Selenium Disulphide
(Selenium Disulfide, Ph. Eur. monograph 1147)
SeS2 143.1 7488-56-4
Action and use
Used in treatment of dandruff and seborrhoeic dermatitis of the scalp.
Preparation
Selenium Sulfide Scalp Application
DEFINITION
Content
52.0 per cent to 55.5 per cent of Se.
CHARACTERS
Appearance
Bright orange or reddish-brown powder.
Solubility
Practically insoluble in water.
IDENTIFICATION
A. Gently boil about 50 mg with 5 mL of nitric acid R for 30 min. Dilute to 50 mL with water R and filter. To 5 mL of the filtrate add 10 mL of water R and 5 g of urea R. Heat to boiling, cool and add 1.5 mL of potassium iodide solution R. A yellow or orange colour is produced which darkens rapidly on standing. This solution is used in identification test B.
B. Allow the coloured solution obtained under identification A to stand for 10 min and filter through kieselguhr for chromatography R. 5 mL of the filtrate gives reaction (a) of sulfates (2.3.1).
TESTS
Soluble selenium compounds
Maximum 5 ppm, calculated as Se.
To 10 g add 100 mL of water R, mix well, allow to stand for 1 h with frequent shaking and filter. To 10 mL of the filtrate add 2 mL of a 115 g/L solution of anhydrous formic acid R, dilute to 50 mL with water R and adjust to pH 2.0-3.0 with an 115 g/L solution of anhydrous formic acid R. Add 2 mL of a 5 g/L solution of 3,3′-diaminobenzidine tetrahydrochloride R.
Allow to stand for 45 min and then adjust to pH 6.0-7.0 with dilute ammonia R1. Shake the solution for 1 min with 10 mL of toluene R and allow the phases to separate. The absorbance (2.2.25) of the upper layer measured at 420 nm is not greater than that of a standard prepared at the same time and in the same manner beginning at the words “add 2 mL of an 115 g/L solution of anhydrous formic acid R” and using 5 mL of selenium standard solution (1 ppm Se) R instead of 10 mL of the filtrate.
ASSAY
To 0.100 g add 25 mL of fuming nitric acid R and heat on a water-bath for 1 h; a small insoluble residue may remain. Cool and dilute to 100.0 mL with water R. To 25.0 mL of this solution add 50 mL of water R and 5 g of urea R and heat to boiling. Cool, add 7 mL of potassium iodide solution R and 3 mL of starch solution R. Titrate immediately with 0.1 M sodium thiosulfate. Carry out a blank titration.
1 mL of 0.1 M sodium thiosulfate is equivalent to 1.974 mg of Se.
