高效液相色谱法分析乙酰乙酸乙酯制备脱氢乙酸反应液中的脱氢乙酸和乙酰乙酸乙酯

乙酰乙酸乙酯经Claisen缩合反应得到脱氢乙酸是目前工业生产脱氢乙酸的一种主要方法。由于乙酰乙酸乙酯存在酮-烯醇式互变异构体,采用高效液相色谱分析时,存在吸光值和最大吸收波长的差异问题,并且容易引起色谱峰分裂和拖尾。通过优化色谱条件,将烯醇式乙酰乙酸乙酯转化为酮式异构体,避开烯醇式异构体的干扰,使乙酰乙酸乙酯的峰形更好,定量更准确,从而以酮式乙酰乙酸乙酯的定性、定量分析替代乙酰乙酸乙酯的定性、定量分析,进而建立一种同时检测乙酰乙酸乙酯法制备脱氢乙酸反应液中脱氢乙酸和乙酰乙酸乙酯的高效液相色谱法。采用Agilent HC-C₁₈色谱柱(250 mm×4.6 mm, 5 μm)分离,紫外检测波长为290 nm,柱温为35 ℃,流动相为甲醇-0.3%醋酸铵缓冲溶液(5:95, v/v,醋酸调节pH 6.0),流速为0.6 mL/min。在线性范围内,脱氢乙酸和乙酰乙酸乙酯的线性相关系数分别为0.99995和0.99992;加标回收率分别为98.5%和101.3%;相对标准偏差均小于1.0%。该方法具有较好的准确性和灵敏度,可简便、快速地同时对反应液中的脱氢乙酸和乙酰乙酸乙酯进行定性、定量分析,从而为乙酰乙酸乙酯法制备脱氢乙酸反应进程的控制提供参考。

Analysis of the reaction solution for dehydroacetic acid preparation by ethyl acetoacetate using high performance liquid chromatography

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.