From molecular structures of ionic liquids to predicted retention of fatty acid methyl esters in comprehensive two-dimensional gas chromatography

Chadin Kulsing, Yada Nolvachai, Annie Xu Zeng, Sung Tong Chin, Blagoj Mitrevski, Philip J Marriott

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26 Citations (Scopus)

Abstract

Ionic liquids (ILs) are attractive stationary phases to broaden selectivity in gas chromatography (GC). The rational design, selection and application of ILs in comprehensive two-dimensional GC is a desirable goal. In this study, methods to predict two-dimensional chromatograms of fatty acid methyl esters (FAMEs) starting from given structures of IL stationary phases and their interactions with FAME solutes are described. Molecular parameters of the dipole moment, lowest unoccupied molecular orbital energy and molar volume of different ILs were calculated by using Gaussian 09. With established correlations between molecular simulation and linear solvation energy relationships, molecular parameters were converted to s, e and l values for stationary phase descriptors. This allowed reliable prediction of the equivalent chain length of FAMEs on each IL column (with the correlation R 2=0.98). Isovolatility curves in GC×GC space of reference saturated FAMEs were then determined for each IL column to take into account the dependence of retention time on temperature in temperature-programmed separation. The resulting predicted GC×GC chromatograms were compared with previously reported experimental results. Correlations with R2 values of 0.99 and 0.98 were achieved for the first- and second-dimension retention times, respectively. Forecasting a result: Prediction of the separation performance of fatty acid methyl ester (FAME) analytes on capillary columns coated with ionic liquid phases by knowledge of their molecular structures is possible (see figure; LSER=linear solvation energy relationship). Whilst providing deeper insight into separation mechanisms, trial-and-error experimentation related to method development in multidimensional gas chromatography can also be reduced. 

Original languageEnglish
Pages (from-to)790-797
Number of pages8
JournalChemPlusChem
Volume79
Issue number6
DOIs
Publication statusPublished - 2014

Keywords

  • ab initio calculations
  • Abraham descriptors
  • fatty acids
  • ionic liquids
  • multidimensional gas chromatography

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