Micro flow filtration system and flow filtration method for a fluid sample

A flow filtration method for concentrating a component contained in a fluid sample using a tangential flow filtration module (3), the method comprising the following steps:

• providing a micro flow filtration system (1) preferably according to any one of the preceding claims comprising
• a fluid channel (2) having two ends (10, 11) and being formed by two conduits (4, 5) allowing a bidirectional flow of the fluid sample through the channel (2);
• a tangential flow filtration module (3) having a first fluid port (14), a second fluid port (15), a permeate outlet (16) and a semipermeable membrane (17) capable of separating the fluid sample;
• at least two pairs (8, 9) of piston pumps (6), each piston pump (6) forming a reservoir (18, 19) being able to contain a fluid;
• a control unit (80) for controlling movement of the pistons of the piston pumps (6);
• wherein
• the TFF-module (3) is located in the fluid channel (2) so that one conduit (4) is connected to the first fluid port (14) and the other conduit 5 is connected to the second fluid port (15);
• at each of the ends (10, 11) of the channel (2) one piston pump (6) of each pair (8, 9) of piston pumps (6) is arranged in such a manner that the piston pumps (6) are connected fluidically;
• the piston pumps (6) of a first pair (8) of piston pumps have a larger volume than the piston pumps (6) of a second pair (9) of piston pumps (6);
• the control unit (80) is arranged and adapted to control of moving the pistons of the piston pumps of each pair (8, 9) of piston pumps synchronously and/or to control the switching and/or the switching time for switching from one pair (8) of piston pumps (8a, 8b) to the other pair (9) of piston pumps (9a, 9b),
• filling at least one piston pump (6) of the first pair (8) of piston pumps with a fluid;
• moving the piston of the first piston pump (8a) of the first pair (8) of piston pumps controlled by the control unit (80) in a first direction to reduce the piston swept volume to drive the fluid sample from the first piston pump (8a) through the fluid channel (2) and to pass the TFF-module (3) thereby increasing the concentration of the components in the fluid sample in the system (1) and withdrawing an amount of fluid in a permeate stream;
• moving the piston of the second piston pump (8b) of the first pair (8) of piston pumps controlled by the control unit (80) in the first direction to enhance the piston swept volume to allow fluid to enter the piston pump (8b) after passage through the fluid channel (2);
• moving the piston of the second piston pump (8b) and the piston of the first piston pump (8a) of the first pair (8) of piston pumps controlled by the control unit (80) in a second direction opposite to the first direction to drive back the fluid sample from the second piston pump (8b) through the TFF-module (3) into the first piston pump (8a);
• determining if the volume of the fluid sample in the system (1) has been reduced below a predetermined value or if an predetermined time interval after starting of the process has been reached;
• repeating the steps of moving the first and second piston pumps (8a, 8b) of the first pair of piston pumps (8) controlled by the control unit (80) in the first and second direction until the predetermined value or the predetermined time interval has been reached, thereby driving the fluid back and forth through the TFF-module (3);
• and
• if the volume of the fluid sample in the system (1) has been reduced below the predetermined value or if the predetermined time interval after starting of the process has been reached, using the piston pumps (9a, 9b) of the second pair (9) of piston pumps according to the steps above thereby establishing a continuous bidirectional flow of fluid in the channel (2).