MIXTURES WITH GRADIENT OF MOBILE PHASES UTILIZED IN HPLC SEPARATIONS OF 2.4-DINITROPHENYLHIDRAZONES PROVIDED BY INFERIOR CARBONYL COMPOUNDS

Abstract

Many mixtures of small quantities of carbonyl compounds are present in foods, con­cer­ning sensorial qua­lities (aroma and fragrance). The inferior carbonyl compounds (C₂-C₄, 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 (2.4-DNPH-ones). 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.