查看更多>>摘要：A B S T R A C T It is an important challenge to effectively extract and determine pesticides in complex samples. Co-valent organic frameworks (COFs) are burgeoning porous crystalline organic materials with good envi-ronmental resistance, thus demonstrating great potential as adsorbents in contaminants detection. In this work, we design and synthesize a novel COF-TpDB via 1,3,5-triformylphloroglucinol (Tp) and 4,4'-diaminobenzoylanilide (DB) as well as its packed cartridge for solid phase extraction (SPE) of carbamate pesticides. Simulation calculations showed H-bonding facilitates the adsorption interactions between the carbamate pesticides and TpDB. A method was developed by coupling TpDB as SPE sorbents with high performance liquid chromatography-ultraviolet (HPLC-UV) detection to determine trace carbamate pesti-cides in vegetables. The established method showed a wide linear range of 0.1-200 ng mL -1 and low limit of detections (0.0 05-0.05 ng mL -1) for four carbamate pesticides. The applicability of TpDB as adsorbent was investigated for determination of trace carbamate pesticides residue in vegetables with satisfactory recoveries of four carbamates in the range of 80.4-101.2%. The results demonstrated that the COF-TpDB offer great potential for efficient extraction of carbamate pesticides from complicate matrices. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：A sensitive capillary electrophoresis strategy was developed by combining salting-out assisted liquid-liquid extraction and online three-step stacking to detect trace quantities of antitumour indole alkaloids in complex biological samples. The proposed strategy fully exploits these two technologies such that extraction, online stacking and separation are combined in a fast and efficient manner. First, salting-out assisted liquid-liquid extraction was used to extract three indole alkaloids (vinblastine sulfate, catharanthine sulfate and vindoline) from complex biomasses. An appropriate volume of acetonitrile (ACN) was mixed with a faecal aqueous solution to precipitate proteins. The mixed solution was vortexed, followed by the addition of ammonium sulfate ((NH4)(2)SO4) to induce two-phase separation. Alkaloids were effectively extracted into the organic phase, which was then subjected to capillary electrophoresis (CE) analysis. The sensitivity of capillary electrophoresis was effectively improved by online three-step stacking. Good linearity of the calibration curve for each indole alkaloid was obtained in the concentration range of 0.1-1 mu g/mL. Under optimal conditions, the sensitivity of ordinary injection was increased by up to 2366-fold, confirming the applicability of the proposed strategy for the sensitive determination of trace indole alkaloids in complex biological samples. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A sensitive and time-saving method for the determination of multi-pesticide residues in honey was developed using magnetic solid phase extraction (MSPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Magnetic polymer (N-vinyl pyrrolidone-divinyl benzene) (MVP-DB) was fabricated and employed as the adsorbent for extraction and enrichment of multi-pesticide residues in honey. MVP-DB contains lipophilic benzene ring, divinyl group, and hydrophilic pyrrolidone group. The good hydrophilic and hydrophobic structure of MVP-DB not only ensures sufficient dispersion in honey samples, but also enhances the ability to enrich target analytes. The predominant factors affecting the recoveries of analytes were systematically investigated, affording a rapid and highly efficient MSPE method. Under the optimal conditions, the method was verified, including the recovery, precision, linearity, sensitivity, and matrix effects. The results displayed that these pesticides showed good linearity in the range of 2-250 mu g L -1 . The MLOQs were 0.5 mu g kg -1 . The recoveries of pesticides in honey at the pre-spiked concentrations of 0.5-25 mu g kg -1 were 61.6%-112% with RSDs less than 18.2%. Hence, the developed method displayed good application prospect for the determination of multi-pesticide residues in honey samples. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Covalent organic frameworks (COFs) have attracted considerable attention in sample pretreatment because of their unique characteristics. However, the submicron or micron size of COFs has restricted their wider applications in solid-phase extraction (SPE). Herein, multiwalled nanotubes (MWNTs) were used as substrate materials to synthesize core-shell structured MWNTs@COFs composites (MWNTs@SNW-1) using a simple self-assembly method. The as-prepared MWNTs@SNW-1 composite exhibited a high BET surface area, good thermal stability, and good adsorption capacity. The MWNTs@SNW-1 composite was used as an adsorbent in cartridge-based SPE to extract four phytohormones before determining their levels by high-performance liquid chromatography. The experimental parameters affecting extraction efficiency, including the amount of adsorbents, solution pH, ionic strength, eluent type, and eluent volume, were investigated. The developed method showed a wide linear range (0.37-100 ng mL(-1)), low detection limits (0.11-0.32 ng mL(-1)), low limits of quantification (0.37-1.07 ng mL (-1)), high enrichment factors (45.9-49.3), and good reproducibility (< 4.8%) for phytohormones. The developed analytical method was used to analyze trace phytohormones in fruit juices with good recoveries, highlighting the potential of the MWNTs@SNW-1 composite as an adsorbent in sample preparation. