RESOLUTION OF TERNARY MIXTURES OF TARTRAZINE, SUNSET-YELLOW AND PONCEAU-4R BY DERIVATIVE SPECTROPHOTOMETRIC RATIO SPECTRUM-ZERO CROSSING METHOD IN COMMERCIAL FOODS

A very simple spectrophotometric method is described for resolving ter nary mixtures of the food colorants Tartrazine, Sunset Yellow and Ponc eau 4R by using the first derivative of the ratio spectra with measure ments at zero-crossing wavelengths. Calibration graphs are linear up t o 20 mg 1(-1) of Tartrazine (E-102), 40 mg 1(-1) of Sunset Yellow (E-1 10) and 32 mg 1(-1) of Ponceau 4R (E-124). Standard deviations of 0.9, 0.8 and 2.4% were obtained for nine standards of 8 mg 1(-1) of Tartra zine, 8 mg 1(-1) of Sunset Yellow and 8 mg 1(-1) of Ponceau 4R, respec tively. This method was satisfactorily used for determining synthetic mixtures of these colorants in different ratios (from 1:1:1 to 1:5:5 o r even higher) with recoveries in 94-105% range and it was successfull y applied over three commercial products containing the three dyes and it did not require any separation step. The results were compared wit h those obtained by HPLC and very similar values were found by both me thods. (C) 1998 Elsevier Science B.V. All rights reserved.