Low-conductivity background electrolytes in capillary zone electrophoresis--myth or reality?

Area of Science:

• Analytical Chemistry
• Separation Science
• Electrophoresis

Background:

• Electromigrational zone dispersion causes asymmetric peaks in capillary electrophoresis.
• Analyte concentration profiles in background electrolytes (BGEs) often exhibit broadening and asymmetry.

Purpose of the Study:

• Introduce the relative velocity slope (SBGE,X) as a parameter to characterize peak broadening and asymmetry.
• Develop SBGE,X vs. analyte ionic mobility diagrams for comparing BGEs.
• Determine optimal BGE composition for capillary zone electrophoresis.

Main Methods:

• Theoretical prediction of peak symmetry.
• Experimental verification using capillary zone electrophoresis.
• Analysis of strong electrolytes (sulfobenzoylated poly(ethylene glycols)) and weak electrolytes (monobasic phenols).

Main Results:

• SBGE,X diagrams effectively characterize peak broadening and asymmetry.
• BGE comparison based on pH, conductivity, pKa, and ionic mobilities is facilitated.
• Optimum BGE composition is primarily dictated by the co-ion's ionic mobility relative to the analyte's.

Conclusions:

• The relative velocity slope (SBGE,X) is a valuable tool for optimizing capillary electrophoresis separations.
• Proper selection of co-ion mobility in BGEs is crucial for minimizing peak asymmetry and broadening.
• Well-chosen monobasic electrolytes can outperform low-conductivity BGEs based on carrier ampholytes.