CHAPTER 3: Capillary Electrophoresis–Mass Spectrometry Using Non-covalently Coated Capillaries for Metabolic Profiling of Biological Samples

Metabolic profiling has become a key approach in contemporary biomedical sciences, aiming to provide an answer to a well-defined biomedical/clinical question. The main analytical techniques currently used in the field of metabolomics encounter difficulties when in-depth analysis of highly polar and charged metabolites is required, and/or when the amount of biological sample becomes a limiting factor for the analytical workflow. In this context, capillary electrophoresis–mass spectrometry (CE-MS) can be considered a very useful analytical tool for the profiling of polar and charged metabolites in volume-limited samples. However, variability of migration time is still an important issue in CE. An effective way to minimize this problem is the use of non-covalently coated capillaries, that is dynamic coating of the bare fused-silica capillary with solutions of charged polymers. In this chapter, a few strategies are described for metabolic profiling of biological samples by CE-MS using multi-layered non-covalent capillary coatings. Capillaries are coated with a bilayer of polybrene (PB) and poly(vinyl sulfonate) (PVS), or with a triple layer of PB, dextran sulfate (DS) and PB. The bilayer and triple-layer coated capillaries have a negative and positive outside layer, respectively. It is shown that the use of such capillaries provides very repeatable migration times.