Abstract:

A way of ethyl acetoacetate by the Claisen condensation reaction is one of the main methods of the industrial production of dehydroacetic acid. There are the problems of the differences in absorbance value and the maximum absorption wavelength, and the chromatographic peak is prone to the phenomena such as bifurcation and tailing when using liquid chromatography to the analysis of ethyl acetoacetate. To avoid the interference of the enol of ethyl acetoacetate, and making the peak shape of ethyl acetoacetate better and quantitatively more accurate, we converted the enol to ketone through optimizing the chromatographic conditions. As a result, qualitative and quantitative analyses of ethyl acetoacetate were replaced by those of the ethyl acetoacetate ketone. A method was developed for the simultaneous determination of dehydroacetic acid and ethyl acetoacetate by HPLC in the reaction mixture for producing dehydroacetic acid. An Agilent HC-C₁₈ column (250 mm×4.6 mm, 5 μm) was used for the separation. The ultraviolet wavelength was 290 nm and the column temperature was 35 ℃, and methanol-0.3% ammonium acetate buffer (5:95, v/v) with pH 6.0 adjusted by acetic acid as mobile phase, and the flow rate was 0.6 mL/min. The correlation coefficients of dehydroacetic acid and ethyl acetoacetate were 0.99995and 0.99992, and the spiked recoveries were 98.5% and 101.3%, respectively; and the relative standard deviations were less than 1.0%. This method has the advantages of good accuracy and high sensitivity, and it can analyse both qualitatively and quantitatively dehydroacetic acid and ethyl acetoacetate rapidly and simply. And it can provide the reference for producing dehydroacetic acid by the way of ethyl acetoacetate.

Key words: dehydroacetic acid, ethyl acetoacetate, high performance liquid chromatography (HPLC), keto-enol tautomerism, reaction solution