The use of two pump modules enables the formation of a binary gradient. The solvents enter the pump heads via the aspiration tubing (input) (solvent A and B). The FEP tubing guides the solvent to the mixing chamber with integrated pressure sensor and from there via the injection system on to the column via the pressure tubing (output). The Pump Manager C-615 regulates the flow rate of the pump modules 1 and 2 and monitors the current pressure. The maximum pressure for Pump Module C-601 is 10 bar (145 psi) and for Pump Module C-605 50 bar (725 psi). In addition, a variety of programs and settings enables the selection of flow rate, pressure, time and gradient of the solvents.