Polyelectrolyte multilayer coatings for the separation of proteins by capillary electrophoresis: Influence of polyelectrolyte nature and multilayer crosslinking.

The present work aims at studying the influence of the nature of the polyelectrolytes used in successive multiple ionic polymers on the performances of protein separation in acetic acid volatile background electrolyte. A broad library of polyelectrolyte multilayers was compared on the basis of 9 different weak/strong polyanions and 8 different weak/strong polycations. More than 20 couples of different polyelectrolytes were investigated. The separation efficiencies (expressed as the N/l ratio, where N is the plate number and l is the capillary effective length) were systematically compared for the separation of a protein test mixture. The coating stability was evaluated by the relative standard deviation of the migration times. For weak polyelectrolyte multilayers, the influence of the polymer crosslinking on the coating stability and separation efficiency has been studied. Intra-day repeatability of 100 successive runs, and capillary-to-capillary reproducibility were tested on coatings of each category (crosslinked and non crosslinked). The main (not obvious) result rising from this study is that the nature of the polyanion constituting the multilayers is of primary importance for the performance in terms of separation efficiency and stability, even when the mulilayers finish with a polycation.