查看更多>>摘要：Chromatography-based refolding is emerging as a promising alternative to dilution-refolding of solubilized inclusion bodies (IBs). The advantages of this matrix-assisted refolding (MAR) lie in its ability to reduce aggregate formation, leading to better recovery of active protein, and enabling refolding at higher protein concentration. However, batch chromatography has the disadvantage of ineffective solvent utilization, under-utilization of resin, and low throughput. In this work, we overcome these challenges by using a 3-column Periodic Counter-current Chromatographic (PCC) system for continuous refolding of IBs, formed during the production of L-asparaginase by recombinant E. coli cultures. Initial experiments were conducted in batch processes using single-column immobilized metal-affinity chromatography. Different gradient operations were designed to improve the protein loading for the single-column, batchMAR processes. Optimized conditions, based on the batch-MAR experiments, were used for designing the continuous-MAR processes using the PCC system. The continuous-MAR experiments were carried out over 3 cycles (similar to 30 h) in the PCC system. A detailed quantitative comparison based on recovery, throughput, buffer consumption, and resin utilization was made for the three modes of operation: pulse-dilution, single-column batch-MAR, and 3-Column PCC-based continuous-MAR processes. While recovery (73%) and throughput (11 mg/h) were the highest in PCC, specific buffer consumption (6.9 ml/mg) was the least. Also, during PCC operation, resin utilization improved by 92% in comparison to the single-column batch-MAR process. These quantitative comparisons clearly establish the advantages of the continuous-MAR process over the batch-MAR and other conventional refolding techniques. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In the present work, several new hydrophobic deep eutectic solvents (HDESs) were prepared with quaternary ammonium salts as hydrogen bond acceptors (HBAs) and salicylate esters as hydrogen bond donors (HBDs). Then, the obtained HDESs were used as extraction solvents to establish an ultrasound-assisted dispersive liquid-liquid microextraction method combined with high-performance liquid chromatographyultraviolet detection technique for the determination of four endocrine-disrupting phenols (EDPs) compounds. One of the obtained HDESs composed of tetrabutylammonium chloride (N 4 4 4 4 Cl) and methyl salicylate possessed a viscosity of 89.28 mPa center dot s lower than most reported ionic HDESs ( > 200 mPa center dot s), and the low viscous HDES was selected as the optimal extraction solvent. Several key parameters affecting the extraction efficiency were investigated, including the type and volume of HDES, ultrasound time, sample solution pH and salt addition. Under the optimized experimental conditions, the proposed method had good coefficients of determination ( R 2 > 0.9976) in the linear range of 0.5-400 mu g center dot L -1 , the limits of quantification and limits of detection respectively were 0.5-2.5 mu g center dot L -1 and 0.25-1 mu g center dot L -1 , and the recoveries were in the range of 81.79-109.82%. Finally, the method was used for the preconcentration and determination of EDPs in different samples, including bottled water, tea beverage and milk. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：The analysis of mineral oil hydrocarbons in vegetable oils is challenging especially regarding the analysis of mineral oil aromatic hydrocarbons (MOAH) since native terpenes like squalene or beta-carotene are usually extracted along with the MOAH fraction and interfere their detection. When applying a recently developed screening method for the analysis of mineral oil saturated hydrocarbons (MOSH) and MOAH in paper and cardboard by planar solid phase extraction (pSPE) to vegetable oils, native terpenes expectably interfered with MOAH analysis. Thus, an adaption of pSPE employing silver ions, named silver ion-planar solid phase extraction (Ag-pSPE), was developed in this study. Impregnation of thin-layers with silver nitrate (AgNO 3 ) was found to be very successful in retaining squalene and beta-carotene. MOAH analysis of vegetable oils after saponification showed good repeatability (relative standard deviation (% RSD ) < 10%) and recoveries of 73.4-112.4% at a spiking level of 4.5 mg/kg ( n = 4). For MOSH analysis, a simple solid phase extraction (SPE) clean-up with aluminum oxide removed native n -alkanes prior to Ag-pSPE. Recoveries for MOSH were 55.3-84.5% with % RSD < 11% at a spiking level of 45.5 mg/kg ( n = 4). Limits of decision and quantitation were at 7.2 and 22.2 ng/zone for MOSH and 1.1 and 3.4 ng/zone for MOAH, respectively, which corresponded to the recently introduced pSPE method, thus showing that analytes were not affected by the impregnation of HPTLC plates with AgNO 3 . The method comparison with LC-GC showed similar results for MOSH, while the amounts for MOAH determined by Ag-pSPE were higher. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Herein, we report the first use of Polymyxin-B antibiotic as a enantio-selector in polymer monolithic capillary. The capillaries were functionalised, characterized and tested for the enantioselective nanoHPLC separation of 50 racemic pharmaceutical drugs. They have been easily prepared by immobilizing Polymyxin-B over the organic polymer for 48 h (P1) or encapsulating Polymyxin-B within the organic polymer (P2) and tested for the enantioselective resolution of racemic drugs. Acceptable resolution was achieved for 21 drugs using RP-HPLC conditions on both (P1) and (P2) capillary columns, while no separation was observed under NP-HPLC conditions. Polymyxin-B is commercially available, easily solubilized and stable in both acidic and neutral media. The developed Polymyxin-B-based polymer monolithic capillaries provide a promising expansion of platform in enantioselective HPLC separations. