Capillary Electrophoresis

Capillary electrophoresis is a technique which utilizes an electric charge to separate the different charged molecules according to their molecular properties, size and charge. The basic machine includes an injector, voltage source (30 kV), capillary column, detector and electrodes. Commonly used detectors include UV-Vis, hemi-luminescence, MS and fluorescence. This capillary is then filled with a buffer which is then connected to electrodes at both ends. When the voltage is applied, potential difference is formed which causes an electro-osmotic flow of charges in the buffer solutions. Usually they flow in the direction of the cathode (negative). Samples are then introduced in the buffer which migrates through the column to be separated by this electrophoresis technique. The separation also depends on the mobility and the interaction in the stationary phase. Neutral molecules, cations and anions are separated by this technique.

The coupling of CE with MS causes some of the similar problems that also occurred with LC-MS coupling. This is related to charged molecules and their high volumes in the liquid medium. That is why the CE-MS use same atmospheric pressure ionization interfaces which are also used by LC-MS instruments.

The CE is an older technique which is considered as new in terms of forensic sciences. The application of this in drug testing have caused many types of drugs of abuse like amphetamines, LSD, cocaine, heroin, barbiturates and benzodiazepines to be identified in different specimen samples. Even though the CE is used successfully in the forensic testing, the emerging technique of CE-MS coupling is causing newer explorations and findings in the field of forensic sciences, which also shows greater potential of discovering further compounds.

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