Field flow fractionation device

A field flow fractionation device, comprising:

• a separation cell group comprised of a plurality of separation cells, each including:
• a separation channel configured for receiving flow of carrier fluid and separating a sample therefrom,
• a first inlet port leading to one end to the separation channel,
• a second inlet port located closer to another other end of the separation channel with respect to the first inlet port, and
• an effluent chamber adjoining the separation channel across a separation membrane, the separation membrane being carrier-fluid-permeable but sample-impermeable, and
• the plurality of separation cells defining at least one separation cell pair consisting of an upper separation cell and a lower separation cell;
• a first carrier fluid supply unit connected to the first inlet port of the upper separation cell of the separation cell group, the first carrier fluid supply unit configured to supply carrier fluid to the separation channel of said upper separation cell;
• a second carrier fluid supply unit provided separately from the first carrier fluid supply unit, the second carrier fluid supply unit configured to feed carrier fluid independently from the first carrier fluid supply unit;
• a channel switching unit configured for switching a connection of the second carrier fluid supply unit to any one port of the second inlet port of the upper separation cell, the first inlet port of the lower separation cell, or the second inlet port of the lower separation cell;
• and
• a control unit configured for controlling the channel switching unit to connect the second carrier fluid supply unit to the second inlet port of the upper separation cell during a process of focusing to generate flow of carrier fluid counter to the flow of carrier fluid from the first inlet port within the upper separation cell, and to connect the second carrier fluid supply unit to the first inlet port or the second inlet port of the lower separation cell after the process of focusing in the upper separation cell.