Low-level detections of Sudan I, II, III and IV in spices and Chili-containing foodstuffs using UPLC-ESI-MS/MS.

Sudan dyes are red, synthetic azo dyes that are not allowed in foodstuffs in the European Union (Council Directive 94/36/EC). However, subppm levels of Sudan dye in spices are regularly reported, and it is assumed that these appearances are due to cross-contamination. In this paper, we present a newly developed fast and sensitive method for the quantification of Sudan I, II, III, and IV, using liquid-liquid extraction and UPLC-MS/MS analysis, and giving quantification limits ranging from 2.5 to 200 μg/kg. The method was applied to 21 samples, and 17 of them contained Sudan dye at low concentrations (3.3-8 709 μg/kg). Interestingly, it was observed that the distribution of Sudan dye in the sample is not homogeneous, which may lead to false negatives or to overestimations of the concentration, and that the pretreatment (blending or not) of the sample seriously influences the final result of the analysis.