The Diaphragm Pump
The unique property of the reciprocating diaphragm pump is that the actuating piston does not come into direct contact with the mobile phase and thus, the demands on the piston-cylinder seal are not so great. The diaphragm has a relatively high surface area and thus, the movement of the diaphragm is relatively small and consequently the pump can be operated at a fairly high frequency. High frequency pumping results in a very significant reduction in pulse amplitude and, in addition, high frequency pulses are more readily damped by the column system. Nevertheless, it must be emphasized that diaphragm pumps are not pulseless. A diagram of a diaphragm pump, showing its mode of action is depicted in figure 10
Figure 12. The Action of a Diaphragm Pump
