Oximes are occurred usually as a mixture of Z-and E-isomers in nature and in preparation.Due to the interconversion of oximes [1,2],the Z-and E-isomers are difficult to be separated completely.In this study,heptanaldoxime and phenylacetaldoxime were synthesized from their respective aldehydes.The products are being heated in solvent causes Z-isomer-to-E-isomer conversion as time increases,to establish equilibrium.Mass spectrometry cannot readily distinguish the each isomer where molecular ions and firagmentation patterns are essentially the same.The isomerisation was revealed by 1D GC and NMR spectra,respectively.In addition,the equilibrated mixture of isomers was investigated by 1D GC on both polar and nonpolar column phases.The results showed that the interconversion rate on polar column phase (SolGel WAX) is faster than on nonpolar column phase (Sol Gel-lms),and higher temperature or higher pressure in either polar or nonpolar column lead to higher extent of interconversion,which resulted in the more difficult isomers separation.1D GC (wax column) does not lead to the separation of Z-and E-isomers because of a broad overlapping band which comprise the interconversion zone.GC × GC was arranged for the isomers separation of oximes,and it provided discrete separation on the second column,of the overlapping peaks on the first column (Figure.1).