Calcium Dobesilate Monohydrate BP
Ph. Eur.
C12H10CaO10S2,H2O --- 436.4 --- 20123-80-2
DEFINITION
Calcium di(2,5-dihydroxybenzenesulfonate) monohydrate.
Content: 99.0 per cent to 101.0 per cent (anhydrous substance).
CHARACTERS
Appearance: White or almost white, hygroscopic powder.
Solubility: Very soluble in water, freely soluble in anhydrous ethanol, very slightly soluble in 2-propanol, practically insoluble in methylene chloride.
IDENTIFICATION
A. Ultraviolet and visible absorption spectrophotometry.
B. Mix 1 mL of ferric chloride solution, 1 mL of a freshly prepared 10 g/L solution of potassium ferricyanide and 0.1 mL of nitric acid R. To this mixture add 5 mL of freshly prepared solution S (see Tests): a blue colour and a precipitate are immediately produced.
C. 2 mL of freshly prepared solution S gives reaction of calcium.
TESTS
Solution S: Dissolve 10.0 g in carbon dioxide-free water and dilute to 100 mL with the same solvent.
Appearance of solution: Solution S, when freshly prepared, is clear and colourless.
pH: 4.5 to 6.0 for solution S.
Related substances: To pass the test of Liquid chromatography
Iron: Maximum 10 ppm, determined on 10 mL of solution S.
Water: 4.0 per cent to 6.0 per cent, determined on 0.500 g.
ASSAY
Dissolve 0.200 g in a mixture of 10 mL of water R and 40 mL of dilute sulfuric acid R. Titrate with0.1 M cerium sulfate, determining the end-point potentiometrically. 1 mL of 0.1 M cerium sulfate is equivalent to 10.45 mg of C12H10CaO10S2.
STORAGE
In an airtight container, protected from light.
IMPURITIES
Specified impurities A: benzene-1,4-diol (hydroquinone).
