Groeneveld, GinoDunkle, Melissa N.Pursch, MatthiasMes, Edwin P. C....
12页
查看更多>>摘要：Comprehensive two-dimensional liquid chromatography (LC x LC) is an attractive separation technique that allows achieving high peak capacities and information on chemical correlations. Unfortunately, its application in industrial practice is still not widespread due to limiting factors such as complex method development, tedious method optimization and solvent-incompatibility (such as solvent-strength mis -match or immiscibility experienced during fraction transfer). A severe case of solvent-incompatibility is encountered in the comprehensive coupling of normal-phase LC and reversed-phase LC (NPLC x RPLC). NPLC x RPLC is considered a desirable LC x LC system, especially for the characterization of synthetic polymers, due to the high orthogonality of the two reten-tion mechanisms. However, its experimental realization often suffers from solvent-injection effects in the RPLC dimension, such as peak-deformation, peak-splitting, or even unretained elution ("breakthrough") of sample components. Such a decrease in performance or loss of retention is highly dependent on the types of solvents used. To explore the boundaries of solvent compatibility, we applied large-volume injections (LVI) of refer-ence analytes (e.g. alkyl benzenes; ethoxylate and propoxylate polymers) dissolved in water-immiscible sample solvents, such as dichloromethane, n-hexane, and isooctane in fast water-based gradient RPLC sep-arations (using methanol or acetonitrile as eluent). It was found that, when using highly aqueous initial gradient conditions, hydrophobic sample diluents were retained and eluted during the applied gradient. Depending on the relative retention of the retained diluent and the sample analytes, good chromatograms for LVI of immiscible solvents were obtained, comparable with injections under ideal conditions. The con-clusions from injection experiments in aqueous RPLC were verified by coupling an NPLC system with a gradient from isooctane to tetrahydrofuran and an RPLC system with a gradient from water to acetonitrile in an online comprehensive NPLC x RPLC separation of a mixture of propoxylate polymers. The separation provided separation of the polymers based on their number of hydroxyl end-groups (NPLC) and oligomer chain-length (RPLC), without suffering from significant band-broadening effects due to solvent-mismatch upon injection in the second-dimension RPLC system. (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )
Wernert, VeroniqueKhac Long NguyenLevitz, PierreCoasne, Benoit...
12页
查看更多>>摘要：The peak parking method was applied to evaluate the surface diffusivity D-s of polystyrenes dissolved in a THF/heptane mixture and transported through porous silica materials with various morphologies. With this method, the overall effective diffusivity D is measured experimentally with coarse-grained models like Maxwell equation allowing one to infer the particle diffusivity D-pz. Such particle diffusivity has two main contributions: in-pore diffusivity D-p and surface diffusivity D-s. The diffusion within the pores is determined experimentally using either non-adsorbing conditions or calculated from particle porosity, particle tortuosity, and hydrodynamic hindrance. The surface diffusion coefficient D-s is usually determined using models considering parallel diffusion in the pores and at the surface but this assumption is rather crude. In this paper, to address this problem, another approach is proposed using the Brownian motion of molecules in the pore space. These two approaches lead to similar equations relating the effective diffusion coefficient D, the in-pore diffusion D-p and surface diffusion D-s. The surface diffusion is analyzed as a function of the surface affinity of the probes considered here (polystyrenes of different molecular weights/lengths). Such surface affinity depends both on the probe chain length and surface chemistry of the host solid (the latter being characterized here through the silanol surface density). For short chain lengths, a non-monotonic change in the surface diffusion with affinity (i.e. retention factor) is observed in some cases. Yet, generally, as expected, surface diffusion decreases upon increasing the surface affinity. In contrast to short chain lengths, the longest chain lengths are less sensitive to the silanol surface density. