METHOD OF IDENTIFYING NATURAL CARMINE DYE IN PRESENCE OF SULPHONATED AZO DYES Russian patent published in 2011 - IPC G01N31/00 G01N30/90 

FIELD: chemistry.

SUBSTANCE: invention can be used to identifying natural carmine dye in the presence of sulphonated azo dyes E102, E110, E122, E124 and E129 during analytical control of food products and pharmaceutical preparations. The method for identification in aqueous solution is characterised by that a mixture of dyes is separated via chromatography in a thin layer using a Sorbfil plate, for which an aqueous sample containing natural carmine dye and a mixture of sulphonated azo dyes E102, E110, E122, E124 and E129 is prepared. Using a micro-syringe, the sample is deposited on the start line of the plate and dried in air. The mobile phase is then placed at the bottom of the chromatographic chamber, where the mobile phase is a mixture of acetone, isobutyl alcohol and potassium hydroxide solution with concentration of 0.1 mol/dm³ in volume ratio of 0.2:0.5:0.3. The plate on which the dye sample is deposited is put into the chamber is chromatography is carried out for 50 minutes. When the mobile phase reaches the finish line, the plate is removed from the chamber and dried. The dyes are identified based on the colour and offset coefficient R_f, which is calculated using the formula: R_f = X/X_f, where X the shift front of the identified dye; X_f is the shift front of the solvent.

EFFECT: high reliability of identification with shorter duration.

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