Evaluating the content of contemporary GC-MS databases (including the NIST database) allows revealing compounds not enough characterized both mass spectra, and GC retention indices (RI). Among relatively simple objects of this type there are the products of carbonyl compounds interaction with hydrazine - non-substituted hydrazones and azines. Revealing the reasons for the lack of reference information for these compounds indicates that non-substituted hydrazones are thermally unstable and converts into azines inside chromatographic column during separation. It is resulted in the appearance of specific profiles of chromatograms and leads to irreproducibility of relative peak areas of these compounds, strong variations of retention times and, hence, low reproducibility of their retention indices. Nevertheless, more then dozen of non-substituted hydrazones and the same number of corresponding azines were characterized first time by standard EI mass spectra and RI values on standard non-polar polydimethyl siloxane stationary phases. On the example of reaction mixtures of alkyl aryl ketones with hydrazine (under medium conversion of substrates into derivatives) the new effect in chromatography is revealed. The chromatograms of these samples contain the diffused zones of hydrazones with retention times less then retention times of such hydrazones from reaction mixtures. The explanation of this anomaly is the formation of volatile hydrazine during hydrazone decomposition, followed by its secondary interaction with initial carbonyl compound taking place in another part of chromatographic column.