Chromatographic behavior of chlorophyll derivatives on reversed phase HPLC was evaluated using four parameters : inorganicity/organicity ratio, group electronegativity, molar volume and molar refractivity. For ten pigments, chlorophyll
a and
b, , pheophytin
a and
b, pyrochlorophyll
a and
b, pyropheophytin
a and
b and methyl pheophorbide
a and
b, the plot of the natural logarithm of the capacity factor, ln
k', against the inorganicity/organicity ratio was linear. However, the plots of ln
k' against group electronegativity, molar volume and molar refractivity were not linear. A plot of ln
k' against the inorganicity/organicity ratio of the mobile phase, examined in analogy with a plot of ln
k' against Snyder's parameter P', was linear. The large variations of interactions, dipole interaction or dispersion force, between the solutes and the two phases caused the plot of ln
k' against the inorganicity/organicity ratio to be nonlinear. However, the inorganicity vs. organicity plot, namely the organic conceptional diagram, readily affords the relationships between the polarities of the solutes, the mobile phase and the stationary phase. Therefore, the effectiveness of the inorganicity/organicity ratio for retention predictions of solutes on HPLC became apparent.
View full abstract