Diethyl Phthalate

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
DOWNLOAD PDF HERE

1 DEFINITION

Diethyl Phthalate contains NLT 98.0% and NMT 102.0% of diethyl phthalate (C₁₂H₁₄O₄), calculated on the anhydrous basis. [Caution-Avoid contact.]

2 IDENTIFICATION

Change to read:

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197F.▲ (CN 1-May-2020) On undried specimen

3 ASSAY

Procedure

Sample: 1.5 g

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Residual titration

Titrant: 0.5 N alcoholic potassium hydroxide VS

Back-titrant: 0.5 N hydrochloric acid VS

Endpoint detection: Visual

Analysis: Transfer the Sample to a flask, add 50.0 mL of the Titrant, and boil with a reflux condenser on a water bath for 1 h. Add 20 mL of water, then add phenolphthalein TS. Titrate the excess potassium hydroxide with the Back-titrant. Perform a blank determination. Each mL of 0.5 N potassium hydroxide is equivalent to 55.56 mg of diethyl phthalate (C₁₂H₁₄O₄).

Acceptance criteria: 98.0%–102.0% on the anhydrous basis

4 IMPURITIES

Residue on Ignition 〈281〉

Sample: 10 g

Analysis: Gently heat the Sample until the liquid has evaporated, and ignite the residue to constant weight.

Acceptance criteria: NMT 0.02%

5 SPECIFIC TESTS

Specific Gravity 〈841〉: 1.118–1.122 at 20°

Refractive Index 〈831〉: 1.500–1.505 at 20°

Acidity

Sample: 20.0 g

Analysis: Mix the Sample with 50 mL of alcohol that previously has been neutralized to a phenolphthalein endpoint, and titrate with 0.1 N sodium hydroxide VS to a phenolphthalein endpoint.

Acceptance criteria: NMT 0.50 mL is required for neutralization.

Water Determination, Method I〈921〉: NMT 0.2%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.

USP Reference Standards 〈11〉

USP Diethyl Phthalate RS