NEW APPROACHES TO CONCENTRATION ON A MICROLITER SCALE OF DILUTE SAMPLES, PARTICULARLY BIOPOLYMERS WITH SPECIAL REFERENCE TO ANALYSIS OF PEPTIDES AND PROTEINS BY CAPILLARY ELECTROPHORESIS .2. APPLICATIONS

On theoretical grounds several approaches for the concentration of ion ic solutes are suggested in ref. 1. The methods are of general applica bility. In this paper we describe how they can be employed in high-per formance capillary electrophoresis (HPCE) for 1000-fold manual and aut omated on-line concentration from microliters down to nanoliters. The risk that the solutes may escape detection -the obvious disadvantage o f HPCE- is, accordingly, reduced considerably. Briefly, the whole capi llary (and for more than 1000-fold concentration also an electrode ves sel or a vessel in contact with an electrode vessel) is filled with th e dilute sample solution. The sample becomes concentrated as it migrat es toward a pH gradient, a small-pore gel, a dialysis tubing attached to one end of the capillary, or by displacement electrophoresis combin ed with a hydrodynamic counterflow. These concentration steps (except the last) require a short mobilization step to prevent the narrow, con centrated sample zone from broadening in the initial phase of the fina l analysis step (free zone electrophoresis).