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

• Published in: Microchemical journal Vol. 162; p. 105741
• Main Authors: Oedit, Amar, Hankemeier, Thomas, Lindenburg, Peter W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2021
• Subjects: Bioanalysis; Capillary electrophoresis; Electroextraction; Electromembrane extraction; Metabolomics; Single-drop microextraction; Electromembrane extraction; Metabolomics; Single-drop microextraction; Electroextraction; Capillary electrophoresis; Bioanalysis
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/j.microc.2020.105741

•Successful development of a fully automated two-phase electroextraction system.•Integration of two-phase electroextraction with CE and MS.•Electroextraction with high yields for polar metabolites.•Greatly improved detection limits and sensitivity compared to conventional CE.•Novel tool for the metabolomics toolbox and the analysis of volume-limited samples. 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.