Plate-height model of ion mobility-mass spectrometry: Part 2-Peak-to-peak resolution and peak capacity

Ion Mobility Mass Spectrometry-Based Disaccharide Analysis of Glycosaminoglycans

Glycosaminoglycans (GAGs) are linear and acidic polysaccharides. They are ubiquitous molecules, which are involved in a wide range of biological processes. Despite being structurally simple at first glance, with a repeating backbone of alternating hexuronic acid and hexosamine dimers, GAGs display a highly complex structure, which predominantly results from their heterogeneous sulfation patterns. The commonly applied method for compositional analysis of all GAGs is "disaccharide analysis." In this process, GAGs are enzymatically depolymerized into disaccharides, derivatized with a fluorescent label, and then analysed through liquid chromatography. The limiting factor in the high throughput analysis of GAG disaccharides is the time-consuming liquid chromatography. To address this limitation, we here utilized trapped ion mobility-mass spectrometry (TIM-MS) for the separation of isomeric GAG disaccharides, which reduces the measurement time from hours to a few minutes. A full set of disaccharides comprises twelve structures, with eight possessing isomers. Most disaccharides cannot be differentiated by TIM-MS in underivatized form. Therefore, we developed chemical modifications to reduce sample complexity and enhance differentiability. Quantification is performed using stable isotope labelled standards, which are easily available due to the nature of the performed modifications.

Preparation of carboxyl-functionalized silica core-shell microspheres and their applications in weak cation exchange chromatography, heavy metal removal, and lysozyme enrichment

Chromatography is a technique of separation based on adsorption and/or interaction of target molecules with stationary phases. Herein, we report the design and fabrication of BTDA@SiO2 core-shell microspheres as a new class of stationary phase and demonstrate its impressive performance for chromatographic separations. The silica microspheres of BTDA@SiO2 were synthesized by in situ method with 1,3,5-benzenetricarboxaldehyde and 3,5-diaminobenzoic to separate peptides and proteins on high-performance liquid chromatography. The BTDA@SiO2 core-shell structure has a high specific surface area and retention factor of 4.27 and 8.31 for anionic and cationic peptides, respectively. The separation factor and resolution were high as well. A typical chromatogram illustrated nearly baseline resolution of the two peptides in less than 3 min. The BTDA@SiO2 was also highly stable in the pH range of 1 to 14. Furthermore, the prepared BTDA@SiO2 core-shell material not only be used for chromatographic separation but also as heavy metal removal from water. Using a BTDA@SiO2, we also achieved a lysozyme enrichment with a maximum saturated adsorption capacity reaching 714 mg/g. In summary, BTDA@SiO2 has great application prospects and significance in separation and purification systems.

Ion mobility-tandem mass spectrometry of mucin-type O-glycans

The dense O-glycosylation of mucins plays an important role in the defensive properties of the mucus hydrogel. Aberrant glycosylation is often correlated with inflammation and pathology such as COPD, cancer, and Crohn's disease. The inherent complexity of glycans and the diversity in the O-core structure constitute fundamental challenges for the analysis of mucin-type O-glycans. Due to coexistence of multiple isomers, multidimensional workflows such as LC-MS are required. To separate the highly polar carbohydrates, porous graphitized carbon is often used as a stationary phase. However, LC-MS workflows are time-consuming and lack reproducibility. Here we present a rapid alternative for separating and identifying O-glycans released from mucins based on trapped ion mobility mass spectrometry. Compared to established LC-MS, the acquisition time is reduced from an hour to two minutes. To test the validity, the developed workflow was applied to sputum samples from cystic fibrosis patients to map O-glycosylation features associated with disease.

