title: Continuous-flow microelectroextraction for enrichment of low abundant compounds.
abstract: We present a continuous-flow microelectroextraction flow cell that allows for electric field enhanced extraction of analytes from a large volume (1 mL) of continuously flowing donor phase into a micro volume of stagnant acceptor phase (13.4 μL). We demonstrate for the first time that the interface between the stagnant acceptor phase and fast-flowing donor phase can be stabilized by a phaseguide. Chip performance was assessed by visual experiments using crystal violet. Then, extraction of a mixture of acylcarnitines was assessed by off-line coupling to reversed phase liquid chromatography coupled to time-of-flight mass spectrometry, resulting in concentration factors of 80.0 ± 9.2 times for hexanoylcarnitine, 73.8 ± 9.1 for octanoylcarnitine, and 34.1 ± 4.7 times for lauroylcarnitine, corresponding to recoveries of 107.8 ± 12.3%, 98.9 ± 12.3%, and 45.7 ± 6.3%, respectively, in a sample of 500 μL delivered at a flow of 50 μL min(-1) under an extraction voltage of 300 V. Finally, the method was applied to the analysis of acylcarnitines spiked to urine, resulting in detection limits as low as 0.3-2 nM. Several putative endogenous acylcarnitines were found. The current flowing-to-stagnant phase microelectroextraction setup allows for the extraction of milliliter range volumes and is, as a consequence, very suited for analysis of low-abundant metabolites.
authors.affiliation: Division of Analytical Biosciences, Leiden Academic Center for Drug Research, Leiden University , Leiden, The Netherlands.
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: Schoonen
authors.forename: Vincent
authors.initials: V
authors.lastname: van Duinen
authors.forename: Amar
authors.initials: A
authors.lastname: Oedit
authors.forename: Paul
authors.initials: P
authors.lastname: Vulto
authors.forename: Thomas
authors.initials: T
authors.lastname: Hankemeier
authors.forename: Petrus W
authors.initials: PW
authors.lastname: Lindenburg
mesh_terms: D002331:Carnitine / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000652:urine; D056148:Chromatography, Reverse-Phase; D055664:Electrochemical Techniques / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D007848:Laurates / Q000302:isolation & purification* / Q000652:urine; D057230:Limit of Detection; D013058:Mass Spectrometry; D052616:Solid Phase Extraction / Q000295:instrumentation*
chemical_list: D007848:Laurates; C116917:acylcarnitine; C061301:hexanoylcarnitine; C091947:lauroylcarnitine; C008698:octanoylcarnitine; D002331:Carnitine