Stefan Böhmdorfer

Pyrolysis–gas chromatography–mass spectrometry (Pyr-GC-MS) has evolved into one of the most powerful methods for microplastics (MPs) analysis. However, analytical challenges are still encountered whenever Pyr-GC-MS is applied to matrices with high organic matter, protein and lipid contents. In this study, a workflow integrating stereomicroscopy, micro-Fourier transform infrared (µ-FTIR) spectroscopy and Pyr-GC-MS was extended to analyse MPs in three endemic fish species ( Protopterus aethiopicus , Rastrineobola argentea and Synodontis victoriae ) from Lake Victoria. Stereomicroscopic analysis only detected MPs in the gastrointestinal tracts of P. aethiopicus and S. victoriae , with the highest mean particle numbers being 16.0 ± 7.8 and 14.7 ± 6.7 items/fish taxon, respectively. No MPs were found in whole samples of R. argentea . The microparticles were mostly blue and brown 0.3–1.9-mm fragments and filaments, which µ-FTIR analysis confirmed to be composed of nylon 66, nylon 6/66, nylon 6/10, nylon 11, polyethylene and polypropylene. Retention time locking and post-column backflush considerably reduced the cycle time and increased stability of the Pyr-GC-MS method. Nylon 66 (243 µg/g in S. victoriae ), nylon 6 (0.24–96 µg/g), polypropylene (6.4 µg/g in P. aethiopicus ), poly(ethylene terephthalate) (1.2–107 µg/g) and styrene-butadiene rubber (8.5–34.8 µg/g) were quantified. Polyethylene and poly(methyl methacrylate) were detected below their limits of quantification. To prevent false positive detection of polyethylene in the lipid-rich tissues, the evaluation focussed on C21-α,ω-alkene as a marker. Polypropylene was not detected in some samples, as it formed several discrete propylene oligomers during pyrolysis, which suppressed the yield of its target quantification marker (2,4-dimethyl-1-heptene).

Background: Etorphine, a highly potent opioid, disrupts multiple steps of the oxygen cascade, including alveolar ventilation, pulmonary gas exchange, systemic oxygen transport, and tissue-level oxygen utilisation, resulting in hypoxaemia and cellular hypoxia during immobilisation of wild ungulates. To evaluate potential mitigating agents, a randomised, prospective, controlled crossover design was used in etorphine-immobilised sheep (0.05 mg·kg ⁻¹ , intramuscularly, n = 6). After etorphine administration, animals received either the serotonergic agonist BIMU-8 (1.5 mg·kg ⁻¹ ), the alpha-2 adrenoceptor antagonist vatinoxan (0.15 mg·kg ⁻¹ ), or sterile water (control) intravenously with a four-week washout period. Immobilisation was reversed with naltrexone 19 min after treatment administration. Sequential steps of the oxygen cascade were assessed using thoracic electrical impedance-derived variables (respiratory rate (RR _EIT ) and tidal impedance variation (TIV)) for ventilation, blood gas analysis and venous admixture for pulmonary gas exchange, oxygen delivery (DO ₂ ) for oxygen transport, and oxygen extraction ratio (ER) for tissue oxygen utilisation. Measurements were obtained at baseline, after etorphine administration, at five-minute intervals following treatment, and after naltrexone. Data was analysed using linear mixed-effects models. Results: Etorphine induced respiratory depression, characterised by reduced RR _EIT ( p < 0.001) and TIV ( p = 0.01), and impaired gas exchange, indicated by increased venous admixture ( p < 0.001) compared with baseline, causing hypercapnia and hypoxaemia in all treatments. Neither BIMU-8 nor vatinoxan improved these variables compared with the control. Consequently, progressive decreases in arterial partial pressure of oxygen (F _3,90 = 104.82, p < 0.001) were observed across treatments during immobilisation, resulting in persistently reduced DO ₂ (F _3,84 = 51.55, p < 0.001) and increased ER (F _3,90 = 8.09, p < 0.001) at similar levels in all treatments. All variables normalised after naltrexone administration. Conclusions: Etorphine profoundly impaired multiple sequential steps of the oxygen cascade in sheep, resulting in hypoxaemia, reduced DO ₂ , and compensatory increases in ER. BIMU-8 and vatinoxan did not effectively mitigate these disturbances at any level of the cascade compared with the control. Future research is needed to develop targeted strategies that address the key mechanisms underlying the disruptions in the oxygen cascade during etorphine immobilisation.

A systematic comparison of SEC solvent systems identifies conditions for a more reliable lignin molar-mass determination, providing practical guidance for lignin characterization.

