A system for investigating a membrane, the system comprising a first sealing chamber comprising a first barrier (10b,10t) configured to seal an inside of the first sealing chamber from a surrounding environment for maintaining a first controlled atmosphere inside the first sealing chamber, a first liquid container contained inside the first sealing chamber, wherein the first liquid container is configured to hold a first liquid medium in open communication with the first controlled atmosphere inside the first sealing chamber; a flow cell, disposed outside the first sealing chamber, the flow cell comprising a first flow channel, a second flow channel, and a clamping structure configured to hold the membrane spanned over an opening between the flow channels (31,32) for separating a respective flow through the flow channels (31,32) by the membrane spanning the opening there between; and a first set of liquid ducts (L13,L31) connected to the first flow channel and configured to carry the first liquid medium from the first liquid container, through the first barrier (10b,10t) to an entrance of the first flow channel into the flow cell, and carry at least part of the first liquid medium (M1') exiting the first flow channel from the flow cell back into the first liquid container; and a first flow distributor connected to the first set of liquid ducts (L13,L31) between the first flow channel and the first sealing chamber, and configured to selectively direct an incoming flow of first liquid medium (M1'), at an entry port of the first flow distributor, to respective exit flows at respective exit ports of the first flow distributor; wherein at least one of the exit ports is connected to a liquid duct through the first barrier (10b,10t) for directing at least part of the first liquid medium (M1') back into the first liquid container; wherein the first sealing chamber further contains one or more sample containers disposed in the first controlled atmosphere inside the first sealing chamber and configured to receive and hold a liquid sample of the first liquid medium, separate from the first liquid container, wherein at least one of the exit ports of the first flow distributor is connected to a liquid duct through the first barrier (10b,10t) for directing at least part of the first liquid medium (M1') into a respective sample container of the one or more sample containers. a first sealing chamber comprising a first barrier (10b,10t) configured to seal an inside of the first sealing chamber from a surrounding environment for maintaining a first controlled atmosphere inside the first sealing chamber, a first liquid container contained inside the first sealing chamber, wherein the first liquid container is configured to hold a first liquid medium in open communication with the first controlled atmosphere inside the first sealing chamber; a flow cell, disposed outside the first sealing chamber, the flow cell comprising a first flow channel, a second flow channel, and a clamping structure configured to hold the membrane spanned over an opening between the flow channels (31,32) for separating a respective flow through the flow channels (31,32) by the membrane spanning the opening there between; and a first set of liquid ducts (L13,L31) connected to the first flow channel and configured to carry the first liquid medium from the first liquid container, through the first barrier (10b,10t) to an entrance of the first flow channel into the flow cell, and carry at least part of the first liquid medium (M1') exiting the first flow channel from the flow cell back into the first liquid container; and a first flow distributor connected to the first set of liquid ducts (L13,L31) between the first flow channel and the first sealing chamber, and configured to selectively direct an incoming flow of first liquid medium (M1'), at an entry port of the first flow distributor, to respective exit flows at respective exit ports of the first flow distributor; wherein at least one of the exit ports is connected to a liquid duct through the first barrier (10b,10t) for directing at least part of the first liquid medium (M1') back into the first liquid container; wherein the first sealing chamber further contains one or more sample containers disposed in the first controlled atmosphere inside the first sealing chamber and configured to receive and hold a liquid sample of the first liquid medium, separate from the first liquid container, wherein at least one of the exit ports of the first flow distributor is connected to a liquid duct through the first barrier (10b,10t) for directing at least part of the first liquid medium (M1') into a respective sample container of the one or more sample containers.