Liquid handling employing a moving drop for electrokinetic sample introduction system for capillary zone...

A simple cost-effective moving drop device, with solenoid valves control for programmable liquid handling, was developed for electrokinetic injection in capillary zone electrophoresis (CZE). With a CZE of 50-μm bore fused silica capillary tube and contactless conductivity detector (C4D), mixed anions (Cl^-, NO₃^-, and SO₄^2- as the model) solution was injected at the ground side. Simultaneous quantitative chemical analysis can be achieved. A linear relationship of concentration and the peak height was achieved in the range of 0.5-10 mg L^-1 for each anion, with LOD and LOQ being 0.02 mg L^-1 and 0.5 mg L^-1, respectively. The MVD-CZE system allows continuous operation with a sample throughput of 40 samples/hour. A real sample application was demonstrated for air samples, with one drop (25 μL) collected from a midget bubbler based air sampling unit. The recoveries were found to be 74.4-115.0 %. The developed device was also preliminarily applied for the injection of mixed cations (NH₄⁺, Na⁺, K⁺, Ca²⁺, and Mg²⁺) at the high voltage side end with optimistic results.