查看更多>>摘要：Magnetic carbon composite (Fe3O4@C) was synthesized and applied as a reversed-dispersive solid phase extraction sorbent for the simultaneous analysis of 40 pesticide residues in tobacco by ultrahigh performance liquid chromatography coupled to quadrupole time-of-fight mass spectrometry. Compared to the traditional QuEChERS method, the optimized Fe3O4@C simplified clean-up process and exhibited better clean-up capability than conventional sorbents. The pesticides were qualitatively identified by accurate mass of protonated molecules, fragment ions, isotopic peak clusters, and retention time, and quantitatively determined by matrix-matched external standard method. Good linearity of the proposed method was obtained with R value greater than 0.997 for all target pesticides at concentration levels of 2-200 mu g/L. The limit of detection ranged from 0.14 to 2.67 mu g/kg. The recoveries and relative standard deviations of all target pesticides at three spiked concentrations of 20, 50 and 200 mu g/kg were in the ranges of 80.8%-113.3% and 0.6%-16.3%, respectively. Compared with the reported methods for the analysis of multiple pesticide residues in tobacco, the proposed method has the advantages of simple to operate, high clean-up ability and less time-consuming in clean-up process. (C) 2022 Elsevier B.V. All rights reserved.
Cruz, Jonas Carneirode Souza, Israel DonizetiLancas, Fernando MauroCosta Queiroz, Maria Eugenia...
16页
查看更多>>摘要：Miniaturized liquid chromatography (LC) has been recognized as one of the most important analytical methods in several research fields. Reduced analytical work-scale provides superior chromatographic resolution and decreases sample and organic solvent consumption. However, frequent clogging of tubing connections and use of small sample volumes are significant limitations when high throughput and sensitive analyses are required. Effective sample preparation could help to overcome these limitations. Online coupling of sample preparation techniques (such as column switching and in-tube solid-phase microextraction) with these miniaturized systems may result in more sensitive and reproducible analyses, improving analytical efficiency. This review describes the most common online miniaturized LC configurations, and the main applications of current online sample preparation techniques coupled to miniaturized LC systems in the bioanalytical, omics, and environmental areas. Relevant features, and challenges of these systems, and innovative sorbents, including restricted access materials, monoliths, and immunosorbents is also discussed. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：In supercritical fluid chromatography (SFC), the variation of pressure, temperature and volumetric flow-rate is most noticeable when the mobile phase contains only neat carbon dioxide. This can be explained by the compressibility of CO2 and introduces several difficulties to the work of chromatographers. The only flow parameter that is considered to be constant across the SFC system is the mass flow-rate. It has been shown that the Coriolis flow meter (CFM) provides different types of information depending on its placement in the instrument. Therefore, the goal of this paper is to investigate several factors affecting the variation of mass flow-rate in SFC, including four different configurations around the column, four sets of experimental conditions along with two columns and a zero-volume union. The effect of disturbances introduced by injections are studied as well. The results show different mass flow-rates when taken at the inlet or the outlet of the column. In addition, different columns produced different tendencies of variations. Study of the injections showed that the initial severe drop of mass flow is reduced when the averages are taken until the elution times of the chosen compounds. Additional testing related to possible leaks and CFM calibration showed that even if all standard operating procedures are strictly followed, reproducibility of the mass-flow rate can still be an issue. (C) 2022 The Author(s). Published by Elsevier B.V.
查看更多>>摘要：In this work, the electrospun polyacrylonitrile/covalent organic frameworks Tp-BD nanofibers (PAN/Tp-BD) were synthesized and applied as an adsorbent for thin film microextraction (TFME) of seven sulfonamides in animal derived food samples. The morphology, structure, porosity, and stability of the prepared nanofibers were investigated. The PAN/Tp-BD nanofibers exhibited good chemical stability, high flexibility, porous fibrous structure, and excellent extraction efficiency. Based on the PAN/Tp-BD nanofibers as the adsorbent, a thin film microextraction-high performance liquid chromatography (TFME-HPLC) method for the determination of seven sulfonamides (SAs) in food samples was developed. Under the optimal conditions, the TFME-HPLC exhibited the low limit of detection (0.10-0.18 ng.mL(-1)), the low limit of quantitation (0.33-0.60 ng.mL(-1)), the wide linear range (0.5-50 ng.L-1) with correlation coefficients between 0.994 and 0.998, and good enrichment factors between 39.7 to 170.1 towards 20 ng/mL SAs solution. The relative standard deviation (RSD) was lower than 11% in the interday and intraday analysis. Furthermore, the applicability of PAN/Tp-BD nanofibers was demonstrated for measuring trace SAs residues in the spiked food samples with recoveries ranging from 85.3% to 115.2%. The results demonstrated that the PAN/Tp-BD nanofibers have great potential for the efficient extraction of sulfonamides from complex food samples. (C) 2022 Elsevier B.V. All rights reserved.
Miller, Joshua D.Means, NicholasLopano, ChristinaHakala, J. Alexandra...
