» Topical Starch consists of the granules separated from the mature grain of corn [Zea mays Linné (Fam. Gramineae)].
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.
A: Prepare a smooth mixture of 1 g of it with 2 mL of cold water, stir it into 15 mL of boiling water, boil gently for 2 minutes, and cool: a translucent, whitish jelly is produced.
B: A water slurry of it is colored reddish violet to deep blue by iodine TS.
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%).
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USP32NF27 Page 3598Pharmacopeial Forum: Volume No. 29(3) Page 669