Free-flow electrophoresis. II. Analysis of the method with respect to preparative cell separation

Electrophoretic cell separation by means of free-flow electrophoresis in an FF5 apparatus was investigated with respect to band resolution, separation capacity, reproducibility and influence on cell viability. Very sharp bands and a large separation capacity were achieved using triethanolamine/acetate buffered glycine media as liquid curtain. Acid buffer ions such as N-2-hydroxyethylpiperazine-N'-ethanesulfonic acid (HEPES) or phosphate produced broader bands. Osmotic expanders such as saccharides, though preserving cell viability excellently, decrease electrophoretic velocity and thus separation capacity. The decrease in cell viability observed in glycine media could be compensated for by addition of Ca2. Band broadening caused by methodologically specific velocity flow profiles could be reduced to a negligible level by coating the chamber walls with albumin and by appropriate adjustment of sample flow rate and liquid curtain velocity. Under the optimum conditions described, selective cell loss and artificial change in electrophoretic mobility of the cells during operation can be disregarded. The main reason for cell loss was cell aggregation at low ionic strength, which can be prevented or reversed by treatment of the cells with deoxyribonuclease.