How do they work
Worldwide there are about 30 manufacturer of high pressure, low pulsation laminar flow pumps.
Ther are three construction principles
1. Double head single piston pumps
2. Tripple head single piston pumps
3. Tandem also referred to as the accumulator-piston pumps as per
All LC pumps have a reciprocating piston design with two or three pump heads. The basic elements of the pump are a cylindrical pump chamber that holds the piston, a motor that operates a driving cam, a pump seal, and a pair of check valves. As the motor rotates, the piston is moved in and out of the pump chamber. In most pump designs, the pistons are made of sapphire, but also stainless steel and graphite are sometimes used. The check valves serve to control the direction of flow of mobile phase through the pump (flow is from bottom to top in all the figures).
In their simplest form, the valves comprise a ruby ball and a sapphire seat that is slightly ground (“lapped”) to ensure a leak-free seal when the ball rests on the seat. The valves open and close in response to pressure and gravity. The pump seal keeps mobile phase from leaking out around the piston when the pump is under pressure and keeps air from leaking in when the pump is filling.
Wit the accumulator piston pump the two pistons deliver at different rates. For example, let’s say that we want a flow rate of 1 mL/min; the top piston will operate at 1 mL/min and the bottom one at 2 mL/min. There are three check valves, an outlet (top) and an inlet (bottom) plus a middle check valve that acts as in inlet check valve for the top piston, but an outlet check valve for the bottom piston. In the cycle shown in Figure 3, the top piston delivers 1 mL/min to the column, with the outlet check valve open and the middle check valve closed, just as if it were a single-piston pump. Meanwhile, the bottom piston fills at 2 mL/min with an inlet check valve open and the middle check valve closed. On the alternate cycle (not shown), the bottom piston delivers at 2 mL/min; 1 mL/min serves to fill the top piston and the other 1 mL/min flows to the column. Thus, 1 mL/min of mobile phase always flows to the column. The accumulator-piston pump is also a very popular pump in modern LC and UHPLC systems.
The choice of pump differences is large. The obvious applications for such pumps is high pressure liquid chromatography. However application in other field such as MPLC, SFC, injection into geological structures etc etc. is permanently growing. When chosing your prefered pump we recommend to list the required parameters that are neccessary for your specifica application. This narrows down the choice to a few pumps.
If you need advice please dont hesitate to contact us with your requirements. We can supply a wide range of enhancement tools and various choices of software to make sure your project will be a success.
Be very carful on chosing the cheapest products available. Most companies and institution depreciate pumps over two or three years.
Our LCC Consensus HPLC pumps are of sturdy build. Some pumps installed in the market run allready for more then 20 years. HPLC pumps are sent and carried around. Our pumps are heavier then other HPLC pumps because they are build on solid base plates to assure sturdy design. Thick base plates of course makes them heavier.
For use in HPLC, MPLC, SFE and constant flow applications.