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Phosphonium-based ionic liquids (ILs) have proven to be successful stationary phases (SPs) for gas chromatography (GC) in several fields of application because of their unique selectivity and good chromatographic properties. This study focuses on the use of two ILs as GC SPs that are based on the phosphonium derivatives trihexyl(tetradecyl)phosphonium chloride ([P-66614(+)][Cl+), and trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)sulfonyl]imide ([P-66614(+)][NTf2-), which have previously been shown to be complementary in terms of chromatographic selectivity and retention. Their application in routine analysis has been limited by their lower maximum allowable operating temperatures (MAOT) (200 degrees C for the [P-66614(+)][Cl-] IL and 180 degrees C for [P-66614(+)][NTf2-), which restricts their use to samples that consist of analytes with relatively high volatility. A previous study carried out in the Authors' laboratory focused on extending the use of the [P-66614(+)][Cl+] IL SP to the analysis of samples with analytes of medium-to-low volatility by optimizing column characteristics and operative conditions. This study addresses the immobilization of both the [P-66614(+)][Cl+] and [P-66614(+)][Ntf(2)(-)] ILs to the inner wall of fused silica columns to increase their MAOT under soft and hard reaction conditions. The resulting MAOT depended on more or less drastic immobilization conditions, and reached 220 degrees C for soft immobilization (So-Im) and 240 degrees C for hard immobilization (Ha-lm) in the [P-66614(+)][Cl-] IL columns, and 200 degrees C for So-Im and 220 degrees for Ha-Im in columns coated with the [P-66614(+)] [NTf2-] IL. The influence of immobilization on the separation power and performance of all the columns has been evaluated using i) the Grob test, ii) a model mixture of 41 compounds of different polarity, structure, and with different organic functional groups representative of the flavor and fragrance field, iii) a standard mixture of 37 fatty acid methyl esters, iv) the peppermint essential oil, v) two mixtures of sesquiterpenic alcohols (farnesols and santalols), and vi) a standard mixture of 16 pesticides. These test samples were also used to demonstrate the complementarity of the two phosphonium-based IL SPs in terms of selectivity and retention. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：In this work, mesoporous silica microspheres with bimodal porous structures for size exclusion chromatography (SEC) supports were synthesized via a pseudomorphic transformation method by using 3.5 and 5 mu m commercial silica particles as sources and cetyltrimethylammonium bromide (CTAB) as a template. The effects of the synthetic conditions on the pore size distribution were examined, including the temperature, reaction time and the molar ratio of SiO2 :NaOH. Bimodal porous silicas (BPSs) with pore sizes of 3.01 and 12.80 nm were obtained with SiO2 :NaOH:CTAB:H2O=1:0.1:0.1:20 at 80 degrees C for 24 h. The BPSs were bonded with diol groups to produce a stationary phase for SEC. The column performance was evaluated with three types of samples, namely, dextran (70 KDa-62 Da), polyethene glycol (PEG) (20 KDa-32 Da) and three biomolecules (36 KDa-1.36 KDa). The column that was packed with a 3.5 mu m stationary phase showed excellent resolution for molecular weights of less than 1 KDa with high column efficiency. Carbohydrate samples (dextran (MW=1296), dextran (MW=972), sucrose (MW=342), glucose (MW=180) and glycerol (MW=92)) were separated. Heptaethylene glycol, hexaethylene glycol, pentaethylene glycol, tetraethylene glycol, triethylene glycol, and diethylene glycol were resolved in a PEG200 sample. In summary, this work shows the advantages of bimodal mesopores in SEC for small molecules less than 1 kDa. In the pseudomorphic synthesis, the pore size can be regulated by template micelles. Thus, the development SEC supports with high accuracy for a specified molecular weight range is expected since the pore size can be regulated by the surfactant template. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：A novel, green, and facile fabric phase sorptive extraction (FPSE) prior to high pressure liquid chromatography with diode array detection (HPLC-DAD) methodology was developed for the efficient extraction and quantitative determination of tocopherols (alpha- , sum of (beta+gamma), and delta-) in edible oils. Among several highly hydrophobic FPSE membranes, sol-gel polycaprolactone-polydimethylsiloxane-polycaprolactone (sol-gel PCAP-PDMS-PCAP) coated polyester FPSE membrane was found as the most efficient in extracting tocopherol homologues from edible oil samples. To maximize the extraction efficiency of FPSE membrane, major parameters of FPSE including the membrane size, sample loading time, the choice of the appropriate elution solvent and the elution solvent volume, desorption time, and the influence of stirring were systematically optimized. The developed FPSE-HPLC-DAD methodology was validated and presented adequately low limits of detection (LODs) and limits of quantification (LOQs) over the ranges 0.05-0.10 mu