Multi-dimensional liquid chromotography with second dimension having a variable flow rate

The multi-dimensional liquid chromatography system, comprising at least one of:

• the control unit is configured to operate the first flow rate of the first mobile phase as a function of the second flow rate of the second mobile phase;
• the control unit is configured to operate the second liquid chromatography system during the second chromatographic separation according to the control value different from the second flow rate, so that a variation in the control value can lead to a variation in the second flow rate.

A method of multi-dimensional liquid chromatography, the method comprising:

• providing a first chromatographic separation of a sample fluid comprised in a first mobile phase and providing a first effluent comprising at least a portion of the separated sample fluid, by maintaining a first flow rate of the first mobile phase substantially constant during the first chromatographic separation, and providing a second chromatographic separation of at least a portion of the first effluent comprised in a second mobile phase, by operating according to a control value different from a second flow rate of the second mobile phase.