Simultaneous determination of eight illegal dyes in chili products by liquid chromatography–tandem mass spectrometry

A sensitive and accurate method based on the use of liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed for the simultaneous determination of eight illegal synthetic dyes (Sudan (I–IV), Para Red, Rhodamine B, Chrysoidin and Auramine O) in chili products. A simple sample treatment procedure entailing the use of an extraction step with acetonitrile/H2O (9/1) without further cleanup was developed. HPLC was performed on a C18 column using a multistep gradient elution with 5 mM ammonium acetate (pH 3.0 with formic acid) and methanol as the mobile phase. Mass spectral acquisition was done in multiple reaction monitoring (MRM) mode using positive electrospray ionization (ESI). Linear calibrations were obtained with correlation coefficients R2 > 0.99. Limit of detection (LOD) and limit of quantification (LOQ) for the studied dyes were in the ranges of 0.05–0.6 μg kg−1 and 0.3–3.0 μg kg−1 depending on matrices, respectively. The recoveries of the eight synthetic dyes in five matrices ranged from 70.5% to 119.2%. The intra- and inter-day precisions (RSDs) were between 2.3–15.8% and 5.7–15.6%, respectively. The applicability of the method to the determination of eight banned dyes in chili products was demonstrated.