Untargeted 4D-metabolomics using Trapped Ion Mobility combined with LC-HRMS in extra virgin olive oil adulteration study with lower-quality olive oils

Metabolomics is widely established in the field of food authenticity to address demanding issues, such as adulteration cases. Trapped ion mobility spectrometry (TIMS) coupled to liquid chromatography (LC) and high-resolution mass spectrometry (HRMS) provides an additional analytical dimension, introducing mobility-enhanced metabolomics in four dimensions (4D). In the present work, the potential of LC-TIMS-HRMS as a reliable analytical platform for authenticity studies is being explored, applied in extra virgin olive oil (EVOO) adulteration study. An integrated untargeted 4D-metabolomics approach is being implemented to investigate adulteration, with refined olive oils (ROOs) and olive pomace oils (OPOs) set as adulterants. Robust prediction models are built, successfully discriminating authentic EVOOs from adulterated ones and highlighting markers in each group. Noteworthy outcomes are retrieved regarding TIMS added value in LC-HRMS workflows, resulting in a significant increase of metabolic coverage, while, thanks to platform's enhanced sensitivity, detection of adulteration is being achieved down to 1%.

Highly Efficient Ion Manipulator for Tandem Ion Mobility Spectrometry: Exploring a Versatile Technique by a Study of Primary Alcohols

In this work, we present a tandem ion mobility spectrometer (IMS) utilizing a highly efficient ion manipulator allowing to store, manipulate, and analyze ions under high electric field strengths and controlled ion-neutral reactions at ambient conditions. The arrangement of tandem drift regions and an ion manipulator in a single drift tube allows a sequence of mobility selection of precursor ions, followed by storage and analysis, mobility separation, and detection of the resulting product ions. In this article, we present a journey exploring the capabilities of the present instrument by a study of eight different primary alcohols characterized at reduced electric field strengths E/N of up to 120 Td with a water vapor concentration ranging from 40 to 540 ppb. Under these conditions, protonated alcohol monomers up to a carbon number of nine could be dissociated, resulting in 18 different fragmented product ions in total. The fragmentation patterns revealed regularities, which can be used for assignment to the chemical class and improved classification of unknown substances. Furthermore, both the time spent in high electrical field strengths and the reaction time with water vapor can be tuned precisely, allowing the fragment distribution to be influenced. Thus, further information regarding the relations of the product ions can be gathered in a standalone drift tube IMS for the first time.

Integrating ion mobility into comprehensive multidimensional metabolomics workflows: critical considerations

BACKGROUND

Ion mobility (IM) separation capabilities are now widely available to researchers through several commercial vendors and are now being adopted into many metabolomics workflows. The added peak capacity that ion mobility offers with minimal compromise to other analytical figures-of-merit has provided real benefits to sensitivity and structural selectivity and have allowed more specific metabolite annotations to be assigned in untargeted workflows. One of the greatest promises of contemporary IM-enabled instrumentation is the capability of operating multiple analytical dimensions inline with minimal sample volumes, which has the potential to address many grand challenges currently faced in the omics fields. However, comprehensive operation of multidimensional mass spectrometry comes with its own inherent challenges that, beyond operational complexity, may not be immediately obvious to practitioners of these techniques.

AIM OF REVIEW

In this review, we outline the strengths and considerations for incorporating IM analysis in metabolomics workflows and provide a critical but forward-looking perspective on the contemporary challenges and prospects associated with interpreting IM data into chemical knowledge.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We outline a strategy for unifying IM-derived collision cross section (CCS) measurements obtained from different IM techniques and discuss the emerging field of high resolution ion mobility (HRIM) that is poised to address many of the contemporary challenges associated with ion mobility metabolomics. Whereas the LC step limits the throughput of comprehensive LC-IM-MS, the higher peak capacity of HRIM can allow fast LC gradients or rapid sample cleanup via solid-phase extraction (SPE) to be utilized, significantly improving the sample throughput.

