Simultaneous determination of banned acid orange dyes and basic orange dyes in foodstuffs by liquid chromatography-tandem electrospray ionization mass spectrometry via negative/positive ion switching mode.

Simultaneous detection of two classes of dyes possessing different chemical properties is difficult. In this study, through negative/positive ion switching mode, simultaneous determination of four typical acid orange dyes and three typical basic orange dyes was achieved by a single high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method, and the analytical efficiency of multiresidues identification was greatly improved. To enhance detection sensitivity, the sample pretreatment conditions and HPLC-MS/MS determining conditions were carefully optimized. Under optimal conditions, good linearity was obtained over the range of 5-500 μg L(-1) with a correlation coefficient (R(2)) >0.9998. Limits of detection (LODs) and limits of quantification (LOQs) of the seven dyes were 0.5-3.0 and 2.0-6.0 μg kg(-1), respectively. The recoveries of the seven dyes in soybean products and marinated eggs were 74-126% with relative standard deviations (RSDs) of 2.22-25.4%, suggesting the developed method is promising for the accurate quantification of the seven dyes at trace levels in foods.