CHAPTER IX 



ELECTROPHORESIS 



David R. Briggs, University of Minnesota 



A. Characteristics of the Method. Definitions 271 



B . Elementary Theory 274 



C . Microelectrophoresis Method 277 



1 . Applications and Relative Advantages 277 



2 . Method of Observation 279 



3 . Choice of Apparatus 282 



4 . Measurements and Calculations 284 



5 . Some Recent Accomplishments 286 



D . Moving-Boundary Method 287 



1 . Applications and Relative Advantages 287 



2 . Essential Requirements 288 



3 . Modern Apparatus and Technique 289 



4 . Limitations 295 



5 . Some Recent Accomplishments 298 



References 298 



A. CHARACTERISTICS OF THE METHOD. DEFINITIONS 



The migration of particles, when suspended in a Hqiiid, that is 

 due to the influence of an imposed electric field is termed electro- 

 phoresis. The phenomenon is not essentially different from that of 

 the migration of any ion in an electric field. It is dependent, funda- 

 mentally, upon the existence of an electric charge on the surface, or 

 within the body, of the particle that is neutralized electrostatically 

 by an equal charge of opposite sign, in the form of ions, distributed 

 within the fluid adjacent to the particle, but at such a distance that, 

 when placed in an externally imposed electric field, some degree of 

 relative motion of these regions of opposite charges is possible against 

 the viscous resistance to shear within the layer of the fluid that sepa- 

 rates them in space. 



The charge carried by a particle can arise from either of two 

 sources. The material of the particle may contain chemical group- 



271 



