Integration of Forward-Scatter Interferometry-Based Refractive Index Detector Into Capillary Electrophoresis With...

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Separation Science

Background:

• Capillary electrophoresis (CE) is a powerful separation technique.
• Integrating universal refractive index (RI) detection with existing epifluorescence CE platforms is challenging.
• Existing methods often require separate detection systems or neutral markers.

Purpose of the Study:

• To demonstrate a simple, inexpensive method for adding universal RI detection to existing CE systems.
• To utilize the existing epifluorescence laser source for RI detection.
• To enable simultaneous, perfectly registered RI and fluorescence detection.

Main Methods:

• Developed a forward-scattered interferometry (FSI) approach using the epifluorescence laser.
• Added a bicell photodiode detector and alignment mechanism for FSI.
• Measured RI and fluorescence signals simultaneously from the same laser source and detection zone.

Main Results:

• FSI provides universal RI detection, complementary to specific fluorescence detection.
• Simultaneous detection yields perfectly registered electropherograms.
• FSI detects sample plugs, serving as intrinsic markers for electroosmotic flow (EOF).
• Continuous EOF monitoring demonstrated using thermal markers.
• FSI signal responds to RI and separation voltage, enhancing signal-to-noise at higher voltages.

Conclusions:

• FSI offers a simple and inexpensive way to add universal RI detection to existing CE-epifluorescence systems.
• This method provides intrinsic EOF markers and enables simultaneous, registered dual-channel detection.
• The approach improves CE analysis by reducing analysis time and enhancing peak efficiency.