Journal of Separation Science
1615-9314
1615-9306
Đức
Cơ quản chủ quản: Wiley-VCH Verlag , WILEY-V C H VERLAG GMBH
Lĩnh vực:
Analytical ChemistryFiltration and Separation
Các bài báo tiêu biểu
Applications of silica‐based monolithic HPLC columns Abstract The recent invention and successive commercial introduction of monolithic silica columns has motivated many scientists from both academia and industry to study their use in HPLC. The first paper on monolithic silica columns appeared in 1996. Currently about 200 papers have been published relating to applications and characterization of monolithic silica columns, including monolithic capillaries. This review attempts to give an overview covering various aspects of this new column type in the field of high throughput analysis of drugs and metabolites, chiral separations, analysis of pollutants and food‐relevant compounds, as well as in bioanalytical separations such as in proteomics. Some of the applications are described in greater detail. The numerous publications dealing with the physicochemical and chromatographic characterization of monolithic silica columns are briefly summarized.
Tập 27 Số 10-11 - Trang 843-852 - 2004
Impact of column temperature and mobile phase components on selectivity of hydrophilic interaction chromatography (HILIC) Abstract The retention mechanism and chromatographic behavior for different polar analytes under hydrophilic interaction chromatography (HILIC) conditions have been studied by application of different mobile phases and stationary phases to various analytes at different temperatures. In addition to the commonly accepted mechanism of analyte liquid‐liquid partitioning between mobile phase and water‐enriched solvent layer which is partially immobilized onto the surface of the stationary phase, hydrogen‐bonding, hydrophobic interaction, and ion‐exchange interactions may also be involved. The predominant retention mechanism in HILIC separation is not always easily predictable. It can depend not only on the characteristics of the analytes but also on the selection of mobile and stationary phase compositions. The objective of this review is to evaluate the potential application of column temperature and mobile phase composition toward improving HILIC selectivity. The functional groups from analyte structures, stationary phase materials and organic mobile phase solvents will be highlighted.
Tập 31 Số 9 - Trang 1449-1464 - 2008
Preparation and HPLC applications of rigid macroporous organic polymer monoliths Abstract Rigid porous polymer monoliths are a new class of materials that emerged in the early 1990s. These monolithic materials are typically prepared using a simple molding process carried out within the confines of a closed mold. For example, polymerization of a mixture comprising monomers, free‐radical initiator, and porogenic solvent affords macroporous materials with large through‐pores that enable applications in a rapid flow‐through mode. The versatility of the preparation technique is demonstrated by its use with hydrophobic, hydrophilic, ionizable, and zwitterionic monomers. Several system variables can be used to control the porous properties of the monolith over a broad range and to mediate the hydrodynamic properties of the monolithic devices. A variety of methods such as direct copolymerization of functional monomers, chemical modification of reactive groups, and grafting of pore surface with selected polymer chains is available for the control of surface chemistry. Since all the mobile phase must flow through the monolith, the convection considerably accelerates mass transport within the molded material, and the monolithic devices perform well, even at very high flow rates. The applications of polymeric monolithic materials are demonstrated mostly on the separations in the HPLC mode, although CEC, gas chromatography, enzyme immobilization, molecular recognition, advanced detection systems, and microfluidic devices are also mentioned.
Tập 27 Số 10-11 - Trang 747-766 - 2004
Stationary phases for hydrophilic interaction chromatography, their characterization and implementation into multidimensional chromatography concepts Abstract Hydrophilic interaction chromatography (HILIC) is becoming increasingly popular for separation of polar samples on polar columns in aqueous‐organic mobile phases rich in organic solvents (usually ACN). Silica gel with decreased surface concentration of silanol groups, or with chemically bonded amino‐, amido‐, cyano‐, carbamate‐, diol‐, polyol‐, or zwitterionic sulfobetaine ligands are used as the stationary phases for HILIC separations, in addition to the original poly(2‐sulphoethyl aspartamide) strong cation‐exchange HILIC material. The type of the stationary and the composition of the mobile phase play important roles in the mixed‐mode HILIC retention mechanism and can be flexibly tuned to suit specific separation problems. Because of excellent mobile phase compatibility and complementary selectivity to RP chromatography, HILIC is ideally suited for highly orthogonal 2‐D LC‐LC separations of complex samples containing polar compounds, such as peptides, proteins, oligosaccharides, drugs, metabolites and natural compounds. This review attempts to present an overview of the HILIC separation systems, possibilities for their characterization and emerging HILIC applications in 2‐D off‐line and on‐line LC‐LC separations of various samples, in combination with RP and other separation modes.
Tập 31 Số 9 - Trang 1421-1437 - 2008
Dispersive liquid–liquid microextraction using extraction solvent lighter than water Abstract For the first time a dispersive liquid–liquid microextraction method on the basis of an extraction solvent lighter than water was presented in this study. Three organophosphorus pesticides (OPPs) were selected as model compounds and the proposed method was carried out for their preconcentration from water samples. In this extraction method, a mixture of cyclohexane (extraction solvent) and acetone (disperser) is rapidly injected into the aqueous sample in a special vessel (see experimental section) by syringe. Thereby, a cloudy solution is formed. In this step, the OPPs are extracted into the fine droplets of cyclohexane dispersed into aqueous phase. After centrifuging the fine droplets of cyclohexane are collected on the upper of the extraction vessel. The upper phase (0.40 μL) is injected into the gas chromatograph (GC) for separation. Analytes were detected by a flame ionization detector (FID) (for high concentrations) or MS (for low concentrations). Some important parameters, such as the kind of extraction and dispersive solvents and volume of them, extraction time, temperature, and salt amount were investigated. Under the optimum conditions, the enrichment factors (EFs) ranged from 100 to 150 and extraction recoveries varied between 68 and 105%, both of which are relatively high over those of published methods. The linear ranges were wide (10–100 000 μg/L for GC‐FID and 0.01–1 μg/L for GC‐MS) and LODs were low (3–4 μg/L for GC‐FID and 0.003 μg/L for GC‐MS). The RSDs for 100.0 μg/L of each OPP in water were in the range of 5.3–7.8% (n = 5).
