Topical Starch

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

DOWNLOAD PDF HERE

1 DEFINITION

Topical Starch consists of the granules separated from the mature grain of corn [Zea mays L. (Fam. Gramineae)].

2 IDENTIFICATION

A.

Sample: 1 g

Analysis: Prepare a smooth mixture of the Sample with 2 mL of cold water, stir it into 15 mL of boiling water, boil gently for 2 min, and cool.

Acceptance criteria: A translucent, whitish jelly is produced.

B. A water slurry of it is colored reddish violet to deep blue by iodine TS.

3 IMPURITIES

RESIDUE ON IGNITION (281)

Sample: 2.0 g

Analysis: Ignite the Sample at a temperature of 575 ± 25°.

Acceptance criteria: NMT 0.5%

Change to read:

IRON (241), Procedures, Procedure 1 _{(CN 1-JUN-2023)}

Sample: The residue obtained in the test for Residue on Ignition

Analysis: Dissolve the Sample 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.

Acceptance criteria: NMT 10 µg/g

3.1 SULFUR DIOXIDE

Analysis: 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.

Acceptance criteria: NMT 2.7 mL of 0.01 N iodine VS is consumed (0.008%).

3.2 OXIDIZING SUBSTANCES

Sample: 4.0 g

Analysis: Add 50.0 mL of water to the Sample in a glass-stoppered, 125-mL conical flask. Insert the stopper, and swirl for 5 min. 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 0.5-1.0 g of potassium iodide. Insert the stopper, swirl, and allow to stand for 25-30 min 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. [NOTE-Each

Acceptance criteria: NMT 12.6 mL of 0.002 N sodium thiosulfate VS is required (0.018%).

4 SPECIFIC TESTS

BOTANIC CHARACTERISTICS: Polygonal, rounded, or spheroidal granules up to about 35 µm in diameter, and usually having a circular or several-

rayed central cleft.

LOSS ON DRYING (731).

Analysis: Dry a sample at 120° for 4 h.

Acceptance criteria: NMT 14.0%

MICROBIAL ENUMERATION TESTS (61) and TESTS FOR SPECIFIED MICROORGANISMS (62): The total aerobic microbial count does not exceed 5 x 102 cfu/g, and the total combined molds and yeasts count does not exceed 5 × 10¹ cfu/g.

PH (791)

Sample: 20.0 g ± 100 mg

Analysis: Prepare a slurry of the Sample in 100 mL of water in a suitable nonmetallic container. Agitate continuously at a moderate rate for 5 min, then stop agitation, and immediately determine the pH potentiometrically to the nearest 0.1 unit.

Acceptance criteria: 4.5–7.0

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers.