Gas chromatography in combination with fast high-resolution time-of-flight mass spectrometry: Technical overview and perspectives for data visualization

A Gated TIMS FTICR MS Instrument to Decipher Isomeric Content of Complex Organic Mixtures

Modern research faces increasingly complex materials with a constant need for new analytical strategies that can provide deeper levels of chemical insight. Ultrahigh resolution mass spectrometry (MS), particularly Fourier transform ion cyclotron resonance (FTICR) MS, has provided a robust analytical foundation. However, MS alone offers limited structural information. Here, we present the first implementation and results from an FTICR MS with fully integrated dual accumulation analysis with gated trapped ion mobility spectrometry (gTIMS) capability. The drastically extended charge capacity and parallel accumulation facilitate the analysis of complex mixtures. We achieved a high dynamic range of 4 orders of magnitude within a single FTICR acquisition event. Simultaneously, the valuable linear relationship between the TIMS elution voltage and reduced mobility was retained over a wide mobility range. Benchmarking the instrument performance with Suwannee River fulvic acid (SRFA) by variable ramp gTIMS analysis allowed separation and unambiguous assignment of different charge state distributions. Application to bio-oils has proven the capability to distinguish the isomeric diversity in these ultracomplex samples, while maintaining the expected FTICR MS resolving power and mass accuracy. Valuable information about the molecular distribution, isomeric diversity, and main molecular differences could directly be extracted within the analysis time of a classical "dilute and shoot" direct infusion experiment. The development of this fully integrated and flexible gTIMS with FTICR MS analysis possesses the potential to significantly change the current landscape of high-resolution mass spectrometric analysis of complex mixtures through the added insight of isomeric complexity afforded by TIMS. The exploration of the added IMS dimension promises transformative effects across diverse fields including energy transition, environmental studies, and biological research.

Gain deeper insights into traditional Chinese medicines using multidimensional chromatography combined with chemometric approaches

Traditional Chinese medicines (TCMs) possess a rich historical background, unique theoretical framework, remarkable therapeutic efficacy, and abundant resources. However, the modernization and internationalization of TCMs have faced significant obstacles due to their diverse ingredients and unknown mechanisms. To gain deeper insights into the phytochemicals and ensure the quality control of TCMs, there is an urgent need to enhance analytical techniques. Currently, two-dimensional (2D) chromatography, which incorporates two independent separation mechanisms, demonstrates superior separation capabilities compared to the traditional one-dimensional (1D) separation system when analyzing TCMs samples. Over the past decade, new techniques have been continuously developed to gain actionable insights from complex samples. This review presents the recent advancements in the application of multidimensional chromatography for the quality evaluation of TCMs, encompassing 2D-gas chromatography (GC), 2D-liquid chromatography (LC), as well as emerging three-dimensional (3D)-GC, 3D-LC, and their associated data-processing approaches. These studies highlight the promising potential of multidimensional chromatographic separation for future phytochemical analysis. Nevertheless, the increased separation capability has resulted in higher-order data sets and greater demands for data-processing tools. Considering that multidimensional chromatography is still a relatively nascent research field, further hardware enhancements and the implementation of chemometric methods are necessary to foster its robust development.

Insights in Pharmaceutical Pollution: The Prospective Role of eDNA Metabarcoding

Environmental pollution is a growing threat to natural ecosystems and one of the world's most pressing concerns. The increasing worldwide use of pharmaceuticals has elevated their status as significant emerging contaminants. Pharmaceuticals enter aquatic environments through multiple pathways related to anthropogenic activity. Their high consumption, insufficient waste treatment, and the incapacity of organisms to completely metabolize them contribute to their accumulation in aquatic environments, posing a threat to all life forms. Various analytical methods have been used to quantify pharmaceuticals. Biotechnology advancements based on next-generation sequencing (NGS) techniques, like eDNA metabarcoding, have enabled the development of new methods for assessing and monitoring the ecotoxicological effects of pharmaceuticals. eDNA metabarcoding is a valuable biomonitoring tool for pharmaceutical pollution because it (a) provides an efficient method to assess and predict pollution status, (b) identifies pollution sources, (c) tracks changes in pharmaceutical pollution levels over time, (d) assesses the ecological impact of pharmaceutical pollution, (e) helps prioritize cleanup and mitigation efforts, and (f) offers insights into the diversity and composition of microbial and other bioindicator communities. This review highlights the issue of aquatic pharmaceutical pollution while emphasizing the importance of using modern NGS-based biomonitoring actions to assess its environmental effects more consistently and effectively.

