气相色谱正构烷烃和直链脂肪酸甲酯两种线性保留指数之间的转换方法

保留指数是气相色谱中用于化合物结构鉴定的重要工具。本研究对基于正构烷烃和直链脂肪酸甲酯的线性保留指数进行线性拟合，发现在所设定的4种不同的升温条件下两种保留指数之间呈现较为固定的线性关系：在弱极性柱（固定液为5%苯基和95%的甲基聚硅氧烷）和极性柱（固定液为聚乙二醇）条件下，正构烷烃保留指数（y）与脂肪酸甲酯保留指数（x）之间的关系分别为y=1.0051x+318.51（r²=1）和y=1.0362x+562.519（r²=1）。采用文献保留指数对所建立的线性关系进行验证，发现通过公式换算得到的保留指数均在其对应文献值的均值加减方差范围内，说明换算公式真实有效。两种保留指数之间关系的建立对于化合物结构鉴定时扩大保留指数搜索范围、减少保留指数测定实验具有重要意义。

Conversion method for linear retention indices in gas chromatography acquired using n-alkanes and n-fatty acid methyl esters

Retention index (RI) is a powerful tool for gas chromatography-based structure elucidation of various compounds. In this study, linear RIs based on n-alkanes and n-fatty acid methyl esters in different temperature programs were fitted. Nearly identical first-order linearities were acquired with different temperature programs. The linear equations were y=1.0051x+318.51 (r²=1) and y=1.0362x+562.519 (r²=1) for polar (packed with polyethylene glycol) and semi-standard non-polar (packed with 5% diphenyl/95% dimethylpolysiloxane) columns, respectively. The variables x and y in the equations stand for RIs based on n-fatty acid methyl esters and n-alkanes, respectively. The established linearity was then verified using the reference RIs collected in the NIST mass spectral library, Golm metabolite library, and Fiehnmetabolite library. The RI values converted using both the acquired equations finely matched those in the references. The established relationship between the two kinds of RIs can be used to expand the RI references and decrease the number of RI acquisition experiments.