Page 112 - phytochemistry general program

as it indicates the number as well as the nature of their components. d- Monitoring
the progress of reaction mixtures.

(2) Quantitative applications

Quantitative determination can be achieved by most techniques of
chromatography. Quantitative applications are routinely used in pharmaceutical
and phytochemical products, where it affords a rapid and efficient method of
analysis of multicomponents mixtures, even in the presence of interfering

substances such as coloring matters.

(3) Preparative applications

When milligram or gram quantities of mixture components are required in a pure
form, chromatography is almost the best choice. Usually column chromatography
is the technique used for isolating relatively larger samples, while paper and thin-
layer chromatography provide smaller quantities. In this regard, chromatography in

an indispensable method in the field of phytochemistry.

Classification of chromatography

Basic principles

All chromatographic methods require one static part (the stationary phase) and
one moving part (the mobile phase). According to the nature of the mobile phase,
chromatography can be divided into two major divisions, Liquid (solution) and gas

chromatography.

Gas chromatography .1
Where the mobile phase is a gas and the stationary phase can be either an
adsorbing solid in gas-solid chromatography (GSC), or it may be a liquid in gas-
liquid chromatography (GLC). The first is an adsorption, while the second is a
partition process. It is mainly used for separating gases and volatile substances.
Non-volatile substances can be analysed by gas chromatography after the

preparation of their volatile derivatives.

Liquid (solution) chromatography .2

It is further subdivided into six subdivisions with respect to the manner or the
sorptive phenomenon upon which separations are based. The techniques rely on

110