As the name of high-pressure liquid chromatography show need to generate the pressure, HPLC require high pressure which gives continuous and reproducible flow of mobile phase throughout the HPLC system, Pump must be able to take solvent from a single or more than one reservoir with pulse-free output and different flow rates, there are three types of pumps to provide the required pressure and flow rate as below.
The types of HPLC pumps are as follows.
Reciprocating Pump:
This is a common and widely used pump technique in modern chromatography because of his precise flow rate, generate high pressure, it should operate as an isocratic and gradient mode. It consists of a small motor-driven piston which moves quickly back and forth in a hydraulic chamber that can vary in the volume of a mobile phase. Produce pulsing flow is the major disadvantage of a reciprocating pump.
Syringe Pump:
This type of pump consists of a large syringe with a plunger motorized by the electronic motor to drive used to carry a constant flow rate to the stationary phase. It is inconvenient for the change of the mobile phase and also for its capacity. This is a simple technique used in the early years.
Pneumatic Pump:
In this type of pump mobile phase run into the column with the help of pressure created from a gas cylinder, this type of column provide continuous flow, this technique does not use as widely because have some limitations like the low capacity of solvents, generate low pressure, pump rate varies with viscosity.