Valveless gated injection for microfluidic chip-based liquid chromatography system with polymer monolithic column

Area of Science:

• Analytical Chemistry
• Microfluidics
• Chromatography

Background:

• Traditional liquid chromatography (LC) systems often involve complex mechanical valves for sample injection.
• Microfluidic systems offer miniaturization advantages but require precise control over fluid handling.
• Developing valve-less sample injection methods is crucial for simplifying microfluidic LC systems.

Purpose of the Study:

• To develop and characterize a microfluidic chip-based LC system with a novel valveless gated sample injection method.
• To demonstrate the system's capability for precise nanoliter-scale sample injection and efficient separation.
• To evaluate the impact of various parameters on system performance.

Main Methods:

• A microfluidic chip integrated with separation and balance columns was designed.
• A valveless sample injection was achieved using controlled syringe pump operation (ON/OFF states).
• A balance column was employed to equalize back pressure, facilitating gated injection.

Main Results:

• Nanoliter-scale sample injection (0.4–2.4 nL) was successfully implemented without mechanical valves.
• Two fluorescently labeled amines were separated in under 220 seconds using a 1 cm column.
• High theoretical plate counts (29,400–35,700 per meter) and low plate heights (28–34 μm) were achieved.

Conclusions:

• The developed valveless microfluidic LC system offers a simplified structure and ease of operation.
• The system provides convenient control over injection volumes and exhibits high sample loading capacity.
• This technology holds promise for efficient and miniaturized analytical separations.