Patent ID: 7550081

Claim:
A liquid chromatograph comprising: a mobile phase supplying apparatus of a high-pressure gradient system configured to supply mobile phases while controlling a composition of the mobile phases, the mobile phase supplying apparatus comprising: a plurality of liquid-feeding pumps configured to feed the mobile phases, respectively; a plurality of liquid-feeding flow paths having the liquid-feeding pumps, respectively; a mixer configured to mix the mobile phases by merging the liquid-feeding flow paths; at least one control device configured to control driving of each of the liquid-feeding pumps based on flow rates being set for the respective liquid-feeding flow paths; a plurality of actual flow rate measuring sections provided downstream of the liquid feeding pump in each liquid-feeding flow path, the plurality of actual flow rate measuring sections configured to measure an actual flow rate and to detect a back-flow in the corresponding liquid-feeding flow path; and a plurality of actual flow rate computing sections configured to compute an actual flow rate in the corresponding liquid feeding flow path; a sample injecting section provided downstream of the mobile phase supplying apparatus in a flow path for analysis where the mobile phases are supplied from the mobile phase supplying apparatus; a separating column for separating an injected sample into its constituents, the separating column provided downstream of the sample injecting section; and a detector for detecting each of the constituents separated by the separating column, wherein when one of the plurality of actual flow rate measuring sections detects a back-flow in the corresponding liquid-feeding flow path, the corresponding actual flow-rate computing section computes an actual back-flow rate and outputs a signal to the corresponding control device, wherein the corresponding control device controls the corresponding liquid-feeding pump so as to cancel the back-flow based on the computed actual flow rate.