Liquid chromatography on a monolithic column microfluidic chip coupled with "three-T" sample injection mode and...

Area of Science:

• Analytical Chemistry
• Microfluidics
• Electrochemistry

Background:

• Traditional liquid chromatography (LC) systems face challenges with sample dilution and leakage during separation.
• Microfluidic devices offer miniaturization advantages but often struggle with efficient sample introduction.
• Amperometric detection coupled with LC provides high sensitivity for analyzing electroactive species.

Purpose of the Study:

• To develop and validate a novel liquid chromatography microfluidic chip (LC chip) with amperometric detection.
• To implement a valve-free "three-T" injection mode for improved sample handling and separation efficiency.
• To demonstrate the chip's capability in separating challenging analytes, including isomers and biomolecules.

Main Methods:

• Fabrication of a 7.5 cm reversed-phase polymethacrylate monolithic LC microfluidic chip.
• Utilization of a unique "three-T" injection mode to prevent sample dilution and leakage.
• Integration of a home-made device for precise control of working electrode distance.
• Amperometric detection for quantitative analysis of separated compounds.

Main Results:

• Successful separation of catechol and hydroquinone isomers within 12 minutes with high reproducibility (RSD <3.0% for retention time, <2.4% for peak area).
• Separation and determination of 5-hydroxy-L-tryptophan, dopamine, and 5-hydroxytryptamine within 25 minutes.
• Achieved low detection limits (0.16-0.51 μmol/L) and good peak area reproducibility (RSD <5%).

Conclusions:

• The developed LC microfluidic chip with "three-T" injection offers superior performance compared to traditional methods.
• The system provides a robust, sensitive, and reproducible platform for analyzing complex mixtures.
• This technology holds promise for various analytical applications requiring efficient and precise separations.