Calcium Alginate

PURITY

Loss on drying

Not more than 15% (105°, 4h)

Arsenic

Not more than 3 mg/kg (Method II)

Lead

Not more than 5 mg/kg Prepare a sample solution as directed for organic compounds in the Limit Test, using 5 m g of lead ion (Pb) in the control

Microbiological criteria

Total plate count: Not more than 5,000 colonies per gram.

Initially prepare a 10 -1 dilution by adding a 50 g sample to 450 ml of Butterfield's phosphate buffered dilution water and homogenizing in a high speed blender.

Yeasts and moulds: Not more than 500 colonies per gram

Coliforms: Negative by test

Salmonella: Negative by test

TESTS

IDENTIFICATION TESTS

Precipitate formation with calcium chloride

To a 0.5% solution of the sample in sodium hydroxide TS add one-fifth of its volume of a 2.5% solution of calcium chloride. A voluminous, gelatinous precipitate is formed. This test distinguishes calcium alginate from gum arabic, sodium carboxymethyl cellulose, carrageenan, gelatin, gum ghatti, karaya gum, carob bean gum, methyl cellulose and tragacanth gum.

Precipitate formation with ammonium sulphate

To a 0.5% solution of the sample in sodium hydroxide TS add one-half of its volume of a saturated solution of ammonium sulfate. No precipitate is formed. This test distinguishes calcium alginate from agar, sodium carboxymethyl cellulose, carrageenan, de-esterified pectin, gelatin, carob bean gum, methyl cellulose and starch.

Test for alginate

Dissolve as completely as possible 0.01 g of the sample by shaking with 0.15 ml of 0.1 N sodium hydroxide and add 1 ml of acid ferric sulfate TS. Within 5 min, a cherry-red colour develops that finally becomes deep purple.

METHOD OF ASSAY

Proceed as directed under Carbon Dioxide Determination by Decarboxylation in the General Methods. Each ml of 0.25 N sodium hydroxide consumed is equivalent to 5.5 mg of carbon dioxide (CO 2 ) or 27.38 mg of calcium alginate (equivalent weight 219).