Anthralin

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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C₁₄H₁₀O₃           226.23

9(10H)-Anthracenone, 1,8-dihydroxy-;

1,8-Dihydroxy-9-anthrone CAS RN®: 1143-38-0; UNII: U8CJK0JH5M.

1 DEFINITION

Anthralin contains NLT 97.0% and NMT 102.0% of anthralin (CHO), calculated on the dried basis.

2 IDENTIFICATION

Change to read:

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197K (CN 1-MAY-2020)

Change to read:

B.SPECTROSCOPIC IDENTIFICATION TESTS (197), Ultraviolet-Visible Spectroscopy: 197U (CN 1-MAY-2020)

Sample solution: 10 µg/mL in chloroform

Acceptance criteria: Meets the requirements

3 ASSAY

PROCEDURE

[NOTE-Use low-actinic glassware.]

Mobile phase: n-Hexane, dichloromethane, and glacial acetic acid (82:12:6)

Internal standard solution: 0.5 mg/ml, of o-nitroaniline in n-hexane prepared as follows. First dissolve o-nitroaniline in a small quantity of dichloromethane, and then dilute with n-hexane.

System suitability stock solution: 0.1 mg/mL of USP Anthralin RS and 0.2 mg/mL of danthron in dichloromethane

System suitability solution: Transfer 5 mL of the System suitability stock solution into a 25-mL volumetric flask, add 5 ml. of n-hexane, and dilute with Mobile phase to volume.

Solvent blank solution: Mobile phase, n-hexane, and dichloromethane (3:1:1)

Standard stock solution: 0.25 mg/mL of USP Anthralin RS in dichloromethane

Standard solution: Transfer 5 mL each of Standard stock solution and Internal standard solution into a 25-ml volumetric flask, and dilute with Mobile phase to volume.

Sample stock solution: 0.25 mg/mL of Anthralin in dichloromethane

Sample solution: Transfer 5 mL each of Sample stock solution and Internal standard solution into a 25-mL volumetric flask, dilute with Mobile phase to volume.

Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: LC

Detector: UV 354 nm

Column: 4.6-mm x 25-cm; packing L3

Flow rate: 2 mL/min

Injection volume: 10 µL

System suitability

Samples: System suitability solution, Solvent blank solution, and Standard solution

[NOTE-The relative retention times for anthralin, danthron, dianthrone, and o-nitroaniline are 1.0, 1.2, 1.7, and 2.3, respectively.]

Suitability requirements

Resolution: NLT 1.3 between anthralin and danthron, System suitability solution

Tailing factor: NMT 1.5, System suitability solution

Relative standard deviation: NMT 2.0% of the ratio of the peak responses, Standard solution

Interference: No discernible signal is observed at the retention time of anthralin, Solvent blank solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of anthralin (C₁₄H₁₀O₃) in the portion of Anthralin taken:

Result = (R_u /R_s ) × (C_s /C_u ) × 100

R_u = peak response ratio of anthralin to o-nitroaniline from the Sample solution

R_s = peak response ratio of anthralin to o-nitroaniline from the Standard solution

C_s = concentration of USP Anthralin RS in the Standard solution (µg/mL)

C_u = concentration of Anthralin in the Sample solution (µg/mL)

Acceptance criteria: 97.0%–102.0% on the dried basis

4 IMPURITIES

4.1 RESIDUE ON IGNITION (281): NMT 0.1%

4.2 CHLORIDE AND SULFATE, Chloride (221)

Sample: 1 g

Analysis: To 15 mL of water add the Sample, mix, and filter. Acidify 5 mL of the filtrate with nitric acid, and add a few drops of silver nitrate TS.

Acceptance criteria: No more opalescence is produced immediately than is present in a 5-mL portion of the filtrate to which nothing has been added.

4.3 CHLORIDE AND SULFATE, Sulfate (221)

Sample: 5 mL of the untreated filtrate obtained in the test for Chloride

Analysis: To the Sample add 3 drops of 3 N hydrochloric acid and 5 drops of barium chloride TS.

Acceptance criteria:

No more turbidity is produced than is present in a 5-ml portion of the filtrate to which nothing has been added.

4.4 SPECIFIC TESTS

MELTING RANGE OR TEMPERATURE, Class (741): 178°-181"

4.5 LOSS ON DRYING (731)

Analysis: Dry a sample over silica gel for 4 h.

Acceptance criteria: NMT 0.5%

4.6 ACIDITY OR ALKALINITY

Analysis: Suspend a sample in water, and filter.

Acceptance criteria: The filtrate is neutral to litmus.

5 ADDITIONAL REQUIREMENTS

PACKAGING AND STORAGE: Preserve in tight containers in a cool place. Protect from light.

USP REFERENCE STANDARDS (11)

USP Anthralin RS