title: Enhancing the coverage of the urinary metabolome by sheathless capillary electrophoresis-mass spectrometry.
abstract: Sheathless capillary electrophoresis-mass spectrometry (CE-MS), using a porous tip sprayer, is proposed for the first time for highly sensitive metabolic profiling of human urine. A representative metabolite mixture and human urine were used for evaluation of the sheathless CE-MS platform. For test compounds, relative standard deviations (RSDs) for migration times and peak areas were below 2% and 12%, respectively, and an injection volume of only ∼8 nL resulted in detection limits between 11 and 120 nM. Approximately 900 molecular features were detected in human urine by sheathless CE-MS whereas about 300 molecular features were found with classical sheath-liquid CE-MS. This difference can probably be attributed to an improved ionization efficiency and increased sensitivity at low flow-rate conditions. The integration of transient-isotachophoresis (t-ITP) as an in-capillary preconcentration procedure in sheathless CE-MS further resulted in subnanomolar limits of detection for compounds of the metabolite mixture, and more than 1300 molecular features were observed in urine. Compared to the classical CE-MS approaches, the integration of t-ITP combined with the use of a sheathless interface provides up to 2 orders of magnitude sensitivity improvement. Hence, sheathless CE-MS can be used for in-depth metabolic profiling of biological samples, and we anticipate that this approach will yield unique information in the field of metabolomics.
authors.affiliation: Biomolecular Mass Spectrometry Unit, Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands. R.Ramautar@lumc.nl
authors.forename: Rawi
authors.initials: R
authors.lastname: Ramautar
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Busnel
authors.forename: André M
authors.initials: AM
authors.lastname: Deelder
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Mayboroda
mesh_terms: D015415:Biomarkers / Q000652:urine*; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D057625:Isotachophoresis; D055442:Metabolome; D055432:Metabolomics; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014556:Urine / Q000737:chemistry*
chemical_list: D015415:Biomarkers