Modular, cost-effective, and portable capillary gradient liquid chromatography system for on-site analysis

This work demonstrates the development of a compact, modular, cost-effective separation system configured to address a specific separation problem. The principles of the separation are based on gradient capillary liquid chromatography where the system consists of precision stepper motor-driven portable syringe pumps with interchangeable glass syringes (100 µL to 1000 µL). Excellent flow-rate precision of ≤ 1% RSD was achieved with typical flow-rates ranging from 1 µL/min to 100 µL/min, which was ideal for capillary columns. A variable external loop volume and electrically actuated miniature injection valve was used for sample introduction. Detection was based upon a commercial Z-type UV absorbance flow-cell housed within a custom-built cooling enclosure (40 mm x 40 mm) which also contained a UV-LED light-source and a photodiode. System and chromatographic performance was evaluated using linear gradient elution, with day to day repeatability of n = 6) for peak area, and n = 6) for retention time, for the separation of a 5 component mixture using a 50 mm X 530 µm ID C18 3 µm particle capillary column. The system can run any commercial or in-house packed columns from 50 mm to 100 mm length with IDs ranging from 200 to 700 µm. The developed portable system was operated using custom-built windows-based chromatography software, complete with data acquisition and system control