Liquid feeding apparatus and liquid feeding method

A liquid feeding apparatus comprising:

• a liquid feeder having a downstream side, a plunger, and a cylinder, wherein the liquid feeder is configured for performing, when the plunger slides, an aspiration operation to aspirate a solvent and a discharging operation to discharge the solvent;
• a pressure sensor installed on the downstream side of the liquid feeder and configured to detect a pressure of the solvent to be discharged;
• at least one selector valve configured to switch between a plurality of solvents to be aspirated and discharged;
• and
• a controller configured to control the liquid feeder and the selector valve, wherein
• the controller is configured to control the selector valve in synchronization with the aspiration operation of the plunger so that a mixing ratio of the solvents changes, control an acceleration of the plunger to cause the plunger to operate at least at a first acceleration and a second acceleration that are different from each other, and suppress a fluctuation of the solvent to be aspirated by the plunger, and
• the second acceleration is negative, an absolute value of the first acceleration is larger than an absolute value of the second acceleration, and the controller causes the plunger to operate at the first acceleration in the aspiration operation and then operate at the second acceleration and stops the plunger.