Tập 32 Số 18 - Trang 3191-3200 - 2009
Molecularly imprinted polymer for solid‐phase extraction of ephedrine and analogs from human plasma Abstract A molecularly imprinted polymer (MIP) was synthesized and evaluated to selectively extract ephedrine from human plasma. The MIP synthesis was performed in chloroform with methacrylic acid as a functional monomer and the target alkaloid as a template molecule. The resulting MIP was applied to the selective extraction of ephedrine from a pure aqueous medium. A recovery about 74% was obtained using the MIP with only 7% on the nonimprinted polymer (NIP). A very straightforward selective SPE procedure was then successfully applied to the direct extraction of ephedrine from spiked human plasma with a high extraction recovery (68%) on the MIP with no recovery on the NIP. Moreover, the MIP was used for the selective extraction of catecholamine neurotransmitters, i.e . adrenaline and noradrenaline.
Tập 32 Số 7 - Trang 1036-1042 - 2009
Measurement of the parameters of the mass transfer kinetics in high performance liquid chromatography Abstract Fundamental studies of the mass transfer kinetics are as essential as those of the retention equilibrium for a detailed understanding of the characteristics and the mechanisms of chromatographic separations. The acquisition of a large amount of reliable experimental data and of meaningful results is necessary for any further progress of our knowledge of kinetics. The main goal of this review is to provide information on the methods used to perform accurate measurements and on the data analysis procedures used for deriving the kinetic parameters characterizing mass transfer in HPLC. First, the general characteristics of several methods of determination of some kinetic parameters are briefly reviewed. Secondly, we give detailed explanations of the experimental conditions of the pulse on a plateau method (i.e., elution chromatography on a plateau of finite concentration or pulse response method) and of the data analysis procedures based on moment analysis. Thirdly, we explain some important requirements for the acquisition of appropriate experimental data and discuss corrections to be applied when deriving several kinetic parameters. Fourthly, we discuss the accuracy of the kinetic parameters derived from the pulse on a plateau method and from moment analysis. Finally, some results concerning the mass transfer kinetics in RPLC systems are demonstrated as examples.
Tập 26 Số 3-4 - Trang 155-173 - 2003
Preparation of methacrylate monoliths Abstract Rigid macroporous polymers developed in the early 1990s are widely used as efficient stationary phases for all types of chromatographic separations. The main advantages of so‐called monolithic supports are their high hydraulic permeability and the dominance of the convection over the diffusion mechanism of mass‐exchange under dynamic conditions that allow the separation to be carried out at extremely high flow rates and, consequently, during very short operation times. Among other types of macroporous polymers, the methacrylate‐based monolithic materials represent the most popular and successfully explored class of sorbents. This review is an attempt to collect together the contributions of different groups working in the area of monolith preparation. Examples of different methcrylate monomers and crosslinkers, as well as porogenic solvents, including polymer ones, used in monolith preparation are discussed.
Tập 30 Số 17 - Trang 2801-2813 - 2007
Ionic liquids: solvents and sorbents in sample preparation Abstract The applications of ionic liquids (ILs) and IL‐derived sorbents are rapidly expanding. By careful selection of the cation and anion components, the physicochemical properties of ILs can be altered to meet the requirements of specific applications. Reports of IL solvents possessing high selectivity for specific analytes are numerous and continue to motivate the development of new IL‐based sample preparation methods that are faster, more selective, and environmentally benign compared to conventional organic solvents. The advantages of ILs have also been exploited in solid/polymer formats in which ordinarily nonspecific sorbents are functionalized with IL moieties in order to impart selectivity for an analyte or analyte class. Furthermore, new ILs that incorporate a paramagnetic component into the IL structure, known as magnetic ionic liquids (MILs), have emerged as useful solvents for bioanalytical applications. In this rapidly changing field, this Review focuses on the applications of ILs and IL‐based sorbents in sample preparation with a special emphasis on liquid phase extraction techniques using ILs and MILs, IL‐based solid‐phase extraction, ILs in mass spectrometry, and biological applications.
Tập 41 Số 1 - Trang 209-235 - 2018
Mass‐spectrometry‐based lipidomics Abstract Lipids, which have a core function in energy storage, signalling and biofilm structures, play important roles in a variety of cellular processes because of the great diversity of their structural and physiochemical properties. Lipidomics is the large‐scale profiling and quantification of biogenic lipid molecules, the comprehensive study of their pathways and the interpretation of their physiological significance based on analytical chemistry and statistical analysis. Lipidomics will not only provide insight into the physiological functions of lipid molecules but will also provide an approach to discovering important biomarkers for diagnosis or treatment of human diseases. Mass‐spectrometry‐based analytical techniques are currently the most widely used and most effective tools for lipid profiling and quantification. In this review, the field of mass‐spectrometry‐based lipidomics was discussed. Recent progress in all essential steps in lipidomics was carefully discussed in this review, including lipid extraction strategies, separation techniques and mass‐spectrometry‐based analytical and quantitative methods in lipidomics. We also focused on novel resolution strategies for difficult problems in determining C=C bond positions in lipidomics. Finally, new technologies that were developed in recent years including single‐cell lipidomics, flux‐based lipidomics and multiomics technologies were also reviewed.
Tập 41 Số 1 - Trang 351-372 - 2018