A method and apparatus for monitoring and controlling the nano-scale flow
rate of fluid in the operating flow path of a HPLC system. A first flow
sensor is disposed in a first flow path between a first flow-divider and
a fluidic tee. A second flow sensor is disposed in a second flow path
between a second flow-divider and the fluidic tee. A first recycle flow
restrictor is disposed in the first recycle flow path in fluid
communication with the first flow-divider. A second recycle flow
restrictor is disposed in the second The permeability of each recycle
flow restrictor can be selected to produce a desired flow rate with each
respective flow path. The output signals of the first and second flow
sensors to control output of a pump within each flow path.