Chapter 25 - Chromatographic Methods And Capillary Electrophoresis Flashcards
In electrophoresis ions experience what?
In electrophoresis ions experience an accelerating force from the electric field that is equal to the frictional force from the surrounding medium.
What is electrophoresis?
Electrophoresis is the separation of ions in solution under the influence of an electric field.
Electrophoretic mobility is…
Mobility is proportional to the charge of the ion and inversely proportional to the friction coefficient.
The movement of analyte in capillary electrophoresis is driven by, what?
It is driven by the diffuse part of the double layer inside the capillary
Which velocity profile is more uniform, hydrodynamic or electroosmotic?
The electroosmotic velocity profile is more uniform.
In capillary electrophoresis, when can an anion travel against the electrolyte flow, yet still be eluted near the cathode?
At a high pH
How can the flow be reversed in capillary electrophoresis?
By using a cationic surfactant layer.
Which sample injection method uses pressure to force the sample into the capillary?
Hydrodynamic injection
Which sample injection method uses an electric field to drive the sample into the capillary?
Electrokinetic injection
What is stacking, and does it increase resolution?
Stacking is when analyte is focused into narrow bands within the capillary.
Yes it also increases resolution.
What is indirect detection?
Indirect detection is when a substance with a steady background signal is added to the background electrolyte. In the analyte band, analyte molecules displace the background substance, so the detector signal decreases when the analyte passes by.
What is sieving?
Sieving is a process in which capillaries may be filled with material that allows small molecules to pass more freely than larger molecules.
What is PAGE?
Polyacrylamide gel electrophoresis.
- molecules are separated based on the number of charges they possess or on their size (larger = more friction)
In SDS PAGE what is the purpose of the SDS?
SDS (sodium dodecyl sulfate) is an anionic surfactant that binds to proteins and “coats” them so that they carry many negative charges… In this way, proteins are all uniformly negative and form long “rod like” structures and therefore separate by PAGE based only on their molecular weight.
What is the isoelectric point of a protein?
The isoelectric point or isoelectric pH of a protein is the pH at which it has a net charge of 0.
