The Coupling of Supercritical Fluid Chromatography and Field Ionization Time-of-Flight High-Resolution Mass Spectrometry for Rapid and Quantitative Analysis of Petroleum Middle Distillates

Abstract

We report the first coupling of supercritical fluid chromatography (SFC) with field ionization time-of-flight high-resolution mass spectrometry (FI-ToF HRMS), in parallel with ultraviolet (UV) detection and flame ionization detection (FID), for rapid and quantitative analysis of petroleum middle distillates. SFC separates petroleum middle distillates into saturates and 1- to 3-ring aromatics. FI generates molecular ions for hydrocarbon species eluted from the SFC. The high resolution and exact mass measurements by ToF mass spectrometry provide elemental compositions of the molecules in the petroleum product. The amounts of saturates and aromatic ring types were quantified using the parallel SFC-FID assisted by SFC-UV. With a proper carbon-number calibration, the detailed composition of the petroleum middle distillate was rapidly determined.

Molecular Characterization of Heavy Petroleum by Mass Spectrometry and Related Techniques

“…These molecules cannot be effectively ionized by APPI due to their higher ionization potentials nor by ESI due to their low polarity. Field ionization/field desorption (FI/FD) have shown to be highly effective for ionizing saturates when used in conjunction with a time-of-flight (TOF) mass spectrometer ,,,− but have not been successful when used in coupling with FT-ICR MS. Severe fragmentation was observed, most likely due to the short life span of the molecule ions and long ion accumulation time in the FT-ICR operations .…”

“…In GC-MS analysis, GC separates petroleum by boiling point (BP) or polarity, while MS identifies petroleum components based on fragmentation pattern. When used in conjunction with a soft ionization method, such as field ionization (FI) ,,,,,, or photon ionization (PI), − it has been realized that mass spectrometry can yield molecular weight (MW) as an additional separation dimension, providing two-dimensional separations similar to that by GC × GC (2DGC). This technology has been coined as GC × MS by Wang et al The use of more polar GC columns can improve the orthogonality of the two-dimensional separations as shown in Figure …”

Detailed Analysis of Olefins in Processed Petroleum Streams by Combined Multi-dimensional Supercritical Fluid Chromatography and Field Ionization Time-of-Flight Mass Spectrometry

“…The second column system is a packed column loaded with high-surface-area silica particles modified with silver ions. The preparation of the silver-loaded silica column can be found in ASTM D6550 . Two switching valves are used to direct different hydrocarbon classes through the chromatographic system.…”

“…MS analyses were conducted on a Waters GCT instrument. The experimental conditions were similar to that described in prior GC FI-TOF MS and SFC FI-TOF MS works. , In brief, FI was used to ionize petroleum molecules eluting from SFC to generate primarily molecular ions with minimum fragmentation. The FI emitter current was set at 0 mA during scan and was flashed by a current of 12 mA during an interscan cycle (0.2 s) to regenerate the emitter.…”

“…In general, molecular-level characterizations of petroleums over a wide boiling point range are well-established. For example, molecules in the naphtha range with a boiling point up to 221 °C (430 °F) are routinely measured by high-resolution gas chromatography (GC) or GC–mass spectrometry (MS) which determine C 4 –C 12 paraffins, isoparaffins, olefins, naphtha, and aromatics (PIONA). , Middle distillates with a nominal boiling point ranging from 221–343 °C (430–650 °F) are characterized by GC–field ionization mass spectrometry (FI MS) in low-resolution , or high-resolution − modes. In a previous work, we have demonstrated the coupling of supercritical fluid chromatography (SFC) and field ionization time-of-flight mass spectrometry (FI-TOF MS) for detailed characterization of saturates and aromatics .…”