查看更多>>摘要：High-performance anion-exchange chromatography (HPAEC) coupled with triple quadrupole mass spectrometry (HPAEC-QqQ-MS) was applied to the determination of xylooligosaccharides (XOS) derived from enzymatically hydrolysed commercial xylan from beechwood and the analytical performance and advantages of the method explored. Separation, eluent suppression, electrospray ionisation, and detection options to enhance XOS sensitivity and selectivity were evaluated, delivering a new simple, fast, selective, and sensitive solution for the characterisation of these complex compounds. The method was fully validated in terms of its analytical performance for those XOS for which standards were available, i.e., degree of polymerisation from 1 to 6. The new method was applied to the analysis of xylan hydrolysates obtained by different enzymatic hydrolysis treatments using endo-xylanase from Thermomyces lanuginosus, characterising 25 different XOS and demonstrating the method's utility for future tailoring of enzymatic hydrolysis conditions to obtain desired XOS profiles in such hydrolysates. Linear XOS and 4-O-methyl glucuronic acid (MeGluA) branched XOS were detected by direct injection of the xylan hydrolysates after a simple 10-fold sample dilution and filtration. Identification of XOS detected by HPAEC-QqQ-MS was additionally confirmed using high-resolution orbitrap mass spectrometry (HR-orbitrap-MS). Further, an ultra sensitive and-selective method was developed by using selected reaction monitoring acquisition mode (SRM), increasing signal-to noise ratio and decreasing the limits of detection, opening future applications to low concentrated sample analysis. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：An integrated dual-functional electrodialytic membrane suppressor (D-EMS) is proposed that can simultaneously conduct suppression of acid and base eluent. It consists of four chambers, equivalent to half an anion electrolytic membrane suppressor (EMS) plus half a cation EMS with typical sandwiched configuration via a bipolar membrane (BPM). Anion exchange membrane, BPM and cation exchange membrane are respectively used to isolate two central eluent channels from two outer regenerant chambers. A constant current source is used to power D-EMS. The device shows similar performance to a separate EMS in terms of suppression capacity (>= 80 mu eq/min, corresponding to 80 mM eluent at the flow rate of 1 mL/min) and the resultant suppressed background (similar to 0.75 mu S/cm and similar to 0.17 mu S/cm for anion and cation section of D-EMS, respectively). (C) 2022 Elsevier B.V. All rights reserved.
da Silva, Josiel Joseda Silva, Bianca FerreiraBoldrin Zanoni, Maria ValniceStradiotto, Nelson Ramos...
10页
查看更多>>摘要：Vinasse - liquid organic residue derived from the production of sugarcane ethanol fuel, has been applied as soil amendment via fertigation for decades in Brazil. This organic residue is an important source of nutrients and water for sugarcane crops. Through fertigation, approximately 400 billion liters of vinasse are recycled annually. Despite the economic and agronomic importance of this practice, vinasse-based fertigation can be a source of antibiotic contamination in the environment. The present work reports the application of solid phase extraction (SPE), salting-out liquid-liquid extraction (SALLE), and on-line solid phase extraction (on-line SPE) as sample preparation techniques for the analysis of the following antibiotics (contaminants) in vinasse sample: monensin, penicillin G, virginiamycin M1, virginiamycin S1, tetracycline and erythromycin. The study also employed a totally automated quantitative method based on on-line SPE and liquid chromatography coupled to quadrupole linear ion trap tandem mass spectrometry (LC-QqLIT-MS/MS) for the analysis of these contaminants in vinasse. The application of the aforementioned sample preparation techniques led to the successful extraction of the analytes, and a comparative analysis of the techniques showed that the on-line SPE technique was the most advantageous among the techniques investigated. The quantitative analytical method applied yielded well-defined chromatographic peaks, working range of 1.0-370.0 ng.mL(-1) , apparent recovery ranging from 80 to 110% for most compounds, repeatability between 3 and 16%, and limits of detection ranging from1.0 to 10 ng.mL(-1) . The analysis of six vinasse samples from different ethanol producing plants led to the detection of monensin at the concentration of 14.3 ng.mL(-1) in their compositions. The results obtained show that fertigation with vinasse is a source of antibiotic contamination in the environment. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Biphasic chiral recognition was first applied for the enantioseparation acidic drugs in capillary electrochromatography. The biphasic recognition system was composed of mobile phase additive (beta-cyclodextrin) and monolithic chiral stationary phase (proteins). The pretreated silica-fused capillary was treated with 3-trimethoxysilyl propyl methacrylate to attach double bond ligand onto the surface. The mixed monolithic chiral stationary phase was constructed with bovine serum albumin and pepsin using one-pot polymerization by chemical covalent coupling, while dimethyl sulfoxide and methanol were used as the progenic solvents. The effects of the type and concentration of beta-cyclodextrin additive as well as pH value of the mobile phase on the separation efficiency were optimized. The performance of the biphasic recognition system was validated by separating acidic drugs (such as ketoprofen, ibuprofen, loxoprofen, flurbiprofen and carprofen) in capillary electrochromatography, achieving outstanding separation efficiency. In terms of migration time and resolution, the run-to-run, intra-day, and inter-day repeatability through relative standards deviation were within 5.0%, exhibiting excellent stability of the biphasic recognition system. Conceivably, the experimental result reveals that biphasic chiral recognition capillary electrochromatography offers a promising prospect for enantioseparation of chiral compounds in a highly efficient manner. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：We performed a systematic study of thirteen alkylamines used as ion-pairing reagents for ion-pair reversed-phase liquid chromatography (IP RP LC) separations of oligonucleotides on a C18 column. We proposed a method to classify the hydrophobicity of alkylamines by their retention in RP LC. The IP reagent hydrophobicity correlated with the retention and resolution of oligonucleotides in the corresponding IP mobile phases. The baseline resolution was achieved up to 30 mer for hydrophilic, or up to 50 mer for hydrophobic IP reagents. Hydrophobic alkylamines permitted useful oligonucleotide separations at relatively low buffer concentrations, such as 5-10 mM alkylamine-acetate IP systems. These buffers were compatible with mass spectrometry detection, however, replacement of acetic acid with hexafluoroisopropanol in the mobile phase improved the MS signal by 2-3 orders of magnitude. Experiments with native and chemically modified oligonucleotides highlighted the mixed-mode nature of IP RP LC. When using hydrophobic IP reagents, the ionic retention mechanism of oligonucleotides is enhanced while hydrophobic retention is diminished. (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：The morphology, composition, and selectivity of a silica-based monolithic stationary phase, grafted by a layer of trioctyl(3/4-vinylbenzyl)phosphonium chloride ([P-888vBn ]Cl), is presented. The results of elemental analysis confirmed that the prepared stationary phase contains 38.8 at.% of silicon, 60.2 at.% of carbon, and 1.0 at.% of phosphorus. Capillary columns (150 x 0.1 mm) for liquid chromatography were evaluated using alkylbenzenes, monosubstituted benzenes, polyaromatic compounds, substituted benzene regioisomers, and aromatic carboxylic and amino acids. The prepared ionic liquid (IL)-based stationary phase exhibits hydrophobic, hydrophilic, and electrostatic interactions, as confirmed by experiments on the evaluation of the effect of the mobile phase composition (content of acetonitrile and ammonium formate) on the isocratic chromatographic separation. Thus, the IL-based capillary column demonstrates a unique separation selectivity compared to Phenyl-, C8-, and C18-stationary phases, and high efficiency for an expanding number of structurally diverse compounds. (C) 2022 Elsevier B.V. All rights reserved.
Kurnia, Kiki A.Almeida, Heloisa H. S.Gaschi, Priscilla S.Coutinho, Joao A. P....
