A multireflection cell for enhanced absorbance detection in microchip-based capillary electrophoresis devices

Area of Science:

• Microfluidics and Analytical Chemistry
• Optical Sensing Technologies

Background:

• Microchip-based capillary electrophoresis (CE) systems require sensitive absorbance detection.
• Existing planar absorbance cells often lack sufficient optical pathlength for high sensitivity.

Purpose of the Study:

• To design, fabricate, and test a novel glass-based multireflection absorbance cell for microfluidic devices.
• To achieve enhanced sensitivity and ease of manufacturing compared to previous designs.

Main Methods:

• Photolithographic fabrication using a three-mask process to create aluminum mirrors within a glass chip.
• Integration of a flow channel with optical apertures for light path manipulation.
• Calibration using bromothymol blue (BTB) with a He:Ne laser source.

Main Results:

• Achieved linear calibration curves (r2 > 0.9997) for BTB up to 0.5 absorbance units.
• Demonstrated effective optical pathlengths of 50-272 microm, a 5-10 fold increase over single-pass.
• Observed minimal impact of pathlength on baseline absorbance noise.

Conclusions:

• The developed multireflection absorbance cell significantly enhances sensitivity for microfluidic applications.
• The photolithographic fabrication method offers a more manufacturable alternative to existing planar devices.
• This technology holds promise for improved detection in capillary electrophoresis and other microfluidic analyses.