Chromatography

Chromatography
 Chromatography (from Greek chroma "color
and graphein "to write") is the collective term for a set
of laboratory techniques for the separation of
mixtures. The mixture is dissolved in a fluid called
the mobile phase, which carries it through a structure
holding another material called the stationary
phase. The various constituents of the mixture travel at
different speeds, causing them to separate. The
separation is based on differential partitioning
between the mobile and stationary phases.

Chromatography, literally "color writing", was first employed
by Russian scientist Mikhail Tsvet in 1900. He continued to
work with chromatography in the first decade of the 20th
century, primarily for the separation of plant pigments such
as chlorophyll, carotenes, and xanthophylls. Since these
components have different colors (green, orange, and
yellow,respectively) they gave the technique its name.

PRINCIPLES
 Chromatography usually consists of mobile phase and
stationary phase.The mobile phase refers to the
mixture of substances to be separated dissolved in a
liquid or a gas.The stationary phase is a porous solid
matrix through which the sample contained in the
mobile phase percolates.The interaction between the
mobile phase and the stationary phase results in the
separation of the compound from the mixture.

APPLICATIONS OF CHROMATOGRAPHY
 The chromatographic technique is used for the
separation of amino acids,proteins & carbohydrates.
 It is also used for the analysis of
drugs,hormones,vitamins & brain amines.
 Helpful for the qualitative & quantitative analysis of
complex mixtures.
 The technique is also useful for the determination of
molecular weight of proteins.

Paper chromatography
 Paper chromatography is a technique that involves
placing a small dot or line of sample solution onto a
strip ofchromatography paper. The paper is placed in a
jar containing a shallow layer of solvent and sealed. As
the solvent rises through the paper, it meets the
sample mixture, which starts to travel up the paper
with the solvent.



 Rf= Distance travelled by the substance
Distance travelled by the solvent front
The Rf value helps for the identification of unknown.

Sometimes,it is rather difficult to separate a
complex mixture of substances by a single run with
one solvent system. In such a case, a second run is
carried out by a different solvent system, in a
direction perpendicular to the first run. This is
referred to as two dimensional chromatography.

Thin layer chromatography
 Thin layer chromatography (TLC) is a widely employed
laboratory technique and is similar to paper
chromatography. However, instead of using a
stationary phase of paper, it involves a stationary phase
of a thin layer of adsorbent like silica gel, alumina,
or cellulose . Compared to paper, it has the advantage
of faster runs, better separations, and the choice
between different adsorbents.

GAS-LIQUID CHROMATOGRAPHY
 Gas chromatography (GC), also sometimes known as
Gas-Liquid chromatography, (GLC), is a separation
technique in which the mobile phase is a gas.It is the
method of choice for the separation of volatile
substances or the volatile derivatives of certain non-
volatile substances.
 Stationary phase is an inert solid material
impregnated with a non-volatile liquid.

 The mixture of volatile material is injected into the
column along with the mobile phase.
 The separation of the volatile mixture is based on the
partition of the components between the mobile
phase(gas) and stationary phase (liq.), hence the name
GAS-LIQUID CHROMATOGRAPHY.

 It is well suited for use in
the petrochemical,environmental monitoring and
industrial chemical fields.
 Sensitive, rapid and reliable.

ADSORPTION TLC
 Adsorbents such as activated silica gel, alumina,
kieselguhr are used.

ADSORPTION COLUMN
CHROMATOGRAPHY
 Column chromatography is a separation technique in
which the stationary bed is within a tube.Adsorbents
are packed into a column in a glass tube.This serves as
the stationary phase,leaving an open unrestricted path
for the mobile phase in the middle of the tube.
 Adsorbents such as silica gel, alumina, charcoal
powder & calcium hydroxyapatite are used.


 The sample mixture in a solvent is loaded on this
column.The individual compounds get differentially
adsorbed on to the adsorbent.
 The elution is carried out by the buffer system which is
the mobile phase.
 The individual compounds come out of the column at
different rates which may be collected separately &
identified.

ION EXCHANGE CHROMATOGRAPHY
 Ion exchange chromatography (usually referred to as
ion chromatography) uses an ion exchange
mechanism to separate molecules on the basis of their
electrical charges.Ion exchange chromatography uses a
charged stationary phase to separate charged
compounds including anions, cations, amino
acids, peptides, and proteins.

 Cation exchangers & anion exchangers are used as ion
exchange resins.
 In conventional methods the stationary phase is
an ion exchange resin that carries charged functional
groups that interact with oppositely charged groups of
the compound to retain.

GEL FILTRATION CHROMATOGRAPHY
 Size-exclusion chromatography (SEC) is also known
as gel permeation chromatography (GPC) or gel
filtration chromatography and separates molecules
according to their size, shape & molecular weight.
 It is also referred to as molecular sieving or molecular
exclusion chromatography.


 Smaller molecules are able to enter the pores of the
media and, therefore, molecules are trapped and
removed from the flow of the mobile phase.However,
molecules that are larger than the average pore size of
the packing are excluded and thus suffer essentially no
retention; such species are the first to be eluted.This is
how the molecules are separated.

 It is generally a low-resolution chromatography
technique and thus it is often reserved for the final,
"polishing" step of a purification. It is also useful for
determining the tertiary structure and quaternary
structure of purified proteins, especially since it can be
carried out under native solution conditions.

AFFINITY CHROMATOGRAPHY
 Affinity chromatography[6] is based on selective non-
covalent interaction between an analyte and specific
molecules, referred to as ligands.
 The immobilized ligands act as molecular fish-hooks
& selectively pick up desired proteins while the
remaining protein pass through the column.

HIGH PERFORMANCE LIQUID
CHROMATOGRAPHY (HPLC )
 Liquid chromatography (LC) is a separation technique in
which the mobile phase is a liquid. Liquid chromatography
can be carried out either in a column or a plane. Present
day liquid chromatography that generally utilizes very
small packing particles and a relatively high pressure is
referred to as high performance liquid
chromatography (HPLC).
 Since the chromatographic techniques are slow & time
consuming,hence the separation can be greatly improved
by using high pressure in the range of 5000-10000
psi(pounds per square inch),hence this technique is also
referred to as high pressure liquid chromatography.

 In HPLC the sample is forced by a liquid at high
pressure (the mobile phase) through a column that is
packed with a stationary phase composed of
irregularly or spherically shaped particles.
 The interaction between the mobile and the stationary
phase leads to the separation of the mixture.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

Chromatography

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