Patent ID: 7186336

Claim:
An apparatus for forming a gradient composition in a chromatographic capillary system comprising: a first flow path having a first pump in fluid communication with a first flow divider said first flow divider being in fluid communication with a first restrictor operatively disposed in a first restrictor flow path and a first sensor flow path with a first sensor operatively disposed within said sensor flow path said first sensor configured to measure flow rates of said liquid in said first sensor flow path to produce a first flow signal said first restrictor having a selected permeability producing a first flow rate; a second flow path having a second pump in fluid communication with a second flow divider said first flow divider being in fluid communication with second restrictor operatively disposed in a second restrictor flow path a second sensor flow path with a second sensor operatively disposed in said second sensor flow path said second sensor configured to measure flow rates of said liquid in said second sensor flow path to produce a second flow signal said second restrictor having a selected permeability producing a second flow rate; means for combining the first sensor flow path and the second flow path; and means for controlling flow in first and second sensor flow paths to form a gradient composition.