Two spectrophotometric methods have been described for determining Tartrazine and Ponceau-4R in binary mixtures. These methods permit the simultaneous determination of these food colorants in various commercially available food samples which contain saccharose and citric acid. Ratio spectra first-order derivative UV spectrophotometric method was studied in the wavelength range 300-700 nm and phosphate buffer pH 7.0 medium. The linearity range was found to be 1.00-60.00 mug mL(-1) for Tartrazine and 1.00-52.00 mug mL(-1) for Ponceau-4R dyes by Vierordt's and ratio spectra first-order derivative UV spectrophotometric methods. The values obtained from developed methods and the high-performance liquid chromatographic (HPLC) method given in the literature were compared. It was found that the difference was not statistically important between these methods. It was concluded that developed Vierordt's and ratio spectra first-order derivative UV spectrophotometric methods were accurate, sensitive, precise, reproducible and could be applied easily and directly to the routine analysis of the food samples. (C) 2002 Elsevier Science Ltd. All rights reserved.