9页
查看更多>>摘要：Countercurrent and centrifugal partition chromatography are techniques applied in the separation and isolation of compounds from natural extracts. One of the key design parameters of these processes is the selection of the biphasic solvent system that provides for the adequate partitioning of the solutes. To address this challenging task, the fully predictive Conductor-like Screening Model for Real Solvents (COSMO-RS) and the semi-predictive Non-Random Two-Liquid Segment Activity Coefficient (NRTL-SAC) model were applied to estimate the partition coefficients (K) of four model phenolic compounds (vanillin, ferulic acid, (S)-hesperetin and quercetin) in different solvent systems. Complementing the experimental data collected in the literature, partition coefficients of each solute in binary, or quaternary, solvent systems were measured at 298.2 K. Higher deviations from the experimental data were obtained using the predictive COSMO-RS model, with an average RMSD (root-mean-square deviation) in log(K) of 1.17 of all four solutes (61 data points), providing a satisfactory quantitative description only for the systems containing vanillin (RSMD = 0.57). For the NRTL-SAC model, the molecular parameters of the solutes were initially calculated by correlating a set of K and solubility (x, in mole fraction) data (16 partition coefficients and 44 solubility data points), for which average RMSD values of 0.07 and 0.41 were obtained in log(K) and log(x), respectively. The predictions of the remaining log(K) data (45 partition coefficients) resulted in an average RMSD of 0.43, suggesting that the NRTL-SAC model was a more reliable quantitative solvent screening tool. Depending on the amount of available solubility and partition data, both models can be valuable alternatives in the preliminary stages of solvent screening destined to select the optimal mobile and stationary phases for a given separation. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this study, the surface thermodynamic properties and more particularly, the dispersive component gamma(d)(s) of the surface energy of crystals of a Zr-based MOF, UiO-66 (Zr6O4(OH)(4)(BDC)(6); BDC = benzene 1,4-dicarboxylic acid), the specific interactions, and their acid-base constants were determined by using different molecular models and inverse gas chromatography methods. The determination of gamma(d)(s) of the O-66 surface was obtained by using several models such as Dorris-Gray and those based on the Fowkes relation by applying the various molecular models giving the surface areas of n-alkanes and polar organic molecules. Six models were used: Kiselev, spherical, geometric, Van der Waals, Redlich-Kwong, and cylindrical models. The obtained results were corrected by using our model taking into account the thermal effect on the surface areas of molecules. A linear equation was obtained between gamma(d)(s) and the temperature. The specific free energy, enthalpy and entropy of adsorption of polar molecules, as well as the acid and base constants of UiO-66 particles were determined with an excellent precision. It was also proved that the UiO-66 surface exhibited an amphoteric acid-base character with stronger acidity. The linear variations of the specific free energy of interaction as a function of the temperature allowed to obtain the specific surface enthalpy and entropy of adsorption, as well as the acid and base constants of UiO-66 by using ten different models and methods. The best results were obtained by using our model that gave the more precise values of the acid constant K-A = 0.57, the base constant K-D = 0.18 of the MOF particles and the ratio K-A/K-D = 3.14 clearly proving a strong acid character of the UiO-66 surface. (C) 2022 The Authors. Published by Elsevier B.V.
Leon, NuriaMiralles, PabloCoscolla, ClaraYusa, Vicent...
7页
查看更多>>摘要：A green analytical method for the simultaneous determination of 30 tropane and pyrrolizidine alkaloids and their N-oxides in dried teas and herbs for infusions has been developed and validated. The proposed method is based on QuEChERS procedure followed by LC-Q-Orbitrap HRMS analysis. The method includes a first screening analysis to assess the presence of alkaloids, followed by the quantification of suspected positive samples (cut-off level, 0.2-2.6 mu g kg(-1)). The method was validated in five different tea and herb matrices showing satisfactory linearity (R-2 >= 0.99), method limits of quantification (5 mu g kg(-1)), accuracy (87-111 %), and precision (RSD <20 %). The greenness of the proposed method was evaluated according to the Analytical Eco-Scale, showing that it could be considered an excellent green analysis. Finally, eleven commercial field samples of tea and herbs for infusions, including rooibos, chamomile, red tea, black tea, green tea, white tea, linden, horsetail, and one infusion containing a mixture of herbs, were analyzed and the obtained results demonstrated that they were in compliance with the current European regulations regarding the studied substances. (C) 2022 Elsevier B.V. All rights reserved.
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