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：The applicability of ultrahigh-performance supercritical fluid chromatography coupled with mass spectrometry (UHPSFC/MS) for the qualitative analysis of metabolites with a wide polarity range (log P: -3.89-18.95) was evaluated using a representative set of 78 standards belonging to nucleosides, biogenic amines, carbohydrates, amino acids, and lipids. The effects of the gradient shape and the percentage of water (1, 2, and 5%) were investigated on the Viridis BEH column. The screening of eight stationary phases was performed for columns with different interaction sites, such as hydrogen bonding, hydrophobic, pi-pi, or anionic exchange type interactions. The highest number of compounds (67) of the set studied was detected on the Torus Diol column, which provided a resolution parameter of 39. The DEA column had the second best performance with 58 detected standards and the resolution parameter of 54. The overall performance of other parameters, such as selectivity, peak height, peak area, retention time stability, asymmetry factor, and mass accuracy, led to the selection of the Diol column for the final method. The comparison of additives showed that ammonium acetate gave a superior sensitivity over ammonium formate. Moreover, the influence of the ion source on the ionization efficiency was studied by employing atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). The results proved the complementarity of both ionization techniques, but also the superior ionization capacity of the ESI source in the negative ion mode, for which 53% of the analytes were detected compared to only 7% for the APCI source. Finally, optimized analytical conditions were applied to the analysis of a pooled human plasma sample. 44 compounds from the preselected set were detected in human plasma using ESI-UHPSFC/MS in MS E mode considering both ionization modes. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：Loblolly fruit (LBF) is mainly used as raw material for beverage, but there are few researches on its quality evaluation or control. The aim of this study was to develop comprehensive evaluation methods for the quality control of Loblolly fruit. firstly, double wavelength coefficient ratio spectrum was used to identify the purity of chromatographic fingerprint peak. It is very important to identify the purity of fingerprint peaks because only the quantitative determination of pure chromatographic peaks is meaningful for its efficient quality control. Then, multi-wavelength fusion fingerprint was established to avoid one-sidedness of a single wavelength for further evaluation by systematically quantified fingerprint method (SQFM). According to the outcome of P-m, 25 batches of LBF were classified into two classifications by hierarchical cluster analysis, which was consistent with the SQFM evaluation results. Two active components, gallic acid (GAC) and ethyl gallate (EGA) in LBF, were quantitatively determined by quantitative analysis of multi-components by single marker (QAMS). In addition, the fingerprint efficacy relationship was established using an off-line antioxidant system and partial least-squares model to explore the connection between chemical components and antioxidant activities. Finally, the evaluation results of high-performance liquid chromatography and gas chromatography were integrated by the mean algorithm, which could reduce the error caused by single method. The results showed that the proposed strategy could provide a method for quality evaluation of LBF and even other traditional Chinese medicines (TCMs). (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The present work aimed at the development of a liquid chromatography-tandem mass spectrometry (LCMS/MS) method for comprehensive determination of twelve organophosphate (OP) triesters, five OP diesters and two hydroxylated degradation products in sediment. As the target compound possess a wide range of physicochemical properties, different LC-MS/MS conditions and sample preparation strategies were tested. The optimal condition is based on the extraction of 2 g of dried sediment by ultrasonicassisted extraction and clean-up by solid phase extraction, and then the extract was separated using a ZORBAX C18 column (4.6 mm x100 mm, 1.8 mu m) and analyzed by MS in multiple reaction monitoring mode. The overall method was validated in terms of linearity, matrix effect, and limits of quantification (LOQs), recoveries and precision. All targets had wide concentration ranges and the correlation coefficients (r) were higher than 0.99. LOQs of all analytes were 0.01-5.0 ng g(-1) dw, most of which are lower than those previously reported. In most cases, the recoveries were from 68.56 to 140.22% at three spiked levels (low, medium and high), with RSDs lower than 22.38%, and the reproducibility obtained in five nonconsecutive days was lower than 26.18%. This method was successfully applied to nineteen marine sediment samples. Tri-n-butyl phosphate (TNBP) and tris (phenyl) phosphate (TPHP) were detected in over 84% of samples and the concentration levels were the highest among all OP triesters. For OP diesters, DPHP was 100% detected in all samples with the highest amount. The total concentrations for OP triesters and their degradation products were n.d.-107.2 ng g(-1) dw and n.d.