HPLC pumps are positive displacement pumps. They use a reciprocating piston and check valves to give a constant flow. Typical HPLC pumps have heads as shown below. At the front of the head there are two check valves (these have the red balls). These allow the fluid to only flow in one direction (in the diagram below the flow is from bottom to top). As the piston moves forward the liquid is pushed up through the outlet check valve. The inlet check valves prevent the liquid flowing back to the reservoir. When the piston is withdrawn (the fill stroke) the liquid is pulled into the pump chamber through the inlet check valve). To help the flow the inlet lines are typically larger than the outlet. For most of our HPLC pumps the inlets are 1/8 whilst the outlets are 1/16. Some HPLC pumps have secondary sets of check valves to allow the piston seals to be flushed. This can be particularly beneficial when pumping salts or buffers as these can quickly degrade the piston seals. Sometimes this effect can be dramatic and extend the seal life time from a few weeks to months.
What are typical applications for HPLC pumps?
HPLC pumps can be used for a wide variety of applications. This ranges from simple metering applications, to HPLC, UPLC, Core flooding and a wealth of different applications. Typically, HPLC pumps are better for applications that require a constant flow over a long time period, or for higher pressures (typically they are used with pressures of 10-400bar, but models are available that will deliver more than 1000bar) Our HPLC pumps are able to work continuously for weeks or months.
Which applications are not recommended for HPLC pumps?
Whilst HPLC pumps are versatile and reliable there are some applications where the use of a syringe pump or peristaltic pump are preferred. These are typically Dosing an accurate volume (syringe pumps are better). Most piston HPLC pumps do not have timers, and whilst it is possible to calculate the amount pumped as “Flow rate x Time” this will not be as accurate as a syringe pump particularly over small periods of time (less than 1min). This is due to the acceleration/deceleration times for the motors and to make allowances for the backstroke. Pumping multiple lines. This is better used with peristaltic pumps or sometimes a multiple capacity syringe pump.