Single drop microextraction using commercial capillary electrophoresis instruments.

Single drop microextraction (SDME), a simple and efficient sample preconcentration method for capillary electrophoresis (CE), was performed using two different commercial CE instruments. With a CE instrument providing adjustable forward and backward pressures, a single drop of an aqueous acceptor phase covered with a thin layer of an organic phase was formed at the capillary tip by programming the sample-handling functions of the instrument to perform 3-phase SDME where the organic film is essentially a membrane. Analytes from an acidic donor phase were concentrated into a basic acceptor phase yielding 190-fold enrichment in 10 min.