Analysis of complex drugs by comprehensive two-dimensional gas chromatography and high-resolution mass spectrometry: detailed chemical description of the active pharmaceutical ingredient sodium bituminosulfonate and its process intermediates

The European pharmacopeia provides analytical methods for the chemical characterization of active pharmaceutical ingredients (APIs). However, the complexity of some APIs exceeds the limitations of the currently prevailing physicochemical methods. Sodium bituminosulfonate (SBS) is described by the collection of key parameters of generalizing criteria such as dry matter, sulfur and sodium content, and neutrality, but techniques to unravel the complexity on a molecular level are lacking. We present a study based on online derivatization with tetramethylammonium hydroxide in combination with comprehensive two-dimensional gas chromatography coupled to an electron ionization high-resolution time-of-flight mass spectrometer (GC × GC-HR-ToF–MS) for the chemical description of SBS as well as its process intermediates. The application of GC × GC allowed the comprehensive description of the chemical components in the API and the process intermediates for the first time. Furthermore, it was possible to classify peaks regarding their elemental and structural composition based on accurate mass information, elution behavior, and mass fragmentation pattern. This work demonstrates not only the general applicability, advantages but also limitations of GC × GC for the characterization of APIs for complex drugs.

Graphical Abstract

Pharmaceutical Pollution in Aquatic Environments: A Concise Review of Environmental Impacts and Bioremediation Systems

The presence of emerging contaminants in the environment, such as pharmaceuticals, is a growing global concern. The excessive use of medication globally, together with the recalcitrance of pharmaceuticals in traditional wastewater treatment systems, has caused these compounds to present a severe environmental problem. In recent years, the increase in their availability, access and use of drugs has caused concentrations in water bodies to rise substantially. Considered as emerging contaminants, pharmaceuticals represent a challenge in the field of environmental remediation; therefore, alternative add-on systems for traditional wastewater treatment plants are continuously being developed to mitigate their impact and reduce their effects on the environment and human health. In this review, we describe the current status and impact of pharmaceutical compounds as emerging contaminants, focusing on their presence in water bodies, and analyzing the development of bioremediation systems, especially mycoremediation, for the removal of these pharmaceutical compounds with a special focus on fungal technologies.

Maillard reaction of food-derived peptides as a potential route to generate meat flavor compounds: A review

Plant-based meat analogues (PBMA) are promising foods to address the global imbalance between the supply and demand for meat products caused by the increasing environmental pressures and growing human population. Given that the flavor of PBMA plays a crucial role in consumer acceptance, imparting meat-like flavor is of great significance. As a natural approach to generate meat-like flavor, the Maillard reaction involving food-derived peptides could contribute to the required flavor compounds, which has promising applications in PBMA formulations. In this review, the precursors of meat-like flavor are summarized followed by a discussion of the reactions and mechanisms responsible for generation of the flavor compounds. The preparation and analysis techniques for food-derived Maillard reacted peptides (MRPs) as well as their taste and aroma properties are discussed. In addition, the MRPs as meat flavor precursors and their potential application in the formulation of PBMA are also discussed. The present review provides a fundamental scientific information useful for the production and application of MRPs as meat flavor precursors in PBMA.

Detection and toxicity modeling of anthraquinone dyes and chlorinated side products from a colored smoke pyrotechnic reaction

"Green" pyrotechnics seek to remove known environmental pollutants and health hazards from their formulations. This chemical engineering approach often focuses on maintaining performance effects upon replacement of objectionable ingredients, yet neglects the chemical products formed by the exothermic reaction. In this work, milligram quantities of a lab-scale pyrotechnic red smoke composition were functioned within a thermal probe for product identification by pyrolysis-gas chromatography-mass spectrometry. Thermally decomposed ingredients and new side product derivatives were identified at lower relative abundances to the intact organic dye (as the engineered sublimation product). Side products included chlorination of the organic dye donated by the chlorate oxidizer. Machine learning quantitative structure-activity relationship models computed impacts to health and environmental hazards. High to very high toxicities were predicted for inhalation, mutagenicity, developmental, and endocrine disruption for common military pyrotechnic dyes and their analogous chlorinated side products. These results underscore the need to revise objectives of "green" pyrotechnic engineering.

