LASER Doppler Electrophoresis (LDE) has appeared recently as an alternative to classical methods of electrophoresis in the study of colloid systems.⁽¹-²⁾ In microelectrophoresis, individual particles are tracked under a microscope, while in LDE the counting of particles of various mobilities is performed automatically by means of optical processes. LDE provides a less time consuming and inherently more objective method than microelectrophoresis for analysing the mobility distribution of a system of particles.
LDE may also have advantages over other classical electrophoretic methods in many cases. Moving boundary electrophoresis is useful for small particles or macromolecules, whereas mass transport electrophoresis is more suited to concentrated suspensions. LDE is applicable to reasonably dilute systems of particles which range in size from molecular dimensions to micrometers. The LDE system described here is designed to study particles in the upper part of this range.