Hand-Portable Gradient Capillary Liquid Chromatography Pumping System.

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Developing miniaturized and efficient gradient systems is crucial for modern analytical separations.
• Existing nanoflow systems often require complex splitters or lack precise gradient control.

Purpose of the Study:

• To develop and evaluate a novel, compact, splitless nanoflow gradient generator integrated with a stop-flow injector.
• To assess the performance of the system for accurate and reproducible gradient elution in liquid chromatography.

Main Methods:

• A gradient pumping system with two nanoflow pumps, micro stepper motors, a mixer, serpentine tube, and high-pressure valve was designed.
• The system was evaluated using an on-column UV-absorption detector and tested with pesticide and phenol mixtures.
• Gradient performance was assessed for accuracy, reproducibility, and separation efficiency on a monolithic capillary column.

Main Results:

• The developed gradient system is compact (4 kg), battery-operable, and capable of generating high pressures (up to 55 MPa).
• It achieves accurate nanoflow rates as low as 10 nL/min without a splitter, suitable for capillary columns.
• Excellent reproducibility was demonstrated for gradient steps (RSD < 1.2%) and retention times (RSD < 1.42%), with successful separation of complex mixtures.

Conclusions:

• The novel splitless nanoflow gradient generator provides a robust, portable, and high-performance solution for gradient elution liquid chromatography.
• The system's accuracy, reproducibility, and low flow rate capability make it highly suitable for capillary chromatography applications.
• This development facilitates advanced analytical separations with improved sensitivity and efficiency.