Capillary zone electrophoresis of phenol and methylphenols at high pH in methanol

Capillary zone electrophoresis of phenol and its three methyl-substituted derivatives (cresols) was investigated in water and methanol as solvents for the electrolyte. In water the acid strengths of o-cresol and p-cresol are too similar to allow their capillary zone electrophoretic separation. In pure methanol the differences in acid strength are amplified and all three cresols and phenol were clearly separated with use of pH 13-14 buffers prepared from maleic acid. The dependence of electrophoretic mobilities on pH in MeOH was investigated, and a slight difference was observed between theoretically calculated mobilities and measured mobilities. Maleate background electrolytes provided highly repeatable separations of the analytes. High pH medium in methanol appears to be a good choice for capillary zone electrophoretic separation of weak acids with similar acidity in water. The effective separation of 2,4-xylenol and 2,6-xylenol was also demonstrated.