On-line dual-stage enrichment via magneto-extraction and electrokinetic preconcentration: A new concept and instrumentation for capillary electrophoresis

This study reports on the development of a new concept of on-line dual preconcentration stages for capillary electrophoresis (CE), in which two completely different preconcentration approaches can be realized in the same capillary. In the first stage, a dynamic magneto-extraction of target analytes on circulating magnetic beads is implemented within the capillary. In the second one, electrokinetic preconcentration of eluted analytes via large volume sample stacking is carried out to focus them into a nano band, prior to CE separation of enriched ana-lytes. To implement the dual-stage preconcentration operation, a purpose-made instrument was designed, combining electrophoretic and microfluidic modules to allow precise control of the movement of magnetic beads and analyte's flow. The potential of this new enrichment principle and its associated instrument was demon-strated for CE separation with light-emitting-diode-induced fluorescent (LEDIF) detection of target double-stranded DNA (ds-DNA). The workflow consists of purification and preconcentration of a target DNA fragment (300 bp) on negatively charged magnetic beads, followed by in-capillary elution and fluorescent labelling of the enriched DNA. Large volume sample stacking of the DNA eluent was then triggered to further preconcentrate the labelled DNA before its analysis by CE-LEDIF. An enrichment factor of 125 was achieved for the target DNA fragment. With our new approach, dual-stage sample pretreatment and CE separation can now be performed in -capillary without any mismatch of working volumes, nor any waste of pretreated samples.

Automated summary

This study introduces a new concept of on-line dual preconcentration stages for capillary electrophoresis (CE), allowing two different preconcentration approaches to be used in the same capillary. The first stage involves dynamic magneto-extraction of target analytes using circulating magnetic beads, while the second stage utilizes electrokinetic preconcentration to focus the eluted analytes into a nano band before CE separation. A purpose-made instrument combining electrophoretic and microfluidic modules is used to control the movement of magnetic beads and analyte flow. The potential of this new enrichment principle and instrument is demonstrated for CE separation of target double-stranded DNA (ds-DNA) using light-emitting-diode-induced fluorescent (LEDIF) detection. The dual-stage preconcentration allows for in-capillary sample pretreatment and CE separation without mismatch of working volumes or waste of pretreated samples.