Determination of distribution factors for heavy n-alkanes (nC12-nC98) in High Temperature Gas Chromatography

Diana M. Hernandez-Baez, Alastair Reid, Antonin Chapoy, Bahman Tohidi

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)
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The ultimate purpose of this research work is to get an insight into the incomplete elution of heavy n-alkanes which along with thermal cracking, is one of the two main factors questioning the reliability of High Temperature Gas Chromatography (HTGC) analysis of heavy oils. For this purpose, knowledge of how the Distribution Factors vary with temperature is an essential requirement in the GC modelling. This study provides an extension of the data set of distribution factors for n-alkanes up to nC98H198 in a HT5 GC column over the temperature range 10 °C–430 °C, and introduces a method to determine the distribution coefficient of heavy n-alkanes by using two complimentary HTGC modes: i.) High-Efficiency mode, for efficient resolution with a long column operated at low flow rate with n-alkanes elution rate up to nC64, and ii.) true SimDist mode, with a short column operated at high flow rate for inefficient resolution with n-alkanes elution rate up to nC100. Furthermore, this study demonstrates the use of the in-house obtained distribution factors as the main input in the in-house GC model for the prediction of the retention times. Its validation has been carried out using distribution factors obtained at both constant flow rate and constant inlet pressure operating conditions, with an average relative error in the GC modelling at the same operating conditions of 4.4% for the former and 1.5% for the latter. This new extension of the data set of heavy n-alkanes distribution factors provides the basis for studying the partitioning and incomplete elution of heavy n-alkanes in HTGC analysis. Also, these new distribution factors can be used as input in GC modelling, to determine the optimum analytical conditions to improve the separation process and thus the HTGC practices.
Original languageEnglish
Pages (from-to)138-146
Number of pages9
JournalJournal of Chromatography A
Early online date14 Jan 2019
Publication statusPublished - 26 Apr 2019


  • Gas chromatography modelling
  • Heavy ends hydrocarbons characterization
  • Heavy n-alkanes distribution factors
  • High temperature gas chromatography

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Organic Chemistry


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