Flow injection analysis–capillary electrophoresis system with hydrodynamic injection Original Research Article

A flow injection analysis–capillary electrophoresis (FIA–CE) system with hydrodynamic injection has been developed. Sample is injected in an electrolyte carrier solution pumped continuously in the FIA part of the system. The interface, connecting the FIA and the CE system moieties, accommodates one end of the separation capillary and a platinum electrode. The other capillary end and the second platinum electrode are immersed in a separate vial containing electrolyte solution. Carrier outflow from the interface is provided by a pinch valve. When the sample plug in the carrier passes the capillary end in the interface, the pinch valve is closed and a fraction of the sample is forced into the capillary. The high voltage supply, shut off during this sample introduction cycle, is then resumed and separation takes place in the capillary. Repeated sample injections in one electrophoretic run are facilitated. The overall repeatability, expressed as relative standard deviation for eight consecutive injections of 50 mg l−1, was about 3%. Quantitative analyses can be accomplished ca. 5 times faster than that obtained using conventional CE instrumentation. The developed instrument was used to determine common inorganic cations (Na+, K+, Ca2+, Mg2+) in water and soft drink samples.