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this study, a series of the functionalized mesoporous polystyrene-based microspheres (FMPMs) with different functional comonomers (acrylamide, AM; ethyleneglycol dimethacrylate, EGDMA; hydroxyethyl methacrylate, HEMA) and ratios of styrene (St) to divinylbenzene (DVB) were designed and synthesized by a double emulsion interface polymerization method. Among them, St and DVB existed in the oil phase, forming the skeleton structure of FMPMs. AM, EGDMA or HEMA in the water phase formed functional layers on the inner and outer surfaces of FMPMs. The experimental results indicated that the optimal functional comonomers and the ratio of St to DVB were AM (provided the hydrophilic -CONH 2 groups) and 1:1, respectively. Thus, A-FMPMs-2 exhibited the highest adsorption capacity of 108.95 +/- 8.13 mg/g and the selectivity of 5.14 +/- 0.17. These results were attributed to the hydrophilic -CONH 2 groups on AFMPMs-2, and these groups were beneficial to ACT molecules diffusion driven by concentration gradient, improving the adsorption performance. Furthermore, hydrophilic -CONH 2 groups on the inner and outer surfaces of A-FMPMs-2 acted as hydrophilic sites that had a high-affinity interaction with ACT molecules, thus increasing the adsorption selectivity. In addition, A-FMPMs-2 had the highest specific surface area and largest pore volume, resulting in the highest adsorption capacity and adsorption selectivity. Therefore, the development of adsorbents with adjustable pore structure and a large number of hydrophilic sites will provide a new strategy for selective separation of bioactive components from natural products. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Semi-packed columns are microfabricated gas chromatography columns which have a large surface area and high aspect ratio. In this paper, a new semi-packed column with high-density elliptic cylindrical posts (SC -HECP) made by a micro-electro-mechanical system (MEMS) technique was reported. Compared to a semi-packed column with cylindrical posts (SC -CP) under the same effective width, the surface area and aspect ratio of SC -HECP were improved by 71.19% and 76.47%, respectively. To compare the performance of these two semi-packed columns, SC -HECP and SC -CP were fabricated. A 10-nm thick alumina film was deposited as the stationary phase by atomic layer deposition technique to ensure the uniformity and repeatability of the stationary-phase film. A contrast experiment was conducted, and the results showed that compared with SC -CP, better separation performance was realized in SC -HECP due to the increase in surface area and aspect ratio. The number of theoretical plates of nonane was increased by 541.84%, and the tailing factor was decreased by 54.31%. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：As a welcomed porous material, covalent organic frameworks (COFs) have many advantages and are widely used in various aspects. Particularly, COFs have aroused great attentions of scientists in chromatographic separation field due to their outstanding advantages, such as high stability, large specific surface area and multiple voids. However, endowing COFs with chirality to construct chiral stationary phase (CSP) function is still facing many challenges. Here, we firstly prepared a beta-cyclodextrin (beta-CD) and covalent organic framework functional silica CSP named as COF@CD@SiO2 by one-pot method to perform high performance liquid chromatography (HPLC) chiral separation. The morphology and structure of the synthesized stationary phase were investigated by a variety of characterization methods including Fourier transform infrared spectrometry (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), N-2 adsorption experiment, powder X-ray diffraction (XRD) and elemental analysis (EA). The prepared stationary phase realized fast separation of six enantiomers in a short time. The separation mechanism was mainly ascribed to the inclusion complexation of beta-cyclodextrin and the mutli-interaction sites from COFs material. In conclusion, the prepared chiral column can be used to achieve fast separation of enantiomers with good stability and reproducibility. These results can open new avenue for using chiral COFs in liquid chromatographic separation. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：To interpret the dependence of solute retention behavior on modifier content in reversed-phase liquid chromatography, a theoretical framework, based on the concentration dependence of solvophobic forces imposed on solutes and the competitive adsorptions of solutes and solvent modifiers, was proposed. The generality of the developed model was demonstrated by comparing the model with conventional retention models. The linear dependence of the Gibbs energy change of solute adsorption with respect to the modifier concentration was assumed, and the model was fitted to the experimental results, with good agreement demonstrated between the experimental data and the model. Retention behaviors were inferred to be determined by two key dimensionless groups that represented the reductions in the retention factors resulting from a weakened solvophobic interaction and modifier competitive adsorption. The retention behaviors were successfully deconvoluted for each contribution as a function of the modifier concentration by using the fitted parameters. The effects of both contributions on the retention behaviors were enhanced for the solutes with aromatic groups. The standard Gibbs energy change oSL of benzene adsorption was found to depend linearly on the number of modifier molecules present but independent of modifier identity. For the solutes associated with hydrogen-bonding groups, the degree of reduction in the solvophobic interactions was considerably reduced. Hence, the relative contributions of both mechanisms to solute retention depend greatly on the solute structure. Perturbation method was performed to investigate the modifier adsorption mechanisms. The results show that the standard Gibbs energy change o SL for the first-layer adsorption of modifiers changed linearly with the carbon number of modifier molecule. These results demonstrated that the proposed model can offer a physically consistent quantitative description of retention when solvent composition is varied. (c) 2021 Elsevier B.V. All rights reserved.