This study reports large microplastics found in Lake Victoria through an analytical workflow that combines the complementary methods stereomicroscopy, micro-Fourier transform infrared (µ-FTIR) spectroscopy and pyrolysis gas chromatography-mass spectrometry (Pyr-GC-MS) for the quantification of 11 environmentally relevant microplastic polymers. Algae-rich surface water samples ( n = 18) were trawled using a 0.3 mm manta net from Lake Victoria, the world’s largest tropical lake. Stereomicroscopy as a determinant analytical technique detected 191 particles, which were primarily blue fragments and fibres. Polyethylene and polypropylene were the dominant polymers identified by µ-FTIR. Pyr-GC-MS allowed the detection and quantification of microplastics (MPs) with LOD and LOQ of 0.01–14.7 µg and 0.03–49.1 µg. Polyethylene (0.058–0.34 µg/L), polypropylene (0.024 µg/L and 0.043 µg/L), nylon 6 (0.0051–0.064 µg/L), nylon 66 (0.0022–0.084 µg/L), poly(ethylene terephthalate) (0.0029–0.027 µg/L) and poly(methyl methacrylate) (0.0036 µg/L) were quantified. µ-FTIR was found to be suitable for the identification of the most abundant polymers in the 0.3–4.9 mm size range whereas Pyr-GC-MS afforded the quantification of seven polymers, most of which were not detected by µ-FTIR. This complementary workflow gave a wider perspective on MP loading, providing both polymer concentrations and physical characteristics (sizes, colours, forms and count) of the MPs. Graphical abstract

Biomass pretreatments often involve swelling in imidazolium-based ionic liquids (ILs) or beta-irradiation. The combination of both pretreatments can be used intentionally or can also occur inadvertently—for instance, upon irradiation of insufficiently washed biomass that still contains IL residues from an earlier pretreatment step. Previous work has shown a high reactivity of the reducing ends of cellulose upon irradiation in the presence of 1-ethyl-3-methyl-imidazolium (EMIm) ionic liquids which was now studied in detail by means of carbohydrate model compounds (monosaccharides, cellobiose, and cellodextrins). The model reactions show a selective loss of C-1 at the unprotected reducing end. This way, D-glucose is converted into D-arabinose, while D-galactose, the C-4-epimer of glucose, gives D-lyxose, the C-3 epimer of arabinose. The yield of the pentoses from the corresponding hexoses is proportional to the irradiation dose and reaches approx. 15% at an irradiation dose of 800 kGy. Also in cellobiose and cellodextrins, the terminal, reducing glucopyranose unit was converted into the lower arabino-homologue. In all of these processes, the removed C ₁ -unit reacts as an umpoled formaldehyde synthon, confirmed by trapping in Stetter-type reactions with nitroethylene or cyclohexen-3-one. The mechanism of the fragmentation reaction is explained by the irradiative formation of the IL-derived N -heterocyclic carbene (NHC) which, as a strong nucleophile, reacts with the reducing ends of carbohydrates. The initially formed, well-known Breslow intermediate undergoes a retro-benzoin cleavage to give the lower homologue and the umpoled HCHO equivalent. By transfer of this IL-bound C ₁ -synthon to suitable acceptors (trapping agents), the NHC can be regenerated so that a reaction cycle is completed and its action becomes catalytic. The structure elucidation of the products of the model compound reactions is presented, along with a discussion of the formation mechanisms. Graphical abstract

BIMU8 ( N ‐[(1 R ,5 S )‐8‐methyl‐8‐azabicyclo[3.2.1]octan‐3‐yl]‐2‐oxo‐3‐propan‐2‐ylbenzimidazole‐1‐carboxamide) is an agonist of the 5‐HT4 receptor. This receptor is of clinical relevance since it affects several neurological processes, amongst others breathing. In this work, we present the crystal structures of BIMU8, both as a free base and as a hydrochloride salt. Crystals of the free base were grown from ethyl acetate, while slow diffusion of hydrogen chloride vapor into a solution of BIMU8 in ethyl acetate afforded the corresponding hydrochloride crystals. Full sets of ¹ H and ¹³ C NMR spectra of BIMU8 and BIMU8‐HCl were recorded, and complete assignments are reported. Two distinct stereoisomers of the hydrochloride salt were observed in solution by NMR, with the ammonium nitrogen either in exo ‐ or endo ‐configuration, at a ratio of 6:1. In crystals, only the exo ‐form was obtained both for the free base and the hydrochloride salt.

