.08)(225C/v),
in which 100.09is the molecular weight of calcium carbonate;40.08is the atomic weight of calcium;and vis the volume of the filtrate taken to prepare the Test solution.
Tolerances— Not less than 75%(Q)of the labeled amount of CaCO3is dissolved in 30minutes.
Uniformity of dosage units á905ñ: meet the requirements.
Acid-neutralizing capacity á301ñ— Where Tablets are labeled for antacid use,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:
0.9(0.02C),
in which 0.02is the theoretical acid-neutralizing capacity,in mEq,of CaCO3;and Cis the quantity,in mg,of CaCO3in the specimen tested,based on the labeled quantity.
Assay— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 200mg of calcium carbonate,to a suitable crucible,and ignite to constant weight.Cool the crucible,add 10mLof water,and dissolve the residue by adding sufficient 3Nhydrochloric acid,dropwise,to achieve complete solution.Transfer the solution completely to a suitable container,dilute with water to 150mL,add 15mLof 1Nsodium hydroxide and 300mg 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).
Auxiliary Information— Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(DSN)Dietary Supplements:Non-Botanicals
USP28–NF23Page 320
Pharmacopeial Forum:Volume No.28(5)Page 1392
Phone Number:1-301-816-8389