Direct on-line injection in capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Capillary electrophoresis (CE) is a powerful separation technique.
• Direct sample introduction into CE can be challenging due to physical limitations and potential disturbance of the capillary inlet.

Purpose of the Study:

• To develop and demonstrate a direct on-line sample introduction method for capillary electrophoresis.
• To evaluate the performance of different injection modes for this direct method.

Main Methods:

• A novel sample introduction system utilizing a cross configuration and high-voltage shunting was employed.
• Both full- and pinched-mode injections were investigated and compared.
• Reproducibility was assessed through replicate injections of nonoverlapping solutes.

Main Results:

• The direct on-line injection method requires no physical disturbance of the separation capillary inlet.
• Pinched-mode injection demonstrated superior performance compared to full-mode injection.
• Peak height reproducibility was better than 4.1%, and area reproducibility was less than 3.1% for nonoverlapping solutes.

Conclusions:

• The developed direct on-line injection method is feasible and effective for capillary electrophoresis.
• Pinched-mode injection minimizes injected volume and wall effects, leading to better performance.
• This method is adaptable to various capillary geometries and CE techniques.