Liquid Chromatography - The Single Piston Reciprocating Pump

The pump takes the form of a large metal syringe, the piston being propelled by an electric motor and driven by a worm gear. The speed of the motor determines the pump delivery. Another motor actuates the piston by a different system of gearing to refill the syringe rapidly when required. The solvent is sucked into the cylinder through a hole in the center of the piston and between the piston and the outlet there is a coil that acts as a dampener. This type of pump is still occasionally used for the mobile phase supply to microbore columns that require small volumes of mobile phase to develop the separation. It is also sometimes used for reagent delivery in post column derivatization as it can be made to deliver a very constant reagent supply at very low flow rates.

The Single Piston Reciprocating Pump

The single piston reciprocating pump was the first of its type to be used with high efficiency LC columns (columns packed with small particles) and is still very popular today. It is simple in design and relatively inexpensive. A diagram of the single piston pump is shown in figure 7.

Figure 7. A Single Piston Reciprocating Pump