The setup of an electrochromatograph is, at least in principle, simple (Fig. 2). Identically as in LC and CE instruments, it comprises three basic parts: injector, separation column, and detector. The high-voltage power supply serves the mobile-phase propulsion through the column by EOF, instead of the pump used in LC. Mostly, either commercial electrophoreographs or laboratory-made devices are used, still substituting specialized CEC instrumentation. Sometimes, a slightly more complicated setup incorporating hydraulic pressure capabilities is employed. The pressure can be applied the same either on both ends of the CEC column maintaining the bubble suppression, or on the injection side only. The latter method is called pressure-assisted CEC and forms a connecting link to pressure-driven LC.
For the injection, the dip of the end of the CEC column into the sample vial and subsequent electrokinetic sample sucking is frequently used (Fig. 2, position A), which is very simple but could bring about a decrease of repeatability. To overcome this problem, another sample injection method exploiting a sample and mobile-phase flow splitter was developed.[10,22]
Because of the predominantly chromatographic character of CEC separation, the mobile-phase gradient elution is important to attain higher peak capacity and shorter separation time, especially for complex samples
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