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

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-#L 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-[micro]L 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 (