Ph Eur
Action and use: Excipient.
DEFINITION
Sodium alginate consists mainly of the sodium salt of alginic acid, which is a mixture of polyuronic acids [C6H8O6)n] composed of residues of D-mannuronic acid and L-guluronic acid. Sodium alginate is obtained mainly from algae belonging to the Phaeophyceae.
CHARACTERS
Appearance: White or pale yellowish-brown powder.
Solubility: Slowly soluble in water forming a viscous, colloidal solution, practically insoluble in ethanol (96 per cent).
IDENTIFICATION
A. Dissolve 0.2 g with shaking in 20 ml of water. To 5 ml of this solution add 1 ml of calcium chloride solution. A voluminous gelatinous mass is formed.
B. To 10 ml of the solution prepared in identification test A add 1 ml of dilute sulphuric acid. A gelatinous mass is formed.
C. To 5 mg add 5 ml of water, 1 ml of a freshly prepared 10 g/l solution of 1,3-dihydroxynaphthalene in ethanol (96 per cent) and 5 ml of hydrochloric acid. Boil for 3 min, cool, add 5 ml of water, and shake with 15 ml of di-isopropyl ether. Carry out a blank test. The upper layer obtained with the substance to be examined exhibits a deeper bluish-red colour than that obtained with the blank.
D. It complies with the test for sulphated ash. The residue obtained, dissolved in 2 ml of water, gives reaction (a) of sodium.
TESTS
Solution S: Dissolve 0.10 g in water, with constant stirring, dilute to 30 ml with the same solvent and allow to stand for 1 h.
Appearance of solution: The solution is not more opalescent than reference and not more intensely coloured than intensity 6 of the range of reference solutions of the most appropriate colour.
Dilute 1 ml of solution S to 10 ml with water R.
Chlorides: Maximum 1.0 per cent.
Calcium: Maximum 1.50 per cent.
Heavy metals: Maximum 20 ppm.
Loss on drying: Maximum 15.0 per cent, determined on 0.1000 g by drying in an oven at 105C for 4 h.
Sulphated ash: 30.0 per cent to 36.0 per cent (dried substance), determined on 0.1000 g.
Microbial contamination: Total viable aerobic count not more than 103 micro-organisms per gram, determined by plate-count. It complies with the tests for Escherichia coli and Salmonella.
Alginic acid, sodium salt --- 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 -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 90.8 percent and not more than 106.0 percent of sodium alginate of average equivalent weight 222.00, calculated on the dried basis.
Identification:
A: To 5 mL of a solution (1 in 100) add 1 mL of calcium chloride: a voluminous, gelatinous precipitate is formed immediately.
B: To 10 mL of a solution (1 in 100) add 1 mL of 4 N sulfuric acid: a heavy, gelatinous precipitate is formed.
Microbial limits: The total bacterial count does not exceed 200 cfu per g, and the tests for Salmonella species and Escherichia coli are negative.
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 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 18.0% and 27.0% of ash is found, calculated on the dried basis.
Arsenic: 1.5 ppm.
Lead: Add 1.0 g to 20 mL of nitric acid in a 250-mL conical flask, mix, and heat carefully until the Sodium 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 microgm of lead (corresponding to not more than 0.001% of Pb), 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: 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%.
Algin
(C6H7O6Na)n Equiv wt, calculated 198.11
Equiv wt, actual (avg.) 222.00
INS: 401 CAS: [9005-38-3]
DESCRIPTION
Sodium Alginate occurs as a white to yellow-brown, fibrous or granular powder. It is the sodium salt of alginic acid. It dissolves in water to form a viscous, colloidal solution. It is insoluble in alcohol and in hydroalcoholic solutions in which the alcohol content is greater than about 30% by weight. It is insoluble in chloroform, in ether, and in acids having a pH lower than about 3.
Function: Stabilizer; thickener; emulsifier; gelling agent.
REQUIREMENTS
Identification: -
A. Add 1 mL of calcium chloride to 5 mL of a 1:100 aqueous solution. A voluminous, gelatinous precipitate forms.
B. Add 1 mL of 2 N sulfuric acid to 10 mL of a 1:100 aqueous solution. A heavy, gelatinous precipitate forms.
C. Place about 5 mg of sample into a test tube, add 5 mL of water, 1 mL of a freshly prepared 1:100 naphtholresorcinol:ethanol solution, and 5 mL of hydrochloric acid. Heat the mixture to boiling, boil gently for about 3 min, and then cool to about 15C. 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. Perform a blank determination and make any necessary correction. The isopropyl ether extract from the sample exhibits a deeper purple hue than that from the blank.
Assay: A sample yields not less than 18.0% and not more than 21.0% of carbon dioxide (CO2), corresponding to between 90.8% and 106.0% of Sodium Alginate (equiv wt 222.00).
Arsenic: Not more than 3 mg/kg.
Lead: Not more than 5 mg/kg.
Loss on Drying: Not more than 15.0%.
