Continuous flow micro-electroextraction for enrichment of low abundant compounds

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It is well known by all the readers that achieving the highest enrichment is the key factor in any miniaturized extraction technique. In this sense, the use of highly efficient materials is a valuable alternative but not the only one. The use of auxiliary energies which force the analyte migration from the sample to the extractant phase is also a widespread alternative. Among them, electromigration-based microextraction is an elegant approach which allows the focusing and stacking of charged compounds within a short temporal window. In this context, Lindenburg and coworkers have proposed a continuous flow micro-electroextraction approach for the enrichment of low abundant compounds of relevance in metabolomics (1). The article has been recently published in Analytical Chemistry and it has been selected for the cover of issue 16.

Analytical Chemistry cover
The authors have designed an electroextraction flow cell incorporated in a microfluidic chip where the organic donor phase flows while the aqueous acceptor phase remains stagnant. In order to stabilize the liquid-liquid interface a phase guide, a microfluidic pinning structure, is located on the bottom of the flow-cell.

For the optimization of the flow cell, the cationic dye crystal violet is employed as it allows the visual monitoring of the stability of the liquid-liquid interface as well as the extraction process. The extraction was carried out using only 13,4 µL of aqueous acceptor phase which was further analyzed by liquid chromatography. The authors have deeply explored all the variables affecting to the flow cell design providing very nice pictures of the experiments. Finally, the performance of the device was evaluated using three acylcarnitines which represents an important metabolites class whose profile variations are related to variations inborn metabolic errors.

Reference
(1) Continuous-Flow Microelectroextraction for Enrichment of Low Abundant Compounds. Link to the article

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