Tricitrates Oral Solution

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

Tricitrates Oral Solution is a solution of Sodium Citrate, Potassium Citrate, and Citric Acid in a suitable aqueous medium. It contains, in each 100 mL, NLT 2.23 g and NMT 2.46 g of sodium (Na), equivalent to NLT 9.5 g and NMT 10.5 g of sodium citrate dihydrate (C₆H₅Na₃O₇ · 2H₂O); NLT 3.78 g and NMT 4.18 g of potassium (K), equivalent to NLT 10.45 g and NMT 11.55 g of potassium citrate monohydrate (C₆H₅K₃O₇ · H₂O); NLT 12.20 g and NMT 13.48 g of citrate (C₆H₅O₇) as sodium citrate and potassium citrate; and NLT 6.34 g and NMT 7.02 g of citric acid monohydrate (C₆H₈O₇ · H₂O). [NOTE-The sodium and potassium ion contents of Tricitrates Oral Solution are each approximately 1 mEq/mL.]

2 IDENTIFICATION

A. IDENTIFICATION TESTS GENERAL, (191)

Sample: 2 mL Oral Solution

Acceptance criteria: Meets the requirements for test A under Sodium

B.

Sample solution: Oral Solution (1 in 20)

Analysis: Add 5 mL of sodium cobaltinitrite TS to 2 mL of Sample solution.

Acceptance criteria: A yellow precipitate is formed immediately (presence of potassium).

C. The retention time of the citrate peak of the Sample solution corresponds to that of Standard solution 1, as obtained in the Assay for Citric Acid.

3 ASSAY

3.1 SODIUM AND POTASSIUM

Sodium stock solution: Transfer 14.61 g of sodium chloride, previously dried at 105° for 2 h, to a 250-mL volumetric flask, and dilute with water to volume.

Potassium stock solution: Transfer 18.64 g of potassium chloride, previously dried at 105° for 2 h, to a 250-ml volumetric flask, and dilute with water to volume.

Diluent: Transfer 1.04 g of lithium nitrate to a 1000-mL volumetric flask, add a suitable nonionic surfactant, then add water to volume. This solution contains 15 mEq of Li/1000 mL..

Standard solution: Pipet 50 mL of Sodium stock solution and 50 mL of Potassium stock solution into a 500-mL volumetric flask, and dilute with water to volume. Each mL of this solution contains 0.1 mEq of sodium (Na) and 0.1 mEq of potassium (K). Transfer 50 µL of this solution to a 10-mL volumetric flask, and dilute with Diluent to volume.

Sample solution: Transfer a volume of Oral Solution, equivalent to 2 g of combined citrates, to a 100-mL volumetric flask, and dilute with water to volume. Transfer 50 µL of this solution to a 10-mL volumetric flask, and dilute with Diluent to volume.

Instrumental conditions

(See Atomic Absorption Spectroscopy (852).)

Mode: Atomic absorption spectrophotometry

Analytical wavelengths

Sodium emission line: 589 nm

Potassium emission line: 766 nm

Blank: Diluent

Analysis

Samples: Standard solution, Sample solution, and Blank

Calculate the quantity, in g, of sodium (Na) in the portion of Oral Solution taken:

Result = (A_r /M_r ) × (R_U,Na /R_S,Na ) × (W/F)

A_r = atomic weight of sodium, 22.99

M_r = molecular weight of sodium chloride, 58.44

R_U,Na = sodium emission reading from the Sample solution

R_S,Na = sodium emission reading from the Standard solution

W = weight of sodium chloride in the Sodium stock solution, 14.61 g

F = conversion factor, 25

Calculate the quantity, in g, of potassium (K) in the portion of Oral Solution taken:

Result = (A_r /M_r ) × (R_u,k /R_s,k ) × (W/F)

A_r = atomic weight of potassium, 39.10

M_r = molecular weight of potassium chloride, 74.55

R_u,s = potassium emission reading from the Sample solution

R_s,k = potassium emission reading from the Standard solution

W = weight of potassium chloride in the Potassium stock solution, 18.64 g

F = conversion factor, 25

Acceptance criteria: 2.23–2.46 g/100 mL of sodium and 9.5–10.5 g/100 mL of potassium

3.2 CITRATE

Mobile phase, Standard solution 1, Chromatographic system, and System suitability: Proceed as directed in Assay for Citric Acid/Citrate and

Phosphate (345).

Sample solution: Transfer an appropriate volume of Oral Solution into a suitable volumetric flask, and proceed as directed in Assay for Citric Acid/Citrate and Phosphate (345). Sample solution (for the assay of citric acid/citrate).

Analysis: Proceed as directed in Assay for Citric Acid/Citrate and Phosphate (345), Procedure.

Calculate the concentration, in g/100 mL, of citrate (C₆H₅O₇) in the portion of Oral Solution taken:

Result = [(r_u /r_s ) × (C_s /C_u ) − A(M_r1 /M_r2 )] × L

r_u = citrate peak area from the Sample solution

r_s = citrate peak area from Standard solution 1

C_s = concentration of citrate in Standard solution 1 (µg/mL)

C_u = nominal concentration of Sample solution

A = concentration of citric acid monohydrate determined in the Assay for Citric Acid (mg/mL)

M_r1 = molecular weight of citrate, 189.10

M_r2 = molecular weight of citric acid monohydrate, 210.14

L = Oral Solution label claim (g/100 mL)

Acceptance criteria: 12.20–13.48 g/100 mL as sodium citrate and potassium citrate

3.3 CITRIC ACID

Sample solution: Transfer 15 ml of Oral Solution into a 250-mL volumetric flask, and dilute with water to volume.

Analysis: Transfer 5 mL of the Sample solution into a suitable flask, and add 25 mL of water and 5 drops of phenolphthalein TS. Titrate with 0.02 N sodium hydroxide VS to a pink endpoint. Each mL of 0.02 N sodium hydroxide is equivalent to 1.401 mg of citric acid monohydrate (C₆H₈O₇ · H₂O)

Acceptance criteria: 6.34-7.02 g/100 mL

4 SPECIFIC TESTS

PH (791); 4.9-5.4

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers.

USP REFERENCE STANDARDS (11)

USP Citric Acid RS