Evaluating the Utility of Temporal Compression in High-Resolution Traveling Wave-Based Cyclic Ion Mobility Separations

Ion mobility spectrometry coupled to mass spectrometry (IMS-MS) is slowly becoming a more integral part in omics-based workflows. With the recent technological advancements in IMS-MS instrumentation, particularly those involving traveling wave-based separations, ultralong pathlengths have become readily available in commercial platforms (e.g., Select Series Cyclic IMS from Waters Corporation and MOBIE from MOBILion). However, a tradeoff exists in such ultralong pathlength separations: increasing peak-to-peak resolution at the cost of lower signal intensities and thus poorer sensitivity of measurements. Herein, we explore the utility of temporal compression, where ions are compressed in the time domain, following high-resolution cyclic ion mobility spectrometry-mass spectrometry-based separations on a commercially available, unmodified platform. We assessed temporal compression in the context of various separations including those of reverse sequence peptide isomers, chiral noncovalent complexes, and isotopologues. From our results, we demonstrated that temporal compression improves IMS peak intensities by up to a factor of 4 while only losing ∼5 to 10% of peak-to-peak resolution. Additionally, the improvement in peak quality and signal-to-noise ratio was evident when comparing IMS-MS separations with and without a temporal compression step performed. Temporal compression can readily be implemented in existing traveling wave-based IMS-MS platforms, and our initial proof-of-concept demonstration shows its promise as a tool for improving peak shapes and peak intensities without sacrificing losses in resolution.

Trapped Ion Mobility Incorporated in LC-HRMS Workflows as an Integral Analytical Platform of High Sensitivity: Targeted and Untargeted 4D-Metabolomics in Extra Virgin Olive Oil

Trapped ion mobility spectrometry (TIMS) is a promising technique for the separation of isomers based on their mobility. In the present work, TIMS coupled to liquid chromatography (LC) and high-resolution mass spectrometry (HRMS) was applied as a comprehensive analytical platform to address authenticity challenges, focusing on extra virgin olive oil (EVOO). Isomers detected in EVOO's phenolic fraction, classified into secoiridoids group, were successfully separated. Thanks to parallel accumulation serial fragmentation (PASEF) acquisition mode, high-quality spectra were obtained, facilitating identification. Moreover, a four-dimensional (4D) untargeted metabolomics approach was implemented to evaluate EVOO's global profile in cases of both variety and geographical origin discrimination. Potential authenticity markers, attributed to isomers, were successfully identified through the proposed workflow that incorporates ion mobility information along with LC-HRMS analytical evidence (i.e., mass accuracy, retention time, isotopic pattern, MS/MS fragmentation). Our study establishes LC-TIMS-HRMS in food authenticity and highlights mobility-enhanced metabolomics in four dimensions.

Investigating the Structure of α/β Carbohydrate Linkage Isomers as a Function of Group I Metal Adduction and Degree of Polymerization as Revealed by Cyclic Ion Mobility Separations

In high-resolution ion mobility spectrometry-mass spectrometry (IMS-MS)-based separations individual, pure, oligosaccharide species often produce multiple IMS peaks presumably from their α/β anomers, cation attachment site conformations, and/or other energetically favorable structures. Herein, the use of high-resolution traveling wave-based cyclic IMS-MS to systematically investigate the origin of these multiple peaks by analyzing α1,4- and β1,4-linked d-glucose homopolymers as a function of their group I metal adducts is presented. Across varying degrees of polymerization, and for certain metal adducts, at least two major IMS peaks with relative areas that matched the ∼40:60 ratio for the α/β anomers of a reducing-end d-glucose as previously calculated by NMR were observed. To further validate that these were indeed the α/β anomers, rather than other substructures, the reduced versions of several maltooligosaccharides were analyzed and all produced a single IMS peak. This result enabled the discovery of a mobility fingerprint trend: the β anomer was always higher mobility than the α anomer for the cellooligosaccharides, while the α anomer was always higher mobility than the β anomer for the maltooligosaccharides. For maltohexaose, a spurious, high mobility, fourth peak was present. This was hypothesized to potentially be from a highly compacted conformation. To investigate this, α-cyclodextrin, a cyclic oligosaccharide, produced similar arrival times as the high mobility maltohexaose peak. It is anticipated that these findings will aid in the data deconvolution of IMS-MS-based glycomics workflows and enable the improved characterization of biologically relevant carbohydrates.