Vacuum Laser Photoionization inside the C-trap of an Orbitrap Mass Spectrometer: Resonance-Enhanced Multiphoton Ionization High-Resolution Mass Spectrometry

State-of-the-art mass spectrometry with ultraviolet (UV) photoionization is mostly limited to time-of-flight (ToF) mass spectrometers with 1000-10 000 m/Δm mass resolution. However, higher resolution and higher spectral dynamic range mass spectrometry may be indispensable in complex mixture characterization. Here, we present the concept, implementation, and initial evaluation of a compact ultrahigh-resolution mass spectrometer with gas-phase laser ionization. The concept is based on direct laser photoionization in the ion accumulation and ejection trap (C-trap) of an Orbitrap mass spectrometer. Resonance-enhanced multiphoton ionization (REMPI) using 266 nm UV pulses from a frequency-quadrupled Nd:YAG laser was applied for selective and efficient ionization of monocyclic and polycyclic aromatic hydrocarbons. The system is equipped with a gas inlet for volatile compounds and a heated gas chromatography coupling. The former can be employed for rapid system m/z-calibration and performance evaluation, whereas the latter enables analysis of semivolatile and higher-molecular-weight compounds. The capability to evaluate complex mixtures is demonstrated for selected petrochemical materials. In these experiments, several hundred to over a thousand compounds could be attributed with a root-mean-square mass error generally below 1 ppm and a mass resolution of over 140 000 at 200 m/z. Isobaric interferences could be resolved, and narrow mass splits, such as 3.4 mDa (SH₄/C₃), are determined. Single laser shots provided limits of detection in the 20-ppb range for p-xylene and 1,2,4-trimethylbenzene, similar to compact vacuum REMPI-ToF systems.

Advances in high resolution GC-MS technology: a focus on the application of GC-Orbitrap-MS in metabolomics and exposomics for FAIR practices

Gas chromatography-mass spectrometry (GC-MS) provides a complementary analytical platform for capturing volatiles, non-polar and (derivatized) polar metabolites and exposures from a diverse array of matrixes. High resolution (HR) GC-MS as a data generation platform can capture data on analytes that are usually not detectable/quantifiable in liquid chromatography mass-spectrometry-based solutions. With the rise of high-resolution accurate mass (HRAM) GC-MS systems such as GC-Orbitrap-MS in the last decade after the time-of-flight (ToF) renaissance, numerous applications have been found in the fields of metabolomics and exposomics. In a short span of time, a multitude of studies have used GC-Orbitrap-MS to generate exciting new high throughput data spanning from diverse basic to applied research areas. The GC-Orbitrap-MS has found application in both targeted and untargeted efforts for capturing metabolomes and exposomes across diverse studies. In this review, I capture and summarize all the reported studies to date, and provide a snapshot of the milieu of commercial and open-source software solutions, spectral libraries, and informatics solutions available to a GC-Orbitrap-MS system instrument user or a data analyst dealing with these datasets. Lastly, but importantly, I provide an account on data sharing and meta-data capturing solutions that are available to make HRAM GC-MS based metabolomics and exposomics studies findable, accessible, interoperable, and reproducible (FAIR). These FAIR practices would allow data generators and users of GC-HRMS instruments to help the community of GC-MS researchers to collaborate and co-develop exciting tools and algorithms in the future.

Endocrine-Disrupting Compounds: An Overview on Their Occurrence in the Aquatic Environment and Human Exposure

Endocrine-disrupting compounds (EDCs) as emerging contaminants have accumulated in the aquatic environment at concentration levels that have been determined to be significant to humans and animals. Several compounds belong to this family, from natural substances (hormones such as estrone, 17-estradiol, and estriol) to synthetic chemicals, especially pesticides, pharmaceuticals, and plastic-derived compounds (phthalates, bisphenol A). In this review, we discuss recent works regarding EDC occurrence in the aquatic compartment, strengths and limitations of current analytical methods used for their detection, treatment technologies for their removal from water, and the health issues that they can trigger in humans. Nowadays, many EDCs have been identified in significant amounts in different water matrices including drinking water, thus increasing the possibility of entering the food chain. Several studies correlate human exposure to high concentrations of EDCs with serious effects such as infertility, thyroid dysfunction, early puberty, endometriosis, diabetes, and obesity. Although our intention is not to explain all disorders related to EDCs exposure, this review aims to guide future research towards a deeper knowledge of EDCs’ contamination and accumulation in water, highlighting their toxicity and exposure risks to humans.

