The document discusses mobile phases in various chromatography techniques. It defines that the mobile phase is a liquid or gas that carries components of a mixture through a stationary phase. The stationary phase interacts differently with each component, causing them to move through the mobile phase at different rates and separating the mixture. The document then provides examples of typical mobile phases used in different chromatography methods, such as gas chromatography, thin layer chromatography, reverse phase chromatography, and more.

1. Mobile phase in chromatography
MD.JABIUR RAHAMAN
DAFFODIL INTERNATIONL UNIVERSITY,BANGLADESH
DEPT. OF PHARMACY

2. Chromatography is a method by which a mixture is separated by
distributing its components between two phases. The stationary
phase remains fixed in place while the mobile phase carries the
components of the mixture through the medium being used. The
stationary phase acts as a constraint on many of the components in
a mixture, slowing them down to move slower than the mobile
phase. The movement of the components in the mobile phase is
controlled by the significance of their interactions with the mobile
and/or stationary phases. Because of the differences in factors such
as the solubility of certain components in the mobile phase and the
strength of their affinities for the stationary phase, some
components will move faster than others, thus facilitating the
separation of the components within that mixture.

3. Mobile phase in Gas Chromatography
A gas chromatograph is a chemical analysis instrument for separating
chemicals in a complex sample. A gas chromatograph uses a flow-
through narrow tube known as thecolumn, through which different
chemical constituents of a sample pass in a gas stream (carrier
gas, mobile phase) at different rates depending on their various
chemical and physical properties and their interaction with a
specific column filling, called the stationary phase. As the chemicals
exit the end of the column, they are detected and identified
electronically. The function of the stationary phase in the column is
to separate different components, causing each one to exit the
column at a different time (retention time). Other parameters that
can be used to alter the order or time of retention are the carrier
gas flow rate, column length and the temperature.

4. Mobile phase in TLC
They all have a stationary phase (a solid, or a
liquid supported on a solid) and a mobile
phase (a liquid or a gas). The mobile phase
flows through the stationary phase and carries
the components of the mixture with it.

5. Mobile Phases in Reverse Phase
chromatography
In reverse phase applications water is usually
the base solvent. Other polar solvents such as
Methanol, Acetonitrile or Tetrahydrofuran are
added in fixed or varying proportions. pH is
adjusted by buffers to modify separations of
ionizable solutes. Ion-pairing reagents also
enhance separation selectivity of charged
analytes by increasing retention on
hydrophobic bonding phases.

6. Mobile Phases in Normal Phase
Chromatography
Typically non polar solvents such as hexane,
heptane, iso-octane are used in combination
with slightly more polar solvents such as
isopropanol, ethyl-acetate or chloroform.
Retention increases as the amount of non
polar solvent increases in the mobile phase.

7. Mobile Phases in Ion Exchange
Chromatography
Aqueous salt solutions are generally used as
mobile phases. Moderate amounts of water
miscible polar organic solvents such as
methanol can be added to buffered mobile
phases. Solvent strength and selectivity can be
adjusted by control of pH, buffer and salt
concentrations.

8. Mobile Phases for Size Exclusion
Chromatography
• The mobile phase composition is not varied as
the detector is sensitive to such changes.
• Choice of mobile phase is dependent on its ability
to dissolve sample and maintain consistent
viscosity at operating temperature. High polarity
solvents such as acetone, alcohols, DMSO and
water are not used with polystyrene packings.
Ionic strength is maintained by addition of salts.
•

9. Mobile phase in paper
chromatography
The stationary phase of paper chromatography is filter paper,
and the mobile phase is an organic solvent or mixture. A
small drop of the liquid mixture is placed at one end of the
paper. The end of the paper is then immersed in a solvent.
As the solvent moves up the paper, any molecules in the
mixture that are soluble in the solvent will move with the
solvent. Based on their solubility to the mobile phase and
attraction to the stationary phase, some molecules will
move faster than others. Each different molecule in the
mixture will move at a different speed and will be at a
different position on the finished chromatogram.