Comprehensive two-dimensional liquid chromatography with inductively coupled plasma mass spectrometry detection for the characterization of sulfur, vanadium and nickel compounds in petroleum products

Abstract

The petroleum industry is increasingly concerned with the conversion of vacuum residues as a consequence of decreased conventional crude oil availability. The compositional analysis of heavy oil products has become a key step in conversion processes, but the complexity of these oil matrices tends to increase with their boiling point. In this study, comprehensive two-dimensional liquid chromatography (LCxLC) coupled to inductively coupled mass spectrometry (ICP-MS/MS) is considered with a view to meet new requirements and to bring additional information regarding the species present in these matrices. In search for a high degree of orthogonality, two separation techniques involving two different retention mechanisms were evaluated: Size Exclusion Chromatography (SEC) and Reverse Phase Liquid Chromatography (RPLC). In SEC, the analytes are separated according to their molecular weight while according to their hydrophobicity in RPLC. The separation power of both individual separation techniques was first evaluated. Off-line and on-line LCxLC were compared on the basis of an optimization approach. It is shown that off-line SECxRPLC can provide, for the same analysis time of 150 min, a higher peak capacity (2600 vs 1700) while a similar dilution factor (close to 30) but also requires far fewer fractions to be analyzed (12 vs 2 400). Asphaltenes which constitute the heaviest fraction of crude oils (obtained from petroleum industry) were analyzed by the developed off-line SECxRPLC method. The resulting 2D-contour plots show that co-elutions could be removed leading, for the first time, to new information on high molecular weight species containing sulfur and vanadium.

Tandem Mass Spectrometry in the Analysis of Petroleum-Based Compounds

“…Upon reactions with O 2 in the reaction chamber of the triple quadrupole mass spectrometer, these small ions produce different oxidation products. By scanning the two analyzer quadrupoles so that the first one passed the small unoxidized cations and the third one passed their oxidized products, it was possible to quickly detect V-, S-, and Ni-containing compounds in the samples. − Detection of specific analytes or elements of interest is of particular importance in the analysis of petroleum-derived mixtures due to regulatory limits on, for example, sulfur content in diesel fuels …”

“…Finally, comprehensive two-dimensional liquid chromatography coupled to ICP MS/MS also has been utilized to detect vanadium and nickel (as well as sulfur) compounds in fractions of asphaltenes and in maltenes (saturated compounds, aromatic compounds, and resins). 22 This setup was used to detect compounds containing vanadium, sulfur, and nickel in the MS/MS mode. Vanadium cations 67 V + (m/z 51) formed 67 VO + cations (m/z 67) upon reactions with O 2 while sulfur cations S + (m/z 32) formed 48 SO + cations.…”

Recent applications of retention modelling in liquid chromatography

“…However, the combination of two dimensions renders method optimization a more complicated endeavor [60]. When retention modelling is applied in the development of 2D separations, the LSS model is often used to optimize the individual (gradient) dimensions [61–64]. The S LSS parameter has also been used as a measure for orthogonality (i.e.…”

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

“…Detection was via cold vapor atomic fluorescence spectrometry, and different extraction procedures for mercury were evaluated; it was found that microwave-assisted extraction had the best efficiency, and that the method was successful in quantifying mercury species in both crude oil and fuel samples. A two-dimensional LC configuration was used to study vanadium and nickel in deasphalted crude oil samples, with detection by both online and offline inductively coupled plasma mass spectrometry . Method development in this case was complex, and required optimization of several parameters and conditions.…”

“…A two-dimensional LC configuration was used to study vanadium and nickel in deasphalted crude oil samples, with detection by both online and offline inductively coupled plasma mass spectrometry. 78 Method development in this case was complex, and required optimization of several parameters and conditions. The multidimensional setup allowed for quantification of heavy oils' contents of metal species that may be too complex for other methods.…”