Abstract: A flow control system including a pump for delivering a carrier containing isocratic or gradient controlled elution solvents under pressure to a liquid chromatographic column at a substantially constant selected controlled flow rate.

Abstract: In the cycle of a positive displacement LC pump system the output pressure is sensed to measure onset of output flow as a time lag from the beginning of the output stroke to give an estimate of the input filling time lag from the beginning of the fill stroke. This estimate is used to recompute a proportional module output for controlling the timing of a proportioning valve at the inlet to the LC pump so as to bring the actual operating conditions of the pump fill cycle into correspondence with the predetermined demanded ratios of the components either in isocratic or gradient program mode.