Packaging and storage— Preserve in well-closed containers.

Botanic characteristics— Polygonal, rounded or spheroidal granules up to about 35 µm in diameter and usually having a circular or several-rayed central cleft.

Identification—

Microbial enumeration tests 61 and Tests for specified microorganisms 62— The total aerobic microbial count does not exceed 500 cfu per g and the total combined molds and yeasts count does not exceed 50 cfu per g.

pH 791— Prepare a slurry by weighing 20.0 g ± 100 mg of Topical Starch, transferring to a suitable nonmetallic container, and adding 100 mL of water. Agitate continuously at a moderate rate for 5 minutes, then stop agitation, and immediately determine the pH to the nearest 0.1 unit: the pH, determined potentiometrically, is between 4.5 and 7.0.

Loss on drying 731— Dry it at 120 for 4 hours: it loses not more than 14.0% of its weight.

Residue on ignition 281: not more than 0.5%, determined on a 2.0-g test specimen ignited at a temperature of 575 ± 25.

Iron 241— Dissolve the residue obtained in the test for Residue on ignition in 4 mL of hydrochloric acid with the aid of gentle heating, dilute with water to 50 mL, and mix. Dilute 25 mL of the resulting solution with water to 47 mL: the limit is 0.001%.

Oxidizing substances— Transfer 4.0 g to a glass-stoppered, 125-mL conical flask, and add 50.0 mL of water. Insert the stopper, and swirl for 5 minutes. Decant into a glass-stoppered, 50-mL centrifuge tube, and spin to clarify. Transfer 30.0 mL of clear supernatant to a glass-stoppered, 125-mL conical flask. Add 1 mL of glacial acetic acid and 0.5 g to 1.0 g of potassium iodide. Insert the stopper, swirl, and allow to stand for 25 to 30 minutes in the dark. Add 1 mL of starch TS, and titrate with 0.002 N sodium thiosulfate VS to the disappearance of the starch-iodine color. Each mL of 0.002 N sodium thiosulfate is equivalent to 34 µg of oxidant, calculated as hydrogen peroxide. Not more than 12.6 mL of 0.002 N sodium thiosulfate is required (0.018%).

Sulfur dioxide— Mix 20 g with 200 mL of water to obtain a smooth suspension, and filter. To 100 mL of the clear filtrate add 3 mL of starch TS, and titrate with 0.01 N iodine VS to the first permanent blue color: not more than 2.7 mL is consumed (0.008%).

Topic/Question	Contact	Expert Committee
Monograph	Hong Wang, Ph.D. Scientist 1-301-816-8351	(EM205) Excipient Monographs 2
61	Radhakrishna S Tirumalai, Ph.D. Senior Scientist 1-301-816-8339	(MSA05) Microbiology and Sterility Assurance
62	Radhakrishna S Tirumalai, Ph.D. Senior Scientist 1-301-816-8339	(MSA05) Microbiology and Sterility Assurance

USP32–NF27 Page 3598