دانلود کتاب الکتروفورز مویرگی – طیف سنجی جرمی

Capillary electrophoresis-mass spectrometry (CE-MS) is still an underutilized technique compared to the widespread liquid chromatography-mass spectrometry (LC-MS). Nevertheless, the selectivity makes CE-MS an attractive tool in many fields of application which is oftentimes considered complementary to traditional LC separation. In general, electromigrative techniques separate ions based on their charge-to-size ratio and/or isoelectric point. Consequently, high separation efficiency can be achieved, ideally resulting in exceptionally sharp peaks under diffusion-limited conditions. In this way, it is possible to resolve closely related species such as isomeric molecules (including enantiomers) or proteoforms varying in only one posttranslational modification. CE requires the application of high electric fields to performreasonably fast and efficient separations, resulting in high electric currents. Consequently, efficient heat dissipation is required to avoid peak broadening and bubble formation due to Joule heating. This leads to small geometries with relatively high surface resulting in total capillary volumes typically in the single digit microliter range. Thus, CE is a microfluidic separation technique considered environmentally friendly due to its low consumption of resources (e.g., solvents). For the same reason, CE-MS is particularly suitable for the analysis of valuable samples, e.g., if only minor amounts are available. However, on the other hand, analytes need to be sufficiently concentrated for sensitive detection. In addition, the handling of small volumes requires special care and can be technically challenging. Mass Spectrometry (MS) acts as a universal and selective technique for molecule characterization and can be applied in both targeted and nontargeted fashion. In the last decades, enormous progress has been made in MS technology leading to high sensitivity, high speed, increased resolving power, the ability for selective fragmentation of small and large molecules, and last but not least improved overall usability. Still, separation techniques are crucial due to possible interference during the ionization process and mass spectrometric resolution being limited, which is especially important in the context of complex samples. Electrospray Ionization (ESI) is the technique of choice for on-line coupling of liquid phase separations, which is particularly true for electromigrative techniques. However, the need for closing the electric circuits for both the CE and the ESI process at the end of the separation capillary requires unique interface designs. Moreover, the selectivity of electromigrative techniques is substantially influenced by the type and concentration of the components of the background electrolyte (BGE). Many CE methods are not compatible with ESI-MS in a direct fashion due to nonvolatile constituents, being required for best separation performance. These special needs for CE-MS are addressed in this book.