Use of derivatisation in GC

A decongestant syrup was basified with ammonia and extracted into ethyl acetate, thus ensuring that the components extracted were in their free base forms rather than their salts, which is important for obtaining good chromatographic peak shape. Salts of bases will thermally dissociate in the GC injector port but this process can cause a loss of peak shape and decomposition. 

Silylating reagents are another popular class of derivatisation reagents. These reagents introduce residues into the sample, although this is not a great problem if the analyte is relatively involatile. An example of a silylation reaction is shown on page 226. 

---