Sodium Alginate

Alginic acid,sodium salt.
Sodium alginate [9005-38-3].
»Sodium Alginate is the purified carbohydrate product extracted from brown seaweeds by the use of dilute alkali.It consists chiefly of the sodium salt of Alginic Acid,a polyuronic acid composed of b-D-mannuronic acid residues linked so that the carboxyl group of each unit is free while the aldehyde group is shielded by a glycosidic linkage.It contains not less than 90.8percent and not more than 106.0percent of sodium alginate of average equivalent weight 222.00,calculated on the dried basis.
Packaging and storage— Preserve in tight containers.
Identification—
A: To 5mLof a solution (1in 100)add 1mLof calcium chloride TS:a voluminous,gelatinous precipitate is formed immediately.
B: To 10mLof a solution (1in 100)add 1mLof 4Nsulfuric acid:a heavy,gelatinous precipitate is formed.
Microbial limits á61ñ— The total bacterial count does not exceed 200cfu per g,and the tests for Salmonellaspecies and Escherichia coliare negative.
Loss on drying á731ñ— Dry it at 105for 4hours:it loses not more than 15.0%of its weight.
Total ash á561ñ— Proceed as directed for Total Ashunder Methods of Analysis,carefully igniting about 3g,accurately weighed,in a tared platinum dish,until the residue is thoroughly carbonized (about 5minutes),and then igniting in a muffle furnace at a temperature of 800±25until the carbon is completely burned off (approximately 75minutes):between 18.0%and 27.0%of ash is found,calculated on the dried basis.
Lead á251ñ— Add 1.0g to 20mLof nitric acid in a 250-mLconical flask,mix,and heat carefully until the Sodium Alginate is dissolved.Continue the heating until the volume is reduced to about 7mL.Cool rapidly to room temperature,transfer to a 100-mLvolumetric flask,and dilute with water to volume.A50.0-mLportion of this solution contains not more than 5µg of lead (corresponding to not more than 0.001%of Pb),15mLof ammonium citrate solution,3mLof potassium cyanide solution,and 0.5mLof hydroxylamine hydrochloride solution being used for the test.After the first dithizone extractions,wash the combined chloroform layers with 5mLof water,discarding the water layer and continuing in the usual manner by extracting with 20mLof 0.2Nnitric acid.
Heavy metals,Method IIá231ñ— Conduct the ignition in a platinum crucible,and use nitric acid in place of sulfuric acid to wet the test specimen:the limit is 0.004%.
Assay— Proceed as directed for Procedureunder Alginates Assay á311ñ,using about 250mg of Sodium Alginate,accurately weighed.Each mLof 0.2500Nsodium hydroxide consumed is equivalent to 27.75mg of sodium alginate.
Auxiliary Information— Staff Liaison:Ravi Ravichandran,Ph.D.,Senior Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3074
Phone Number:1-301-816-8330