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Background: Polyesters are applied in high-end products in many industrial applications, including resins and powder-coating applications. The characterization of the chemical heterogeneities within a polyester is of utmost interest to develop new products or improve existing applications. Unfortunately, characterization is a difficult task, as polyesters may feature distributions in end-group functionality, molecular weight, chemical composition, and degree of branching. Currently, no analytical method can characterize all these interdependent distributions in a single analysis., Results: We report the use of comprehensive normal-phase liquid chromatography × size-exclusion chromatography hyphenated with ultraviolet-light spectroscopy and high-resolution mass spectrometry in parallel (NPLC × SEC-UV/HRMS) to characterize polyesters according to their end-group-functionality and molecular-weight distributions. The chemical composition can be measured with HRMS, while relative quantitation can be performed with UV detection. A supercharging agent was used during ionization allowing to extend the molecular-weight range of the detected chemical species., Significance: The presented platform allows characterization of polyesters with varying fractions of carboxyl or hydroxyl end-group functionalities and varying distributions of molecular weight, degree of branching, and chemical compositions. The number-average and weight-average molar masses are obtained in the same analysis. This information cannot be obtained by any one-dimensional technique. The developed NPLC × SEC-UV/HRMS platform is a valuable tool for characterizing polyesters in an industrial setting., Competing Interests: Declaration of competing interest “The authors declare that they have no known competing financial interest or personal relationship that could have appeared to influence the work reported in this paper.”, (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Fischer-Tropsch synthesis combined with product workup is a promising route toward synthetic aviation fuel from renewable hydrogen and carbon sources like biomass, CO 2 , and waste. Cost savings can be achieved by reducing the number of gas treatment steps in new plants, but the consequence of contaminants in the feed needs investigation. While feeding 2.6 ppmV ammonia to a Fischer-Tropsch reactor, it was shown that ammonia was predominantly chemically converted into organic amines, with most nitrogen found in the water phase (89%), followed by heavy wax (7%) and light wax (1%). The concentration difference between water and light wax was shown to be due to the post-condensation separation of amines on polarity. Amines up to a chain length of 120 were detected in the heavy wax with MALDI-FT-ICR-MS, which, in combination with the high nitrogen content, suggests that amines have a similar chain growth probability compared to the main hydrocarbon products. Detailed product analysis with three independent analytical techniques showed that tertiary N , N -dimethylalkylamines were by far the most abundant amine class. This suggests that ammonia is decomposed on the cobalt surface and, potentially as a dimethylamine fragment, incorporated in the growing chain. Further evidence was obtained from the abundance of trimethylamine and from the reconciled nitrogen product analysis up to C100, which showed that the amine product distribution followed from naphtha onward the same ASF kinetics as alkanes and oxygenates while being distinctively different from the alkene distribution. The presented findings provide further avenues for studies of the Fischer-Tropsch reaction mechanism and indicate the opportunity of cost saving on gas treatment, while further validation is required to assess the impact on hydrocracking and product quality., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Trapped ion mobility spectrometry-time-of-flight mass spectrometry (TIMS-TOFMS) has emerged as a tool to study protein conformational states. In TIMS, gas-phase ions are guided across the IM stages by applying direct current (DC) potentials (D1-6), which, however, might induce changes in protein structures through collisional activation. To define conditions for native protein analysis, we evaluated the influence of these DC potentials using the metalloenzyme bovine carbonic anhydrase (BCA) as primary test compound. The variation of DC potentials did not change BCA-ion charge and heme content but affected (relative) charge-state intensities and adduct retention. Constructed extracted-ion mobilograms and corresponding collisional cross-section (CCS) profiles gave useful insights in (alterations of) protein conformational state. For BCA, the D3 and D6 potential (which are applied between the deflection transfer and funnel 1 [F1] and the accumulation exit and the start of the ramp, respectively) had most profound effects, showing multimodal CCS distributions at higher potentials indicating gradual unfolding. The other DC potentials only marginally altered the CCS profiles of BCA. To allow for more general conclusions, five additional proteins of diverse molecular weight and conformational stability were analyzed, and for the main protein charge states, CCS profiles were constructed. Principal component analysis (PCA) of the obtained data showed that D1 and D3 exhibit the highest degree of correlation with the ratio of folded and unfolded protein (F/U) as extracted from the mobilograms obtained per set D potential. The correlation of D6 with F/U and protein charge were similar, and D2, D4, and D5 showed an inverse correlation with F/U but were correlated with protein charge. Although DC boundary values for induced conformational changes appeared protein dependent, a set of DC values could be determined, which assured native analysis of most proteins., (© 2024 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons Ltd.)

