Allantoin CAS 97-59-6 Assay 98.5-101.0% (Titration) High Purity

ALLANTOIN
Allantoinum
C4H6N4O3  158.1 [97-59-6]
DEFINITION
Allantoin contains not less than 98.5 per cent and not more than the equivalent of 101.0 per cent of (RS)-(2,5-dioxoimidazolidin-4-yl)urea.
CHARACTERS
A white or almost white, crystalline powder, slightly soluble in water, very slightly soluble in ethanol (96 per cent).
It melts at about 225℃, with decomposition.
IDENTIFICATION
First identification: A.
Second identification: B, C, D.
A. Examine by infrared absorption spectrophotometry (2.2.24), comparing with the spectrum obtained with allantoin CRS.
B. Examine the chromatograms obtained in the test for related substances. The principal spot in the chromatogram obtained with test solution (b) is similar in position, colour and size to the principal spot in the chromatogram obtained with reference solution (a).
C. Boil 20 mg with a mixture of 1 mL of dilute sodium hydroxide solution R and 1 mL of water R. Allow to cool. Add 1 mL of dilute hydrochloric acid R. To 0.1 mL of the solution add 0.1 mL of a 100 g/L solution of potassium bromide R, 0.1 mL of a 20 g/L solution of resorcinol R and 3 mL of sulfuric acid R. Heat for 5 min to 10 min on a water-bath. A dark blue colour develops, which becomes red after cooling and pouring into about 10 mL of water R.
D. Heat about 0.5 g. Ammonia vapour is evolved, which turns red litmus paper R blue.
TESTS
Solution S. Dissolve 0.5 g in carbon dioxide-free water R, with heating if necessary, and dilute to 100 mL with the same solvent.
Acidity or alkalinity. To 5 mL of solution S add 5 mL of carbon dioxide-free water R, 0.1 mL of methyl red solution R and 0.2 mL of 0.01 M sodium hydroxide. The solution is yellow. Add 0.4 mL of 0.01 M hydrochloric acid. The solution is red.
Optical rotation (2.2.7). The angle of optical rotation, determined on solution S, is -0.10° to +0.10°.
Reducing substances. Shake 1.0 g with 10 mL of water R for 2 min. Filter. Add 1.5 mL of 0.02 M potassium permanganate.
The solution must remain violet for at least 10 min.
Related substances. Examine by thin-layer chromatography (2.2.27), using a suitable cellulose for chromatography R as the coating substance.
Test solution (a). Dissolve 0.10 g of the substance to be examined in 5.0 mL of water R with heating. Allow to cool. 
Test solution (b). Dilute 1 mL of test solution (a) to 10 mL with a mixture of 1 volume of methanol R and 1 volume of water R.
Reference solution (a). Dissolve 10 mg of allantoin CRS in a mixture of 1 volume of methanol R and 1 volume of water R and dilute to 10 mL with the same mixture of solvents.
Reference solution (b). Dissolve 10 mg of urea R in 10 mL of water R. Dilute 1 mL of this solution to 10 mL with methanol R.
Reference solution (c). Mix 1 mL of reference solution (a) and 1 mL of reference solution (b).
Apply to the plate 10 μL of test solution (a) and 5 μL each of test solution (b), reference solution (a), reference solution (b) and reference solution (c). Develop over a path of 10 cm using a mixture of 15 volumes of glacial acetic acid R, 25 volumes of water R and 60 volumes of butanol R. Allow the plate to dry in air. Spray the plate with a 5 g/L solution of dimethylaminobenzaldehyde R in a mixture of 1 volume of hydrochloric acid R and 3 volumes of methanol R. Dry the plate in a current of hot air. Examine in daylight after 30 min. Any spot in the chromatogram obtained with test solution (a), apart from the principal spot, is not more intense than the spot in the chromatogram obtained with reference solution (b) (0.5 per cent). The test is not valid unless the chromatogram obtained with reference solution (c) shows two clearly separated principal spots.
Loss on drying (2.2.32). Not more than 0.1 per cent, determined on 1.000 g by drying in an oven at 105℃.
Sulfated ash (2.4.14). Not more than 0.1 per cent, determined on 1.0 g.
ASSAY
Dissolve 120.0 mg in 40 mL of water R. Titrate with 0.1 M sodium hydroxide, determining the end-point potentiometrically (2.2.20).
1 mL of 0.1 M sodium hydroxide is equivalent to 15.81 mg of C4H6N4O3.
IMPURITIES
A. glyoxylic acid,
B. carbamide (urea).