Ch26-To-PDF

Ch26-To-PDF - Chapter 26 Section 5 and pp 611, 614, 615...

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Chapter 26 Section 5 and pp 611, 614, 615 Principles of Capillary Electrophoresis Capillary electrophoresis (CE) apparatus
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2 The Column A small single intact living cell just after injection onto a capillary
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3 In CE, in principle, there is no stationary phase: ( technically, not a chromatographic technique) Recall the van Deemter equation . .. Here, A = 0 and C = 0, and so and only longitudinal (diffusional) broadening is present. Thus, extremely high resolution is available with CE H = A + B + Cu x u x u x H = B CH 2 OH benzyl alcohol
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4 Total mobility of an ion down a capillary electrophoresis column has two main components – Electrophoretic Mobility and Electroosmotic Mobility Let’s take a look at each of these …
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5 Electrophoretic Mobility An ion in solution with charge q (coulombs) in an electric field E (V/m) reaches a constant velocity where f q E = u ep accelerating force frictional force u ep = q E = µ ep E f or = electrophoretic mobility = electrophoretic velocity of ion u ep ep = coefficient of friction of molecule in solvent f For a spherical particle of radius r moving through a fluid of viscosity, η , … = 6 πη r f Stokes equation Most molecules are not spherical, but this defines an effective hydrodynamic radius of the particle.
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6 Electroosmotic Mobility At pH < ~2 the capillary surface is neutral. At pH > ~3 the capillary surface is strongly anionic. This negative charge leads to the establishment of an electrical “double layer” as follows:
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7 The strong negative charge tightly adsorbs cations from solution. These
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Ch26-To-PDF - Chapter 26 Section 5 and pp 611, 614, 615...

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