Solid Phase Extraction - Principe of SPE

General considerations

Gas chromatography is used to separate volatile organic compounds.

By modifying the functionality of a molecule to increase– or sometimes decrease – volatility, derivatizing reagents enable chromatographers to analyze compounds that otherwise are not readily monitored by GC.
Derivatization also reduces analyte adsorption in the GC system and improves detector response, peak separations, and peak symmetry.

Derivatives are used for the following reasons:

to improve resolution and reduce tailing of polar compounds (–OH, –COOH, =NH, –NH2, –SH, and other functional groups)
to analyze relatively nonvolatile compounds
to improve analytical efficiency and increase detectability
to improve stability of compounds

The choice of a derivatizing reagent is based on the functional group requiring derivatization, the presence of other functional groups in the molecule, and the reason for performing the derivatization.
The chemical structure and properties of the molecule influence the reagent choice.
In choosing a suitable derivatization reagent, certain criteria must be used as guidelines.

A good reagent:

produces a derivatization reaction that is 95-100% complete
will not cause any rearrangements or structural alterations during formation of the derivative
does not contribute to loss of the sample during the reaction
produces a derivative that will not interact with the analytical (GC or HPLC) column
produces a derivative that is stable with respect to time

Download "Derivatization Reagents for GC and Procedures Guide" for additional information.