Kinetic−Fluorometric Determination of Malonaldehyde Based on the Hantzsch Reaction: Application to Olive Oil Analysis

Abstract

A kinetic study was completed on the formation of 1,4-disubstituted-1,4-dihydropyridine-3,6 dicarbaldehyde from malonaldehyde and methylamine, via the Hanztsch reaction. The influence of n-hexylaldehyde and acetaldehyde in the reaction has been studied, and it has been concluded that the presence of the aldehydes is not necessary for the reaction. The fluorescence emission of the reaction product was monitored at 470 nm, with excitation at 405 nm, and the effect of instrumental and experimental variables on the reaction was investigated. A pH of 4.0, obtained by a 0.25 M sodium acetate-acetic acid buffer solution, a 10 mM methylamine concentration, a 30% (v/v) 2-propanol content, and a temperature of 75 degrees C were selected for the reaction. A kinetic-fluorometric method to determine malonaldehyde has been proposed, for malonaldehyde concentrations ranging from 0.5 to 2.8 micrograms/mL-1, and a wide study of the possible interferences in the reaction has been performed. The kinetic-fluorometric method was applied to olive oil samples.