Dibasic Calcium Phosphate Tablets
DEFINITION
Dibasic Calcium Phosphate Tablets contain NLT 92.5% and NMT 107.5% of the labeled amount of dibasic calcium phosphate dihydrate (CaHPO4·2H2O).
[Note—An equivalent amount of Dibasic Calcium Phosphate with less water of hydration may be used in place of CaHPO4·2H2O in preparing Dibasic Calcium Phosphate Tablets. ]
IDENTIFICATION
• A. Identification Tests—General, Calcium 
191
191 Sample solution: A filtered portion of the Sample solution from the Assay
Acceptance criteria: Meets the requirements
• B. Identification Tests—General, Phosphate 191
191 Sample solution: A filtered portion of the Sample solution from the Assay, neutralized with ammonium hydroxide
Acceptance criteria: Meets the requirements
ASSAY
• Procedure
Sample solution: Transfer a portion of powder, equivalent to 1 g of dibasic calcium phosphate dihydrate, from NLT 20 powdered Tablets, to a 100-mL volumetric flask containing 15 mL of hydrochloric acid and 10 mL of water. Heat on a steam bath, with occasional mixing, to dissolve the dibasic calcium phosphate, but not longer than 30 min. Cool, add water to volume, and mix. If the solution is not clear, filter, discarding the first 10 mL of the filtrate.
Blank: Water
Titrimetric system
(See Titrimetry 541.)
541.)Mode: Direct titration
Titrant: 0.05 M edetate disodium VS
Indicator: Hydroxy naphthol blue
Endpoint detection: Visual
Analysis: Transfer 25.0 mL of the Sample solution to a 250-mL beaker equipped with a magnetic stirrer. With constant stirring, add, in the order named, 0.5 mL of triethanolamine, 300 mg of Indicator, and from a 50-mL buret, about 23 mL of Titrant. Add sodium hydroxide solution (45 in 100) until the initial red color changes to clear blue. Continue to add it dropwise until the color changes to violet, and add an additional 0.5 mL. The pH is 12.3–12.5. Continue the titration dropwise with the Titrant to the appearance of a clear blue endpoint that persists for NLT 60 s. Perform a blank determination.
Calculate the percentage of the labeled amount of dibasic calcium phosphate dihydrate (CaHPO4·2H2O) in the portion of Tablets taken:
Result = {[(VS 
VB) × N × F]/W} × 100
VB) × N × F]/W} × 100| VS | = | = Titrant volume consumed by the Sample solution (mL) |
| VB | = | = Titrant volume consumed by the Blank (mL) |
| M | = | = actual molarity of the Titrant (mM/mL) |
| F | = | = equivalency factor, 172.08 mg/mM |
| W | = | = nominal weight of dibasic calcium phosphate dihydrate in the Sample solution taken for Analysis (mg) |
Acceptance criteria: 92.5%–107.5%
PERFORMANCE TESTS
• Dissolution 711
711 Medium: 0.1 N hydrochloric acid; 900 mL
Apparatus 2: 75 rpm
Time: 45 min
Standard solution: Solution having a known concentration of calcium in Medium
Sample solution: Filtered portion of the solution under test, suitably diluted with Medium if necessary
Instrumental conditions
Mode: Atomic absorption spectrophotometry
Analytical wavelength: 422.7 nm
Lamp: Calcium hollow-cathode
Flame: Air-acetylene
Analysis
Samples: Standard solution and Sample solution
Determine the concentration of calcium (Ca) in the Sample solution in comparison with a Standard solution.
Calculate the percentage of the labeled amount of dibasic calcium phosphate dihydrate (CaHPO4·2H2O) dissolved:
Result = (AU/AS) × (CS × D × V/L) × (Mr/Ar) × 100
| AU | = | = absorbance of the Sample solution |
| AS | = | = absorbance of the Standard solution |
| CS | = | = concentration of calcium in the Standard solution (mg/mL) |
| D | = | = dilution factor for the Sample solution |
| V | = | = volume of Medium, 900 mL |
| L | = | = label claim (mg/Tablet) |
| Mr | = | = molecular weight of dibasic calcium phosphate, 172.08 |
| Ar | = | = atomic weight of calcium, 40.08 |
Tolerances: NLT 75% (Q) of the labeled amount of dibasic calcium phosphate dihydrate (CaHPO4·2H2O) is dissolved.
• Uniformity of Dosage Units 905: Meet the requirements
905: Meet the requirementsADDITIONAL REQUIREMENTS
• Packaging and Storage: Preserve in well-closed containers.
• Labeling: The quantity of dibasic calcium phosphate stated in the labeling is in terms of dibasic calcium phosphate dihydrate (CaHPO4·2H2O).
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Natalia Davydova Scientific Liaison 1-301-816-8328 | (DS2010) Monographs - Dietary Supplements |
| 711 | Margareth R.C. Marques, Ph.D. Senior Scientific Liaison 1-301-816-8106 | (GCDF2010) General Chapters - Dosage Forms |
USP35–NF30 Page 2465