The maximum pressure that the pump can deliver depends on the following:
Selected flow rate
Viscosity of the solvent that is used in either channel (channel A or channel B)
For the pre-calibrated solvents, the graph shows how the maximum available pump pressure depends on the selected flow rate and channel.
For other solvents, observe the following:
For gradient flow rates up to 10 µL/min, use the aqueous (weak) solvent in channel A and the organic (strong) solvent in channel B.
If the total flow rate exceeds 10 µL/min and the expected system backpressure exceeds 140 MPa (1400 bar), use the solvent with the highest viscosity in channel A.
During operation, the pump continuously monitors whether the selected flow rate can be delivered at the resulting pressure. If the system backpressure becomes so high that the pump cannot deliver the selected flow rate, the following happens:
The injection or sequence is aborted.
A message appears indicating, for example, that the pump could not deliver the requested flow at this pressure (code 4531) or that the pressure exceeded the absolute limit (code 4503).
When you reduce the flow rate, the system backpressure decreases. At the same time, the amount of pressure available from the pump increases. If the pump is still unable to deliver the selected flow rate, reduce the system backpressure further. For example, by further reducing the flow rate, by increasing the column temperature, or by increasing the inner diameter of the fluidic capillaries.