De Luca, ChiaraBuratti, AlessandroUmstead, WestonFranco, Pilar...
8页
查看更多>>摘要：The growing popularity of cannabis products and recent legalization of cannabis for recreational purposes have contributed to the increase of the demand for analytical methods able to give a detailed character-ization of cannabis samples and derivatives. In this context, one of the aspects that is strongly emerging is about the hazardous potential of uncharacterised minor cannabinoids, including chiral ones, for which achiral potency testing methods currently employed do not give any information. For this reason, there is a growing interest towards the development of liquid chromatographic methods for the enantiosepa-ration of cannabinoids. Much work is needed in this field where one of the major limitations is the lack of optically pure standards. This manuscript reports about the chromatographic behavior of five popular cannabinoids (including the cannabichromene racemate, CBC) on nine immobilised polysaccharide-based chiral stationary phases (CSPs) differently substituted, under reversed phase conditions. Results showed that chemo-selectivity of CSPs is not affected by changes in mobile phase composition, in the range of mobile phase investigated. In addition, the presence of electron withdrawing groups on the CSPs sys-tematically leads to shorter retention times compared to when electron donating groups are present. An application of separation of cannabinoids from a real hemp extract on two of the chiral columns em-ployed in this work revealed the presence of both CBC enantiomers in the sample. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Glyphosate is the best-selling herbicide worldwide. The toxicity on ecosystems and the possible effects on human health have long been at the centre of a complex controversy concerning the authorisation for its use. The peculiar chemical-physical properties of glyphosate, AMPA and glufosinate make their determi-nation at trace levels in the water a real analytical challenge. All three compounds can be derivatised to less polar ones and FMOC-Cl (9-fluorenylmethyl chloroformate) is the most common pre-column derivati-sation reagent used for this analysis. It can be successfully combined with Ultra-High-Performance Liquid Chromatography with Mass Spectrometry (UHPLC-MS/MS) to determine all three analytes in one method as part of water monitoring programs. The developed method aims to determine glyphosate with AMPA and glufosinate at sub-micrograms/L levels in groundwater, surface and water by UHPLC-MS/MS after derivatisation with FMOC-Cl. The novelty of this method is its high simplicity, robustness and sensitivity allowing the identification and quantification of the compounds at the detection limits required by the European regulations (0.1 mu g /L). No pre-concentration or purification steps (by using Solid Phase Extrac-tion cartridges) are necessary for our method saving time and consumables costs. The method demon-strated an excellent linear relationship (R 2 >= 0.999) in the concentration range from 0.025 to 10 mu g /L for glyphosate and AMPA and 0.025 to 5 mu g /L for glufosinate. The method Limit Of Quantification (LOQ) is 0.025 mu g/L, the lowest among all previously published studies, and it was demonstrated according to the European SANTE guidelines.(c) 2022 The Author(s). Published by Elsevier B.V.This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
查看更多>>摘要：The aspect of the different spatial arrangement of anionic cobalt bis(dicarbollides) and dicarba- nido undecaboranes remains grossly overlooked despite increased scientific interest. Regarding their growing potential, which does not limit only to medicinal chemistry, suitable enantioseparation methods are needed. The presented paper explores the possibilities of chiral separations of anionic cobalt bis(dicarbollide) and dicarba-7,8- nido -undecaborane derivatives on four polysaccharide-based columns under reversed-phase conditions. The chromatographic behavior of anionic derivatives was evaluated and compared with that of zwitterionic clusters. The isocratic procedure for HPLC method development was suggested. The main parameters for the optimization of separations were described. Successful chiral separations were critically compared to previously reported results in normal phase and polar-organic mode. Reversed-phase separations are superior in resolution, lower consumption of organic solvents, and flexibility during the method development. Moreover, the first chiral discrimination of some hydroxyalkyl derivatives of anionic cobalt bis(dicarbollides) is reported. The outcomes of this work may be used for method development in any area, where the chirality of these interesting molecules is of concern.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The unsaturation patterns of molecular fossils are critical in distinguishing their biological precursors and diagenetic processes. However, questions regarding the determination of double-bond positions of unsaturated dialkyl glycerol ethers (DAGEs) in submarine hydrocarbon seep ecosystems remain unsolved. To address this problem, a protocol for dimethyl disulfide (DMDS) derivative analysis using gas chromatography (GC)-mass spectrometry was optimised. Herein, the double-bond positions of monounsaturated short-chain alcohols, monoalkyl glycerol ethers (MAGEs), and DAGEs in seep carbonates were analysed. Among these compounds, the double-bond positions of trimethylsilyl (TMS) derivatives of the monounsaturated DAGE-DMDS adducts were determined for the first time, with mass spectra characterized by molecular ions (M (+)(.)) and two major diagnostic ions (omega(+)& nbsp;and delta(+) ) cleaved at the double bonds. For both the MAGEs and DAGEs, the double-bond positions of the monounsaturated n-C 16:1-alkyl moieties were identified at omega 5 and omega 7. Compared to monounsaturated short-chain alcohols and MAGEs, both ionization efficiency and relative sensitivity for the TMS derivatives of DAGE-DMDS adducts were low as indicated by the high limit of detection at a signal-to-noise ratio of 3. In addition, the appropriate injection parameters and oven temperature program during GC analyses may be crucial in determining the double-bond positions within monounsaturated DAGEs. (C) 2022 Elsevier B.V. All rights reserved.
