Selenium Sulfide
SeS2 143.09

Selenium sulfide (SeS2).
Selenium sulfide (SeS2) [7488-56-4].
»Selenium Sulfide contains not less than 52.0percent and not more than 55.5percent of selenium (Se).
Packaging and storage— Preserve in well-closed containers.
Identification—
A: Filter 20mLof the solution of Selenium Sulfide prepared as directed in the Assay,and to 10mLof the filtrate add 5mLof water and 5g of urea.Heat to boiling,cool,and add 2mLof potassium iodide solution (1in 10):a yellowish orange to orange color is produced,and it darkens rapidly (presence of selenium).
B: Allow the solution obtained in Identificationtest Ato stand for 10minutes,filter,and to the filtrate add 10mLof barium chloride TS:the solution becomes turbid (presence of sulfur).
Residue on ignition á281ñ: not more than 0.2%.
Soluble selenium compounds—
Test solution— Mix 10.0g of Selenium Sulfide with 100.0mLof water in a 250-mLflask,allow to stand for 1hour,with frequent agitation,and filter.To 10.0mLof the filtrate add 2mLof 2.5Mformic acid,dilute with water to 50mL,mix,and adjust,if necessary,to a pHof 2.5±0.5.Add 2mLof freshly prepared 3,3¢-diaminobenzidine hydrochloride solution (1in 200),mix,allow to stand for 45minutes,and adjust with 6Nammonium hydroxide to a pHof 6.5±0.5.Transfer to a separator,add 10.0mLof toluene,shake vigorously for 1minute,allow the layers to separate,and discard the aqueous phase.
Standard solution— Using 10.0mLof a solution of selenious acid containing 0.5µg of selenium per mL,prepare a solution as directed under Test solution,beginning with “add 2mLof 2.5Mformic acid.”
Procedure— Concomitantly determine the absorbances of the toluene layers of the Test solutionand the Standard solutionin 1-cm cells at 420nm,with a suitable spectrophotometer,using a blank consisting of the same quantities of the same reagents treated in the same manner as the Test solution:the absorbance of the Test solutionis not greater than that of the Standard solution(5ppm).
Assay— Place about 100mg of Selenium Sulfide,accurately weighed,in a suitable container,add 25mLof fuming nitric acid,and digest over gentle heat until no further solution occurs.Cool,transfer the solution to a 250-mLvolumetric flask containing 100mLof water,cool again,dilute with water to volume,and mix.Pipet 50mLof the solution into a suitable flask,add 25mLof water and 10g of urea,and heat to boiling.Cool,add 3mLof starch TS,then add 10mLof potassium iodide solution (1in 10),and immediately titrate with 0.05Nsodium thiosulfate VS.Perform a blank determination,and make any necessary correction.Each mLof 0.05Nsodium thiosulfate is equivalent to 987.0µg of Se.
Auxiliary Information— Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(PA6)Pharmaceutical Analysis 6
USP28–NF23Page 1764
Phone Number:1-301-816-8389