Derivative spectrophotometric methods were originally developed for determining Ponceau 4R and Tartrazine in order to resolve their binary mixtures. The method permits the simultaneous determinations of these food colorants in various food samples. Recovery by derivative methods was nearly 100 \%.
SAYAR, Sedat and ÖZDEMİR, Yüksel (1997) "Determination of Ponceau 4R and Tartrazine in Various Food Samples by Derivative Spectrophotometric Methods," Turkish Journal of Chemistry: Vol. 21: No. 3, Article 5. Available at: https://journals.tubitak.gov.tr/chem/vol21/iss3/5