Exploring a reversible adaptation of conventional HPLC for capillary-scale operation

Area of Science:

• Analytical Chemistry
• Chromatography
• Instrument Development

Background:

• Conventional High-Performance Liquid Chromatography (HPLC) systems often operate at higher flow rates, posing challenges for miniaturized or capillary-scale analyses.
• Detecting analytes at capillary flow rates (1-10 µL/min) requires specialized cells to maintain sensitivity and minimize band broadening.
• Adapting existing HPLC infrastructure for microscale applications is desirable for cost-effectiveness and accessibility.

Purpose of the Study:

• To develop a feasible system for capillary-scale liquid chromatography using a conventional HPLC instrument.
• To engineer an active flow splitter and a compatible UV-visible detection cell for microflow rates.
• To validate the performance of the miniaturized system for analytical applications.

Main Methods:

• An Arduino Uno board was utilized to control a stepper motor-driven split valve, automating flow rate adjustments for capillary scale (1-10 µL/min).
• A custom-designed capillary UV-visible detection cell with a 14 nL volume and optimized optical path length was developed.
• System performance was evaluated using a lab-packed capillary LC column (0.25 mm x 15 cm, 3.0 µm C18) and model compounds (polycyclic aromatic hydrocarbons).

Main Results:

• The developed active flow splitter successfully achieved reproducible capillary-scale flow rates from a standard HPLC pump.
• The custom UV-vis cell minimized extra-column band broadening and enabled sensitive detection at microflow rates.
• Performance assessment demonstrated good theoretical plates, resolution, and minimal band broadening for polycyclic aromatic hydrocarbons.

Conclusions:

• The proposed system provides a profitable, reliable, and cost-effective solution for miniaturized liquid chromatography.
• This approach enables the use of conventional HPLC instruments for capillary-scale separations, expanding analytical capabilities.
• The integrated flow splitter and detection cell address key challenges in microscale chromatography, offering a practical tool for researchers.