Electroosmotic flow changes due to interactions of background electrolyte counter-ions with polyethyleneimine coating in capillary zone electrophoresis of proteins

Abstract

The properties and behavior of polyethyleneimine (PEI) covalently coated capillaries with respect to different background electrolytes used in capillary zone electrophoresis (CZE) are described. The coating stability and changes of inner surface charge in the capillary were followed by measurement of electroosmotic flow (EOF). Interest was focused mainly on conjugate bases of carboxylic acids as anionic background electrolyte components (acetate, citrate, malate, malonate, tartrate, and succinate). An interesting phenomenon was observed in PEI-coated capillaries: The direction (and the magnitude) of EOF depends on the composition of the background electrolyte and at a certain pH it can undergo reversible change. Ionic complex formation was suggested as a hypothesis to explain this behavior. With this knowledge, the PEI-coated capillary was used for the separation of basic proteins in the above-mentioned background electrolytes. A standard protein mixture of cytochrome c, ribonuclease A, and lysozyme at a concentration of 0.25 mg/mL each was chosen as model sample.

Capillary electrophoresis of proteins 2005–2007

“…A permanent coating based on PEI layer covalently attached to the capillary wall was prepared and used to separate a model mixture of basic proteins by CZE [33].…”

Determination of oxalyl-coenzyme A decarboxylase activity in Oxalobacter formigenes and Lactobacillus acidophilus by capillary electrophoresis

“…In this regard, PEI resulted to be a useful compound for the preparation of permanent coated capillaries: in fact as it has been previously proposed [13], PEI is a polycationic branched polymer able to be permanently adsorbed by the silica surface of the capillary wall. Detailed studies were reported on the EOF variations in PEI-coated capillaries using different running buffer nature and pH [13,[21][22][23][24]. In the present study, a fused silica capillary was modified by adsorption of a 10% (w/v) PEI aqueous solution and it was used, in the presence of a BGE consisting of phosphate running buffer (50 mM, pH 7.0), in the analysis of actual enzymatic mixtures containing Ox-CoA and For-CoA.…”

Poly(N‐vinylimidazole)‐grafted capillary for electrophoresis prepared by surface‐initiated atom transfer radical polymerization

“…Different kinds of polymers have been covalently bonded onto the capillary wall using several strategies 16–19, which can effectively shield silanol groups of the capillary to control the EOF. However, using conventional methods such as the radical polymerization technique 20, it is difficult to produce uniform and dense coverage of the polymer on the inner surface of the capillary.…”