Engineering Chemistry S Datta

510 ENGINEERING CHEMISTRY
Highlight:
• Nernst’s isotherm:
K A
= C s
Cm
where K A
= constant of distribution of component A at a given temperature.
C s
= concentration of component in stationary phase (Adsorbent)
C m
= concentration of component in mobile phase (Adsorbate)
Some parameters of gc
• Retention time. It refers to the time taken by the component to be extracted from the
column and arrive at the detector. It is measured on the abscissa of the chromatogram
from the start to the maximum peak.
• Retention volume. It refers to the volume of the solvent that is required to extract a
component and bring it to the detector. It is measured from the start to the maximum
of the peak on the abscissa of chromatogram.
• Chromatogram. It is a volume/speed curve which illustrates a chromatographic
separation. The concentration component is found to be proportional to the signal. The
signal illustrates the progress of a chromatographic separation.
Signal (Concentration)
Start
A
0 1 2
Volume or time
of retention
Fig. 23.4 Chromatogram.
• Separation factor (α):
α = K A
K B
where K A
and K B
are the constants of distribution of two components A and B respectively.
• Efficiency. It refers to the capacity of column to separate the components.
• Resolution. It refers to the capacity of a column to separate two consecutive peaks of
a chromatogram.