Difficult Analytes to Improve GC Elution Behavior

Derivitization of Difficult Analytes to Improve GC Elution Behavior 

One way to deal with the recalcitrant compounds described in the preceding paragraph is to modify the troublemaking functional group(s) to a more tractable form. Their reactivity and polarity is the cause of their bad behavior. We can use this reactivity to add a substituent which converts them to a less-active, less-polar group. 

Such agents function less instantaneously than diazomethane. They react faster at quite high temperatures. One way to achieve those has been to mix them with the injection solution. Upon flash vaporization in the hot injection port or the start of the column, the derivitization reaction is nearly instantaneous and complete. This procedure is known as on-column derivitization. Such a mode of introduction of this reagent also achieves the purpose of reacting 

To summarize, derivitization for GC can confer greater thermal stability to an analyte. It can convert the analyte to a form which is more volatile, less polar, and with less tendency to produce tailing peaks by interaction with column active sites. It can introduce elements into it which make it detectable by more sensitive or selective detectors (remember, in real-world analyses, selectivity often confers more effective sensitivity to an assay). The scope of derivatization for GC is far greater than the several examples listed here. See the bibliography (Grob, Jennings, Scott) or product literature from specialty derivitization agent vendors (Appendix 12.1) for more examples. 

---