Snyder solvent strength plots were generated for methanol using
five methanol–water–acetic acid mobile phases: 15%, 20%, 25%, 30%,
and 35% methanol in water with 0.2% acetic acid and for butanol using
at least twelve butanol–water–acetic acid mobile phases with the concentration
of butanol varying from 0.75%,−3% v/v. The methanol in
water and butanol in water mobile phases yielded plots similar to C18.
Therefore, log–log plots of retention [14] for C18 and C8 alkyl bonded
phase columns were constructed to better understand the differences
in behavior of these two alkyl bonded phases. Linear correlations with
slopes of unity in such plots are termed “homoenergetic” and are indicative
of the same retention mechanism for the two columns, whereas
linear correlations with slopes different from unity are termed “homeoenergetic”
and are indicative of similar but nonidentical thermodynamic
retention behavior. Log–log plots are shown in Fig. 6 for
methanol–water and in Fig. 7 for butanol–water. It is evident from an