Lactose

C12H22O11,H2O 360.3

Action and use Pharmaceutical aid.

DEFINITION

Lactose monohydrate is the monohydrate of O -D-galactopyranosyl-(1,4)-á-D-glucopyranose. It

may be modified as to its physical characteristics and may contain varying proportions of amorphous lactose.

CHARACTERS

A white or almost white, crystalline powder, freely but slowly soluble in water, practically insoluble in alcohol.

IDENTIFICATION

First identification: A, D.

Second identification: B, C, D.

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

obtained with lactose CRS.

B. Examine by thin-layer chromatography (2.2.27), using silica gel G R 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 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.

Reference solution (b). Dissolve 10 mg each of fructose CRS, glucose CRS, lactose CRS and sucrose 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 separately to the plate 2 μl of each solution and thoroughly dry the starting points. Develop

over a path of 15 cm using a mixture of 10 volumes of water R, 15 volumes of methanol R, 25

volumes of anhydrous acetic acid R and 50 volumes of ethylene chloride R, measured accurately since a slight excess of water produces cloudiness. Dry the plate in a current of warm air. Repeat the

development immediately, after renewing the mobile phase. Dry the plate in a current of warm air

and spray evenly 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 at 130°C 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 four clearly separated spots.

C. Dissolve 0.25 g in 5 ml of water R. Add 5 ml of ammonia R and heat in a water-bath at 80°C for

10 min. A red colour develops.

D. It complies with the test for water (see tests).

TESTS

Appearance of solution Dissolve 1.0 g in water R, heating to 50°C, dilute to 10 ml with the same

solvent and allow to cool. The solution is clear (2.2.1) and not more intensely coloured than

reference solution BY7 (Method II, 2.2.2).

Acidity or alkalinity Dissolve 6.0 g by boiling in 25 ml of carbon dioxide-free water R, cool and add 0.3 ml of phenolphthalein solution R. The solution is colourless. Not more than 0.4 ml of 0.1M sodium hydroxide is required to change the colour of the indicator to pink.

Specific optical rotation (2.2.7). Dissolve 10.0 g in 80 ml of water R, heating to 50°C. Allow to

cool 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 +54.4° to +55.9°, calculated with reference to the anhydrous substance.

Absorbance (2.2.25). Dissolve 1.0 g in boiling water R and dilute to 10.0 ml with the same solvent

(solution A). The absorbance of the solution measured at 400 nm is not greater than 0.04. Dilute

1.0 ml of solution A to 10.0 ml with water R. Examine the solution from 210 nm to 300 nm. At

wavelengths from 210 nm to 220 nm, the absorbance is not greater than 0.25. At wavelengths from

270 nm to 300 nm, the absorbance is not greater than 0.07.

Heavy metals (2.4.8). Dissolve 4.0 g in water R with warming, add 1 ml of 0.1M hydrochloric acid

and dilute to 20 ml with water R. 12 ml of the solution complies with limit test A for heavy metals

(5 ppm). Prepare the standard using lead standard solution (1 ppm Pb) R.

Water (2.5.12). 4.5 per cent to 5.5 per cent, determined on 0.50 g by the semi-micro determination

of water, using a mixture of 1 volume of formamide R and 2 volumes of methanol R as the solvent.

Sulphated ash Not more than 0.1 per cent. To 1.0 g add 1 ml of sulphuric acid R, evaporate to

dryness on a water-bath and ignite to constant mass.

Microbial contamination Total viable aerobic count (2.6.12) not more than 102 micro-organisms

per gram, determined by plate-count. It complies with the test for Escherichia coli (2.6.13).

STORAGE

Store in an airtight container.

Дата добавления: 2014-12-26