Rapid analysis of four Sudan dyes using direct analysis in real time-mass spectrometry

A simple direct analysis in a real time-mass spectrometry (DART-MS) method was developed for the rapid determination of four Sudan dyes (I–IV) in chili powder. Simple liquid extraction by hexane without further clean-up was used for sample preparation. DART parameters were systematically optimized to achieve the best detection performance. A DIP-it sampler was used for automatic sampling. The matrix effect was measured by comparing the limit of detection (LOD) in matrix solution with that in pure organic solution. Eventually, the identification of the Sudan dyes was confirmed by MS/MS results and the LODs for four analytes in matrix solution were ∼0.5 μg mL−1. The method showed good linearity with correlation coefficients (R2) greater than 0.99 for concentrations ranging from 1 to 20 μg mL−1. The whole analytical process could be completed within 15 minutes with good recoveries (88–116%) and satisfactory repeatability (<26%, n = 3).