Abstract

A similarity of electron ionization mass spectra of various alkyl esters of benzene-1,2-dicarboxylic (phthalic) acid places special demands on the reliability of the identification of monoalkyl phthalates, often recognized as dialkyl phthalates and vice versa. An original mass spectrometric criterion is proposed for the group identification of monoalkyl phthalates (assignment to a subgroup of homologues), which assumes the calculation of the total relative intensity of ion peaks at m/z > 170. In the mass spectra of monoalkyl esters, this value does not exceed 1%, whereas for dialkyl ethers, it varies from 1 to 172%. Within the set subgroups of isomers, it becomes effective to use the homologous increments of the retention indices, i_RI = RI – 100x, where x = int (M/14), to refine the identification results. Using predefined i_RI values and the ratio М ≈ 0.14(RI – i_RI) + y, we can estimate the molecular weights of compounds in the mass spectra of which the molecular ion signals are not detected or are of low intensity (including monoalkyl phthalates). In addition, i_RI values are in many cases informative for estimating the number of branches of the sp³ carbon skeleton of molecules (Z) based on regression relations of the form of i_RI = aZ + b. The examination of homologous increments of the retention indices of dialkyl phthalates revealed an anomalous dependence of their values on the number of carbon atoms in the alkyl fragments of the molecules: from +125 (СН₃) to –33 (С₁₀Н₂₁). In the subgroup of monoalkyl phthalates, such anomalies were not observed.

中文翻译：

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邻苯二甲酸单烷基酯的气相色谱-质谱鉴定

摘要

苯-1，2-二羧酸（邻苯二甲酸）的各种烷基酯的电子电离质谱的相似性对鉴定邻苯二甲酸单烷基酯（通常被认为是邻苯二甲酸二烷基酯）的可靠性提出了特殊要求。提出了一种原始的质谱标准，用于邻苯二甲酸单烷基酯的基团鉴定（分配给同系物的一个子组），该标准假设计算出m / z > 170的离子峰的总相对强度。在单烷基酯的质谱图中，该值不超过1％，而对于二烷基醚，其从1至172％变化。在异构体的子集内，使用保留指数的同源增量i _RI = RI – 100变得有效。x，其中x = int（M / 14），以细化识别结果。使用预定义的i _RI值和比率М≈0.14（RI – i _RI）+ y，我们可以估计质谱图中未检测到分子离子信号或强度低的化合物（包括邻苯二甲酸单烷基酯）的分子量）。另外，在许多情况下，i _RI值对于基于i _RI =的形式的回归关系估计分子（Z）的sp ³碳骨架的分支数_很有用。aZ + b。苯二甲酸二烷基酯的保留指数的同源增量的检查发现它们的值的碳原子上的分子中的烷基片段数目的反常依赖性：从125（СН ₃）到-33（С ₁₀ Н ₂₁）。在邻苯二甲酸单烷基酯的亚组中，未观察到这种异常。