[The application of multi-pulse stripping amperometric detection to capillary electrophoresis]

There are some drawbacks in amperometric detection in capillary electrophoresis since there is influence of high voltage from electrophoretic instrument. Three electrodes of electrochemical detection system and electrochemical system of capillary electrophoresis are separately placed in capillary outlet buffer reservoir, which can lead to a reduction in the influence of high voltage in the great degree. A carbon fiber with diameter of 7 microns is used as working electrode, and placed just at the separation capillary outlet. The multi-pulse stripping amperometric detection has 1.1 s deposition step and several stripping steps with 0.02 s, which can increase the detection amperometric current and identify the species of each separated component in some classes by different pulse stripping potentials. This detection technique was applied in the separation of Cu, Zn, Pb, Tl and Cd of 25 mg/L by the capillary electrophoresis, and separation efficiency is over 60 thousands theoretical plates. The limit of the multi-pulse stripping amperometry detection was 0.10 microgram/L for cadmium by using water plug field amplified injection.