Capillary electrophoresis dependent parameters

The use of mass spectrometry (MS) as a detection system is inevitable in the evolution of any separation method, especially CE where the liquid flow rate ( 1 ml/min) is compatible with conventional mass spectrometers. The combination of a high-efficiency liquid-phase separation technique, such as capillary electrophoresis, with MS detection provides a powerful system for the analysis of complex mixtures. Analyte sensitivity and the mass spectrum obtained depend on the electrospray ionization (ESI) voltage, ion-focusing parameters, and buffer composition. In general, the greatest sensitivity is obtained by employing conditions that facilitate desolvation and minimize cluster formation.47 Three ways of interfacing for CE-MS... 

Reproducible injection for capillary electrophoresis on a microdevice/Lab-on-Chip is not easy to achieve. Different injection designs (e.g., T type, double-T type, and cross type) and different injection techniques have been applied (pinched injection, gated injection, double-L injection) within microfluidic devices. The volume and the concentration of the dispensed sample are the key parameters of this dispensing process, and they depend on the applied electrical field, the flow field, and the concentration field during the injection and separation processes. The problems and properties of the different modes are described below. 

The glass frit in the Teorell oscillator can be replaced by nanoporous Alter membranes [33-35], or even capillary electrophoresis tubes [36]. By these means, important parameters such as salt and hydraulic permeability, salt concentration, pore width, and fixed charge relevant to electro-osmotic flow (which may in turn depend on pH) can be varied systematically. 

The direct detection of a complex from an equilibrium mixture is certainly the most obvious evidence of specific molecular interactions between components. Electrophoresis of an equilibrium mixture is an easily performed experiment, enabling the determination of complex formation parameters. When the dissociation kinetics of the complex is slow, the complex gives rise to a new peak in the electropherogram, in addition to the peaks of the free component molecules. Since the separation of the free components prevents the reformation of the complex inside the capillary, the complex peak should decrease in size during electrophoresis. The extent of this decrease depends on dissociation kinetics and separation time. In view of that fact, short analysis times, as obtained in CE, are required to detect less stable complexes, which would hardly be detected using previous formats of electrophoresis with longer separation times. 

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