Subraveti, Sai GokulLi, ZukuiPrasad, VinayRajendran, Arvind...
14页
查看更多>>摘要：The design and optimization of chromatographic processes is essential for enabling efficient separations. To this end, hyperbolic partial differential equations (PDEs) along with nonlinear adsorption isotherms must be solved using computationally expensive numerical solvers to understand, simulate, and design the complex behavior of solute movement in chromatographic columns. In this study, physics-based artificial neural network framework for adsorption and chromatography emulation (PANACHE) is used to simulate and optimize chromatographic processes in a computationally faster and reliable manner. The proposed approach relies on learning the underlying PDEs in the form of a physics-constrained loss function to improve the accuracy of process simulations. The effectiveness of this approach is demonstrated by considering the complex dynamics of binary solute mixtures for generic pulse injections subjected to different isotherm systems, namely, the four cases of the generalized Langmuir isotherms. Unique neural network models were developed for each isotherm and the models accurately predicted the spatiotemporal concentrations of solute mixture in chromatographic columns for an arbitrary feed concentrations and injection volumes by facilitating up to 250 times computational speed-ups. Moreover, the neural network models were incorporated with process optimization routines to precisely determine the optimal injection volumes to enable baseline separation of solute components of the feed mixture. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Artificial neural networks (ANN; feed-forward mode) are used to quantitatively estimate the enantioreso-lution (Rs) in cellulose tris(3,5-dimethylphenylcarbamate) of chiral molecules from their structural infor-mation. To the best of our knowledge, for the first time, a dataset of structurally unrelated compounds is modelled using ANN, attempting to approach a model of general applicability. After setting a strategy compatible with the data complexity and their relatively limited size (56 molecules), by prefixing ini-tial ANN inner weights and the validation and cross-validation subsets, the ANN optimisation based on a novel quality indicator calculated from 9 ANN outputs allows selecting a proper (predictive) ANN archi-tecture (a single hidden layer of 7 neurons) and performing a forward-stepwise feature selection process (8 variables are selected). Such relatively simple ANN offers reasonable good general performance in pre-dicting Rs (e.g. validation plot statistics: mean squared error = 0.047 and R = 0.98 and 0.92, for all or just the validation molecules, respectively). Finally, a study of the relative importance of the selected vari-ables, combining the estimation from two approaches, suggests that the surface tension (positive overall contribution to Rs) and the -NHR groups (negative overall contribution to Rs) are found to be the main variables explaining the enantioresolution in the current conditions. (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
查看更多>>摘要：Polychlorinated naphthalenes (PCNs) are emerging organic pollutants that are harmful to the environment and human health. In this study, a headspace solid-phase-microextraction (HS-SPME)-gas chromatography-tandem mass spectrometry method for the separation and enrichment of PCNs in shrimp was developed and validated. A graphene aerogel was prepared by modifying graphene oxide with a deep eutectic solvent to prevent graphene oxide stacking. As a result, the aerogel had a threedimensional porous structure, which resulted in easy sorption/desorption for PCNs, and was used as the SPME fiber coating. Next, the experimental parameters for the saponification of the sample matrix and the extraction and desorption of the PCNs were systematically optimized. After optimization, the method showed good linearity ( R-2 >= 0.9968), low limits of detection (0.00983-0.0661 pg g( -1) ), and satisfactory recoveries (80.4-108%). Crucially, compared with previously reported methods, this method does not require the use of large amounts of organic reagents or complex operations, giving it the advantages of simplicity, sensitivity, and environmental friendliness. As an example of the practical application of the developed method, the PCNs in river and sea shrimp were quantified. