Electrophoresis microchip with integrated waveguides for simultaneous native UV fluorescence and absorbance detection

Area of Science:

• Analytical Chemistry
• Microfluidics
• Spectroscopy

Background:

• Electrophoresis microchips require sensitive detection methods for analyzing complex mixtures.
• Label-free detection is desirable to avoid sample modification and preserve native compound properties.
• Simultaneous detection of multiple signals can improve analytical information and reduce analysis time.

Purpose of the Study:

• To develop and demonstrate a simultaneous label-free detection system for UV absorbance and native UV-excited fluorescence in an electrophoresis microchip.
• To evaluate the performance of the system for compound detection and separation.
• To assess the benefits of simultaneous detection for compound identification and quantification.

Main Methods:

• Utilized UV transparent integrated waveguides for light delivery (254 nm) and collection within a 1-mm detection cell.
• Employed perpendicular detection geometry and a PMT insensitive to excitation light to suppress background scattering.
• Eliminated the need for a fluorescence filter by optimizing detection setup.
• Performed electrophoresis and microchip capillary electrophoresis (MEKC) separations.
• Measured calibration curves for serotonin, tryptophan, propranolol, and acetaminophen.

Main Results:

• Achieved simultaneous label-free detection of UV absorbance and native UV-excited fluorescence.
• Demonstrated successful separation of four model compounds using electrophoresis and MEKC.
• Detected all compounds in the micromolar range via absorbance.
• Improved detection limits by up to ten times for fluorescent compounds using fluorescence detection.
• Showcased the utility of simultaneous detection for identifying compounds with similar retention times and quantifying co-eluting compounds.

Conclusions:

• The developed system enables sensitive and simultaneous label-free detection of UV absorbance and native fluorescence in electrophoresis microchips.
• This approach enhances analytical capabilities for compound identification and quantification, particularly for co-eluting species.
• The elimination of fluorescence filters and optimized background suppression contribute to a simplified and effective analytical platform.