New psychoactive substances (NPS) are synthetic derivatives of illicit drugs designed to mimic their psychoactive effects. NPS are typically not controlled under drug acts or their legal status depends on their molecular structure. Discriminating isomeric forms of NPS is therefore crucial for forensic laboratories. In this study, a trapped ion mobility spectrometry time-of-flight mass spectrometry (TIMS-TOFMS) approach was developed for the identification of ring-positional isomers of synthetic cathinones, a class of compounds representing two-third of all NPS seized in Europe in 2020. The optimized workflow features narrow ion-trapping regions, mobility calibration by internal reference, and a dedicated data-analysis tool, allowing for accurate relative ion-mobility assessment and high-confidence isomer identification. Ortho-, meta- and para-isomers of methylmethcathinone (MMC) and bicyclic ring isomers of methylone were assigned based on their specific ion mobilities within 5 min, including sample preparation and data analysis. The resolution of two distinct protomers per cathinone isomer added to the confidence in identification. The developed approach was successfully applied to the unambiguous assignment of MMC isomers in confiscated street samples. These findings demonstrate the potential of TIMS-TOFMS for forensic case work requiring fast and highly-confident assignment cathinone-drug isomers in confiscated samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Trapped ion-mobility spectrometry combined with quadrupole time-of-flight mass spectrometry (TIMS-QTOFMS) was evaluated as a tool for resolving linear and branched isomeric polyester oligomers. Solutions of polyester samples were infused directly into the ion source employing electrospray ionization (ESI). TIMS-MS provides both mobility and m / z data on the formed ions, allowing construction of extracted-ion mobilograms (EIMs). EIMs of polyester molecules showed multimodal patterns, indicating conformational differences among isomers. Subsequent TIMS-MS/MS experiments indicated mobility differences to be caused by (degree of) branching. These assignments were supported by liquid chromatography-TIMS-MS/MS analysis, confirming that direct TIMS-MS provided fast (500 ms/scan) distinction between linear and branched small oligomers. Observing larger oligomers (up to 3000 Da) using TIMS required additional molecular charging to ensure ion entrapment within the mobility window. Molecular supercharging was achieved using m -nitrobenzyl alcohol (NBA). The additional charges on the oligomer structures enhanced mobility separation of isomeric species but also added to the complexity of the obtained fragmentation mass spectra. This complexity could be partly reduced by post-TIMS analyte-decharging applying collision-induced dissociation (CID) prior to Q1 with subsequent isolation of the singly charged ions for further fragmentation. The as-obtained EIM profiles were still quite complex as larger molecules possess more possible structural isomers. Nevertheless, distinguishing between linear and symmetrically branched oligomers was possible based on measured differences in collisional cross sections (CCSs). The established TIMS-QTOFMS approach reliably allows branching information on isomeric polyester molecules up to 3000 Da to be obtained in less than 1 min analysis time.

Size-exclusion chromatography employing aqueous mobile phases with volatile salts at neutral pH combined with electrospray-ionization mass spectrometry (SEC-ESI-MS) is a useful tool to study proteins in their native state. However, whether the applied eluent conditions actually prevent protein-stationary phase interactions, and/or protein denaturation, often is not assessed. In this study, the effects of volatile mobile phase additives on SEC retention and ESI of proteins were thoroughly investigated. Myoglobin was used as the main model protein, and eluents of varying ionic strength and pH were applied. The degree of interaction between protein and stationary phase was evaluated by calculating the SEC distribution coefficient. Protein-ion charge state distributions obtained during offline and online native ESI-MS were used to monitor alterations in protein structure. Interestingly, most of the supposedly mild eluent compositions induced nonideal SEC behavior and/or protein unfolding. SEC experiments revealed that the nature, ionic strength, and pH of the eluent affected protein retention. Protein-stationary phase interactions were effectively avoided using ammonium acetate at ionic strengths above 0.1 M. Direct-infusion ESI-MS showed that the tested volatile eluent salts seem to follow the Hofmeister series: no denaturation was induced using ammonium acetate (kosmotropic), whereas ammonium formate and bicarbonate (both chaotropic) caused structural changes. Using a mobile phase of 0.2 M ammonium acetate (pH 6.9), several proteins (i.e., myoglobin, carbonic anhydrase, and cytochrome c) could be analyzed by SEC-ESI-MS using different column chemistries without compromising their native state. Overall, with SEC-ESI-MS, the effect of nonspecific interactions between protein and stationary phase on the protein structure can be studied, even revealing gradual structural differences along a peak.