香精中巨豆三烯酮E/Z异构体的相对量比和在4种常用气相色谱柱上的出峰顺序

The relative percentage of megastigmatrienones E/Z isomers in flavors and elution order from four commonly used GC columns

气相色谱上用MP2和B3LYP方法,进行了巨豆三烯酮E/Z异构体热力学参数的理论计算,以4种常用毛细管气相色谱柱进行了巨豆三烯酮香精中各异构体含量的分析.结果表明:(1)在常用的DB-WAX、DBFFAP(等效于SGE BP-21)、HP-5MS、RXi-5sil MS毛细管色谱柱上,巨豆三烯酮各异构体的出峰顺序完全相同,依次为(4,7E,9)-、(4,6Z,8Z)-、(4,6Z,8E)-、(4,6E,8Z)-、(4,6E,8E)-巨豆三烯酮;(2)巨豆三烯酮各异构体分子结构的内能决定了合成产物中各异构体的量比;(3)不同机理或路线合成的巨豆三烯酮香精样品中,(4,6Z,8E)-和(4,6E,8E)-巨豆三烯酮的量比显著大于(4,6Z,8Z)-和(4,6E,8Z)-异构体.理论计算和实验结果一致,对香精中巨豆三烯酮E/Z异构体的定性和定量具有一定的意义.

The thermodynamic parameters of megastigmatrienone E/Z isomers are calculated in gas phase by MP2 and B3LYP methods respectively.A megastigmatrienone flavor sample is analyzed by four types commonly used capillary gas chromatographic columns.The analysis and calculation results show that the elution order of megastigmatrienone E/Z isomers are exactly the same as （4,7E,9）-,（4,6Z,8Z）-,（4,6Z,8E）-,（4,6E,8Z）-,（4,6E,8E）- megastigmatrienone in turn by DB-WAX,DB-FFAP（identical to SGE BP-21）,HP-5MS and RXi-5sil MS columns.The molecular energies of synthesized megastigmatrienone isomers naturally predetermine their relative percentage.For megastigmatrienone flavor samples synthesized by different mechanisms and routes,the percentages of （4,6Z,8E）- and （4,6E,8E）- are dramatically higher than that of （4,6Z,8Z）- and （4,6E,8Z）- isomers,which are consistent with the Boltzmann population in gas phase.The theoretical calculation results agree well with the experimental elution order and percentage of megastigmatrienone E/Z isomers.It may play roles on both qualification and quantification for isomers of megastigmatrienone in flavors.