Reach New Heights with LECO at Pittcon 2024

Goggles and safety glasses are critical components of laboratory personal protective equipment. Unfortunately, goggles and safety glasses are prone to fog up especially if worn with protective masks. This combination can be hazardous since visibility can drop significantly during the time spent in the lab. Many vendors provide protective eyewear with anti-fog properties. In addition, anti-fog sprays and/or cloths are utilized regularly to improve visibility while wearing the protective gear. A recent Duke University publication indicated that anti-fog sprays or cloths may contain high levels of polyfluorinated alkyl substances (PFAS). Formulation impurities, as well as degradation products, may be present as well. Some of these substances have been linked to disease (e.g., cancer). Therefore, it is important to characterize anti-fog solutions to determine the identity and safety of their constituents. The objective of this study was to characterize anti-fog solution compounds using gas chromatography with time-of-flight mass spectrometry (GC-TOFMS). A large number of anti-fog constituents were not present in commercially available mass spectral databases (NIST, Wiley). Enhanced chromatography and high-resolution time-of-flight mass spectrometry (GCxGC-HRTOFMS) were employed to identify unknowns. The advantages of GCxGC-HRTOFMS included enhanced chromatographic resolution and the ability to determine chemical formulas using accurate mass measurements for molecular ions, adducts, and fragment ions. The superior chromatographic resolution together with the selectivity and accurate mass measurements of the HR-TOFMS instrument lead to confident anti-fog component annotation.

Mineral oil hydrocarbons (MOHs) are complex mixtures deriving from crude oil. They consist of two main fractions, namely mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH). The analysis of MOHs in food is a challenging task, due to the high complexity of the matrices and the high affinity of mineral oil towards the lipid fraction and/or other interfering components (e.g., carotenoids, terpenoids, olefins). The method of election for the quantitative determination of MOHs is LC-GC-FID. The resulting chromatograms are typically containing “humps”, also known as unresolved complex mixtures (UCM). In many cases, UCM is very difficult to interpret as the FID is a non-selective detector, and additional confirmatory methods are needed. In this respect, GC×GC-ToFMS is a well-established solution to characterize the MOSH and MOAH fractions in detail revealing the presence of markers of contamination (e.g., hopanes, dibenzothiophenes, diisopropylnaphthalenes POSH, PAO, etc.) as well as natural interferences (e.g., terpenoids). In addition, the GC×GC-ToFMS contour plots provide highly detailed qualitative information on the characterization of MOSH and MOAH fractions answering, as an example, the request of the EFSA and the European Union to characterize more in detail the 3-7 ring MOAH fractions. Recently, a full solution, including all hardware and software tools, was developed and validated, enabling automatic processing of quantitative data (GCxGC-FID), thanks to the use of a novel software algorithm developed to integrate 2D humps. We are able to demonstrate full qualitative and quantitative results for a range of challenging food sample matrices, such as palm oil and coconut oil.

An increase in the desire for waste plastics converted to pyrolysis oils to be used as fuel has led to the development of processes that create potential feedstocks with chemical characteristics very different from traditional geochemical sources. A deeper, detailed understanding of their chemical composition is necessary to avoid problems at refineries because these nontraditional materials carry higher risks of poisoning catalysts or otherwise reducing efficiency, even though they may possess similar physical properties to traditional petroleum products. This presentation focuses on full characterization of plastic-derived pyrolysis oils throughout different stages of the production process using comprehensive two-dimensional gas chromatography (GCxGC) coupled to time-of-flight mass spectrometry (TOFMS) and simultaneous flame ionization detection (FID). For the chromatographic separation of these pyrolysis oils, GCxGC not only provides improved chromatographic resolution that leads to cleaner spectral information for identification by the full mass range TOFMS, but also structured chromatograms that reveal clusters of compound classes not typically seen in traditional petroleum fuels, such as multi-branched paraffins and heteroatom-containing species that would otherwise not be resolved by single-dimension GC separation. A novel splitter design ensures that a constant ratio of analytes is sent to each detector throughout the analysis, eliminating boiling-point temperature-biased hydrocarbon group-type results from the FID while maintaining the integrity of the GCxGC separation for an analytical method that concurrently provides rich qualitative and quantitative information.

Fragrance samples often contain many chemical components, and determination of the individual species can be important for many objectives, including reformulation. Reformulation goals typically involve determining the identification and relative amounts of the components in a sample. This information facilitates product matching or development and can also be useful for characterization, authentication, and verification. It is usually not practical to calibrate and quantify all of the components with standards. More commonly, workflows to achieve this use MS for identification and FID for relative area % quantification. This often requires separate injections to each detector per sample. Particularly complex samples may need multiple one-dimensional separations with different stationary phases to address coelutions and isolate individual compounds. Here, we demonstrate an improved workflow using GCxGC with dual TOFMS/FID detection to yield reliable identification and area % quantification in a single injection. GCxGC provides enhanced chromatographic separations to address coelutions, removing the need for separate 1D analyses with different stationary phases to handle complex samples. Dual MS and FID detection enables both identification and area % quantification from the same injection rather than from each detector independently. Several hardware and software attributes were designed to support this workflow and ensure reliable data. A novel controlled splitter maintains a consistent split ratio between the MS and FID through the chromatographic separation. A reverse fill flush (RFF) modulator with software verification of method parameters ensures total transfer of the primary effluent to the secondary column. Novel software algorithms align the MS and FID peaks, streamlining data interpretation. Results for various fragrance samples, capabilities, and benefits are shown.

The push for sustainable aviation fuels has led to the development of many pathways for production of synthetic aviation fuels, each currently requiring varying levels of physical and chemical testing to gain regulatory approval for use in commercial aviation equipment. Comprehensive characterization using two-dimensional gas chromatography (GCxGC) for group-type analysis has widely been accepted as a valuable means of providing detailed compositional information for not only hydrocarbons, but also polar oxygenated and aromatic compounds in these new synthetic aviation fuels. In recent years, splitter technology that allows the coupling of low-cost, flow-modulated GCxGC with dual detection from time-of-flight mass spectrometry (TOFMS) and flame ionization detection (FID) has been developed and refined to provide simultaneous identification of compounds and hydrocarbon group-type quantitation. In this presentation, a back-pressure regulated reverse fill-flush (RFF) flow modulator is used with built-in software controls to ensure full transfer of analytes from the primary to secondary GC column, an important consideration when any type of flow modulation is used. This separation technique is coupled with a novel splitter that eliminates the quantitative bias which occurs because flows to vacuum versus atmospheric pressure outlets on the different detectors change as temperatures increase during the chromatographic separation. A variety of chemical standards and both traditional and synthetic fuel samples are used to demonstrate optimal method parameters that provide both full transfer conditions and proper splitting for accurate characterization of aviation fuels.