Complex formations between some food dyes and the transition metal ions of the first row

Abstract

In this thesis, the appropriate conditions for the food dyes; Azorubine, Sunset Yellow FCF, Orange G, Orange RN, Tartrazine and Green S to react with some transition metal ions of the first row such as Ti (IV), Cr (III), Mn (II), Co (II), Fe (II), Fe (III), Ni (II), Cu (II) and Zn (II) ions were investigated by spectrophotometric technique. The food dyes used are of high purity; using spectrophotometric and chromatographic tests, their percentage of purities are over 85. The buffer systems used were phosphate buffer, acetate buffer, McIlvaine buffer, acetic acid, phosphoric acid and diethylamine. It was found that every metal ion could not react with every dye studied, except Cu (II) ion. The Cu (II) complexes were found to have the molar ratios of 1:2 for Cu (II)-Azorubine in acetate buffer pH 6.10 and in phosphate buffer pH 5.85 or 7.00, 1:1 for Cu (II)-Azorubine in acetate buffer pH 5.10, 1:1 for Cu (II)-Sunset Yellow FCF in acetate buffer pH 5.10 or 4.00, 2:1 for Cu (II)-Sunset Yellow FCF in acetate buffer pH 6.10, 1:1 for Cu (II)-Orange G or Cu (II)-Orange RN in acetate buffer pH 6.10, 5.10 or 4.00. The stability constants of the complexes were determined. It was found that the stability constants of these complexes were in the order of seventh for 1:1 Cu (II)-Azorubine, Cu (II)-Sunset Yellow FCF, Cu (II)-Orange G or Cu (II)-Orange RN complex and in the order of tenth for 1:2 Cu (II)-Azorubine or 2:1 Cu (II)-Sunset Yellow FCF complex.