METHOD OF DETECTING RED NATURAL CARMINE DYE IN PRESENCE OF RED SYNTHETIC DYE E122 IN AQUEOUS SOLUTION Russian patent published in 2010 - IPC G01N21/25 C09B61/00 

FIELD: chemistry.

SUBSTANCE: invention describes a method of detecting red natural carmine dye in the presence of synthetic dye E122 in an aqueous solution, involving addition of crystalline sodium chloride to the aqueous solution of the mixture of carmine and synthetic dye E122 until attaining salt concentration of 35 wt % in the solution, ethyl acetate is added in volume ratio of solvent to aqueous salt solution equal to 1:10 and extracted after 10 minutes on vibromixer. Further, the organic phase which contains synthetic dye E122 is extracted. Optical density A of the equilibrium aqueous salt solution is measured and content of carmine is calculated using the formula: C = A / ℓ· k, where k is light absorption coefficient, dm³/(mol·cm); ℓ is thickness of the light absorbing layer (ℓ = 1 cm); C is concentration of carmine dye, mol/dm³.

EFFECT: method enables selective extraction of red synthetic dye E122 from a saturated sodium chloride solution through extraction with ethyl acetate (R=96%) in 10 minutes, red natural carmine dye is virtually not extracted in these conditions (R=0%).