Preparation and evaluation of a novel molecularly imprinted SPE monolithic capillary column for the determination of auramine O in shrimp

A novel method combining molecular imprinting and SPE was developed in a capillary column for the determination of auramine O in shrimp. The capillary monolithic column was prepared by UV‐initiated in situ polymerization, using auramine O as template and methacrylic acid and ethylene dimethacrylate as functional monomer and cross‐linker, respectively. The properties of the prepared capillary monolithic column were investigated under the optimized conditions coupled with HPLC, and then the morphologies of the inner polymers were characterized by SEM. The calibration curve was expressed as A = 103C + 19.8 (r = 0.9992) with a linear range of 0.25–25.0 μg/mL, and the recoveries of auramine O at different concentrations in shrimp ranged from 90.5 to 92.4% with RSDs ranging from 2.1 to 4.4%. The capacities of the molecularly imprinted polymer and nonimprinted polymer columns were 0.722 and 0.147 μg/mg, respectively, and the LOD (S/N = 3) of auramine O in shrimp was 17.85 μg/kg. Under the selected conditions, the enrichment factors obtained were higher than 70‐fold. The results indicate that the prepared molecularly imprinted capillary monolithic column was reliable and applicable to the analysis of auramine O in shrimp.     

Properties of two amide‐based hydrophilic interaction liquid chromatography columns

Hydrophilic interaction liquid chromatography is a separation technique suitable for the separation of moderately and highly polar compounds. Various stationary phases (SPs) for hydrophilic interaction liquid chromatography are commercially available. While the SPs based on the same type of ligand are available from different providers, they can display a distinct retention characteristics and separation selectivity. The current work is focused on characterization and comparison of the separation systems of two amide‐based HPLC columns from two producers, i.e. XBridge Amide column and TSK gel Amide‐80 column. Several characterization procedures (tests) were used to investigate the differences between these columns. The chromatographic behavior of selected analytes indicates that multimodal interactions are responsible for retention and separation on these columns. Multiple testing approaches were used in order to reveal subtle differences between the SPs. Both amide‐based columns showed certain differences in retention, selectivity, and plate counts. Based on the tests used in this study, we conclude that the investigated columns provide a different degree of H‐bonding interactions.     

Preparation and characterization of octadecyl acrylate monoliths for capillary electrochromatography by photochemical,thermal, and chemical initiation†

Monolithic stationary phases based on octadecyl acrylate for CEC using different initiating systems (UV irradiation, thermal, and chemical initiation) in the presence of lauroyl peroxide as initiator were synthesized. For each initiation mode, the influence of the porogenic solvent composition on both the morphological and electrochromatographic properties of the resulting monoliths was investigated. Under optimal conditions, excellent efficiencies for the photochemically and chemically polymerized monoliths (minimum plate heights of 6.9–10.7 and 6.5–12.6 μm, respectively) were achieved. Thermally initiated columns gave lower efficiency values, permeabilities, and longer analysis times compared to these initiating systems. The produced monolithic stationary phases were evaluated in terms of reproducibility and gave RSD values below 9.2, 10.6, and 9.8% for UV, thermally, and chemically initiated columns, respectively.     

Open tubular columns with mixed‐mode reversed‐phase and weak anion‐exchange stationary phase for capillary electrochromatography

Columns for open tubular capillary electrochromatography, coated with a mixed‐mode (RP/ion‐exchange) stationary phase, were prepared by using the sol–gel method. The synthetic procedure was optimized by changing the ratios of tetraethoxysilane, octyltriethoxysilane, and 3‐aminopropyltriethoxysilane in the initial sol. SEM studies reveal that a coating with about 400 nm thickness can be obtained. The inner surface properties of these capillaries were probed by measuring the EOF as a function of pH. The surface of this stationary phase contains octyl, amine, and residual silanol moieties; the amine and silanol groups determine the net charge on the inner surface of the capillary and can produce a switchable EOF (anodal/cathodal). The performances of the columns were evaluated by open tubular capillary electrochromatography using a wide range of compounds (polycyclic aromatic hydrocarbons, aromatic acids, and aromatic amines).     

Nondestructive damage assessment in fiber reinforced composites with the pulsed ultrasonic polar scan

This study investigates the use of both amplitude and time-of-flight based pulsed ultrasonic polar scan (P-UPS) as a sophisticated non-destructive damage sensor for fiber reinforced composites. Focus is put on stiffness related damage phenomena, which are in general difficult to monitor nondestructively, and their associated signature in the P-UPS image. Various composite samples, with different damage states, have been inspected at multiple material spots with the P-UPS technique. The results demonstrate the capability of the P-UPS method to obtain a unique signature of the local material damage characteristics. Several indicators in the acquired P-UPS images have been identified from which the type and level of material degradation can be obtained. The P-UPS extracted characteristics are fully supported by simulations, conventional tests as well as visual inspection.     

