Alginic acid or Algin or Alginate

Alginic acid, also called algin, is a polysaccharide distributed widely in the cell walls of brown algae that is hydrophilic and forms a viscous gum when hydrated. Available in different types of salt, alginic acid has been used in a variety of uses in food, cosmetics and pharmaceutical products. Alginic acid is an FDA-approved food ingredient in soup and soup mixes as an emulsifier, thickener, and stabilizer. It is also available in oral dietary supplements and is found in antacids.

Properties and General Specifications of Alginic acid or algin or alginate:
Appearance: White to yellow, fibrous powder.
Relative Density: 1.6
Appearance of solution: Colorless to Faint Yellow, clear to faintly hazy.
pH of 3% dispersion in water: 1.5 - 3.5
Loss on drying: 15% maximum at 105C for 4 hours.
Arsenic: 3 mg/kg maximum.
Lead: 5 mg/kg maximum.
Mercury: 1 mg/kg maximum.
Cadmium: 1 mg/kg maximum.
Coliforms: Negative by test.
Salmonella: Negative by test.
Boiling point: 716C to 718C literature.

Specifications of Alginic acid USP NF Grade:
[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: 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: The total bacterial count does not exceed 200 per g, and the tests for
Salmonella species and Escherichia coli are negative.
pH: between 1.5 and 3.5, in a 3 in 100 dispersion in water.
Loss on drying: Dry it at 105 for 4 hours: it loses not more than 15.0% of its weight.
Total ash: Proceed as directed for Total Ash under Articles of Botanical
Origin: 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.
Arsenic: 3 ppm.
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 microg of lead (corresponding to not more than 0.001%) when tested according to the test for Lead, 15 mL of ammonium citrate solution, 3 mL of potassium cyanide solution, and 500 microL 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: 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: 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 and then titrate the liberated acetic acid with 0.1 N sodium hydroxide. 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.

Specifications of Alginic Acid BP Ph Eur Grade:

Action and use: Treatment of gastro-oesophageal reflux disease; excipient; thickening agent.

DEFINITION
Mixture of polyuronic acids [(C6H8O6)n] composed of residues of d-mannuronic and l-guluronic acids, obtained mainly from algae belonging to the Phaeophyceae. A small proportion of the carboxyl groups may be neutralised.
Content: 19.0 per cent to 25.0 per cent of carboxyl groups (-CO2H) (dried substance). CHARACTERS
Appearance: White or pale yellowish-brown, crystalline or amorphous powder.
Solubility: Very slightly soluble or practically insoluble in ethanol (96 per cent), practically insoluble in organic solvents. It swells in water but does not dissolve; it dissolves in solutions of alkali hydroxides.

For Original Monographs of IP Indian Pharmacopoeia BP British Pharmacopoeia USP US Pharmacopoeia FCC Food Grade product, please check with the respective web-pages or books.