Biochemical Techniques and Instrumentation

2.7.2.2.1. Types of pumps

a. Reciprocating Piston Pumps

They consist of a small, motor driven piston, which moves rapidly back and forth in a hydraulic chamber. These pumps can push a solvent volume between 35-400 ml. On the backstroke, the column valve is closed and the piston pulls in the solvent from the mobile phase reservoir. On the forward stroke, the pump pushes solvent out to the column from the reservoir. Advantages of this pump are small internal volume, high output pressure of upto 10,000 psi, ready adaptability to gradient elution and constant flow rates. These pumps sometimes create small pulses, which can be corrected by pulse damper.

b. Screw-driven syringe pumps

Screw driven syringe displacement pumps are most suitable for small-bore columns because they deliver only a finite volume of solvent. These pumps can push a solvent volume between 250-500ml. They are pulse free and ideal for isocratic elution.