-101.7 ng g(-1) dw, respectively. This is the first study reporting contamination of both OP triesters and their degradation products, especially hydroxylated degradation products, in sediment. Considering the ubiquitous existence of targets as well as their toxicity to biota, study on the OPEs and their degradation products in marine environment deserves a special attention. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Quantitative recovery of plutonium from lean effluents is one of the most challenging tasks for separation scientists. Four extraction chromatography (XC) resins containing substituted diglycolamide ligands viz. N,N,N',N'-tetra-n-pentyl diglycolamide (TPDGA), N,N,N',N'-tetra-n-hexyl diglycolamide (THDGA), N,N,N',N'-tetra-n-octyl diglycolamide (TODGA) and N,N,N',N'-tetra-n-decyl diglycolamide (TDDGA) and a room temperature ionic liquid (RTIL) were tested for the extraction of plutonium (IV) from nitric acid feed solutions. The relative efficiency of uptake of the metal ion in the entire range of HNO3 studied was: TPDGA > THDGA > TODGA > TDDGA, which was opposite to the chain length of the attached alkyl groups. Also, for all the four XC resins the uptake of Pu(IV) was found to decrease with increasing nitric acid concentration in the lower acidity range followed by an increase thereafter. The uptake of Pu(IV) with all the four XC resins was fitted into different kinetic and isotherm models. It was found that all the four resins followed the pseudo-second order kinetic model and Langmuir monolayer adsorption model. Column studies with these XC resins using a loading solution containing 1.2 g/L Pu(IV) in 3 M HNO3 showed early breakthrough for the higher homolog DGA ligands as compared to the lower homologs. Effective elution of the loaded Pu(IV) from the column was done in about 5.5 column volumes using a solution containing 0.5 M oxalic acid in 0.5 M HNO3. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：Coexistence of matrices and analytes makes the analysis, determination, and quantification of volatiles in beer a tedious process that is difficult to conduct. Bubbling extraction, a newly established sample pretreatment method, directly releases analytes from liquid phase to gas phase by bubble bursting. In this study, we combined bubbling extraction with gas chromatography-mass spectrometry (GC-MS) for direct molecular characterization as well as effective qualitative and quantitative analysis of three types of fermented beers. This method was found to have a high extraction efficiency (bubbling time of 30300 s), short analysis time (< 30 min), and rational recovery rates (85.6-97.3%) with relative standard deviations (RSDs) less than 10%. Thirteen volatiles were extracted at a wide concentration range of 0.1-10,000 ng/g with correlation coefficient (R-2) > 0.990, while the limits of detection (LODs) and limits of quantification (LOQs) were found in scope of 0.001-50 ng/g. Analytical Eco-Scale, Green Analytical Procedure Index (GAPI), and Analytical Greenness (AGREE) approaches proved that our proposed method has a good greenness. In addition, Ale-type, Lambic, and Lager-type beer were successfully classified by the orthogonal partial least squares-discriminant analysis (OPLS-DA). In conclusion, bubbling extraction coupled with GC-MS has potential as a routine analysis tool for identifying volatiles in alcoholic beverages. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The unascertained, constant mutation and emergence of new types of microorganisms present significant challenges to their detection. Differing from the focus on the limited local 16S rRNA gene or protein markers, characteristic whole fingerprint technologies at the omic level are particularly suitable for unknown analytes since accurate knowledge about the constituents is not necessarily required. Herein, through a combination of several innovative strategies, including pure water isotachophoresis integrated (2 + 1)D electrophoresis, inversion-funnel peak stacking channel geometry and COMSOL computer-aided fluid simulation, high-resolution whole protein 2D native microfluidic chip electrophoresis was achieved within less than 1 min. The highest ever reported peak capacity for native 2D chip electrophoresis was obtained. Furthermore, taking Escherichia coli, Staphylococcus aureus, and Bacillus subtilis as model analytes without protein biomarker information, the feasibility of the identification and semiqualification of unknown microbes in pure or mixed samples was explored with the utilisation of original algorithms, including SIFT feature abstraction and a global information entropy combined support vector machine. As such, the multidisciplinary cooperation in the present study demonstrates monstrated promising prospects for microfluidic chip electropherogram fingerprint-based quick microorganism assays, biointeraction studies, and drug screenings, even if the analytes are not fully ascertained. (c) 2021 Published by Elsevier B.V.
