Cupric Sulfate

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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CuSO₄ . 5H₂0     249.69

CuSO₄     159.61

Sulfuric acid, copper(2+) salt (1:1), pentahydrate;

Copper(2+) sulfate (1:1) pentahydrate CAS RN®: 7758-99-8; UNII: LRX7AJ16DT.

Anhydrous CAS RN®: 7758-98-7; UNII: KUW2Q3U1VV.

1 DEFINITION

Cupric Sulfate is anhydrous or contains five molecules of water of hydration. It contains NLT 98.5% and NMT 100.5% of cupric sulfate (CuSO₄), calculated on the dried basis.

2 IDENTIFICATION

2.1 A. IDENTIFICATION TESTS-GENERAL, Sulfate (191):

A 100-mg/mL solution meets the requirements.

2.2 B. IDENTIFICATION TESTS-GENERAL, Copper (191):

A 100-mg/mL solution meets the requirements.

3 ASSAY

3.1 PROCEDURE

Sample solution: Place 650 mg of Cupric Sulfate in a weighed container fitted with a ground-glass stopper. Dry, allow to cool in a desiccator, and weigh again to obtain the weight of the sample. Dissolve in 50 mL of water. Add 4 mL of 6 N acetic acid and 3 g of potassium iodide.

Titrimetric system

Mode: Direct titration

Titrant: 0.1 N sodium thiosulfate VS

Endpoint detection: Visual

Analysis: Titrate the liberated iodine in the Sample solution with the Titrant, adding about 2 g of potassium thiocyanate and 3 mL of starch TS as the endpoint is approached. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium thiosulfate is equivalent to 15.96 mg of cupric sulfate (CuSO₄).

Acceptance criteria: 98.5%-100.5% on the dried basis

4 IMPURITIES

4.1 LIMIT OF SODIUM

Sample stock solution: 0.2 g/mL of cupric sulfate in water, prepared as follows. Transfer 40.0 g of Cupric Sulfate to a 200-mL volumetric flask, add water, and swirl to dissolve. Add 5 mL of nitric acid, and dilute with water to volume.

Sample solutions: To three 25-mL volumetric flasks add a volume of Sample stock solution equivalent to the Sample Weight given in Table 1. To two of the flasks add the amounts of reference analyte ion specified in Table 1. Add 2 mL of potassium chloride solution (1 in 20) to each flask, and dilute with water to volume.

Analysis: Using atomic absorption spectrophotometry (see Atomic Absorption Spectroscopy (852)), analyze the Sample solutions by the method of standard addition analysis given in Table 1.

Table 1

Acceptance criteria: NMT 0.02%

4.2 LIMIT OF POTASSIUM

Sample stock solution: Prepare as directed in the test for Limit of Sodium.

Sample solutions: To three 25-mL volumetric flasks add a volume of Sample stock solution equivalent to the Sample Weight given in Table 1. To two of the flasks add the amounts of reference analyte ion specified in Table 1, and dilute with water to volume.

Analysis: Using atomic absorption spectrophotometry (see Atomic Absorption Spectroscopy (852)), analyze the Sample solutions by the method of standard addition analysis given in Table 1.

Acceptance criteria: NMT 0.01%

4.3 LIMIT OF CALCIUM

Sample stock solution: Prepare as directed in the test for Limit of Sodium.

Sample solutions: To three 25-mL volumetric flasks add a volume of Sample stock solution equivalent to the Sample Weight given in Table 1. To two of the flasks add the amounts of reference analyte ion specified in Table 1, and dilute with water to volume.

Analysis: Using atomic absorption spectrophotometry (see Atomic Absorption Spectroscopy (852)), analyze the Sample solutions by the method of standard addition analysis given in Table 1.

Acceptance criteria: NMT 0.005%

4.4 LIMIT OF IRON

Sample stock solution: Prepare as directed in the test for Limit of Sodium.

Sample solutions: To three 25-mL volumetric flasks add a volume of Sample stock solution equivalent to the Sample Weight given in Table 1. To two of the flasks add the amounts of reference analyte ion specified in Table 1, and dilute with water to volume.

Analysis: Using atomic absorption spectrophotometry (see Atomic Absorption Spectroscopy (852)), analyze the Sample solutions by the method of standard addition analysis given in Table 1.

Acceptance criteria: NMT 0.003%

4.5 LIMIT OF NICKEL

Sample stock solution: Prepare as directed in the test for Limit of Sodium.

Sample solutions: To three 25-mL volumetric flasks add a volume of Sample stock solution equivalent to the Sample Weight given in Table 1. To two of the flasks add the amounts of reference analyte ion specified in Table 1, and dilute with water to volume.

Analysis: Using atomic absorption spectrophotometry (see Atomic Absorption Spectroscopy (852)), analyze the Sample solutions by the method of standard addition analysis given in Table 1.

Acceptance criteria: NMT 0.005%

5 SPECIFIC TESTS

5.1 LOSS ON DRYING (731)

Analysis: Dry it at 250° to constant weight.

Acceptance criteria: 33.0%-36.5% for the pentahydrate form; NMT 1.0% for the anhydrous form

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE:

Preserve in tight containers. Store at controlled room temperature.

6.2 LABELING:

Label the product to indicate whether it is anhydrous or it is the pentahydrate.