Relative molecular mass. 372.2
Chemical name. Disodium dihydrogen (ethylenedinitrilo)tetraacetate dihydrate; N,N'-1,2-ethanediylbis[N-(carboxymethyl)glycine] disodium salt, dihydrate; CAS Reg. No. 6381-92-6.
Other name. Edetate disodium.
Description. A white, crystalline powder; odourless.
Solubility. Soluble in water; slightly soluble in ethanol (~750 g/l) TS; practically insoluble in ether R.
Category. Stabilizer; chelating agent.
Storage. Disodium edetate should be kept in a well-closed container.
Additional information. Solutions of disodium edetate should not come into contact with metal.
Disodium edetate contains not less than 98.5% and not more than the equivalent of 101.0% of C10H14N2Na2O8,2H2O.
• Either test A alone or tests B, C, and D may be applied.
A. Carry out the examination as described under 1.7 Spectrophotometry in the infrared region. The infrared absorption spectrum is concordant with the spectrum obtained from disodium edetate R or with the reference spectrum of disodium edetate.
B. To 3 drops of ferric chloride (25 g/l) TS add 3 drops of ammonium thiocyanate (75 g/l) TS; to the deep red solution produced add 0.05 g of Disodium edetate; the colour is discharged, leaving a yellowish solution. (Keep this solution for test D.)
C. Dissolve 2 g in 25 ml of water, add 2 ml of lead nitrate (100 g/l) TS, shake, and add 6 ml of potassium iodide (80 g/l) TS; no yellow precipitate is observed.
D. To the solution from test B, add ammonia (~100 g/l) TS, drop by drop, until an alkaline reaction is obtained with pH-indicator paper R. Add 5 ml of ammonium oxalate (25 g/l) TS; no precipitate is produced (distinction from sodium calcium edetate).
Heavy metals. Use 1.0 g for the preparation of the test solution as described under 2.2.3 Limit test for heavy metals, Procedure 3; determine the heavy metals content according to Method A; not more than 20 μg/g.
pH value. pH of a 0.05 g/ml solution, 4.0-5.5.
Assay. Dissolve 0.5 g, accurately weighed, in sufficient water to produce 300 ml. Add 2 g of methenamine R and 2 ml of hydrochloric acid (~70 g/l) TS. Titrate with lead nitrate (0.1 mol/l) VS to which 50 mg of xylenol orange indicator mixture R has been added.
Each ml of lead nitrate (0.1 mol/l) VS is equivalent to 37.22 mg of C10H14N2Na2O8,2H2O.