Development of an on-chip injector for microchip-based flow analyses using laminar flow.

Area of Science:

• Analytical Chemistry
• Microfluidics
• Biotechnology

Background:

• Microchip-based flow analysis requires efficient sample injection methods.
• Conventional injection schemes can suffer from band broadening and peak asymmetry.
• Developing integrated, high-performance injectors is crucial for advancing microfluidic devices.

Purpose of the Study:

• To design and characterize a new on-chip injector for microchip-based flow analyses.
• To evaluate the injector's performance using fluorescence and amperometric detection.
• To demonstrate the injector's capability for sample lysis in a microfluidic format.

Main Methods:

• A microchip design with parallel laminar flow streams for buffer and sample.
• Utilized a conventional 6-port injection valve for sample loop loading and injection.
• Characterized performance using fluorescence detection of fluorescein and amperometric detection of catechol.
• Demonstrated erythrocyte lysis following injection into a sodium dodecyl sulfate flow stream.

Main Results:

• Fluorescence detection showed high reproducibility (RSD 1.18%) and low peak skew.
• Amperometric detection yielded a linear response (r(2) = 0.998) with a low limit of detection (155 nM).
• Significant reduction in plug dilution, band broadening, and peak asymmetry compared to off-chip methods.
• Successful demonstration of erythrocyte lysis within 5.72 seconds post-injection.

Conclusions:

• The new on-chip injector provides reproducible sample introduction with reduced band broadening and peak asymmetry.
• The device is compatible with various detection methods and enables real-time monitoring of concentration changes.
• This technology simplifies microfluidic systems by avoiding complex valving and high pressures.
• The injector facilitates rapid sample processing, such as erythrocyte lysis, within microfluidic devices.