Determination of Sudan Dyes in Juice Samples via Solidification of Ionic Liquid in Microwave-Assisted Liquid-Liquid Microextraction Followed by High-Performance Liquid Chromatography

Solidification of ionic liquid (SIL) has been applied in microwave-assisted liquid-liquid microextraction method for analyzing Sudan dyes in juice samples. 1-Ethy-3-methylimidazolium hexafluorophosphate ([C2MIM][PF6]) was selected as the extraction solvent due to its relatively high melting point. With the aid of microwave irradiation, the dyes could be easily extracted into ionic liquid phase without dispersive solvent. The solid microdroplet could be easily separated from liquid. Compared with traditional dispersive liquid-liquid microextraction, this method will greatly simplify the collection procedure and shorten the operation time. Several experimental parameters, including the amount of ionic liquid, microwave power and irradiation time, pH of sample solution, and ionic strength, were systematically investigated and optimized. The limits of detection for Sudan I, II, III, and IV were 1.08, 1.30, 1.14, and 1.19 μg/L, respectively. The recoveries of the analytes ranged from 83.42 to 115.56 % and relative standard deviations were lower than 11.53 %, when the present method was applied to the analysis of real samples.