Yc. Guillaume et al., Migration behavior modeling of anionic species in a hydroorganic background electrolyte, J LIQ CHR R, 23(18), 2000, pp. 2789-2806
The migration of benzoate derivatives in a hydroorganic background electrol
yte (BGE) was predicted using a novel mathematical model. In capillary elec
trophoresis (CE), with an acetonitrile (ACN)/buffer mixture as BGE, the inf
luence of pH and the ACN cluster fraction can be quantitatively described b
y a general equation which was used to study the separation optimization. T
he cluster solute solvation energies in an ACN/buffer mixture over a 0.50-0
.80 buffer fraction were calculated.
The energetics of the ACN cluster exchange process in the BGE was investiga
ted in relation to the difference in pK(a) (Delta pK(a)) between a solute u
sed as reference and the other solutes. A linear correlation was found betw
een the Gibbs free energy change of the solvent exchange process and Delta
pK(a) confirming that the solute solvation by ACN clusters was enhanced for
the lesser polar solutes.
Enthalpy-entropy compensation revealed that the solute solvation mechanism
was independent of both the benzoate derivative structure and the BGE ionic
strength.