g/g, and 0.17-0.33 mu g/g, respectively. The RSD% of the within-day and between-day assays were lower than 1.3, and 11.8, respectively, demonstrating good method precision. The trueness of the method was assessed by means of relative percentage of recovery and ranged between 90.8 and 95.1% for within-day assay, and between 88.7-92.8% for between-day assay. The developed methodology was applied in the analysis of edible oils. (C) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Seeking for single-column versatile chiral separation methodology is the ultimate goal for analysts engrossed in enantioseparation. However, the versatility and selectivity are always contradictory due to negative influence among the recognition domains and the relatively low surface concentrations in a limited support surface area. Herein, we reported a novel series of quinine (QN) bridged cyclodextrin (CD) chiral stationary phases (CSPs) with satisfied surface concentration of both selectors, prepared via a facile surface-up 'thiol-ene click' approach, where QN and CD can not only nicely exhibit their individual resolution capability but also afford possible synergism in resolving difficult-to-separate analytes. QN bridged phenylcarbamoylated CD CSP exhibits powerful resolution ability by positive combining the resolving ability of QN and functional CD and achieves the resolution of almost a double number of race mates over QN or CD CSPs. Meanwhile, it exhibits comparable and even better chiral selectivity over the widely used chemical-bonded chiral column (CHIRALPAK (R) IA, CHIRALPAK (R) IB and CHIRALPAK (R) IC of Daicel) for the studied analytes. This work thus advances the duplex QN-CD structure as a relatively versatile platform for chiral resolution and commendably promotes the design of functional CSPs with chiral molecular bridge. (c) 2021 Elsevier B.V. All rights reserved.
查看更多>>摘要：Monoclonal antibodies (mAb) are used as therapeutics and for diagnostics of a variety of diseases, and novel antibodies are continuously being developed to find treatments for new diseases. Therefore, the manufacturing process must accommodate a range of mAb characteristics. Acid-sensitive mAbs can severely compromise product purity and yield in the purification process due to the potential formation of aggregates. To address this problem, we have developed an integrated downstream process for the purification of pH-sensitive mAbs at mild conditions. A calcium-dependent Protein A-based ligand, called Z Ca , was used in the capture step in a 3-column periodic counter-current chromatography operation. The binding of Z Ca to antibodies is regulated by calcium, meaning that acidic conditions are not needed to break the interaction and elute the antibodies. Further, the virus inactivation was achieved by a solvent/detergent method, where the pH could remain unchanged. The polishing steps included a cation and an anion exchange chromatography step, and screening of the capture and polishing steps was performed to allow for a seamless integration of the process steps. The process was implemented at laboratory scale for 9 days obtaining a high yield, and a consistently pure drug substance, including high reduction values of the host cell protein and DNA concentrations, as well as aggregate levels below the detection limit, which is attributed to the mild conditions used in the process.
查看更多>>摘要：High-Performance Liquid Chromatography (HPLC) is a key technique in the evaluation of biopharmaceuticals. To improve the separation of biopharmaceuticals, it is crucial to improve the fundamental understanding of the parameters governing their band broadening behavior. This can be obtained by a detailed assessment of the individual contributions to their mass transfer. For this purpose, a precise knowledge of the molecular diffusion coefficient (D-m) of biopharmaceuticals is required. Only little experimental data is available for the D-m-values of biopharmaceuticals under HPLC relevant conditions. Furthermore, none of the available equations that can be used to calculate D-m-values, allows to account for any conformational changes that might occur. The Taylor-Aris method is a very simple and absolute method that is often employed to determine D-m-coefficients. The Taylor-Aris method measures the band broadening of an analyte in an open tube under laminar conditions, wherein (1) longitudinal diffusion can be ignored, (2) the sample is fully radially equilibrated and (3) the contribution of the extra-column variance to the total variance is negligible. Moreover, since the open tubes are typically coiled for practical reasons, (4) the influence of secondary flows on the band broadening should be insignificant. In this tutorial paper, the impact of the four conditions mentioned above on the accuracy of the obtained D-m values is revisited. For this purpose, D-m values are measured for two representative compounds (Bovine Serum Albumin and Thiourea), and the obtained values are compared with literature data and theoretical recommendations. Based on these observations, a set of 'rules' for accurate and fast D-m measurements is put forward. Finally, an Interactive Tool (IT), combining these rules in a comprehensive way, is introduced and can be used to set up TA experiments. (C) 2021 Elsevier B.V. All rights reserved.
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