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

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, NO, and SO 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 for each anion, with LOD and LOQ being 0.02 mg L and 0.5 mg L, 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 (NH, Na, K, Ca, and Mg) at the high voltage side end with optimistic results.