On-line coupling of two-phase microelectroextraction to capillary electrophoresis – Mass spectrometry for metabolomics analyses

Microchemical Journal, vol. 162, pp. 105741

Abstract

We have integrated two-phase electroextraction (EE), capillary electrophoresis (CE) and mass spectrometry (MS) to combine rapid sample extraction, high performance separation and sensitive detection of metabolites. EE took place from a sample vial containing organic donor phase into a ~100 nL droplet of background electrolyte, which was hanging at the inlet of the capillary. In order to enable the EE process while the outlet of the capillary was connected to the MS several modifications were made. A modification was made to the sheath-liquid CE-MS interface, based on the use of a corrosion-resistant titanium ESI sprayer and a 6-port valve to switch between the CE-MS sheath liquid and the EE make-up liquid. Furthermore, a counter-pressure was applied, in order to prevent EOF from retracting the droplet during EE. Then, using five model metabolites (namely, leucine, isoleucine, adenosine, phenylalanine and guanosine) and crystal violet (CV) the extraction time and voltage were optimized and found to be 2000 s and 1 kV, respectively. Using these optimized conditions, the effect of various sodium chloride concentrations was examined to assess the influence of varying salt concentrations in biological samples. A set of 9 amino acids was used to validate the method. The detection limits ranged between 5 and 100 nM. LODs were improved 50–250 times in comparison with conventional CE-MS. Finally, to demonstrate the potential of the EE-CE-MS platform for bioanalysis of volume-limited samples, a urine sample of 300 nL was analyzed. This resulted in detection of 122 putative metabolites. The results indicate that EE-CE-MS could become a powerful tool for metabolomics analyses of volume-limited samples.

Authors 3

1. Amar Oedit Aachen Division of Systems Biomedicine and Pharmacology Leiden Academic Centre for Drug Research

   Leiden University

   Affiliation as printed

   Division of Systems Biomedicine and Pharmacology, Leiden Academic Center for Drug Research, Einsteinweg 55, 2300 RA Leiden, the Netherlands

2. Thomas Hankemeier Aachen Division of Systems Biomedicine and Pharmacology Leiden Academic Centre for Drug Research

   Leiden University

   Affiliation as printed

   Division of Systems Biomedicine and Pharmacology, Leiden Academic Center for Drug Research, Einsteinweg 55, 2300 RA Leiden, the Netherlands

3. Peter W. Lindenburg corresponding Aachen Division of Systems Biomedicine and Pharmacology Leiden Academic Centre for Drug Research Research Group Metabolomics Leiden Centre for Applied Bioscience

   Leiden University · University of Applied Sciences Leiden

   Affiliation as printed

   Division of Systems Biomedicine and Pharmacology, Leiden Academic Center for Drug Research, Einsteinweg 55, 2300 RA Leiden, the Netherlands

   Research Group Metabolomics, Leiden Centre for Applied Bioscience, University of Applied Sciences Leiden, Mailbox 382, 2300 AJ Leiden, the Netherlands