Class Separation of the Trace Polar Species Present in Diesel Using Hydrophilic Interaction Chromatography and High Resolution Mass Spectrometry

Abstract

The analysis of fuels is not straightforward, due to its complex nature, and many different techniques have been developed to address this complexity. This paper reports on the use of hydrophilic interaction liquid chromatography (HILIC) as a complementary and green method for classifying diesel fuel composition. For comparative reasons, analyses with and without chromatographic pre-separation were performed. Selective ionization of polar species was achieved with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). High resolution time of flight mass spectrometry (TOFMS) was used to summarize the fuel composition in terms of compound classes based on accurate mass based elemental compositions. These compound classes showed different retention characteristics and were separated to a certain extent under hydrophilic interaction conditions. In normal phase liquid chromatography, the separation is based on heteroatom content, whereas alkylation (chain length) and degree of unsaturation (or double bond equivalents, DBE) play an important role in reversed phase liquid chromatography. The separation achieved with the proposed HILIC method depended on heteroatom content, DBE as well as hydrogen bonding, whilst alkylation did not influence retention significantly. This work therefore presents an alternative and complementary method for fuel analysis, compared to traditional reverse and normal phase liquid chromatography, by considering specific advantages and limitations.

Analytics Driving Kinetics: Advanced Mass Spectrometric Characterization of Petroleum Products

“…Lubricant base oils; 166 Asphaltene fractions; 193,194,[231][232][233][234] Bitumen; 235 S-containing compounds; 28,182,232,[236][237][238][239] polychlorinated naphthalenes (PCNs); 225 polycyclic aromatic hydrocarbons (PAHs); 28,78,226,233,240 Cycloalkanes; 78,241,242 Steroids compounds; 243 N-, O-containing compounds 28,206,232,244,245 More suitable for non-polar samples than ESI but less than APPI. Thermal degradation and fragmentation are problems.…”

“…Vanadium compounds; 296 Non-polar aromatic compounds; 297 thiols; [298][299][300] Sulfides; 301,302 N-, S-, and O-containing species; 129,198,205,207,212,214,221,224,236,244, Porphyrins; [348][349][350][351][352] Molecular structure of Asphaltenes; 185,216,353,354 naphthenic acids; 284,285,[355][356][357][358][359][360] petroleum sulfonates; [361][362][363][364] acidic compounds; 213,215,216,323,362,[365][366][367][368][369][370][371]…”

Applications of High Performance Liquid Chromatography in the Petroleomic Analysis of Crude Oil: A Mini-Review

“…Another approach to the analysis of polar compounds is to isolate them from the sample by extraction from the hydrocarbon matrix. This was done on diesel fuels, in order that the extracts could be analyzed by hydrophilic interaction liquid chromatography (HILIC), which utilizes a hydrated polar stationary phase for separation . The separation of analytes by HILIC is based on polarity, as analytes partition between the mobile phase, and the hydrated liquid layer on the stationary phase.…”

“…This was done on diesel fuels, in order that the extracts could be analyzed by hydrophilic interaction liquid chromatography (HILIC), which utilizes a hydrated polar stationary phase for separation. 74 The separation of analytes by HILIC is based on polarity, as analytes partition between the mobile phase, and the hydrated liquid layer on the stationary phase. The HILIC-MS analysis of extracts showed coelution of many polar compound classes, but enabled more chemical class assignments than analysis of unseparated diesel extracts.…”