Capillary zone electrophoresis in methanol: migration behavior and background electrolytes

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Nonaqueous (NA) solutions and organic modifiers are crucial for optimizing separations in capillary zone electrophoresis (CZE).
• Understanding pH* and pK* in NA solvents is challenging, with limited knowledge on phenomena like system zones.
• Methanol is a common NA solvent used in CZE.

Purpose of the Study:

• To investigate the concepts of pH* and pK* in methanol as a solvent for CZE.
• To determine pK* values for components in water-methanol mixtures.
• To develop and validate a mathematical model for predicting peak characteristics and system zones in NA CZE.

Main Methods:

• Determination of pK* values in various water-methanol mixtures.
• Adaptation of a mathematical model for calculations in methanol.
• Experimental verification using background electrolytes (BGEs) for cationic species separation in indirect UV mode.

Main Results:

• The study determined pK* values for several components in water-methanol mixtures.
• A mathematical model was developed to describe peak fronting/tailing and the existence of system zones in methanol.
• Experimental results confirmed the model's applicability and showed comparable peak behavior to aqueous systems.

Conclusions:

• The mathematical model developed for aqueous BGEs is applicable to BGEs in methanol.
• Behavior of BGEs in methanol is comparable to water regarding peak characteristics and system zones.
• While mobilities and pK values can change significantly, the predictive model aids in optimizing NA CZE separations.