What is electroosmotic flow Why does it occur?
What is electroosmotic flow Why does it occur?
Electroosmotic flow occurs because the walls of the capillary tubing are electrically charged. The surface of a silica capillary contains large numbers of silanol groups (–SiOH). At pH levels greater than approximately 2 or 3, the silanol groups ionize to form negatively charged silanate ions (–SiO–).
What is electroosmotic flow how is it useful in separation of chemical substances in capillary electrophoresis?
Electroosmotic Flow The EOF works best with a large zeta potential between the cation layers, a large diffuse layer of cations to drag more molecules towards the cathode, low resistance from the surrounding solution, and buffer with pH of 9 so that all the SiOH groups are ionized.
What is the difference between electrophoretic mobility and electroosmotic flow?
Mobility is proportional to the q/r ratio (q = charge and r = solute size). Solvated cations drag water molecules during the migration, hence there is net solution movement from anode toward cathode. Electroosmotic flow results because of the electric double layer than forms near the capillary wall.
How does electroosmotic flow work?
Electroosmotic flow occurs when an applied driving voltage interacts with the net charge in the electrical double layer near the liquid/solid interface resulting in a local net body force that induces the bulk liquid motion.
What is capillary electrophoresis used for?
Capillary electrophoresis (CE) is the primary methodology used for separating and detecting short tandem repeat (STR) alleles in forensic DNA laboratories worldwide. This chapter examines the general principles and components of injection, separation, and detection of STR alleles using CE.
What is the purpose of capillary electrophoresis?
Capillary electrophoresis is used to generate aptamers for targets with an electrophoretic mobility different from that of DNA fragments.
Why is capillary electrophoresis important?
Capillary electrophoresis (CE) is an important technique for analytical chiral separations. It is applied, for example, in the pharmaceutical industry during different stages of drug development. It is very flexible with respect to the nature of the analytes and the separation conditions.
How can electroosmotic flow be reduced?
Electroosmotic flow can be reduced by coating the capillary with a material that suppresses ionization of the silanol groups, such as polyacrylamide or methylcellulose.
How do you control electroosmotic flow?
In aqueous capillary electrophoresis the electroosmotic flow (EOF) can be strongly suppressed or eliminated by coating the capillary surface silanols either by buffer additive adsorption or chemical modification.
What is capillary electrophoresis method?
Capillary electrophoresis, or CE, is a technique used in chemical analysis to separate molecules in an electric field according to size and charge. The molecules are then separated based on the difference in their velocity, which is influenced by charge, size, and the solvent’s viscosity.
What can capillary electrophoresis detect?
Which is the bulk flow in capillary electrophoresis?
Electrophoretic flow SiOH SiO- + H+ Electroosmotic flow is a bulk flow that is created by the build up of charge on a capillary wall. POP polymer minimizes this effect Electroosmotic flow Issues with CE separations
How is capillary electrophoresis different from HPLC and EOF?
Unlike HPLC, in capillary electrophoresis there is no mass transfer between phases. In addition, the flow profile in EOF-driven systems is flat, rather than the rounded laminar flow profile characteristic of the pressure-driven flow in chromatography columns as shown in figure 5.
How big is a capillary electrophoresis ( CE ) tube?
High-Performance Liquid Chromatography (HPLC) or Gas Chromatography (GC) use liquid and gas respectively to force the sample through a column, but electrophoresis utilizes an electric field. In capillary electrophoresis (CE), the conducting buffer is retained within a capillary tube whose inner diameter is typically 25–75 μm.
What are the different types of capillary electroseparation?
There are six types of capillary electroseparation available: capillary zone electrophoresis (CZE), capillary gel electrophoresis (CGE), micellar electrokinetic capillary chromatography (MEKC), capillary electrochromatography (CEC), capillary isoelectric focusing (CIEF), and capillary isotachophoresis (CITP).
What is electroosmotic flow Why does it occur? Electroosmotic flow occurs because the walls of the capillary tubing are electrically charged. The surface of a silica capillary contains large numbers of silanol groups (–SiOH). At pH levels greater than approximately 2 or 3, the silanol groups ionize to form negatively charged silanate ions (–SiO–). What…