查看更多>>摘要：Ambient gas-and particle-phase intermediate volatility and semi-volatile organic compounds (I/SVOCs) of Beijing were analyzed by a thermal desorption comprehensive two-dimensional gas chromatography quadrupole mass spectrometry (TD-GC x GC-qMS). A pixel-based scheme combing the integration-based approach was applied for partition coefficients estimation and fingerprints identification. Blob-by-blob recognition was firstly utilized to characterize I/SVOCs from the molecular level. 412 blobs in gas-phase and 460 blobs in particle-phase were resolved, covering a total response of 47.5% and 43.5%. A large pool of I/SVOCs was found with a large diversity of chemical classes in both gas-and particle-phase. Acids (8.5%), b-alkanes (5.8%), n-alkanes (C8-C25, 5.3%), and aromatics (4.4%) were dominant in gas-phase while esters (7.0%, including volatile chemical product compounds, VCPs), n-alkanes (C9-C34, 5.7%), acids (4.6%), and siloxanes (3.6%) were abundant in particle-phase. Air pollutants were then evaluated by a two-parameter linear free energy relationship (LFER) model, which could be further implemented in the two-dimensional volatility basis set (2D-VBS) model. Multiway principal component analysis (MPCA) and partial least squares-discriminant analysis (PLS-DA) implied that naphthalenes, phenol, propyl-benzene isomers, and oxygenated volatile organic compounds (OVOCs) were key components in the gas-phase under different pollution levels. This work gives more insight into property estimation and fingerprints identification for complex ambient samples. (c) 2022 Elsevier B.V. All rights reserved.
An, XinghaiHayat, AdnanLee, Ju WeonQamar, Shamsul...
12页
查看更多>>摘要：The amount of substance adsorbed on solid surface depends on temperature. Therefore, the migration velocities of the solutes in a chromatographic column can be altered by introducing temperature gradients. Such gradients designed to change retention behaviours can be exploited to improve the separation performances in preparative chromatography. To describe key process features, we used analytical solutions of the equilibrium model with instant stepwise shift of temperature. To achieve a more realistic description, the equilibrium dispersion model was additionally applied to treat finite column efficiencies. The effect of temperature gradients was illustrated experimentally using two identical columns sequentially connected. Temperature of the second column was modulated by thermostats. Wide pulse injections of a single component led to instructive elution profiles in a preliminary investigation. The observations were found to be in qualitative agreement with predictions of the equilibrium dispersion model. Subsequently, the separation of a ternary model mixture was investigated considering a simple two-step temperature gradient. To support the quantitative analysis and to identify suitable switching and cycle times, the temperature dependencies of the Henry constants were determined by short pulse injections. A meaningful variation of the parameters of the temperature gradient is required for adjusting the cycle times, which is the time difference between two consecutive injections that needs to shorten. Decreasing this time is connected with a desirable increase in process productivity. The results achieved revealed that relatively simple to implement stepwise temperature gradients offer an option to improve and fine-tune the performance of repetitive batch chromatography. (c) 2022 Elsevier B.V. All rights reserved.
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