05-07-2012, 02:47 PM
Electrophoresis
Electrophoresis.pdf (Size: 367.05 KB / Downloads: 54)
planar electrophoresis
porous layer 2-10 cm long - paper,
cellulose acetate, polymer gel
soaked in electrolyte buffer
slow
simple but difficult to automate
poor quantitation
large quantities (mL)
Capillary electrophoresis
narrow (25-75 mm diameter) silica
capillary tube 40-100 cm long
filled with electrolyte buffer
fast
complex but easy to automate
quantitative
small quantities (nL)
(A) Analyte dissolved in background electrolyte and pH buffer
(B) Silica capillary wall coated with silanol (Si-OH) and Si-O-
© Wall attracts cations - double-layer forms
(D) Cations move towards cathode and sweep fluid in one direction
Electroosmotic flow proportional to V - usually greater than
electrophoretic flow
Injection:
1. remove anode end capillary from buffer
2. place end of capillary in sample
3. apply field for short time (electrokinetic injection -
discriminates against low migration rate analytes)
or apply pressure for short time (pressure injection)
4. replace in buffer