A method is described for isolating from foodstuffs, and then separating Two The by column chromatography, twelve synthetic dyes used in Israel. adsorbents were used: alumina, a t different pH values, and silica gel. eluents used were water, n-butanol and methanol.IN a previous publication1 a paper chromatographic method was described for separating and identifying a group of twelve synthetic water-soluble food dyes in use in Israel. The procedure described can be applied directly to commercial dyes. Dyes to be determined in food must be extracted and then purified before they can be identified, since the impurities associated with food often cause considerable difficulty in identifying the dyes, by either paper chromatography, spectrophotometry or any other means of identification. Wool has been used for extracting coal-tar dyes from f o o d -~t u f f s , ~~~~~ and by suitable modification of this method, basic dyes could be separated from acidic ones.596 Helbergs suggested the use of solutions of different pH values for eluting the adsorbed dyes from the wool. This procedure involved the use of strong acids and heat, conditions liable to alter the chemical structure of the dyes. Other procedures for isolating and separating dyes include solvent extraction at different pH values' and column chr~matography.~ y 9 Kaolin, alumina and silica gel have been used as adsorbents in chromatography.l0y11J2 91391*The ninth edition of the "Official Methods of Analysis" of The Association of Official Agricultural Chemists, describes a method for separating dyes by using a powdered-cellulose column and a series of sodium chloride solutions as e1~ents.l~ This technique, however, was not always found to give the desired separation.16A procedure for extracting dyes from foods and separating them by column chromatography is described in this paper. By using silica gel and alumina adjusted to different pH values, and with water, butanol and methanol as solvents, the dyes tested could be separated. The adsorbents acted as partition, adsorption or ion-exchange columns, depending on the conditions used. The dyes were obtained chemically pure, and could subsequently be identified with ease. METHOD REAGENTS-All reagents used were of analytical-reagent grade. Hydrochloric acid, 2 N and N. Ammonia solution, sp.gr. 0-88, and N. Ammonia water-Dilute I ml of ammonia solution, sp.gr. 0.88, with 99 ml of water. Methanol, redistilled. Methanol, 90 per cent. v / v . Ammoniacal methanol-Dilute 1 ml of ammonia solution, sp.gr. 0.88, with 99 ml of n-B.utanol, dry. n-Butanol-Saturate with 2 N hydrochloric acid by shaking the two reagents together Chloroform, redistilled. Acetone, redistilled. Sodium hydroxide solution, 5 N. Sodium acetate solutions, M, 0-5 M and 0.1. M aqueous. methanol. for a few minutes. -_ _ , Anal. Chim. Acta, 1955, 13, 46. "Offikial Methods of Analysis," Ninth Edition, The Association of Ofi'icial A4gricultural Chemists, "Separation and Identification of Food Colours Permitted by the Colouring Matters in Food
