[Determination of four Sudan dyes in chili oil by high performance liquid chromatography with on-line photochemical derivatization and fluorescence detection].

A method for the measurement of Sudan I, Sudan II, Sudan III and Sudan B in chili oil using high performance liquid chromatography (HPLC) with on-line photochemical derivatization and fluorescence detection has been developed. The Sudan dyes were separated on an SB-C18 column in a single run by the mixed mobile phase of acetonitrile-water with a gradient program. A laboratory-built time/energy programmed photochemical reactor (PCR) with an ultraviolet mercury lamp was installed between a photodiode array detector (PDA) and a fluorescence detector (FLD), and it was applied to convert the non-or weakly fluorescent Sudan dyes into fluorescence emission components. The photochemical derivatization conditions and fluorescence detection parameters have been investigated and optimized. The recoveries of the standards spiked in real chili oil samples for all the dyes were 81.3% - 100.4%. The relative standard deviations (RSDs, n = 6) of the fluorescence signal intensity at the spiked level of 0.8 mg/kg were 2.6% - 3.8%. The limits of detection (LODs) were in the range of 0.009 - 0.054 mg/kg and the limits of quantification (LOQs) were 0.030 - 0.181 mg/kg, which were better than those of the commonly used HPLC coupled with PDA. The developed method which is simple, sensitive, and selective can be applied to the routine analysis of Sudan dyes.