Propylene Glycol Diacetate

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

Propylene Glycol Diacetate contains NLT 98.0% and NMT 102.0% of propylene glycol diacetate (C₇H₁₂O₄).

2 IDENTIFICATION

A. SPECTROSCOPIC IDENTIFICATION TESTS 〈197〉 , Infrared Spectroscopy : 197F

B. CHROMATOGRAPHIC IDENTITY

Analysis: Proceed as directed in the Assay.

Acceptance criteria: The retention time of the major peak of the Sample solution, excluding the solvent and internal standard peaks, corresponds to the propylene glycol diacetate peak of the Standard solution.

3 ASSAY

PROCEDURE

Internal standard solution: 20 mg/mL of triacetin in methanol

System suitability solution: 20 mg/mL each of USP Propylene Gly col Diacetate RS and USP Benzyl Alcohol RS in Internal standard solution Standard solution: 20.0 mg/mL of USP Propylene Glycol Diacetate RS in Internal standard solution

Sample solution: 20.0 mg/mL of Propylene Glycol Diacetate in Internal standard solution Chromatographic system

(See Chromatography 〈621〉, System Suitability.) Mode: GC

Detector: Flame ionization

Column: 0.53-mm × 30-m fused silica; coated with a 1.0-µm film of phase G46 Temperatures

Injection port: 280°

Detector: 280° Column: See Table 1.

Table 1

Carrier gas: Hydrogen Flow rate: 5.0 mL/min Injection volume: 1 µL

Injection type: Split ratio, 60:1 Run time: 10.8 min

System suitability

Samples: System suitability solution and Standard solution

[NOTE—The relative retention times for propylene glycol diacetate, benzyl alcohol, and triacetin are 1.0, 1.1, and 1.4, respectively.]

Suitability requirements

Resolution: NLT 10 between the propylene glycol diacetate and benzyl alcohol peaks, System suitability solution Tailing factor: NMT 1.5 for the propylene glycol diacetate and triacetin peaks, Standard solution

Relative standard deviation: NMT 1.0% for the peak area ratio of propylene glycol diacetate to the internal standard, Standard solution Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of propylene glycol diacetate in the portion of Propylene Glycol Diacetate taken:

Result = (R /R ) × (C /C ) × P × 100

= peak area ratio of propylene glycol diacetate to the internal standard from the Sample solution

= peak area ratio of propylene glycol diacetate to the internal standard from the Standard solution

= concentration of USP Propylene Glycol Diacetate RS in the Standard solution (mg/mL)

= concentration of Propylene Glycol Diacetate in the Sample solution (mg/mL)

P    = labeled purity of USP Propylene Glycol Diacetate RS Acceptance criteria: 98.0%–102.0%

4 IMPURITIES

Change to read:

4.1 ORGANIC IMPURITIES

System suitability solution and Chromatographic system: Proceed as directed in the Assay. Sensitivity solution: 0.2 mg/mL of USP Propylene Gly col Diacetate RS in methanol

Sample solution: 20.0 mg/mL of Propylene Glycol Diacetate in methanol System suitability

Samples: System suitability solution and Sensitivity solution

[NOTE—The relative retention times for propylene glycol diacetate, benzyl alcohol, and triacetin are 1.0, 1.1, and 1.4, respectively.] Suitability requirements

Resolution: NLT 10 between the propylene glycol diacetate and benzyl alcohol peaks, System suitability solution Signal-to-noise ratio: NLT 20 for the propylene glycol diacetate peak, Sensitivity solution

Analysis

Sample: Sample solution

Identify the impurities in the Sample solution by comparing with those listed in Table 2.

Calculate the percentage of any individual impurity in the portion of Propylene Glycol Diacetate taken:

Result = (r /r ) × 100

= peak area of any individual impurity from the Sample solution

S    = sum of all the peak areas, excluding the solvent peaks from the Sample (ERR 1-Mar-2022) solution

Table 2

Acceptance criteria

Individual impurity: NMT 0.1% Total impurities: NMT 0.5%

4.2 ACETIC ACID

Sample: 10 g

Analysis: Dissolve the Sample in 30 mL of a mixture of alcohol and water (1:1), previously neutralized to phenolphthalein. Titrate with 0.1 N sodium hydroxide VS to a phenolphthalein endpoint. Each milliliter of 0.1 N sodium hydroxide is equivalent to 6.005 mg of acetic acid (C₇H₁₂O₄).

Acceptance criteria: NMT 0.2%

5 SPECIFIC TESTS

PH 〈791〉

Sample: 1 in 20 solution

Acceptance criteria: 4.0–6.0

SPECIFIC GRAVITY 〈841〉: 1.040–1.060

REFRACTIVE INDEX 〈831〉: 1.4130–1.4150 at 20°

WATER DETERMINATION 〈921〉 , Method I, Method Ic: NMT 0.1%

6 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers.

USP REFERENCE STANDARDS 〈11〉

USP Benzyl Alcohol RS

USP Propylene Glycol Diacetate RS