Packaging and storage—
Preserve in well-closed containers, and store at controlled room temperature.
Labeling—
Label the Tablets in terms of zinc sulfate (ZnSO4 · H2O) and in terms of elemental zinc.
Identification—
Test solution—
Dissolve the equivalent of 1 g of finely powdered Tablets in 50 mL of water. Use in the following two tests.
A:
To 5 mL of the Test solution add 0.2 mL of concentrated sodium hydroxide. A white precipitate is formed. Dissolve the precipitate in 2 mL of concentrated sodium hydroxide. The solution remains clear after the addition of 10 mL of ammonium chloride solution and forms a white precipitate after the addition of 0.1 mL of sodium sulfide solution.
B:
To 5 mL of the
Test solution add 1 mL of dilute hydrochloric acid and 1 mL of
barium chloride TS: a white precipitate is formed.
Dissolution—
Medium:
purified water with resistivity below 1 µS/cm; 750 mL.
Apparatus:
basket-rack assembly (see
Disintegration 
701
).
Time:
20 seconds.
Procedure—
Place 1 Tablet in each of the six tubes of the basket, lower the basket-rack assembly into the beaker containing the Medium, and introduce the electrode of the resistivity meter into the beaker without hindering the motion of the basket. Measure the resistivity every 2 seconds.
Tolerances—
The disintegration of the Tablets is complete in 20 seconds, and the resistivity stabilizes at about 255 to 260 µS in 20 seconds.
Assay—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 90 mg of zinc, to a 200-mL volumetric flask. Dissolve in 15 mL of dilute acetic acid, and sonicate for 15 minutes. Dilute with water to volume, and mix. Add 50 mg of xylenol orange triturate to the solution, and mix. Neutralize the solution with about 2 g of methenamine until the solution is a violet-pink color. Titrate with 0.1 M edetate disodium VS until the solution is yellow. Each mL of 0.1 M edetate disodium VS is equivalent to 17.946 mg of ZnSO
4·H
2O.
USP29
Auxiliary Information—
Staff Liaison :
Lawrence Evans, III, Ph.D., Scientist
Expert Committee : (DSN05) Dietary Supplements - Non-Botanicals
USP29–NF24 Page 2293
Pharmacopeial Forum : Volume No. 31(1) Page 82
Phone Number : 1-301-816-8389