One‐step strategy for the synthesis of a derivatized cyclodextrin‐based monolithic column

Derivatized β‐cyclodextrin (β‐CD) functionalized monolithic columns were prepared by a “one‐step” strategy using click chemistry. First, the intended derivatized β‐CD monomers were synthesized by a click reaction between propargyl methacrylate and mono‐6‐azido‐β‐CD and then sulfonation or methylation was carried out. Finally, monolithic columns were prepared through a one‐step in situ copolymerization of the derivatized β‐CD monomer and ethylene glycol dimethacrylate. The sulfated β‐CD‐based monolith was successfully applied to the hydrophilic interaction liquid chromatography separation of nucleosides and small peptides, while the methylated β‐CD‐functionalized monolith was useful for the separation of nonpolar compounds and drug enantiomers in capillary reversed‐phase liquid chromatography. The structures of the monomers were characterized by Fourier transform infrared spectroscopy and mass spectrometry. The physicochemical properties and column performance of monoliths were evaluated by scanning electron microscopy and micro high performance liquid chromatography. This strategy has considerable prospects for the preparation of other derivatized CD‐functionalized methacrylate monoliths.     

Development and evaluation of gas and liquid chromatographic methods for the analysis of fatty amines

In contrast to the plethora of publications on the separation of fatty acids, analogous studies involving fatty amines are scarce. A recently introduced ionic‐liquid‐based capillary column for GC was used to separate trifluoroacetylated fatty amines focusing on the analysis of a commercial sample. Using the ionic liquid column (isothermal mode at 200°C) it was possible to separate linear primary fatty amines from C₁₂ to C₂₂ chain length in less 25 min with MS identification. The log of the amine retention factors are linearly related to the alkyl chain length with a methylene selectivity of 0.117 kcal/mol for the saturated amines and 0.128 kcal/mol for the mono‐unsaturated amines. The sp² selectivity for unsaturated fatty amines also could be calculated as 0.107 kcal/mol for the ionic liquid column. The commercial sample was quantified by GC with flame ionization detection (FID). An LC method also was developed with a reversed phase gradient separation using acetonitrile/formate buffer mobile phases and ESI‐MS detection. Native amines could be detected and identified by their single ion monitoring chromatograms even when partial coelution was observed. The analysis of the commercial sample returned results coherent with those obtained by GC–FID and with the manufacturer's data.     

高内相乳液法制备整体柱及其分离性能研究

建立了高内相乳液(HIPE)法制备以甲基丙烯酸十二烷酯为功能单体(LMA),二乙烯基苯(DVB)为交联剂的新型毛细管电色谱整体柱。polyHIPE整体柱利用扫描电镜与BET进行了表征,表明了制备的整体柱具有较大的孔径与较好的比表面积,更好的通透性,可更好地满足高效快速分离分析的需要。实验中K2S2O8不仅可以作为引发剂,同时加热后残基能为固定相提供电渗流。优化表面活性剂span80含量、W/O比例对整体柱制备的影响,以硫脲与苯系物为目标化合物考察了整体柱的分离性能与效果。该方法用实际水样品苯系物分析,取得良好的效果。     

基于窄内径多孔层毛细管开管柱的纳流高效液相色谱用于N-衍生化氨基酸对映体的分离

窄内径多孔层毛细管开管柱（NPLOT柱）在生命科学领域,特别是单细胞分析领域具有较好的应用前景。本研究采用原位热引发聚合法来制备窄内径奎尼丁类手性固定相多孔层开管柱,在6 μ m i.d.的毛细管中制备有机聚合物多孔层,考察了不同热聚合时间（3、6和9 h）对NPLOT柱形貌的影响,热聚3 h和6 h制备的NPLOT柱形貌均一,多孔层厚度分别为103±51 nm和210±51 nm。将热聚合3 h制备的NPLOT柱用于纳流高效液相色谱分离N-衍生化氨基酸对映体,在2 min内即可实现基本分离,消耗的样品量仅为皮升级别。该研究将为单细胞分析提供研究手段。     

Analysis of ginseng root and leaf by multiple columns and detections liquid chromatography

Abstract

A multiple columns and detections liquid chromatography system, including size exclusion chromatography (SEC) and reversed phase liquid chromatography (RPLC), for the analysis of macromolecules and micromolecules in ginseng root and leaf was developed. The columns were connected by two switching valves. Macromolecules were separated on a SEC column (TSK gel SuperMultipore PW-H column, 6?mm× 150?mm, 8?μm) by isocratic elution of 50?mM ammonium acetate aqueous solution, 0.3?mL/min of flow rate and detected by evaporative light scattering detection (ELSD). Micromolecules were analyzed on a Poroshell RP column (Agilent Poroshell 120?SB-Aq column, 4.6?mm × 50?mm, 2.7 µm) with gradient elution of water and acetonitrile, 0.6?mL/min of flow rate and detected by ultraviolet detection (UV). As a result, in the macromolecules chromatogram of ginseng root sample showed two main peaks while only one major peak for ginseng leaf. For micromolecules analysis, 17 compounds (3 nucleosides + 14 saponins) and 17 compounds (3 nucleosides + 1 flavonoid + 13 saponins) were found in ginseng root and leaf, respectively. The developed method is helpful for the quality evaluation of ginseng root and leaf.