On-line preconcentration of protein in capillary electrophoresis with an end-column cellulose acetate-based porous membrane

A simple on-line preconcentration method of protein for capillary electrophoresis (CE) using a cellulose acetate (CA)-coated porous membrane was proposed. CA membrane is fabricated at one of the ends of the column that allows the passage of buffer ions but excludes larger protein molecules. Protein sample is continuously electrokinetically loaded and trapped by the membrane. When injection is completed, the direction of the electric field is switched and the trapped proteins are then separated by conventional CE procedure. The results achieved showed that the preconcentration mechanism of this method was based on size-exclusion effect. Bovine serum albumin (BSA) was used for model protein sample, and signal enhancement of 550-fold with 15 min injection time was achieved.