Simultaneous determination of Indigotin and Ponceau-4R in food samples by using Vierordtʹs method, ratio spectra first order derivative and derivative UV spectrophotometry

Three sensitive and accurate methods for determination of Indigotin and Ponceau-4R in mixtures by Vierordtʹs method, ratio spectra first order derivative and first order derivative UV spectrophotometry are described. No separation step was required for these novel methods. Ratio spectra first order derivative and first derivative UV spectrophotometric methods were studied in the wavelength range of 300–700 nm and phosphate buffer pH 7.0 medium. The linearity ranges were found as 1.00–50.00 μg ml−1 for Indigotin and 1.00–52.00 μg ml−1 for Ponceau-4R dyes at developed UV spectrophotometric methods. In order to determine both dyes these procedures were applied to the commercially available food samples containing saccharose and citric acid such as powdered drinks, sweets and jellies. Developed spectrophotometric methods were found accurate, precise, reproducible, directly and easily applicable for the analysis of Indigotin and Ponceau-4R in food samples. ta obtained from these spectrophotometric methods to determine Indigotin and Ponceau-4R dyes in food were compared with data from HPLC methods which have been previously reported. No statistically significant difference was found between these methods.