Capillary electrophoresis-mass spectrometry for metabolic profiling of body fluids

Combined capillary electrophoresis-time-of-flight mass spectrometry (CE-ToF-MS) is a powerful technique for the fast and efficient analysis of ionogenic compounds. The application of CE-ToF-MS to metabolic profiling of body fluids, however, may be hindered by reproducibility and coverage problems. In this thesis a novel approach for reproducible and comprehensive metabolic profiling by CE-ToF-MS is presented. Very stable CE performance is accomplished by the use of noncovalent capillary coatings comprised of double and triple layers of charged polymers. These easy-to-produce coatings provide high migration-time reproducibility and good tolerance against sample matrix compounds. Moreover, one capillary with different coatings can be used for both cationic and anionic compounds demonstrating the flexibility of this approach for providing an extended coverage of metabolites in only two CE runs. Incorporation of in-capillary preconcentration by pH-mediated stacking further aids the detection of low-level metabolites. The performance of this novel CE-ToF-MS platform for metabolic profiling of body fluids has been studied for large groups of urine samples. Using multivariate techniques, it is demonstrated that the CE-ToF-MS platform allows high quality metabolomic data to be obtained. Accordingly, it can be applied for delineation of the urinary metabolome in a clinical setting. For example, the applicability and usefulness of the CE-ToF-MS platform will be outlined by the elucidation of metabolites involved in complex regional pain syndrome (CRPS) and urinary tract infection (UTI). Multivariate statistical analysis of the recorded profiles revealed biomarker candidates, which were subsequently identified by accurate mass and/or MS-MS using QToF-MS.