Emulsification liquid phase microextraction followed by on-line phase separation coupled to high performance liquid chromatography.

An emulsification liquid phase microextraction followed by on-line phase separation coupled to high performance liquid chromatography (HPLC) is introduced based on a novel idea for the separation of dispersed organic phase from aqueous phase. In this method, the dispersed organic extraction phase was filtered using an in-line filter and it was separated from the water sample. The new approach is simple and, in addition to improving some limitations of the conventional emulsification liquid phase microextraction, eliminates the need for centrifugation in the phase separation step. To demonstrate the applicability of the method, it was applied for the extraction and determination of trace amounts of selected parabens as model analytes. In this procedure, 30 μL of 1-octanol was injected slowly into 10 mL of the aqueous sample inside the ultrasonic water bath. Then, the emulsion formed was passed through the in-line filter located in the loop of the HPLC valve and the organic extraction phase was separated and it was retained in the filter. By changing the position of the valve, the filter was located in the mobile phase pass and the retained organic phase was eluted and transferred to the separation column. The effects of some important parameters such as types of extraction solvent and its volume, ionic strength, and ultrasonication time on extraction efficiency were investigated and optimized. Under optimal conditions, preconcentration factors and limits of detection for the compounds studied were obtained in the ranges of 289-595 and 0.05-0.2 μg L(-1), respectively. Finally, the method was successfully applied to determine selected parabens in some water and cosmetic samples.