Sudol, Paige E.Galletta, MicaelaTranchida, Peter Q.Zoccali, Mariosimone...
11页
查看更多>>摘要：The volatile fraction of food, also called the food volatilome, is increasingly used to develop new fingerprinting approaches. The characterization of the food volatilome is important to achieve desired flavor profiles in food production processes, or to differentiate different products, with winemaking being one popular area of interest. In the present research, headspace solid-phase microextraction (HS SPME) coupled to flow-modulated comprehensive two-dimensional gas chromatography with time-of flight mass spectrometry (FM GC xGC-TOFMS) was used to characterize geographical-based differences in the volatilome of five white "Grillo" wines (of Sicilian origin), comprising the five sample classes. All wines were produced with the same vinification method in 2019. To minimize the influence of minor bottle-to-bottle differences, three bottles of the same wine were randomly selected, and three samples were collected per bottle, resulting in nine sample replicates per wine. Particular emphasis was devoted to the operational conditions of a novel low duty cycle flow modulator. A fast FM GC xGC-TOFMS method with a modulation period of 700 ms and a re-injection period of 80 ms was developed. Following, the instrumental software was exploited to identify class-distinguishing analytes in the dataset via tile-based Fisher ratio analysis (i.e., ChromaTOF Tile). A tile size of 10 modulations (7 s) on the first dimension and 45 spectra (300 ms) on the second dimension was used to encompass average peak widths and to account for minor retention time shifting. Off-line software was used to apply an ANOVA test. A p-value of 0.01 was applied in order to select the most important class-distinguishing analytes, which were input to principal component analysis (PCA). The PCA scores plot showed distinct clustering of the wines according to geographical origin, although the loadings revealed that only a few analytes were necessary to differentiate the wines. However, a comprehensive flavor profile assessment underscored the importance of all the information output by the ChromaTOF Tile software. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Hydrogel is a kind of three-dimensional network structure polymer that can absorb water and swell in water. It has been widely used in many fields due to its flexible functionality. We proposed the design strategy of dual-network hydrogel assisted by a metal-organic-framework (MOF) and modified them on the surface of silica (with average particle diameter of 5 mu m and average pore diameter of 76 A). On the basis of effectively avoiding shortcomings such as osmotic pressure caused by swelling, abundant mesh types of composite material also improves the separation selectivity of the stationary phase. A variety of analytes such as nucleosides/bases, antibiotics, organic acids, carbohydrates, alkylbenzenes, polycyclic aromatic hydrocarbons, pesticides and anions can be selectively separated. The research on the retention behavior and the interaction mechanism proves that the column can be used in mixed mode liquid chromatography. By comparing with the optimized chromatographic conditions of commercial HILIC column and C18 column, this new type of stationary phase also has some significant advantages in the selective separation of mixed analytes. This new stationary phase also has excellent acid/base stability. The intraday relative standard deviation of their retention time under acidic conditions is 0.05%-0.26% ( n = 10), and the intraday relative standard deviation under basic conditions is 0.11-0.14% ( n = 10). After optimizing the chromatographic conditions, the efficiency of this new type of chromatographic column can reach 90,300 plates/m (sucrose). In short, a new strategy for applying hydrogel to liquid chromatography with high selectivity and chromatographic separation performance is proposed. (c) 2021 Elsevier B.V. All rights reserved.
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