A Comparison of Normal and Reversed Phase Columns in Oil Analysis by Comprehensive Two-dimensional Gas Chromatography With Time-of-flight Mass Spectrometry

Abstract

Four typical crude oil samples collected from the Junggar Basin of northwest China were analyzed by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) under different experimental conditions, which include normal phase column system (nonpolar × polar) and reversed phase column system (polar × nonpolar). A comparative study was conducted on the general chromatogram features, and chromatogram features of saturate and aromatic hydrocarbons. Analytical results show that the normal phase (NP) column system has higher resolution for the identification of high molecular weight polycyoalkanes and polycyclic aromatic hydrocarbons, while the reverse phase (RP) column system has higher separation on the saturate hydrocarbons, especially on medium-low molecular weight iso-alkanes and cycloalkanes. In addition, the RP system can also meet the separation requirements of aromatic compounds, by the extraction of diverse organic compounds by characteristic ions. Therefore, the RP system has special advantages in the analysis of medium-low molecular weight hydrocarbon compounds in crude oil, and can be applied more widely in the future besides the presently common use of the NP system.