Tribasic Calcium Phosphate

Calcium hydroxide phosphate;    
Calcium hydroxide phosphate    [12167-74-7].
Tribasic Calcium Phosphate consists of a variable mixture of calcium phosphates having the approximate composition 10CaO·3P2O5·H2O. It contains NLT 34.0% and NMT 40.0% of calcium (Ca).
•  A.
Sample solution: Dissolve 100 mg in 5 mL of diluted nitric acid.
Analysis: Warm the Sample solution, and add ammonium molybdate TS.
Acceptance criteria: A yellow precipitate is formed.
•  B. Identification Tests—General, Calcium 191: Meets the requirements of the flame test
•  Procedure
Sample: 150 mg of Tribasic Calcium Phosphate
Blank: Proceed as directed in the Analysis, omitting the test specimen.
Titrimetric system 
Mode: Direct titration
Titrant: 0.05 M edetate disodium VS
Endpoint detection: Visual
Analysis: Dissolve the Sample, with the aid of gentle heat if necessary, in a mixture of hydrochloric acid and water (5:3), contained in a 250-mL beaker equipped with a magnetic stirrer, and cautiously add 125 mL of water. With constant stirring, add, in the following order, 0.5 mL of triethanolamine, 300 mg of hydroxy naphthol blue, and from the titration 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.
Calculate the percentage of calcium (Ca) in the Sample taken:
Result = {[(VS VB ) × M × F]/W} × 100
VS== Titrant volume consumed by the Sample (mL)
VB== Titrant volume consumed by the Blank (mL)
M== actual molarity of the Titrant (mM/mL)
F== equivalency factor, 40.08 mg/mM
W== Sample weight (mg)
Acceptance criteria: 34.0%–40.0%
•  Chloride and Sulfate, Chloride 221
Standard: 1.0 mL of 0.020 N hydrochloric acid
Sample: 0.500 g of Tribasic Calcium Phosphate
Analysis: Dissolve the Sample in 25 mL of 2 N nitric acid, and add 1 mL of silver nitrate TS.
Acceptance criteria: NMT 0.14%
•  Chloride and Sulfate, Sulfate 221
Standard: 1.0 mL of 0.020 N sulfuric acid
Sample: 0.500 g of Tribasic Calcium Phosphate
Analysis: Dissolve the Sample in the smallest possible amount of 3 N hydrochloric acid. Dilute with water to 100 mL, and filter, if necessary. To 25 mL of the filtrate add 1 mL of barium chloride TS.
Acceptance criteria: NMT 0.8%
•  Arsenic, Method I 211
Test preparation: Dissolve 1.0 g in just sufficient 3 N hydrochloric acid.
Acceptance criteria: NMT 3 ppm
•  Barium
Sample: 500 mg of Tribasic Calcium Phosphate
Analysis: Mix the Sample with 10 mL of water, heat, add hydrochloric acid, dropwise, until solution is effected, and then add 2 drops of the acid in excess. Filter, and add to the filtrate 1 mL of potassium sulfate TS.
Acceptance criteria: No turbidity appears within 15 min.
•  Heavy Metals, Method I 231
Test preparation: Mix 1.3 g with 9 mL of 3 N hydrochloric acid, dilute with water to 50 mL, and heat to boiling. Cool to room temperature, and filter. [Note—Filter the mixture after the pH adjustment. ]
Acceptance criteria: NMT 30 ppm
•  Carbonate
Sample: 2 g of Tribasic Calcium Phosphate
Analysis: Mix the Sample with 20 mL of water, and add 3 N hydrochloric acid, dropwise, to effect solution.
Acceptance criteria: No effervescence is produced.
•  Acid-Insoluble Substances
Analysis: If an insoluble residue remains in the test for Carbonate, boil the solution, filter, wash the residue well with hot water until the last washing is free from chloride, and ignite the residue to constant weight.
Acceptance criteria: The weight of the residue does not exceed 4 mg (NMT 0.2%).
