Capillary zone electrophoresis in methanol: Migration behavior and background electrolytes

Nonaq. (NA) solns. are often used as background electrolytes (BGEs) and NA solvents are added to aq. BGEs as org. modifiers in capillary zone electrophoresis (CZE), to optimize the sepns. This can be tricky, however, because the pH* and pK* concepts may be totally different in NA solvents, whereas often less knowledge is available concerning phenomena, such as system zones, applying NA solvents. The concepts of pH* and pK* are considered for methanol as a solvent and pK* values are detd. for several components in mixts. of water and methanol. With a math. model, adapted for calcns. in methanol, parameters are calcd. describing the fronting or tailing character of peaks and the question of peaks or dips, and the existence of system zones is discussed for pure methanol as a solvent. These aspects are exptl. verified, applying BGEs useful for the sepn. of cationic species in the indirect UV mode. The math. model developed for aq. BGEs is applicable to BGEs in methanol, too, and the behavior of BGEs in methanol is comparable with that in water concerning the fronting or tailing character of peaks and the question of peaks and dips, although the mobilities and pK values can change significantly. [on SciFinder (R)]