Abstract: A sample solution is sent into a concentration column through a three-way joint and a three-way switching valve to trap and concentrate the sample components on the concentration column, followed by injecting the sample solution into an injector by operating a first dilution solvent pump. When a large volume of the sample solution is to be sent or when the sample solution has a high solvent strength, trapping and concentration on the concentration column may be facilitated by replacing the sample solvent with a second dilution solvent by allowing the second dilution solvent to flow into the three-way joint after setting the flow rate of the second dilution solvent from a second dilution solvent vessel to a prescribed flow rate using a second dilution solvent pump.

Abstract: A sample solution is sent into a concentration column through a three-way joint and a three-way switching valve to trap and concentrate the sample components on the concentration column, followed by injecting the sample solution into an injector by operating a first dilution solvent pump. When a large volume of the sample solution is to be sent or when the sample solution has a high solvent strength, trapping and concentration on the concentration column may be facilitated by replacing the sample solvent with a second dilution solvent by allowing the second dilution solvent to flow into the three-way joint after setting the flow rate of the second dilution solvent from a second dilution solvent vessel to a prescribed flow rate using a second dilution solvent pump.

Abstract: A liquid transfer pump includes a housing having an inner space, a cross head disposed in the inner space of the housing and attached to a driving mechanism to reciprocate inside the housing, a plunger attached to and held by a plunger holder of the cross head, and a pump head situated near the cross head. The pump head includes a pump chamber with an inlet path and an outlet path, and the plunger is disposed in the pump chamber to be reciprocated therein together with the cross head. A resilient O-ring is disposed in the plunger holder, and a plunger seal is disposed in the pump head, wherein one side of the plunger is engaged with and held by the resilient O-ring and the other side of the plunger is engaged with and held by the plunger seal. Accordingly, the plunger can be flexibly supported by the O-ring and the plunger seal. The plunger seal can be used for a long time without leakage.

Abstract: In the inventive plunger pump, a plunger is pressed on a shaft by a spring via a thrust bearing having rolling elements clamped by a pair of bearing washers. By such a configuration, the motion of the shaft is immediately transmitted to the plunger, irrespective of whether the radius of the profile of a cam for driving the shaft back and forth is in the increment phase or decrement phase, so that the suction and discharge of liquid is performed without delay, since no play (or gap) exists in the transmission mechanism between the cam and the plunger. Thus, the fluctuation in the pressure is minimized during the operation of the pump and, when a low pressure gradient elusion is carried out, the solvents are supplied at the desired flow rates accurately.