Accurate mass measurements for the confirmation of Sudan azo-dyes in hot chilli products by capillary liquid chromatography–electrospray tandem quadrupole orthogonal-acceleration time of flight mass spectrometry

The potential of capillary liquid chromatography (microLC)–quadrupole/time-of-flight mass spectrometry (Q-TOF MS) for the confirmation of Sudan I, II, III and IV azo-dyes as contaminants in hot-chilli food products was demonstrated. Using the microLC–electrospray ionization (ESI)–Q-TOF MS technique, accurate mass measurements of Sudan dyes were performed both on standard solutions and on matrices. Precision of exact mass measurements was calculated taking into account the ion statistics according to the number of ion sampled in the measurement. Accurate mass measurements by MS/MS experiments were performed to elucidate azo-dye fragmentation patterns. Selectivity of the microLC–Q-TOF MS method was assessed by evaluating matrix suppression effects by pre-column injection of blank hot chilli tomato sauce matrices. The results were compared with those obtained on a LC–triple quadrupole–MS system. Confirmation of Sudan I present in hot chilli tomato sauce samples was obtained by accurate mass measurements. In real samples trueness of exact mass measurements was estimated to be 1.6 and 4.4 ppm when calculated for hot chilli tomato sauce and hot chilli tomato with cheese sauce samples, respectively; precision was calculated around 9.5 ppm.