UMD CHEM 425 - CE_ADV (11 pages)

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1 Introduction For this experiment we will be using capillary electrophoresis CE CE is an analytical lab technique that allows for the separation of different components within a compound by applying a voltage potential and exploiting their differences in electrophoretic mobility cp Electrophoretic mobility describes an analyte s ability to move in an electric field and is dependent upon its atomic radius ionic charge viscosity and the strength of the applied electric field In the event that two species are of the same atomic size the one with the larger charge will have a higher migration rate In the case where two atoms contain the same charge the atom with the smaller radius will have the higher migration rate Larger applied voltages are also associated with higher migration rates Species that contain no charge i e neutral species do not react to applied electric fields and are thus immobile meaning CE is not useful for analyzing such compounds In order to properly understand capillary electrophoresis one must first examine the instrumentation behind the technique An example of a typical instrumental set up for CE is depicted below in Figure 11 Most CE instruments usually consist of a high voltage power supply connected to the anode and cathode some sort of introduction system sample trays a capillary to connect the source and destination vials a detection method and an output device such as a computer1 In addition a temperature control device can also be included as part of the instrumentation This is to ensure there are no fluctuations in temperature that could cause a variance in viscosity a property that we want to keep constant for each analyte 2 Figure 1 Block diagram of a typical set up for Capillary Electrophoresis Instrument1 Each side of the capillary tube is placed inside of an aqueous buffer that contains the electrolytic species of study Prior to beginning the experiment it is important to make sure the capillary tube is rinsed out using the buffer