Patent ID: 7141161

Claim:
A liquid chromatograph comprising: a pump apparatus comprising: a first pump capable of mixing and feeding plural types of solutions; a second pump capable of feeding a solution; a switching valve for switching the solutions fed from said first pump to be sent to an analytic section with the solution fed from said second pump, or to be drained; a first pressure sensor for sensing a solution feed pressure of said first pump; a second pressure sensor for sensing a solution feed pressure of said second pump; and a control unit for computing the difference between the pressure sensed by said first pressure sensor and the pressure sensed by said second pressure sensor, extracting a solution feed pressure of said second pump in accordance with the computed pressure difference, shifting said switching valve such that the solutions fed from said first pump are sent to said analytic section with the solution fed from said second pump, and controlling operation of said second pump in match with shift timing of said switching valve such that the solution feed pressure of said second pump approaches at a value of said extracted solution feed pressure; a column; and a detector for liquid chromatography.