Liquid Chromatography - The LC Pump 1

The LC Pump

There are a number of different types of pumps that can provide the necessary pressures and flow-rates required by the modern liquid chromatograph. In the early years of the LC renaissance, there were two types of pump in common use; they were the pneumatic pump, where the necessary high pressures were achieved by pneumatic amplification, and the syringe pump, which was simply a large, strongly constructed syringe with a plunger that was driven by a motor. Today the majority of modern chromatographs are fitted with reciprocating pumps fitted with either pistons or diaphragms.

For more information on HPLC pump requirements see the pump section in the HPLC supplement.

The Pneumatic Pump

The pneumatic pump has a much larger flow capacity than the piston type pumps but, nowadays, is largely used for column packing and not for general analysis. The pneumatic pump can provide extremely high pressures and is relatively inexpensive, but the high pressure models are a little cumbersome and, at high flow rates, can consume considerable quantities of compressed air. A diagram of a pneumatic pump is shown in figure 4.

Figure 4. A Diagram of the Pneumatic Pump