PUMPS 

The HPLC pump is considered to be one of the most important components in a liquid chromatography system which has to provide a continuous constant flow of the eluent through the HPLC injector, column, and detector. An understanding of each type of pump and familiarity with the advantages and disadvantages of each is extremely useful. The two basic classifications are the constant-pressure and the constant-flow pump. The first is used only for column packing and we will describe it only briefly. The second type is the most widely used in all common HPLC applications.

Standard HPLC pump requirements are
Flow rate range: from 0.01 to 10 ml/min
Pressure range: from 1 to 5,000 psi
Pressure pulsations: less than 1% for normal and reversed phase mode
less than 0.2% for size exclusion mode.