Purified Rayon

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

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

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1 DEFINITION 

Purified Rayon is a fibrous form of bleached, regenerated cellulose. 

2 IDENTIFICATION 

Add the following: 

A. Auxiliary Packaging Components 〈670〉, Pharmaceutical Coil, Rayon Pharmaceutical Coil: Meets the requirements (USP 1-Dec-2020) Add the following: 

B. Fluorescence: No intense blue with UV

3 IMPURITIES 

Residue on Ignition 〈281〉 

Sample: 5.0 g of Purified Rayon 

Acceptance criteria: NMT 1.50% 

Acid-Insoluble Ash 

Analysis: To the residue obtained in the test for Residue on Ignition, add 25 mL of 3 N hydrochloric acid, and boil for 5 min. Collect the insoluble matter on a tared filtering crucible, wash with hot water, ignite, and weigh. 

Acceptance criteria: NMT 63.0 mg (1.25%) 

Water-Soluble Substances 

Sample: 10 g of Purified Rayon, accurately weighed 

Analysis: Place the Sample in a beaker containing 1000 mL of water and boil gently for 30 min, adding water as required to maintain the volume. Pour the water through a funnel into another vessel, and press out the excess water from the rayon with a glass rod. Wash the rayon in the funnel with two 250-mL portions of boiling water, pressing the rayon after each washing. Filter the combined extract and washings, and wash the filter thoroughly with hot water. Evaporate the combined extract and washings to a small volume, transfer to a tared porcelain or platinum dish, evaporate to dryness, and dry the residue at 105° to constant weight. 

Acceptance criteria: NMT 100 mg (1.0%) 

4 SPECIFIC TESTS 

Alkalinity or Acidity 

Sample: About 10 g of Purified Rayon 

Analysis: Immerse the Sample in 100 mL of recently boiled and cooled water and decant 25-mL portions of the water, with the aid of a glass rod, into each of two dishes. To one portion add 3 drops of phenolphthalein TS, and to the other portion add 1 drop of methyl orange TS. Acceptance criteria: Neither portion appears pink when viewed against a white background. 

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Fiber Length 

Sample: Remove Purified Rayon from its wrappings, and condition it for NLT 4 h in a standard atmosphere of 65 ± 2% relative humidity at 21 ± 1.1° before determining the fiber length. 

Analysis: Determine the fiber length using a suitable method. (USP 1-Dec-2020) 

Acceptance criteria:  (USP 1-Dec-2020) NMT 5.0%, by weight, of the fibers are 6.25 (USP 1-Dec-2020) mm or less in length. Change to read: 

Absorbency 

Sample: Remove Purified Rayon from its wrappings, and condition it for NLT 4 h in a standard atmosphere of 65 ± 2% relative humidity at 21 ± 1.1° before determining the absorbency. 

Analysis: Prepare a test basket, weighing NMT 3 g, from copper wire approximately 0.4 mm in diameter (No. 26, B. & S. gauge) in the form of a cylinder approximately 5 cm in diameter and 8 cm deep, with spaces of about 2 cm between the wires. Take portions of rayon weighing 1 ± 0.05 g from ve different parts of the package by pulling, not cutting, the specimens. Combine the portions in the basket and weigh. Hold the basket on its side approximately 12 mm above the surface of water at 25 ± 1°, and drop it into the water. Determine, preferably by use of a stopwatch, the time in seconds required for complete submersion. Remove the basket from the water, allow it to drain for 10 s in the same horizontal position, then place it immediately in a tared, covered vessel, and weigh, deducting the weight of the test basket and of the rayon to find the weight of water absorbed. (USP 1-Dec-2020) 

Acceptance criteria: Submersion is complete in 5 s, and the rayon retains NLT 16 times its weight of water. 

Dyes 

Sample: About 10 g of Purified Rayon 

Analysis: Pack the Sample in a narrow percolator, and extract slowly with alcohol until the percolate measures 50 mL. Acceptance criteria: When observed downward through a column 20 cm in depth, the percolate may show a yellowish color, but neither a blue nor a green tint. 

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Other Foreign Matter: The samples of Purified Rayon taken for the determination of fiber length in the test for Fiber Length contain no oil stains or metallic particles on visual inspection.