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Sulfur as a stereogenic center can be found in synthetic compounds and natural products. The current study evaluated the enantioseparation of 16 chiral (benzylsulfinyl)benzamide compounds by capillary electrophoresis using charged cyclodextrins (CDs) as chiral selectors in 50 mM sodium acetate buffer, pH 5.5. The sulfoxides varied in the type and position of the substituent of the benzyl moiety as well as the position and methylation of the amide group. Typically, randomly substituted CDs separated the majority of the model analytes in contrast to single isomer CDs. In case of random substitution, gamma-CD derivatives displayed higher resolution ability toward the set of model compounds followed by beta-CD and alpha-CD derivatives. Except for a few examples, the ( + )-enantiomer of the analytes migrated before the (-)-isomer irrespective of the type of the CD so that the chiral recognition appeared to be also mostly independent on the structure of the sulfoxides. Evaluation of complexation constants and complex mobilities of selected CD-analyte pairs revealed that the separations were based on the stereoselective complexation by the CD expressed as complexation constants but examples for complex mobilities as the determining factor for the enantiomer migration order were also found. In case of 2-(4-bromobenzylsulfinyl)-N-methyl benzamide in the presence of heptakis(2,3-di-O-methyl-6-O-sulfo)-alpha-CD reversal of the enantiomer migration order as a function of the CD concentration was observed. Using neutral CD derivatives in the presence of sodium dodecyl sulfate-based micelles at pH 9.0 only few sulfoxides could be enantioseparated. (C)& nbsp;2022 Elsevier B.V. All rights reserved.
Gisbert-Alonso, A.Lopez-Urena, S.Torres-Lapasio, J. R.Garcia-Alvarez-Coque, M. C....
13页
查看更多>>摘要：We report here the improvement of a procedure to obtain global models, able to describe the retention behaviour of several sample components simultaneously. The reported global models include parameters that account for the general effects of column and solvent on retention and are common for all components, whereas other parameters are specific of each sample component. These models are fitted by alternate regression and offer a prediction performance comparable to individual retention models. The approach is suitable to samples of natural products including a large number of components in extremely diverse concentrations and in the absence of standards. Guidelines are given for the successful development of sample-oriented experimental designs (i.e. adapted to the elution of the components of the natural products), constituted by multi-linear gradients. These designs also facilitate peak tracking. The model proposed by Neue and Kuss to describe the retention was found to yield the best predictions. The approach is applied to the extracts of samples of green tea, lemon balm and linden, yielding excellent predictions of retention for selected components.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
Carbonell-Rozas, LauraHorstkotte, BurkhardGarcia-Campana, Ana M.Lara, Francisco J....
10页
查看更多>>摘要：In this work, it is proposed for the first time an electrophoretic approach based on micellar electrokinetic chromatography coupled with tandem mass spectrometry (MEKC-MS/MS) for the simultaneous determination of nine neonicotinoids (NNIs) together with the fungicide boscalid in pollen and honeybee samples. The separation was performed using ammonium perfluorooctanoate (50 mM, pH 9) as both volatile surfactant and electrophoretic buffer compatible with MS detection. A stacking strategy for accomplishing the on-line pre-concentration of the target compounds, known as sweeping, was carried out in order to improve separation efficiency and sensitivity. Furthermore, a scaled-down QuEChERS was developed as sample treatment, involving a lower organic solvent consumption and using Z-Sep + as dispersive sorbent in the clean-up step. Regarding the detection mode, a triple quadrupole mass spectrometer was operating in positive ion electrospray mode (ESI +) under multiple reaction monitoring (MRM). The main parameters affecting MS/MS detection as well as the composition of the sheath-liquid (ethanol/ultrapure water/formic acid, 50:49.5:0.5 v/v/v) and other electrospray variables were optimized in order to achieve satisfactory sensitivity and repeatability. Procedural calibration curves were established in pollen and honeybee samples with LOQs below 11.6 mu g kg( -1) and 12.5 mu g kg -1, respectively. Precision, expressed as RSD, lower than 15.2% and recoveries higher than 70% were obtained in both samples. Two positive samples of pollen were found, containing imidacloprid and thiamethoxam. Imidacloprid was also found in a sample of honeybees. The obtained results highlight the applicability of the proposed method, being an environmentally friendly, efficient, sensitive and useful alternative for the determination of NNIs and boscalid in pollen and honeybee samples. (C)& nbsp;2022 The Author(s). Published by Elsevier B.V.& nbsp;
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