11页
查看更多>>摘要：This study outlines the development and subsequent validation of a method using chelation ion chromatography (CIC) pretreatment followed by traditional ion chromatography (IC) and post column UV/vis detection to measure transition metals in fossil fuel wastewaters, such as oil & gas (O&G) brines and coal mine drainage (CMD) waters. Measurement of transition metals is often an important characterization step in the research of environmental and energy systems. IC represents one way to measure these metals with the advantages of being versatile, simple and relatively low cost compared to other analytical methods. However, high concentrations of alkali and alkaline earth metals present in fossil fuel wastewaters will decrease IC detectability of transition metals in these waters. In this study, a CIC method was developed for the analysis of transition metal ions (Fe3+, Cu2+, Ni2+, Zn2+, Co2+, Mn2+, and Fe2+) in fossil fuel associated wastewaters such as Appalachian CMD and O&G wastewaters from the Permian and Bakken shale basins in the United States. CIC system incorporated an on-line chelator column (e.g., the MetPac CC-1) with high selectivity for transition metals over alkali and alkaline earth metals for salt matrix removal prior to transition metal separation and detection. Additional method developments also included acidifying all samples to 2% v/v HCl and using gradient elution rather than isocratic. The recoverability of transition metals in simple salt solutions commonly found in CMD and brine samples (e.g. NaCl, Na2SO4, CaCl2) using CIC was evaluated and compared to that using traditional IC. Our results found that the CIC system significantly improved transition metal recoveries for samples in 10,0 0 0 mg/L CaCl2 matrix, reaching 87%-108% recovery for all analytes, as opposed to 2-323% recovery in traditional IC. The limits of detection in this study achieved 10.09-161.2 mu g/L, comparable to reported values in similar IC studies. The developed method was also verified with certified water samples, resulting in 89%-111% recoveries in samples with higher analyte concentrations (i.e. > 4x the LoDs). The developed method achieved 87%-112% recoveries for most analytes in CMD samples and 72%-138% recoveries for Bakken shale samples, relative to ICP-MS values. Overall, the current IC method can be a very good screening tool for fast and cheap analysis for transition metals at mg/L level, to facilitate selection of samples for more detailed ICP-MS analysis. (C) 2022 Published by Elsevier B.V.
Cheung, Ming YuiBruce, JamesEuerby, Melvin R.Field, Jennifer K....
12页
查看更多>>摘要：The paper describes a simple and rapid reversed-phase UHPLC method development screening strategy for the purity determination of peptide-based pharmaceuticals. The protocol utilises five disparate column and six volatile or non-volatile mobile phases (i.e., 30 combinations). The method development strategy has been demonstrated to be highly effective in identifying conditions which generate complementary selectivity and good peak shape. Columns with varying degrees of charge (positive and negative), in addition to their differing hydrophobic character, were used in combination with mobile phases within the pH range of 2.3 to 5.1. The novel ion-pair / chaotropic reagent ammonium hexafluorophosphate at pH 2.3 was shown to be an extremely useful mobile phase additive in that it produced excellent complementary separation and good peak shape. Methanesulfonic acid was demonstrated to be a good alternative to the ubiquitously employed trifluoroacetic acid which failed to generate optimum separation for the peptides investigated highlighting the importance of screening disparate mobile phase additives. Both ammonium hexafluorophosphate and methanesulfonic acid were shown not to adversely affect the stability of C18 columns or demonstrated any irreversible adsorption / memory effects. No pH hysteresis effects were demonstrated with any of the stationary phases on mobile phase pH cycling. No major problems have been observed with the novel mobile phase additives ammonium hexafluorophosphate and methanesulfonic acid, however, it is recommended that they be used with caution until long-term routine use has been established. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The combination of mixed-mode chromatography (MMC) and molecular imprinting technology (MIT) has been proven to be successful for protein separation, but suffered from cumbersome material prepara-tion and limited performance. In this work, a new modification method marrying atom transfer radical polymerization (ATRP) and multicomponent reaction was proposed to simplify the preparation process. Using regenerated cellulose (RC) membrane as the substrate, immunoglobulin G (IgG) as the template protein and tryptamine as the ligand, a dual-recognition membrane adsorbers (MIM) was prepared by mild Ugi four-component reaction (Ugi-4CR) and surface initiated ATRP. Control the ATRP time is the key for surface imprinting. The static IgG uptake and selectivity of UGI membrane were 45 mg/mL and 1.8, respectively, while those of MIM-0.5 were 42.5 mg/mL and 14, indicating that the introduction of molec-ular imprinting technology significantly improved the selectivity of the membrane to IgG. The MIM-0.5 membrane retains the pH-dependent and salt-tolerant of HCIC. The dynamic flow-through results showed that the MIM-0.5 membrane could effectively separate IgG from IgG/BSA mixed solution with the purity of 88% and retained its bioactivity. This work demonstrated the feasibility of bonding HCIC and MIT to the membrane surface by Ugi-4CR and ATRP. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：The existence of chiral compounds is a very common phenomenon in the field of medicine, and nearly 60% of drugs are chiral. The separation of racemic drugs is the key to safe use of drugs. Molecularly imprinted technique (MIT) has attracted wide attention in the separation of chiral drugs in recent years due to its simple operation and strong specific recognition ability of target molecules. Molecularly imprinted polymers (MIPs) have been used as selective adsorbents in a variety of analytical techniques, and excellent progress has been made in the separation of chiral drugs. In this paper, the MIT for the separation of drug in recent ten years is reviewed. We will introduce how to achieve chiral drug resolution in different chromatographic techniques based on the morphological differences of MIPs (micron-sized particles, nanoparticles and monolithic column materials) as the classification criteria. Furthermore, the contributions of surface molecularly imprinted technique (SMIT) and molecularly imprinted membrane (MIM) technology in racemic drug resolution are also introduced. Finally, the main application challenges of chiral MIT are briefly introduced, and the future development direction of this field is prospected. (c) 2022 Elsevier B.V. All rights reserved.
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