Comparison of Thermal and Flow-Based Modulation in Comprehensive Two-Dimensional Gas Chromatography—Time-of-Flight Mass Spectrometry (GC × GC-TOFMS) for the Analysis of Base Oils

Abstract

Base oils are produced by refining crude oil or through chemical synthesis. They are a key component of engine oils. With an immense range of carbon numbers and boiling points, analyzing such complex mixtures is very difficult. The need to monitor industrial petroleum processing steps, as well as to identify petrochemical environmental pollutants, drives the search for improved characterization methods. Comprehensive two-dimensional gas chromatography (GC × GC) is one of the best tools for that. The modulator used in GC × GC is responsible for trapping/sampling the first dimension (1D) column analytes, then reinjecting them in the form of narrow bands onto the second dimension (2D) column for further separation. Modulators used today generally fall into two categories, thermal and flow ones. Heater-based thermal modulators trap the 1D column effluent at or above ambient temperatures. Flow-based modulators utilize storage loop(s) to collect the 1D effluent, which is subsequently flushed into the second-dimension column for further separation. A single-stage, consumable-free thermal modulator and a reverse fill/flush flow modulator were compared for the characterization of base oils. Both were evaluated on their ability to achieve separation of several conventional and synthetic engine oils components. A reverse column set, polar 1D and nonpolar 2D, allowed group-type analysis of all classes, including linear, branched, and aromatic species. The results show the ability to achieve a comprehensive separation of specific compound classes and the differentiation of engine oil types and manufacturers. Soft ionization assisted in tentative identification of two alkylated diphenylamines in each sample. The advantages and limitations of both thermal and flow modulation are presented.

Analytics Driving Kinetics: Advanced Mass Spectrometric Characterization of Petroleum Products

“…By using the EI method, molecules can be identified based on analyzing their fragmentation mass spectra and matching them with a published EI MS library (NIST library). 442 Many publications have been reported using GC × GC-EI-TOF-MS for analyzing the aromatic components in the petroleum samples. [443][444][445] In one of the scientific papers published by Hamilton et al 102 demonstrated the usefulness of GC × GC-EI-TOF-MS for the analysis of the feed and the product from the hydrocracker coal liquefaction process.…”

“…Compositional elucidation of heavy petroleum base oil GC×GC-EI/PI/CI/FI-TOFMS Boswell et al, 442 Characterization of base oils through thermal and flow modulators Bowman et al, 490 2020 Naphthenic acids in oils Gieleciak et al, 491 2020 Sulfur-containing hydrocarbons in the bitumen-derived gas oil GC×GC-TOFMS/SCD/FID, Karakhanov et al, 492…”

“…Many different ionization methods can be used for a time-of-flight-mass analyzer, in which electron ionization (EI) at 70 eV, a standard technique, is often employed. By using the EI method, molecules can be identified based on analyzing their fragmentation mass spectra and matching them with a published EI MS library (NIST library) . Many publications have been reported using GC×GC-EI-TOF-MS for analyzing the aromatic components in the petroleum samples. − In one of the scientific papers published by Hamilton et al, the usefulness of GC×GC-EI-TOF-MS has been shown regarding the analysis of the feed and the products during the hydrocracker coal liquefaction process.…”

Quantitative performance of forward fill/flush differential flow modulation for comprehensive two-dimensional gas chromatography

“…Both types of modulator technologies have been extensively applied across various applications. Following references involve the use of CFT reverse fill/flush modulation [19][20][21][22][23][24][25][26][27], while [28][29][30][31][32][33][34] employ INSIGHT reverse fill/flush modulator.…”

Profiling Olefins in Gasoline by Bromination Using GC×GC-TOFMS Followed by Discovery-Based Comparative Analysis

“…Subsequent analysis of the brominated products by a separation method, such as one-dimensional (1D) GC, facilitates a more precise analysis of the olefin content. , However, 1D-GC is inherently limited in its peak capacity; thus, the total number of mixture components that can be resolved within a reasonable analysis time is also limited. , Comprehensive two-dimensional (2D) GC, or GC×GC, − provides an enhancement in peak capacity of about an order-of-magnitude, , increased detectability, , and additional selectivity with compound class-ordered separations. Coupling GC×GC with time-of-flight mass spectrometry (GC×GC-TOFMS) creates a powerful instrument, well-suited to the characterization of petroleum-based fuels. − Unsurprisingly, several researchers have investigated the utility of GC×GC to analyze olefins in various mixtures, including Fischer–Tropsch products, commercial dodecenes, , diesel, and unsaturated fatty acids …”