Galactose

C6H12O16 180.2

DEFINITION

Galactose is D-galactopyranose.

CHARACTERS

A white, crystalline or finely granulated powder, freely soluble or soluble in water, very slightly

soluble in alcohol.

IDENTIFICATION

First identification: A.

Second identification: B, C.

A. Examine by infrared absorption spectrophotometry (2.2.24), comparing with the spectrum

obtained with galactose CRS. Examine the substances prepared as discs.

B. Examine by thin-layer chromatography (2.2.27), using a suitable silica gel as the coating

substance.

Test solution. Dissolve 10 mg of the substance to be examined in a mixture of 2 volumes of water R

and 3 volumes of methanol R and dilute to 20 ml with the same mixture of solvents.

Reference solution (a). Dissolve 10 mg of galactose CRS in a mixture of 2 volumes of water R and 3 volumes of methanol R and dilute to 20 ml with the same mixture of solvents.

Reference solution (b). Dissolve 10 mg of galactose CRS, 10 mg of glucose CRS and 10 mg of lactose CRS in a mixture of 2 volumes of water R and 3 volumes of methanol R and dilute to 20 ml with the same mixture of solvents.

Apply to the plate 2 μl of each solution and thoroughly dry the starting points. Develop in an

unsaturated tank over a path of 15 cm using a mixture of 15 volumes of water R and 85 volumes of

propanol R. Dry the plate in a current of warm air. Spray uniformly with a solution of 0.5 g of

thymol R in a mixture of 5 ml of sulphuric acid R and 95 ml of alcohol R. Heat in an oven at 130ºC for 10 min. The principal spot in the chromatogram obtained with the test solution is similar in position, colour and size to the principal spot in the chromatogram obtained with reference solution (a). The test is not valid unless the chromatogram obtained with reference solution (b) shows three clearly separated spots.

C. Dissolve 0.1 g in 10 ml of water R. Add 3 ml of cupri-tartaric solution R and heat. An orange to red precipitate is formed.

TESTS

Solution S Dissolve with heating in a water-bath at 50ºC, 10.0 g in carbon dioxide-free water R

prepared from distilled water R and dilute to 50 ml with the same solvent.

Appearance of solution Solution S is clear (2.2.1) and not more intensely coloured than reference

solution B8 (Method II, 2.2.2).

Acidity or alkalinity To 30 ml of solution S add 0.3 ml of phenolphthalein solution R. The solution is colourless. Not more than 1.5 ml of 0.01M sodium hydroxide is required to change the colour of the indicator to pink.

Specific optical rotation (2.2.7). Dissolve 10.00 g in 80 ml of water R and add 0.2 ml of dilute

ammonia R1. Allow to stand for 30 min and dilute to 100.0 ml with water R. The specific optical

rotation is +78.0º to +81.5º, calculated with reference to the anhydrous substance.

Barium Dilute 5 ml of solution S to 10 ml with distilled water R. Add 1 ml of dilute sulphuric acid R. When examined immediately and after 1 h, any opalescence in the solution is not more intense than that in a mixture of 5 ml of solution S and 6 ml of distilled water R.

Lead (2.4.10). It complies with the limit test for lead in sugars (0.5 ppm).

Water (2.5.12). Not more than 1.0 per cent, determined on 1.00 g by the semi-micro determination

of water.

Sulphated ash To 5 ml of solution S add 2 ml of sulphuric acid R, evaporate to dryness on a waterbath and ignite to constant mass. The residue weighs not more than 1 mg (0.1 per cent).

Microbial contamination Total viable aerobic count (2.6.12) not more than 102 microorganisms

per gram.

STORAGE

Store in a well-closed container.

Дата добавления: 2014-12-26