Calcium Carbonate Tablets
» Calcium Carbonate Tablets contain not less than 90.0 percent and not more than 110.0 percent 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 90.0 percent and not more than 115.0 percent 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 6 N acetic acid to the Tablets produces effervescence, and the resulting solution, after being boiled to expel carbon dioxide and neutralized with 6 N ammonium hydroxide, meets the requirements of the tests for Calcium 191.
Dissolution 711 For Tablets labeled for any indication other than, or in addition to, antacid use.
Medium: 0.1 N hydrochloric acid; 900 mL.
Apparatus 2: 75 rpm.
Time: 30 minutes.
Determine the amount of CaCO3 dissolved by employing the following method.
Lanthanum chloride solution, 5% Prepare a solution of lanthanum chloride in 0.1 N hydrochloric acid having a concentration of about 50 mg per mL.
Blank Pipet 25 mL of Lanthanum chloride solution, 5% into a 250-mL volumetric flask, dilute with 0.1 N hydrochloric acid to volume, and mix.
Standard stock solution Dissolve an accurately weighed quantity of calcium carbonate in 0.1 N hydrochloric acid, and dilute quantitatively, and stepwise if necessary, with 0.1 N hydrochloric acid to obtain a solution having a known concentration of about 100 µg of calcium per mL.
Standard solutions Into four 100-mL volumetric flasks, each containing 10.0 mL of Lanthanum chloride solution, 5%, separately pipet 3-, 4-, 5-, and 6-mL portions of Standard stock solution. Dilute each with 0.1 N hydrochloric acid to volume, and mix to obtain Standard solutions having known concentrations of about 3, 4, 5, and 6 µg of calcium per mL, respectively.
Test solution Filter a portion of the solution under test. Pipet a volume of the filtrate, estimated to contain 1 mg of calcium, into a 250-mL volumetric flask, add 25.0 mL of Lanthanum chloride solution, 5%, dilute with 0.1 N hydrochloric acid to volume, and mix.
Procedure Concomitantly determine the absorbances of the Standard solutions and the Test solution at the calcium emission wavelength of 422.8 nm, with a suitable atomic absorption spectrophotometer (see Spectrophotometry and Light-Scattering 851), equipped with a calcium hollow-cathode lamp and an airacetylene 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 CaCO3 dissolved by the formula:
(100.09 / 40.08)(225C / v)in which 100.09 is the molecular weight of calcium carbonate; 40.08 is the atomic weight of calcium; and v is the volume of the filtrate taken to prepare the Test solution.
Tolerances Not less than 75% (Q) of the labeled amount of CaCO3 is dissolved in 30 minutes.
Uniformity of dosage units 905: meet the requirements.
Acid-neutralizing capacity 301 Where Tablets are labeled for antacid use, not less than 5 mEq 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 0.02 is the theoretical acid-neutralizing capacity, in mEq, of CaCO3; and C is the quantity, in mg, of CaCO3 in the specimen tested, based on the labeled quantity.
Assay Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 200 mg of calcium carbonate, to a suitable crucible, and ignite to constant weight. Cool the crucible, add 10 mL of water, and dissolve the residue by adding sufficient 3 N hydrochloric acid, dropwise, to achieve complete solution. Transfer the solution completely to a suitable container, dilute with water to 150 mL, add 15 mL of 1 N sodium hydroxide and 300 mg of hydroxy naphthol blue, and titrate with 0.05 M edetate disodium VS until the solution is deep blue. Each mL of 0.05 M edetate disodium is equivalent to 5.004 mg of calcium carbonate (CaCO3).
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USP32NF27 Page 1755Pharmacopeial Forum: Volume No. 28(5) Page 1392