%-Gradient

A change in the composition of the delivered solvent mixture during the analysis in liquid chromatography is referred to as a gradient. Usually, the eluting power of the solvent is increased to accelerate the elution of the later eluting substances.

To distinguish this gradient type from the Flow Gradient, which is quite unusual in liquid chromatography, it is also referred to as a %-gradient. The composition can be modified immediately (Step Gradient) or over a certain period (Ramp).

 Tips:

Depending on the dead volume of the pump, the time required for changing the mixing ratio varies. The greater the dead volume is, the later the new mixing ratio will be realized on the pump output and the later the solvent mixture will reach the column. Therefore, make sure to perform gradient courses in sensible intervals.

Usually, the solvent composition at the beginning of the analysis widely differs from the composition at the end. Therefore, before you start the next analysis, make sure that the column has been sufficiently conditioned, that is, that the solvent composition in the column corresponds again to the original composition at the beginning of the analysis.