Patent ID: 7311502

Claim:
A method of supplying solvent to a chromatographic system comprising: providing a hydraulic cylinder comprising: an inlet chamber; an outlet chamber; a primary piston disposed between said inlet chamber and said outlet chamber,; a secondary piston chamber; and a secondary piston disposed in said secondary piston chamber, wherein a cross-sectional area of said primary piston is larger than a cross-sectional area of said secondary piston, such that pressure in said secondary piston chamber is greater than a pressure in said inlet chamber, and a flow rate through said secondary piston chamber is less than a flow rate through said outlet chamber; providing a pump, said pump supplying pressurized hydraulic fluid; driving said primary piston with said pressurized hydraulic fluid; activating said secondary piston by said primary piston; moving and pressurizing said solvent; and supplying said pressurized solvent to said chromatographic system from said hydraulic cylinder.