9. AGAR OR AGAROSE GEL
Agarose gels are fragile
They are held together by weak hydrogen bonds
Pore size is large so used to separate large molecules such as
nucleic acids, large proteins and protein complexes
15. ELECTROOSMOTIC FLOW
(V.IMP)
■ DEFINITION
Electroosmotic flow (or electro-osmotic flow, often
abbreviated EOF; synonymous with electroosmosis or
electroendosmosis) is the motion of liquid induced by
an applied potential across a porous material,
capillary tube, membrane, microchannel, or any other
fluid conduit (a tube or channel for conveying water
or any other fluid).
18. EXPLANATION
The electroosmotic flow (EOF) is caused by applying high-voltage to an
electrolyte-filled capillary. This flow occurs when the buffer running
through the silica capillary has a pH greater than 3 and the SiOH
groups lose a proton to become SiO- ions. The capillary wall then has a
negative charge, which develops a double layer by attracting cations
towards it. Here cations get adhere to anions and this double layer
becomes stationary, while the other layer of cations along with anions is
free to move along the capillary tube. The applied electric field causes
the free cations to move toward the cathode creating a powerful bulk
flow. The rate of the electroosmotic flow is governed by the following
equation
μEOF=ϵEζ/4πη
19. ZETA POTENTIAL (IMP)
■ In this equation ε is the dielectric constant of the solution,
■ η is the viscosity of the solution, E is the field strength, and
ζ is the zeta potential. It is considered as the effective
charge on the particle
■ Because of the separation of positively charged particles
negatively charged particles, which are naturally attracted
to the positively charged anode, will separate out as well.
■ The EOF works best with a large zeta potential between
the cation layers.
20. DEFINITION
■ The potential difference existing between the surface of a
solid particle immersed in a conducting liquid (e.g. water)
and the bulk of the liquid.
OR
■ In other words, zeta potential is the potential difference
between the dispersion medium and the stationary layer of
fluid attached to the dispersed particle.
■ Units are volts(V) or millivolts(mV).
■ Zeta potential explain the stability of particles in a colloidal
system
21. EXPLANATION
■ Zeta potential is a measure of charges carried by particles suspended
in a liquid (mostly water).
■ Most particles suspended in water and wastewater, e.g. clays, silica,
hydrated metal oxides, paper fibers, biological cells, etc., possess
negative surface charges.
■ Positive ions in the solution are attracted to the negatively charged
surface where they may be strongly adsorbed.
■ The adsorbed layer remains rigidly attached and forms what is
known as the Stern layer.
■ Outside the Stern layer is a diffuse layer
■ In which positive ions outnumber negative ions and balance the
excess in the Stern layer.
■ The Stern layer and diffuse layer are called double layers.
