4-Hydroxy-2-nonenal (HNE) has been prepared from the corresponding dimethylacetal (HNE-DMA), in turn synthesized by a conventional approach with a few modifications of the experimental protocol and some improvements in the purification of the final product. In order to exploit the sensitivity of gas-chromatography with electron capture detector (GC-ECD) in the analysis of HNE derivatives, reaction of HNE with 2,4,6-trichlophenylhydrazine (TCPH) and 3,5-dichloro-phenylhydrazine (DCPH) was tested. Reaction with TCPH afforded a mixture of products, whereas with DCPH a single major product was formed that was prepared on a millimolar scale and purified. (1)H-NMR analysis established that the derivative of HNE with DCPH is HNE 3,6-dichloro-phenylhydrazone, that can be used as standard for GC-ECD analysis.