extracts, subdividing the whole spectra of extracted substances into fractions
according to the separation mechanism used. This approach is called fractionation
and is introduced in the following.
3.3.2 Fractionation by Low-Performance Liquid
Chromatography
A prerequisite for any successful chromatographic fractionation is a
preconcentration of the raw extracts. Depending on the extraction method the raw
extracts can have a few milliliters up to 500 mL. These volumes are commonly
Eluent
Eluate
SeparaƟng
Material
(e.g. silica gel,
alumina oxide)
Sample (A+B)
Glass wool
t 0
t 1
t 2
t 3
C
EluƟon technique
B
A
t
2 nd order chromatogram
B
B
A
A
A
B
Fig. 3.16 Scheme of a second order chromatogram
3.3 Fractionation
33