•  Dibasic Salt and Calcium Oxide
Sample: 1.5 g of Tribasic Calcium Phosphate
Blank: 25.0 mL of Titrant
Titrimetric system 
Mode: Residual titration
Titrant: 1 N hydrochloric acid VS
Back-titrant: 0.1 N sodium hydroxide VS
Endpoint detection: Potentiometric
Analysis: Dissolve the Sample by warming with 25.0 mL of the Titrant. Cool, and slowly titrate the excess of Titrant, while agitating constantly, with the Back-titrant to a pH of 4.0.
Acceptance criteria: 13.0–14.3 mL of 1 N hydrochloric acid is consumed for each g of salt, calculated on the ignited basis.
•  Limit of Fluoride
[Note—Prepare and store all solutions in plastic containers. ]
Buffer solution: 294 mg/mL of sodium citrate dihydrate in water
Standard stock solution: 1.1052 mg/mL of USP Sodium Fluoride RS in water
Standard solution: Transfer 20.0 mL of Standard stock solution to a 100-mL volumetric flask containing 50.0 mL of Buffer solution, dilute with water to volume, and mix. Each mL of this solution contains 100 µg of fluoride ion.
Sample solution: Transfer 2.0 g of Tribasic Calcium Phosphate to a beaker containing a plastic-coated stirring bar. Add 20 mL of water and 3.0 mL of hydrochloric acid, and stir until dissolved. Add 50.0 mL of Buffer solution and sufficient water to make 100 mL.
Electrode system: Use a fluoride-specific ion-indicating electrode and a silver–silver chloride reference electrode connected to a pH meter capable of measuring potentials with a minimum reproducibility of ±0.2 mV (see pH 791).
Samples: Standard solution and Sample solution
Standard response line: Transfer 50.0 mL of Buffer solution and 3.0 mL of hydrochloric acid to a beaker, and add water to make 100 mL. Add a plastic-coated stirring bar, insert the electrodes into the solution, stir for 15 min, and read the potential, in mV. Continue stirring, and at 5-min intervals add 100, 100, 300, 500, and 500 µL of Standard solution, reading the potential 5 min after each addition. Plot the logarithms of the cumulative fluoride ion concentrations (0.1, 0.2, 0.5, 1.0, and 1.5 µg/mL) versus potential, in mV.
Rinse and dry the electrodes, insert them into the Sample solution, stir for 5 min, and read the potential, in mV. From the measured potential and the Standard response line determine the concentration, C (in µg/mL), of fluoride ion in the Sample solution.
Calculate the content of fluoride in the portion of Tribasic Calcium Phosphate taken:
Result = (V × C)/W
V== volume of the Sample solution (mL)
C== concentration of fluoride ion in the Sample solution (µg/mL), determined from the Standard response line
W== weight of Tribasic Calcium Phosphate taken to prepare the Sample solution (g)
Acceptance criteria: NMT 75 ppm
•  Limit of Nitrate
Sample: 200 mg of Tribasic Calcium Phosphate
Analysis: Mix the Sample with 5 mL of water, and add just sufficient hydrochloric acid to effect solution. Dilute with water to 10 mL, add 0.20 mL of indigo carmine TS, then add, with stirring, 10 mL of sulfuric acid.
Acceptance criteria: The blue color persists for NLT 5 min.
•  Water-Soluble Substances
Sample: 2 g of Tribasic Calcium Phosphate
Analysis: Digest the Sample with 100 mL of water on a steam bath for 30 min. Cool, add sufficient water to restore the original volume, stir well, and filter. Evaporate 50 mL of the filtrate in a tared porcelain dish on a steam bath to dryness, and dry the residue at 120 to constant weight.
Acceptance criteria: The weight of the residue does not exceed 5 mg (NMT 0.5%).
•  Loss on Ignition 733
Analysis: Ignite a sample at 800 for 30 min.
Acceptance criteria: NMT 8.0%
•  Packaging and Storage: Preserve in well-closed containers.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/QuestionContactExpert Committee
MonographHuy T. Dinh, M.S.
Scientific Liaison
(DS2010) Monographs - Dietary Supplements
USP35–NF30 Page 1719
Chromatographic Column— 
Chromatographic columns text is not derived from, and not part of, USP 35 or NF 30.