Filter-Based Low-Toxic Emulsification Microextraction Followed by High-Performance Liquid Chromatography for Determination of Sudan Dyes in Foodstuff Samples

In the present work, we describe an efficient filter-based microextraction method with a proper sample clean-up for the simple determination of the banned Sudan dyes (I, II, III, and IV) in the foodstuff and water samples. The method is based upon the dispersion of a low-toxic solidifiable organic solvent (1-undecanol, 75 mu L) into an aqueous sample solution and utilization of a syringe filter for the emulsion breaking. This syringe filter with a nylon membrane is compatible with a broad range of solvents and thus is ideal for the rapid filtration of most aqueous and organic solutions. Hence, along with the passage of a mixture of an aqueous sample solution and an organic solvent through the membrane, fine droplets of the extractant solvent are aggregated, separated from the aqueous sample solution. By implementing this simple method, the overall extraction time is just 3-4 min; it is environmentally friendly and centrifuge-free, and it provides a high sample clean-up by filtration of the acceptor phase. The parameters influencing the extraction efficiency including the type and volume of the extraction solvent, pH, ionic strength, and number of extractions are thoroughly examined and optimized. Under the optimal experimental conditions, the proposed method provided a good linearity in the range of 1.0-1500 ng mL(-1), good extraction repeatabilities (relative standard deviations below 8.9%, n = 5), low limits of detection (0.2-0.7 ng mL(-1)), and enrichment factors of 105-138.