Liquid-phase separation techniques using columns of capillary size have recently gained large acceptance for qualitative and quantitative analyses as well as physicochemical characterizations. High throughput, small sample amount requirement, and high separation efciency are the major advantages of these microscale separation techniques. Additional advantages include straightforward optimization of separation, use of small amounts of chemicals, reduced waste, and a wide

6.1 Introduction .......................................................................................................................... 155 6.2 Basic Concepts of Electrokinetic Phenomena ...................................................................... 157

6.2.1 Electroosmosis .......................................................................................................... 157 6.2.1.1 Electric Double Layer ................................................................................ 157 6.2.1.2 Dependence of EOF on the Zeta Potential ................................................ 160 6.2.1.3 Factors Inuencing the EOF ...................................................................... 160

6.2.2 Electrophoresis ......................................................................................................... 161 6.2.2.1 Electrophoretic Mobility ............................................................................ 161 6.2.2.2 Absolute and Effective Mobility ................................................................ 162

6.3 Instrumentation for Capillary Electromigration Techniques ............................................... 163 6.3.1 Separation Unit ......................................................................................................... 163 6.3.2 Detection ................................................................................................................... 165

6.3.2.1 Absorbance ................................................................................................ 165 6.3.2.2 Fluorescence and Laser-Induced Fluorescence ......................................... 166 6.3.2.3 Electrochemical ......................................................................................... 168 6.3.2.4 Other Detection Modes and Hyphenated Techniques ............................... 170

6.4 Factors Inuencing Performance and Separation Parameters .............................................. 174 6.4.1 Joule Heating ............................................................................................................ 174 6.4.2 Interactions with the Inner Wall of Fused-Silica Capillaries ................................... 176 6.4.3 Separation Parameters .............................................................................................. 178

6.5 Separation Modes ................................................................................................................. 181 6.5.1 Capillary Zone Electrophoresis ................................................................................ 182 6.5.2 Capillary Afnity Electrophoresis ........................................................................... 185 6.5.3 Capillary Sieving Electrophoresis ............................................................................ 186 6.5.4 Capillary Isoelectric Focusing .................................................................................. 188 6.5.5 Electrokinetic Chromatography ............................................................................... 190 6.5.6 Capillary Electrochromatography ............................................................................ 196 6.5.7 Capillary Isotachophoresis ....................................................................................... 199

References ...................................................................................................................................... 201

range of possible detection methods, which include absorbance, uorescence, electrochemical, nuclear magnetic resonance spectroscopy, and mass spectrometry.