Abstract: There is disclosed a maintenance reminder system for a pump. The system of the invention is coupled to the pump or the control system for the pump and determines the volume of fluid pumped by the pump. In the preferred embodiment, a piston pump is used and piston strokes are counted and converted to total volume of liquid pumped. The computer of the system maintains a database for each maintenance item containing the threshold value for each item and the total volume pumped since the last maintenance. When the total volume exceeds the threshold, a maintenance reminder is displayed and the user may display information from the database as to which item needs service. The computer updates the appropriate fields of the database after the service is performed.

Abstract: There is disclosed herein an apparatus and method for controlling a dual piston pump for a liquid chromatography system so as to pump a flow of solvent through the liquid chromatography column at a constant flow rate and with a solvent composition which is substantially equal to the desired solvent composition despite changing conditions of compressibility of the solvent. The control system uses a computer which measures the time it takes the pump shaft to move through an overlap region in the pump cycle when both pistons are simultaneously pumping as normalized to the time taken by the pump to move through a constant velocity portion of the piston travel defined by the user.

Abstract: An apparatus and method controls a dual piston pump for a liquid chromatography system so as to pump a flow of solvent through the liquid chromatography column at a constant flow rate and with a solvent composition which is substantially equal to the desired solvent composition despite changing conditions of compressibility of the solvent. A computer is used which measures the time it takes the pump shaft to move through an overlap region in the pump cycle when both pistons are simultaneously pumping as normalized to the time taken by the pump to move through a constant velocity portion of the piston travel defined by the user. This time is compared to the time stored in the computer for the particular flow rate used to measure the time defined above for the pump to move through the overlap region for an incompressible solvent at low pressure as normalized to the time taken by the input piston to move through the same user defined segment of the constant velocity portion of the travel of the input piston.

Abstract: Apparatus and method for liquid chromatography applicable to systems employing more than one solvent for the carrier. The forming of bubbles in the pumping means employed is prevented by special pretreatment of at least one solvent of the carrier, the pretreatment involving sparging of the solvent with inert gas.