Diethanolamine

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

Diethanolamine is a mixture of ethanolamines, consisting largely of diethanolamine. It contains NLT 98.5% and NMT 101.0% of ethanolamines, calculated on the anhydrous basis as NH(C₂H₄OH)₂.

2 IDENTIFICATION

Change to read:

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

3 ASSAY

Procedure

Sample: 2 g

Blank: 50 mL of water

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Direct titration

Titrant: 0.5 N hydrochloric acid VS

Endpoint detection: Visual

Analysis: To the Sample add 50 mL of water and bromocresol green TS. Titrate with the Titrant. Perform a blank determination.

Calculate the percentage of diethanolamine, expressed as NH(C₂H₄OH)₂, in the Sample taken:

Result = {[(V_S− V_B) × N × F]/W} × 100

V_S= Titrant volume consumed by the Sample (mL)

V_B= Titrant volume consumed by the Blank (mL)

N = actual normality of the Titrant (mEq/mL)

F = equivalency factor, 105.14 (mg/mEq)

W = Sample weight (mg)

Acceptance criteria: 98.5%–101.0% on the anhydrous basis

4 IMPURITIES

Limit of Triethanolamine

Mixed indicator: 1.5 mg/mL of methyl orange and 0.8 mg/mL of xylene cyanole FF in water

Sample: 20 g

Blank: 100 mL of methanol and 6–8 drops of Mixed indicator

Titrimetric system

(See Titrimetry 〈541〉.)

Mode: Direct titration

Titrant: 0.5 N alcoholic sulfuric acid VS

Endpoint detection: Visual

Analysis: Place 100 mL of methanol and 6–8 drops of Mixed indicator in a 500-mL glass-stoppered conicalflask, and neutralize with 0.1 N alcoholic sulfuric acid or 0.1 N alcoholic potassium hydroxide. The neutral solution is amber when viewed by transmitted light and is red-brown when viewed by reflected light. Add the Sample. Cautiously add 75 mL of acetic anhydride, and swirl to effect complete solution.

Cool to room temperature, if necessary, and allow to stand at room temperature for 30 min. Titrate with the Titrant. Perform a blank determination.

Calculate the percentage of triethanolamine in the Sample taken:

Result = {[(V_S − V_B) × N × F]/W} × 100

V_S= Titrant volume consumed by the Sample (mL)

V_B= Titrant volume consumed by the Blank (mL)

N = actual normality of the Titrant (mEq/mL)

F = equivalency factor, 149.2 mg/mEq

W = Sample weight (mg)

Acceptance criteria: NMT 1.0% by weight

5 SPECIFIC TESTS

Refractive Index 〈831〉: 1.473–1.476 at 30°

Water Determination, Method I 〈921〉

Sample: 20 g

Solvent: A mixture of methanol and glacial acetic acid (40:25)

Acceptance criteria: NMT 0.15%

6 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight, light-resistant containers.

USP Reference Standards 〈11〉

USP Diethanolamine RS