Manipulation of Sample Fractions on a Capillary Electrophoresis Chip

Abstract

A microfabricated capillary electrophoresis chip has been used for selective isolation of fraction zones after fast size separation of a synthetic mixture of fluorescent phosphorothioate oligonucleotides. Withdrawal of preselected sample zones is achieved by simple automated switching of the applied potentials to a channel system which has been etched into a glass plate by conventional microfabrication techniques. Both single sample zones and groups of zones can be selectively isolated from unwanted sample components on a time scale of a few minutes. A single sample component, originally injected into a volume of ∼90 pL prior to the separation, was still confined within a volume of ∼300 pL after the separation and removal procedure ; i.e., extensive dilution is avoided. Complex timing protocols allow for the withdrawal of any subset in the sequence of separated fractions. The results demonstrate the high degree of sample control that can be obtained on gel-filled microstructures with samples in the pico- to nanoliter range. They are of particular relevance for future developments of micromanipulation and microanalysis systems for biochemical analysis.