An extraction system for distributing a test product in an extraction fluid, the system including a flow cell and a pump The flow cell has walls defining an internal passageway having an extraction region for holding the test product and also an upstream end and a downstream end between which the extraction region extends. The internal cross-sectional area of the upstream end is larger than the internal cross-sectional area of the downstream end the and extraction region tapers from the upstream end to the downstream end. The pump has an inlet in fluid communication with the downstream end and an outlet in fluid communication with the upstream end. The pump re-circulates extraction fluid from the downstream end back to the upstream end so as to progressively erode the test product and distribute the test product in the extraction fluid.