Although NVA and VFA have frequrntly been analysed separately on a single gas chromatography, hight-performance liquid chromatography (HPLC) methods offer the advantages of detaction of NVA without the need for derivatization, detaction of both VA and NVA in a single chromatography run and increased sensitivity for detaction of NVA. Capillary GLC method do involve simultaneous derivatization of VA and NVA, but both can be separated in a single chromatography run. Summaries of these methods are given below.