1HNMR based approach for the identification and quantification of Sudan dyes, a potential adulterant of saffron

This study introduces an NMR-basd approach to identify and determine the adulteration of saffron with Sudan (I-IV) azo-dyes. A complete 1H and 13C resonance assignment for Sudan I-IV, achieved by two-dimensional homonuclear and heteronuclear NMR experiments, is reported herein. Specific different proton signals for the identification of each Sudan dye in adulterated saffron can be utilised for quantitative 1H NMR (qHNMR), a well-established method for quantitative analysis. The quantification of Sudan III, as a paradigm, was performed in varying levels (0.14-7.1 g/Kg) by considering the NMR signal occuring at 8.064 ppm. The high linearity, accuracy and rapidity of investigation enable high resolution 1H NMR spectroscopy to be used for evaluation of saffron adulteration with Sudan dyes, with no need for laborious sample preparation.