CE - Capillary Electrophoresis The heart of capillary...

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Capillary Electrophoresis The heart of capillary electrophoresis (CE) is electroosmotic flow (EOF). This is the mobile phase “pump” in CE. Unlike gas chromatography (GC), there is no pressurized gas acting as the mobile phase in CE. Unlike high performance liquid chromatography (HPLC) these is no (high pressure) pumped mobile phase. And unlike paper chromatography, there is no capillary action that pulls the solvent through the stationary phase. Instead, the electrical potential maintained across the CE’s capillary tube by the electrical circuit of the 1) capillary, 2) buffer, 3) reservoirs, 4) electrodes, and 5) power supply sets up some pretty interesting conditions that makes the buffer solution flow from one buffer reservoir to the other, just as if it were being pumped. This flow is called electroosmotic flow . Here’s what a naked fused silica capillary column looks like. They’re often between 25 and 100 μm inside diameter and the walls—if they’re uncoated, and this is important—are negatively charged because the inside wall has silanol groups (SO x - ). This means that the inner wall has a net negative charge, The buffer solution in each reservoir has equal amounts of cations and anions, and the capillary ends are each placed in a buffer reservoir. Each reservoir also has an electrode connected to the power supply. When the voltage is applied to the circuit, one electrode become net positive and the other net negative. The (wall’s) immobile silanol anions pair with mobile buffer cations, forming a double layer along the wall (wall--> buffer cations-->buffer anions-->bulk buffer solution). The remaining buffer cations are attracted to the negative
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This note was uploaded on 03/03/2012 for the course CHEM 100 taught by Professor Chasteen during the Fall '06 term at Sam Houston State University.

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CE - Capillary Electrophoresis The heart of capillary...

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