shows Snyder solvent strength plots generated for each test
mixture compound using at least twelve butanol–water–acetic acid
mobile phases with the concentration of butanol varying from 0.75%
to 4% v/v. All ln k′ plots are bilinear, with the break occurring at the
same mobile phase composition (2.5% butanol in water with 0.2%
acetic acid) for each compound. Scott [9] has shown that saturation of
the C18 stationary phase by butanol occurs at 2.5% v/v.