Rapid and sensitive determination of Sudandyes in hot chilli products by solid-phase extraction directly combined with time-of-flight mass spectrometry

Abstract

A novel method based on combination of a solid-phase extraction (SPE) with humic acid-bonded silica (HAS) as sorbent with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF MS) was developed for rapid and sensitive determination of four Sudan dyes in hot chilli products. A SPE procedure was optimized for the improvement of extraction efficiency and the removal of the matrix interferences such as the pigments and lipophilic compounds from hot chilli products. Under the optimum conditions, the desorbed analytes from the SPE sorbent allowed direct analysis by ESI-QTOF MS without time-consuming chromatographic separation. In the positive ion mode and MS/MS mode, linearities for concentration ranges of two orders of magnitude were obtained with the correlation coefficients (R²) greater than 0.9990; the limit of detection (LOD) and limit of quantification (LOQ) for four Sudan dyes were in the ranges of 1.1–4.3 and 3.8–14.3 ng g⁻¹ depending on matrices, respectively. The recoveries of four Sudan dyes in two matrices ranged from 85.6 to 119.7%, with relative standard deviations (n = 4, 3) less than 11.3% and 11.6%. The developed method was successfully applied for the determination of Sudan dyes in six hot chilli products and the positive samples were confirmed with a high number of identification points (IPs) according to IPs system defined by Commission Decision 2002/657/EC.