The role of the pump is to force a liquid (called the mobile phase) through the liquid
chromatograph at a specific flow rate, expressed in milliliters per min (mL/min).
• Normal flow rates in HPLC are in the 1- to 2-mL/min range.
• Typical pumps can reach pressures in the range of 6000-9000 psi (400- to 600-bar).
• During the chromatographic experiment, a pump can deliver a constant mobile phase composition
(isocratic) or an increasing mobile phase composition (gradient).