Alginic acid, potassium salt.
Potassium alginate [9005-36-1].
» Potassium Alginate is the purified carbohydrate product extracted from various species of brown seaweeds by the use of dilute alkali. It consists chiefly of the potassium salt of Alginic Acid, a linear glycuronoglycan consisting of -1,4 linked d-mannuronic acid and l-guluronic acid units in the pyranose ring form. It yields not less than 16.5 percent and not more than 19.5 percent of carbon dioxide (CO2), equivalent to not less than 89.2 percent and not more than 105.5 percent of potassium alginate, calculated on the dried basis.
Packaging and storage Preserve in well-closed containers. No storage requirements specified.
A: To 5 mL of a 1 in 100 solution in 0.1 N sodium hydroxide, add 1 mL of calcium chloride TS: a voluminous, gelatinous precipitate is formed.
B: To 10 mL of a 1 in 100 solution in 0.1 N sodium hydroxide, add 1 mL of 2 N sulfuric acid: a heavy, gelatinous precipitate is formed.
C: To about 5 mg in a test tube add 5 mL of water, 1 mL of a freshly prepared 1 in 100 solution of 1,3-naphthalenediol in alcohol, and 5 mL of hydrochloric acid. Heat the mixture to boiling, boil gently for 3 minutes, then cool to about 15. Transfer the contents of the test tube to a 30-mL separator with the aid of 5 mL of water, and extract with 15 mL of isopropyl ether: the isopropyl ether extract exhibits a deeper purplish hue than that from a blank, similarly prepared.
D: Ignite completely 0.2 g at as low a temperature as possible: a solution of the residue meets the requirements of the tests for Potassium 191.
Microbial enumeration tests 61 and Tests for specified microorganisms 62 The total aerobic microbial count does not exceed 1000 cfu per g, and the total combined molds and yeasts count does not exceed 100 cfu per g.
Loss on drying 731 Dry it at 105 for 4 hours: it loses not more than 15% of its weight.
Total ash 561 Proceed as directed for Total Ash under Methods of Analysis, carefully igniting about 3 g, accurately weighed, in a tared platinum dish, until the residue is thoroughly carbonized (about 5 minutes), and then igniting in a muffle furnace at a temperature of 800 ± 25 until the carbon is completely burned off (approximately 75 minutes): between 24.0% and 32.0% of ash is found, calculated on the as-is basis.
Arsenic, Method II 211: 1.5 µg per g.
Lead 251 Add 1.0 g to 20 mL of nitric acid in a 250-mL conical flask, mix, and heat carefully until the Potassium Alginate is dissolved. Continue the heating until the volume is reduced to about 7 mL. Cool rapidly to room temperature, transfer to a 100-mL volumetric flask, and dilute with water to volume. A 50.0-mL portion of this solution contains not more than 5 µg of lead (corresponding to not more than 0.001% of lead), 15 mL of ammonium citrate solution, 3 mL of potassium cyanide solution, and 0.5 mL of hydroxylamine hydrochloride solution being used for the test. After the first dithizone extractions, wash the combined chloroform layers with 5 mL of water, discarding the water layer and continuing in the usual manner by extracting with 20 mL of 0.2 N nitric acid.
Heavy metals, Method II 231 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 under Alginate Assay 311.
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USP32NF27 Page 1321Pharmacopeial Forum: Volume No. 31(5) Page 1426