Peak-shape correction to symmetry for pressure-driven sample injection in capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Separation Science
• Physical Chemistry

Background:

• Capillary electrophoresis (CE) often suffers from asymmetric peaks during pressure-driven sample injection.
• This asymmetry arises from differing shapes of the sample plug's front (parabolic) and back (flat) boundaries due to uneven flow velocity.
• Existing methods may not fully address peak asymmetry or sample transfer to cooled zones.

Purpose of the Study:

• To introduce and validate a novel pressure-driven propagation method for correcting peak asymmetry in capillary electrophoresis.
• To demonstrate that this method achieves peak symmetry comparable to electroosmotic injection.
• To show the utility of this method for sample transfer into actively cooled CE systems.

Main Methods:

• A pressure-driven propagation step was applied post-injection to reshape the sample plug interface.
• The sample plug was propagated to establish a parabolic sample-buffer interface at the back.
• Experimental validation was performed to assess peak symmetry and compare it with electroosmotic injection.

Main Results:

• The proposed propagation procedure effectively corrected peak asymmetry in pressure-driven injection.
• Achieved peak symmetry was comparable to that obtained with electroosmotic injection.
• The method facilitated efficient transfer of the sample plug into the cooled zone of the capillary.

Conclusions:

• Pressure-driven propagation is a simple and effective method for correcting peak asymmetry in capillary electrophoresis.
• This technique offers advantages for CE instruments with active cooling, improving sample handling.
• The method has broad applicability in CE techniques reliant on peak shape analysis, such as nonequilibrium capillary electrophoresis of equilibrium mixtures.