Dynamic three-phase microextraction as a sample preparation technique prior to capillary electrophoresis

Abstract

Dynamic three-phase (liquid - liquid - liquid) microextraction was developed for capillary electrophoresis. Four aromatic amines as model compounds were extracted from 4-mL aqueous samples adjusted to basic condition (donor solution) through a small volume of organic solvent impregnated in a hollow fiber, which was held by the needle of a conventional syringe, and retracted into a 5-μL acidic acceptor solution inside the syringe. A renewable organic film and aqueous sample plug were formed inside the hollow fiber with the repeated movement of the syringe plunger enabled by a programmable syringe pump. This is believed to be the first reported instance of a semi-automated dynamic liquid - liquid - liquid microextraction (LLLME) procedure. Following this microextraction, the 5-μL acceptor solution was analyzed by capillary zone electrophoresis (CE). This new technique provided ∼ 140-fold enrichment in 20 min. Utilizing 4-chloroaniline as internal standard, dynamic LLLME could provide good reproducibility (<4.0%). In addition, this method allowed the direct transfer of extracted analytes to a CE system for analysis.