Page 111 - phytochemistry general program

the mobile phase in the order of their increasing distribution coefficients with
respect to the stationary phase; separation is achieved”.
Chromatographic systems

All chromatographic separations depend upon interactions among the sample
mixture (components to be separated), the sorbent (stationary phase) and the
developer (mobile phase). The components of the sample mixture are distributed
between the two phases (stationary and mobile phases). This group of interactions
among the components of the chromatographic system may be represented

schematically in the following way,

The overall process of chromatography is a differential migration phenomenon. It
refers to the varying rates of movement of different compounds.

Differential migration results from the different equilibrium distribution of different
components of the sample mixture between the particles of the stationary phase
and the flowing or moving phase. Therefore, differential migration is determined by
those experimental variables which affect this distribution such as the composition
of the moving phase, the nature and composition of the stationary phase and the
separation temperature. When we want to change the differential migration to

improve separation, we must change one or more of these three variables.

Uses and applications of chromatography

Chromatography is among the most selective and most widely applicable
separation techniques. Generally, there are three dimensions of application:
(1) Qualitative applications

These can be summarized as follows: a- Identification and comparison of
substances. b- Determination of the purity of substances. c- Analysis of mixtures,

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