Zinc Oxide Powder

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

Zinc oxide Powder contains NLT 90.0% and NMT 110.0% of the labeled amount of zinc oxide (ZnO).

2 IDENTIFICATION

A. The retention time of the zinc peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay.

3 ASSAY

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Procedure

Proceed as directed in Zinc Determination 〈591〉, Ion Chromatographic Method (CN 1-May-2020) .

Diluent: 0.2% (w/v) hydrochloric acid

Standard solution: 20 µg/mL of USP Zinc Oxide RS in Diluent, prepared as directed in the chapter

Sample stock solution: Nominally 500 µg/mL of zinc oxide prepared as follows. Transfer an appropriate amount of Powder to a suitable volumetric flask. Add hydrochloric acid to about 15% of the nal volume of the flask. [Note—Sonication or shaking may be necessary.] Dilute with water to volume. Centrifuge or pass a portion of this solution through a suitable filter.

Sample solution: Nominally 20 µg/mL of zinc oxide in water from the Sample stock solution

System suitability

Sample: Standard solution

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 2.0%

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of zinc oxide (ZnO) in the portion of Powder taken:

Result = (r_U /r_S ) × (C_S /C_U ) × 100

r_U = peak response of zinc from the Sample solution

r_S = peak response of zinc from the Standard solution

C_S = concentration of USP Zinc Oxide RS in the Standard solution (µg/mL)

C_U = nominal concentration of zinc oxide in the Sample solution (µg/mL)

Acceptance criteria: 90.0%–110.0%

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers, and store at room temperature.