Control of electrohydrodynamic distortion of sample streams in continuous flow electrophoresis using oscillating fields.
Continuous flow electrophoresis is a method to separate ions contained in a sample continuously injected into a laminar flow of electrolyte as a cylindrical stream. Usually, the sample is more conductive than the electrolyte, and the charges created at the sample-electrolyte interface lead to electrohydrodynamic distortions which reduce the separation power of this technique. We demonstrate theoretically that the rate of electrohydrodynamic distortion of a cylindrical sample stream can be reduced to zero, by superimposing to the AC field responsible for the separation of a DC field transverse to it and to the flow direction, with an appropriate frequency, and an effective strength equal to that of the DC field. Using a continuous flow electrophoresis chamber, in which such a field is produced using capacitive electrodes, the major predictions of the theory are confirmed. In particular, it is shown that a sample stream more conductive than the carrying electrolyte, which was seriously deformed in the absence of a transverse AC field, recovers its cylindrical shape in presence of the field. The implications of this discovery for the separating power of continuous-flow electrophoresis are discussed.
Heller
C
C
Laboratoire de Physico-Chimie Théorique, URA CNRS 1382, Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris.
Limat
L
L
Sergot
P
P
Viovy
J L
JL
D002021:Buffers; D004563:Electrochemistry; D004586:Electrophoresis / Q000379:methods*; D008433:Mathematics; D008956:Models, Chemical
D002021:Buffers