Simultaneous Absorbance and Fluorescence Measurements Using an Inlaid Microfluidic Approach.

Area of Science:

• Analytical Chemistry
• Microfluidics
• Optical Sensing

Background:

• Microfluidic devices offer advantages for chemical analysis due to reduced sample volumes.
• Simultaneous optical measurements (absorbance and fluorescence) can provide richer analytical information.
• Existing microfluidic optical cells may face challenges with light interference and path length limitations.

Purpose of the Study:

• To present a novel microfluidic optical cell for simultaneous absorbance and fluorescence measurements.
• To demonstrate the utility of an inlaid fabrication technique using poly(methyl methacrylate) (PMMA).
• To evaluate the performance of the developed optical cell for quantitative analysis.

Main Methods:

• Fabrication of a microfluidic optical cell using an inlaid technique with clear and opaque PMMA.
• Design features include a 20.2 mm long optical path for enhanced light interaction.
• Performance evaluation using rhodamine B dye for absorbance and fluorescence measurements across a concentration range.

Main Results:

• Achieved simultaneous absorbance and fluorescence measurements on microlitre fluid volumes.
• Demonstrated excellent linearity (R² > 0.99) for both absorbance and fluorescence from 0.1-10 µM rhodamine B.
• Accurately measured the molar attenuation spectrum of rhodamine B between 460-550 nm.

Conclusions:

• The novel microfluidic optical cell effectively enables simultaneous absorbance and fluorescence detection.
• The inlaid PMMA fabrication approach minimizes external light interference over centimeter path lengths.
• This technology represents a significant advancement for multipurpose lab-on-chip sensors in colorimetric and fluorescence assays.