Miniature field-flow fractionation system for analysis of blood cells

Field-flow fractionation is an analytical tool that has been historically used to separate species, ranging from molecules to particles or cells several micrometers in size. This technology can effect separation by size, density, charge, or other physical properties, depending on the configuration of the field-flow system. We have developed a miniature field-flow system to analyze cell populations in a small, 125-microns-deep channel 19 cm long. Gravity is used as the primary field to effect separation, and cell analysis is performed in < 20 min. Erythrocytes elute as a single peak when diluted blood is fractionated in this system. Analysis of blood samples from several donors (normal controls and patients with sickle cell anemia) yields erythrocyte peaks with slightly different mobilities (elution times). Peak mobility does not directly correlate with mean cell volume or other standard erythrocyte parameters. Cell density appears to be a key factor in determining cell mobility with this system.