Electroosmotic flow suppressing additives for capillary zone electrophoresis in a hydrodynamically closed separation system

Electroosmotic flow in a hydrodynamically closed capillary zone electrophoresis (CZE) separation compartment must be minimized to achieve high efficiency CZE separations. A group of eight potential electroosmotic flow suppressors was investigated in this context for the separations in fluorinated ethylene–propylene capillary tubes. The suppressors included water soluble methylhydroxyethyl derivatives of cellulose, polyvinylalcohol, polyvinylpyrrolidones and polyethyleneglycols of different molecular masses and Triton X-100. Methylhydroxyethylcellulose derivatives and polyvinylalcohol were found to provide the highest separation efficiencies for a group of model anions when the electroosmotic flow suppressors were used as the carrier electrolyte additives. Using a methylhydroxyethylcellulose coated separation compartment very significant improvements in the separation efficiencies were achieved for polyvinylpyrrolidones and polyethyleneglycols applied in the carrier electrolyte solutions. For example, polyvinylpyrrolidone K 90 applied in this way gave for some of the model analytes the plate height values approaching those estimated in the calculations as theoretical limits for our experimental conditions (H≈3.5 μm). CZE experiments with albumin and γ-globulin showed that the use of methylhydroxyethylcellulose derivative in the carrier electrolyte solution at pH=9.2 was effective in eliminating potential disturbances in the separation efficiencies of the analytes due to adsorption of the proteins.