An in-house made autosampler for capillary electrophoresis

Researchers are developing customized capillary electrophoresis (CE) instruments due to their affordability, and versatility. CE's simplicity, compared to chromatography-based methods, allows for low-cost designs using commercially available components. Injection methods, however, necessitate particular attention because of the high reproducibility required for quantitative determinations. Traditional manual hydrodynamic and electrokinetic injections involve one or more actions by the user thus increasing the number of potential sources of error. Automation efforts, such as using syringe pumps and pressure controllers, have improved injection precision, achieving results comparable to commercial systems. Despite progress, many methods still require manual sample loading and flushing, highlighting the need for further innovation in CE automation.

A compact (26 x 9 × 9 cm) autosampler for a capillary electrophoresis (CE) system was designed, optimized and tested. The entire system was built in-house using the Open-Source Hardware (OSH) approach. It facilitates the fully automated analysis of a sequence of samples reducing the number of manual operations required by the user. The device allows hydrodynamic injection by pressure from six vials, as well as automatic rinsing of the capillary, and was coupled to a purpose made CE instrument with contactless conductivity detector (C4D). A precision better than 2.4 % was obtained for peak areas in the measurement of inorganic cations. The in-house made autosampler was used for analysing mineral water and the accuracies regarding the determination of the analytes were comparable to those observed for already published approaches.

The significance of this research lies in running automated analysis sequences with an in-house-built injector that performs on par with commercial systems. The open-source hardware approach simplifies upgrades, supports the integration of new features, and allows the creation of complementary devices, making the system highly adaptable to evolving challenges and requirements.