Continuous-flow microelectroextraction for enrichment of low abundant compounds

Anal Chem. 2014 Aug 19;86(16):8048-56. doi: 10.1021/ac500707v. Epub 2014 Jun 19.

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.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carnitine / analogs & derivatives*
  • Carnitine / isolation & purification
  • Carnitine / urine
  • Chromatography, Reverse-Phase
  • Electrochemical Techniques / instrumentation*
  • Equipment Design
  • Humans
  • Laurates / isolation & purification*
  • Laurates / urine
  • Limit of Detection
  • Mass Spectrometry
  • Solid Phase Extraction / instrumentation*

Substances

  • Laurates
  • acylcarnitine
  • hexanoylcarnitine
  • lauroylcarnitine
  • octanoylcarnitine
  • Carnitine