Question

In preparing a hexane acetone gradient on a normal phase HPLC column, is it desirable to increase or decrease the proportion of hexane as the column is eluted?

Answer 1

A normal phase HPLC column contains polar functional groups terminated stationary phase. Thus from such a gradient, one should start with less polar solvent to high polar solvent in order to force the late eluting solutes to leave the column since they gets strongly adsorbed with the polar groups... Thus it is desirable to decrease the proportion of hexane