Cryogenic trapping as a versatile approach for sample handling, enrichment and multidimensional analysis in gas chromatography

Cryogenic methods - those that employ cryogenic fluids/gases but also other approaches to generate reduced temperature - are versatile, functional and relatively easily implemented as part of a total gas chromatographic method. The general utility of a cold region is almost invariably as a trapping or focussing step, to collect analyte into a sharp zone. The success in effectively trapping analyte depends on analyte volatility and the temperature of the cold region. Analytes collection into a sorbent phase supported by cryotrapping usually provide a greater capacity trapping for the sorption step. Stripping analyte from a sample into a cryogenic trap, with subsequent introduction to GC as in a purge-and-trap method, sample introduction into an injector with incorporation of a cooling zone, manipulation and management of chromatographic bands during chromatography elution such as employed in multidimensional gas chromatography, and focussing analyte just prior to the detector, all have the same goal of concentrating the band, reducing its dispersion, and maximising response. This review summarises various approaches that demonstrate how cryogenic methods have been incorporated into gas chromatographic analysis.

Recent Advances in the Rejection of Endocrine-Disrupting Compounds from Water Using Membrane and Membrane Bioreactor Technologies: A Review

Water is a critical resource necessary for life to be sustained, and its availability should be secured, appropriated, and easily obtainable. The continual detection of endocrine-disrupting chemicals (EDCs) (ng/L or µg/L) in water and wastewater has attracted critical concerns among the regulatory authorities and general public, due to its associated public health, ecological risks, and a threat to global water quality. Presently, there is a lack of stringent discharge standards regulating the emerging multiclass contaminants to obviate its possible undesirable impacts. The conventional treatment processes have reportedly ineffectual in eliminating the persistent EDCs pollutants, necessitating the researchers to develop alternative treatment methods. Occurrences of the EDCs and the attributed effects on humans and the environment are adequately reviewed. It indicated that comprehensive information on the recent advances in the rejection of EDCs via a novel membrane and membrane bioreactor (MBR) treatment techniques are still lacking. This paper critically studies and reports on recent advances in the membrane and MBR treatment methods for removing EDCs, fouling challenges, and its mitigation strategies. The removal mechanisms and the operating factors influencing the EDCs remediation were also examined. Membranes and MBR approaches have proven successful and viable to eliminate various EDCs contaminants.

Cyclic Ion Mobility Spectrometry Coupled to High-Resolution Time-of-Flight Mass Spectrometry Equipped with Atmospheric Solid Analysis Probe for the Molecular Characterization of Combustion Particulate Matter

Anthropogenic air pollution has a severe impact on climate and human health. The immense molecular complexity and diversity of particulate matter (PM) is a result of primary organic aerosol (POA) as well as secondary organic aerosols (SOAs). In this study, a direct inlet probe (DIP), i.e., atmospheric solids analysis probe (ASAP), with ion mobility high-resolution mass spectrometric detection is applied. Primary particulate matter emissions from three sources were investigated. Furthermore, photochemically aged emissions were analyzed. DIP introduction allowed for a direct analysis with almost no sample preparation and resulted in a complex molecular pattern. This pattern shifted through oxidation processes toward heavier species. For diesel emissions, the fuel's chemical characteristic is partially transferred to the particulate matter by incomplete combustion and characteristic alkylated series were found. Polycyclic aromatic hydrocarbons (PAHs) were identified as major contributors. Ion mobility analysis results in drift time profiles used for structural analysis. The apex position was used to prove structural changes, whereas the full-width-at-half-maximum was used to address the isomeric diversity. With this concept, the dominance of one or a few isomers for certain PAHs could be shown. In contrast, a broad isomeric diversity was found for oxygenated species. For the in-depth specification of fresh and aged spruce emissions, the ion mobility resolving power was almost doubled by allowing for three passes in the circular traveling wave design. The results prove that ASAP coupled with ion mobility spectrometry-mass spectrometry (IMS-MS) serves as a promising analytical approach for tackling the vast molecular complexity of PM.