Zinc Sulfate Ophthalmic Solution

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 Sulfate Ophthalmic Solution is a sterile solution of Zinc Sulfate in Water rendered isotonic by the addition of suitable salts. It contains NLT 95.0% and NMT 105.0% of the labeled amount of zinc sulfate (ZnSO₄).

2 IDENTIFICATION

A. Identification Tests - General 〈191〉, Chemical Identification Tests,Sulfate: Meets the requirements

B. 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 stock solution: Prepare as directed in the chapter.

Standard solution: 20 μg/mL of USP Zinc oxide RS in Diluent from the Standard stock solution

Sample solution: Nominally 40 μg/mL of zinc sulfate from a suitable volume of Ophthalmic Solution in Diluent

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 sulfate (ZnSO₄) in the portion of Ophthalmic Solution taken:

Result = (r_U/r_S) × (C_S/C_U) × (M_r1/M_r2) × 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 sulfate in the Sample solution (μg/mL)

M_r1 = molecular weight of zinc sulfate, 161.44

M_r2 = molecular weight of zinc oxide, 81.38

Acceptance criteria: 95.0%–105.0%

4 SPECIFIC TESTS

Sterility Tests 〈71〉: Meets the requirements

pH 〈791〉: 5.8–6.2, or if it contains sodium citrate, 7.2–7.8

Other Requirements: It meets the requirements in Ophthalmic Products—Quality Tests 〈771〉.

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers.