Sodium Caprylate

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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C₈H₁₅NaO₂ 166.19

Sodium octanoate CAS RN®: 1984-06-1.

1 DEFINITION

Sodium Caprylate contains NLT 99.0% and NMT 101.0% of sodium caprylate (C₈H₁₅NaO₂), calculated on the anhydrous basis.

2 IDENTIFICATION

A. The retention time of the major peak of Sample solution A corresponds to that of the Standard solution, as obtained in the test for Chromatographic Purity in Impurities.

B.

Methoxyphenylacetic reagent: Dissolve 2.7 g of methoxyphenylacetic acid in 6 mL of 10% tetramethylammonium hydroxide solution in methanol, and add 20 mL of alcohol. Store in a polyethylene container.

Sample solution: 20 mg

Analysis: Dissolve the Sample in 0.5 mL of water, add 1.5 mL of Methoxyphenylacetic reagent, and cool in ice water for 30 min. A voluminous, white, crystalline precipitate is formed. Place in water at 20°, and stir for 5 min. The precipitate does not disappear. Add 1 mL of ammonia TS. The precipitate dissolves completely. Add 1 mL of ammonium carbonate solution (160 mg/mL).

Acceptance criteria: No precipitate is formed.

3 ASSAY

Procedure

Sample: 150 mg

Blank: Glacial acetic acid

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Direct titration

Titrant: 0.1 N perchloric acid VS

Endpoint detection: Potentiometric

Analysis: Transfer the Sample to a 125-mL volumetric flask, and dissolve in 50 mL of glacial acetic acid. Titrate with Titrant. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 16.62 mg of sodium caprylate (C₈H₁₅NaO₂).

Acceptance criteria: 99.0%–101.0% on the anhydrous basis

4 IMPURITIES

Chromatographic Purity

Standard solution: 1.0 mg/mL of USP Caprylic Acid RS in ethyl acetate

Sample solution A: Dissolve 116 mg of Sodium Caprylate in 5 mL of water, add 1 mL of dilute sulfuric acid (1 in 35), and extract with 10 mL of ethyl acetate. Separate the organic layer, and dry it over anhydrous sodium sulfate.

Sample solution B: Dilute 1.0 mL of Sample solution A with ethyl acetate to 100 mL, transfer 5.0 mL of the solution obtained, and dilute with ethyl acetate to 50 mL.

Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.25-mm × 30-m fused silica; coated with a 0.25-μm layer of phase G25

Temperatures

Injection port: 250°

Detector: 250°

Column: See Table 1.

Table 1

Flow rate: 1.5 mL/min

Carrier gas: Helium

Injection volume: 1 μL

Injection type: Split ratio, 100:1

System suitability

Sample: Sample solution B

Suitability requirements

Signal-to-noise ratio: NLT 5

Analysis

Samples: Standard solution, Sample solution A, and Sample solution B

Disregard any peaks with an area less than half of the area of the principal peak from Sample solution B and any peak due to the solvent.

Calculate the percentage of each impurity in the portion of Sodium Caprylate taken:

Result = (r_U/r_T) × 100

r_U = peak response of the individual impurity

r_T = sum of all the peak responses

Acceptance criteria

Individual impurities: NMT 0.3%

Total impurities: NMT 0.5%

5 SPECIFIC TESTS

Appearance of Solution

Standard stock solution: Combine 30.0 mL of ferric chloride CS, 30.0 mL of cobaltous chloride CS, and 24.0 mL of cupric sulfate CS, and dilute with 1% (w/v) hydrochloric acid to 100.0 mL.

Standard solution: Dilute 1.0 mL of Standard stock solution with 1% (w/v) hydrochloric acid to 100.0 mL.

Sample solution: Dissolve 2.5 g of Sodium Caprylate in 25.0 mL of freshly boiled and cooled water.

Acceptance criteria: The Sample solution is clear and colorless, or not more intensely colored than the Standard solution.

pH 〈791〉

Sample solution: Use the Sample solution in the test for Appearance of Solution.

Acceptance criteria: 8.0–10.5

Water Determination, Method I〈921〉: NMT 3.0%

6 ADDITIONAL REQUIREMENTS

USP Reference Standards 〈11〉

USP Caprylic Acid RS