Seedy bananas are used as a traditional medicine in many Asian countries. Even though evidence for the presence of compounds with declared bioactivity in seedy bananas exists, direct assays to ascertain and identify bioactive compounds have not been undertaken so far. In this study, the effect-directed analysis after thin-layer chromatography was used to evaluate the anti-α-glucosidase and anti-acetylcholinesterase activity of seedy banana extracts. High-performance thin-layer chromatography (HPTLC)‒bioautography revealed that the extracts indeed contained inhibitors of both studied enzymes. Four main compounds were isolated, and their structures were determined by mass spectrometry and nuclear magnetic resonance spectroscopy. Piceatannol, scirpusin A, scirpusin B, and cassigarol E (or its isomer, maackin) were confirmed. This study establishes the bioactivity of seedy bananas on the basis of the stilbenes, which strengthens the evidence for the folk medicine use of this plant.

This study aimed at identifying the bioactive compounds in the seeds of three seedy banana varietiesMusa acuminata, Musa itinerans, and Ensete glaucum. GC-MS of extracts and NMR of isolated compounds were used for the identification of the components and GC-MS/FID was employed for quantification. The proportion of seeds in all samples was around 50% of the dried fruit weight. The seeds were rich in piceatannol, (+)-epiafzelechin, and epiafzelechin dimers. Piceatannol and epiafzelechin dimers were reported in seedy bananas for the first time. The highest piceatannol content was found in Ensete, accounting for 713 ± 71.9 mg/100 g dry weight (DW), followed by the seeds of ripe Musa acuminata and Musa itinerans at 440 ± 56.7 and 242 ± 17.4 mg/100 g DW, respectively. Musa seeds with a higher content of piceatannol had lower concentrations of epiafzelechin and its dimers, in the ranges of 287 to 553 mg/100 g of DW and 533 to 976 mg/100 g of DW, respectively. The content depended on maturity. Compared with ripe fruits, green Musas contained hardly any piceatannol and higher levels of epiafzelechin dimers. Gallocatechin was detected only in Ensete glaucum at 145 ± 19.7 mg/100 g of DW, and a major part of the phenolic compounds in g was found in the seed coat. The identified phenolic compounds in the seeds suggest that seedy bananas could be a potential new crop for food supplements.

Solvents are an essential part of liquid chromatography. For categorization, the diversity of solvent properties was captured in several different models. A meaningful description of solvent properties required models with more than two parameters. Showing solvent properties in a graph fosters the reader’s understanding of the diversity of solvent properties, their similarities and dissimilarities. However, there is no universally appropriate solution to prepare such graphs for data sets that comprise more than two parameters. We prepared self-organizing maps for solvents using their descriptors in the solvent parameter model, which were taken from literature. The maps sorted the solvent by similarity and matched solvent classes. In combination with the U-matrix, which captures the change of properties across the map, these maps gave an intuitively comprehensible overview of solvent similarities and dissimilarities. By inspection of the underlying component planes, the grouping of solvents was attributed to an overall framework of solvent properties. The maps are useful both to get an overview of the diversity of the included solvents and to learn how the properties of the solvent parameter model influence the observed solvent differences.

1,3-Dialkylimidazolium carboxylate ionic liquids (ILs) have recently undergone a surge of interest as media for spinning of cellulosic fibers. For 1-alkyl-3-methylimidazolium acetates, the acetylation of cellulose in the process of dope preparation and spinning is a recognized side reaction. In this work, acylation of cellulose by the carboxylate anions of 1-ethyl-3-methylimidazolium-based ILs was shown to be a general side reaction, studied in detail for a series of the corresponding acetates, propanoates and octanoates. The acylation does not proceed in neat, freshly purified ILs, but requires free imidazole which is present in aged (long-term stored) or thermally stressed ILs as a common degradation product of 1,3-dialkylimidazolium cations. Imidazole (Im), in combination with the free acids from the conjugated carboxylate anions, forms N-acylimidazoles as well-known potent, catalytically acting acylation reagents which also effect acylation of cellulose and related carbohydrates. N-Methylimidazole (MIm), another common aging product of 1-alkyl-3-methylimidazolium cations, cannot form similar acyl transfer reagents and thus does not have such a catalytic effect. The amount of resulting esters in cellulose samples spun from aged (thermally stressed and/or long-term stored) 1,3-dialkylimidazolium carboxylates (acetate, pentanoate, octanoate) was determined, according to an established method for accurate quantification of small amounts of acetate esters in biomaterials, based on Zemplén saponification/transesterification. The reactivity decreases with the chain length of the carboxylate anion: a ternary IL mixture that contains the anions acetate, pentanoate and octanoate in a molar ratio of 1:1:1 caused acylation in an approximate molar ratio of 16:4:1. The underlying reaction mechanisms and ways to minimize unwanted cellulose acylation as side reactions are discussed.