Page 124 - Applied Pharmacognosy

Types of Chemical markers

• The column temperature has to be above the dew points of the
compounds to prevent condensation in the column.

• The temperature of the oven can be kept constant (isothermal), or
gradually be changed (gradient or temp. programming).

• Temp. programming often provides a better separation due to the
fact that the differences in boiling points can additionally be used to
separate the compounds.

• Most Flame Ionization Detectors (FIDs) require a certain minimum
temperature in order to ignite (>150 oC).