Many mixtures of small quantities of carbonyl compounds are present in foods, concerning sensorial qualities (aroma and fragrance). The inferior carbonyl compounds (C 2-C 4 , boiling point <100°C)-mono and dicarbonyl-can be identified and their concentrations can be measured, after being separated by distillation on water bath. They are transferred into a strongly acid solution of 2.4-dinitrophenylhidrazine (2.4-DNPH), generating a mixture of insoluble 2.4-dinitrophenylhidrazones

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... . The 2.4-DNPH-ones are organic compounds with weak polarity, solids, crystallized, yellow and water insoluble, but soluble in organic solvents. The mixture of 2.4-DNPH-ones may be separated by liquid chromatography, using HPLC the reverse phase mechanism [1-3]. This paper contains experimental and theoretical considerations on the means of separation through liquid chromatography of two models and a natural mixture containing 2.4-DNPH-ones provided by inferior carbonyl compounds; to obtain decisive results, in the model mixtures 2.4-DNPH-ones provided by carbonyl compounds having three (acetone and propanal) and four atoms of carbon (isobutylaldehyde) were introduced.