Advantages and disadvantages of pneumatic pumps

These pumps, especially the direct gas displacement pumps, are the cheapest chromatographic pumps. With pneumatic amplifier pumps, it is possible to obtain high pressures (400 or 500 atm) at low cost. No electric power but only a gas supply and a pressure controller are required. 

However, in isochratic steady-state conditions, a constant pressure is generally 

It is impossible, however, to carry out column recycle chromatography even with pneumatic amplifier pumps because the compounds partially separated would be re-mixed in the hydraulic chamber. Here recycle operation must be understood 

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