U.S. PHARMACOPEIA

Search USP29  
Zinc Sulfate
ZnSO4·xH2O.

Sulfuric acid, zinc salt (1:1), hydrate.
Zinc sulfate (1:1) monohydrate 179.46

Zinc sulfate (1:1) heptahydrate 287.56 [7446-20-0].

Anhydrous 161.46 [7733-02-0].
» Zinc Sulfate contains one or seven molecules of water of hydration. The monohydrate contains not less than 89.0 percent and not more than 90.4 percent of ZnSO4, corresponding to not less than 99.0 percent and not more than 100.5 percent of ZnSO4·H2O, and the heptahydrate contains not less than 55.6 percent and not more than 61.0 percent of ZnSO4, corresponding to not less than 99.0 percent and not more than 108.7 percent of ZnSO4·7H2O.
Packaging and storage— Preserve in tight containers.
Labeling— The label indicates whether it is the monohydrate or the heptahydrate. Label any oral or parenteral preparations containing Zinc Sulfate to state the content of elemental zinc.
Identification— A solution of it responds to the tests for Zinc 191 and for Sulfate 191.
Acidity— A solution containing the equivalent of 28 mg of ZnSO4 per mL is not colored pink by methyl orange TS.
Arsenic, Method I 211— Prepare a Test Preparation by dissolving a portion equivalent to 215 mg of ZnSO4 in 35 mL of water: the limit is 14 ppm.
Lead 251— Dissolve a portion equivalent to 0.25 g of ZnSO4 in 5 mL of water, and transfer the solution to a color-comparison tube (A). Add 10 mL of Potassium Cyanide Solution (1 in 10), mix, and allow the mixture to become clear. In a similar, matched color-comparison tube (B) place 5 mL of water, and add 0.50 mL of Standard Lead Solution (see Heavy Metals 231) and 10 mL of Potassium Cyanide Solution (1 in 10). Add to the solution in each tube 0.1 mL of sodium sulfide TS. Mix the contents of each tube, and allow to stand for 5 minutes: viewed downward over a white surface, the solution in tube A is no darker than that in tube B. The lead limit is 0.002%.
Alkalies and alkaline earths— Dissolve the equivalent of 1.12 g of ZnSO4 in about 150 mL of water contained in a 200-mL volumetric flask. Precipitate the zinc completely by means of ammonium sulfide TS, and dilute with water to volume. Mix, and filter through a dry filter, rejecting the first portion of the filtrate. To 100 mL of the subsequent filtrate add a few drops of sulfuric acid, evaporate to dryness in a tared dish, and ignite: the weight of the residue does not exceed 5 mg (0.9%).
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Dissolve an accurately weighed quantity of Zinc Sulfate, equivalent to about 170 mg of ZnSO4, in 100 mL of water. Add 5 mL of ammonia–ammonium chloride buffer TS and 0.1 mL of eriochrome black TS, and titrate with 0.05 M edetate disodium VS until the solution is deep blue in color. Each mL of 0.05 M edetate disodium is equivalent to 8.072 mg of ZnSO4.
Auxiliary Information— Staff Liaison : Feiwen Mao, M.S., Senior Scientific Associate
Expert Committee : (MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals
USP29–NF24 Page 2292
Phone Number : 1-301-816-8320