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Alginic Acid

Alginic acid.
Alginic acid [9005-32-7].
» Alginic Acid is a hydrophilic colloidal carbohydrate extracted with dilute alkali from various species of brown seaweeds (Phaeophyceae).
Packaging and storage— Preserve in well-closed containers.
Identification—
A: To 5 mL of a 1 in 150 solution in 0.1 N sodium hydroxide add 1 mL of calcium chloride TS: a voluminous, gelatinous precipitate is formed.
B: To 5 mL of a 1 in 150 solution in 0.1 N sodium hydroxide add 1 mL of 4 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.
Microbial limits 61— The total bacterial count does not exceed 200 per g, and the tests for Salmonella species and Escherichia coli are negative.
pH 791: between 1.5 and 3.5, in a 3 in 100 dispersion in water.
Loss on drying 731— Dry it at 105 for 4 hours: it loses not more than 15.0% of its weight.
Total ash 561— Proceed as directed for Total Ash under Articles of Botanical Origin—Methods of Analysis 561, carefully igniting about 4 g of Alginic Acid, 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 (20 to 35 minutes): not more than 4.0% of ash is found.
Lead— Add 1.0 g to 20 mL of nitric acid in a 250-mL conical flask, mix, and heat carefully until the Alginic Acid is dissolved. Continue 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%) when tested according to the test for Lead 251, 15 mL of ammonium citrate solution, 3 mL of potassium cyanide solution, and 500 µL of hydroxylamine hydrochloride solution being used. After the first dithizone extraction, 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: 0.004%, a platinum crucible being used for the ignition and nitric acid being used in place of sulfuric acid to wet the test specimen.
Acid value 401— Suspend about 1 g of Alginic Acid, accurately weighed, in a mixture of 50 mL of water and 30.0 mL of calcium acetate solution (11 in 250). Shake thoroughly, allow the mixture to stand for 1 hour, add phenolphthalein TS, and then titrate the liberated acetic acid with 0.1 N sodium hydroxide VS. Perform a blank determination, and calculate the acid value taken by the formula:
5.611(A B) / W,
in which 5.611 is one-tenth the molecular weight of potassium hydroxide; A and B are the volumes, in mL, of 0.100 N sodium hydroxide consumed in the titrations of the test preparation and blank, respectively; and W is the weight, in g, of Alginic Acid taken. The acid value of Alginic Acid, calculated on the dried basis, is not less than 230.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Auxiliary Information— Staff Liaison : Hong Wang, Ph.D. , Senior Scientific Associate
Expert Committee : (EM205) Excipient Monographs 2
USP29–NF24 Page 3269
Phone Number : 1-301-816-8351