Two LAMBDA peristaltic pumps are used to mix the eluents for gradient elution.

1. The change in the composition over time can be programmed directly on LAMBDA peristaltic liquid pumps or it can be recorded and displayed as a real-time graph using the PNet PC control software.
2. PNet process control software allows to remote control the peristaltic pumps and generate the gradients.
3. The gradient mixture passes through the liquid chromatography column and the components are separated.
4. The eluate from the column passed through the detector to measure the pH, absorption 280 nm and conductance.
5. Automated fraction collector LAMBDA OMNICOLL, fractionates the eluate and collects the fractions based on the programmed time or drop counter.

Gradient elution can also be carried out with one peristaltic pump: the containers with elution buffer A & B are connected by a siphon or tube at the bottom with a valve to adjust the flow.

1. Elution buffer A is consistently drawn into the well-stirred beaker with elution buffer B, where the buffer concentration being altered.
2. Programmable LAMBDA peristaltic pump used to pump the gradient mixture into the liquid chromatography column.
3. The eluate from the column passed through the detector to measure pH, Absorbance 280 nm & conductance.
4. From the detector, the eluate fractionation collected by the OMNICOLL fraction collector into the desired containers (e.g.: bottles, beakers, tubes, vials, etc.).

The most important requirements of the pumping system for column chromatography are:

• Constant and reproducible flow rate
  The reproducibility depends on the retention times of the peaks. The retention times are again dependent on the flow rate.

• Pulsation-free flow
  The stationary phase has to be protected against pressure surges. The baseline of the detector should remain stable.