A low-cost gradient system for high-performance liquid chromatography. Quantitation of complex pharmaceutical raw...

Area of Science:

• Analytical Chemistry
• Chromatography
• Separation Science

Background:

• Traditional gradient systems often involve expensive dual-pump setups.
• Achieving low dead volume and high reproducibility in gradient elution is crucial for accurate analysis.

Purpose of the Study:

• To describe a cost-effective gradient generation device utilizing an eight-port motor valve.
• To evaluate its performance in separating complex mixtures, particularly glycosides and alkaloids.
• To assess its suitability for quantitative routine control of pharmaceutical products.

Main Methods:

• Development of a gradient device with an eight-port motor valve and automatic control.
• Low-pressure gradient generation on the outlet side of a piston pump.
• Application to reversed-phase chromatography using water and organic solvent mixtures.
• Comparison with two-pump high-pressure gradient systems.

Main Results:

• The device achieves low dead volume and enables step gradient generation.
• Cost is approximately half that of dual-pump systems.
• Excellent reproducibility of retention data over several months.
• Quantitative determination of major components with <2% relative standard deviation using loop injectors.
• Successful application for analyzing complex mixtures of glycosides and alkaloids.
• Capability for injecting large sample volumes (up to 1 L) for trace analysis (<1 ppb).

Conclusions:

• The described gradient device provides a cost-effective and highly reproducible alternative for chromatographic separations.
• It is well-suited for quantitative analysis in pharmaceutical quality control.
• The system's versatility extends to large-volume sample injection for trace-level detection.