Page 137 - phytochemistry general program

D. Circular (Radial) Paper Chromatography

Horizontal (or circular) paper chromatography was performed in two ways. In the
classical method, a spot of the sample to be analysed was placed at the centre of
a circular filter paper. Then a short wick was made by making parallel incisions c. 2
mm apart from the edge of the filter paper to its centre. This wick was then cut to
an appropriate size and bent so that it dipped into the solvent contained in a Petri
dish. Subsequently, apparatus became available that eliminated the need for
cutting the paper to form a wick. Horizontal development is advantageous in the
improved reproducibility of Rf values, also it is usually faster than ascending
development, thirdly, temperature can be easily controlled (incubator or

refrigerator).

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