Fluorinated stationary phases provide unique separation effect on basic compounds, due to the fluorine atoms, and pentafluorophenyl stationary phases (PFPs) are the most widely used. Considering that some fluoroalkyls have higher fluorine contents than PFPs do, it is speculated that fluoroalkyl stationary phases should have potential new applications. Herein, we synthesized a silica-based stationary phase bonding perfluoroctyl (FC8) proved by characterization through elemental analysis and solid-state 13C cross-polarization/magic-anglespinning nuclear magnetic resonance. The chromatographic behavior of the stationary phase was evaluated with test compounds. In addition, to further study the applicability of FC8 materials, Corydalis decumbens (Thunb.) Pers. fraction, considered as a challenging medicine on reversed-phase chromatography columns, was chosen as a test sample. Results demonstrated that the FC8 stationary phase had better and more satisfactory separation performance than the PFP stationary phase on basic compounds.
Organic modifiers have shown promising potential for regulating the activity and selectivity of heterogeneous catalysts via tuning their surface properties. Despite the increasing application of organic modification technique in regulating the redox-acid catalysis of metal oxides, control of the acidity of metal oxide catalysts for enhanced reaction selectivity without sacrificing their redox activity remains a substantial challenge. Herein, we show the successful control of redox-acid catalysis of metal oxides with aprotic tertiary amine modifiers. Robust modification of manganese dioxide catalysts with N,N-dialkylcyclohexylamine selectively blocks the Lewis acid sites, with their redox activity mostly unaffected. This enables efficient synthesis of imines in high to excellent selectivity via aerobic oxidation of structurally diverse aryl amines. 相似文献
Water-soluble fluorescent carbon dots (CDs) were synthesized by a hydrothermal method using citric acid as the carbon source and ethylenediamine as the nitrogen source. The repeated and scale-up synthetic experiments were carried out to explore the feasibility of macroscopic preparation of CDs. The CDs/Fe3+ composite was prepared by the interaction of the CDs solution and Fe3+ solution. The optical properties, pH dependence and stability behavior of CDs or the CDs/Fe3+ composite were studied by ultraviolet spectroscopy and fluorescence spectroscopy. Following the principles of fluorescence quenching after the addition of Fe3+ and then the fluorescence recovery after the addition of asorbic acid, the fluorescence intensity of the carbon dots was measured at λex = 360 nm, λem = 460 nm. The content of ascorbic acid was calculated by quantitative analysis of the changing fluorescence intensity. The CDs/Fe3+ composite was applied to the determination of different active molecules, and it was found that the composite had specific recognition of ascorbic acid and showed an excellent linear relationship in 5.0–350.0 μmol·L−1. Moreover, the detection limit was 3.11 μmol·L−1. Satisfactory results were achieved when the method was applied to the ascorbic acid determination in jujube fruit. The fluorescent carbon dots composites prepared in this study may have broad application prospects in a rapid, sensitive and trace determination of ascorbic acid content during food processing. 相似文献
Polyethylene glycol-modified canine uricase (PEG-UHC) was prepared by modifying the ε-amino group of lysine residues on the canine uricase (UHC) protein to near-saturation with 5 kDa monomethoxyl-polyethylene glycol succinimide (mPEG-SPA-5k). In order to accurately determine the PEGylation uniformity of PEG-UHC, CZE, 3–8% gradient gel SDS-PAGE, and imaging CIEF (iCIEF) analyses were compared. CZE could not effectively separate PEG-UHC proteins with different degrees of modification, 3–8% gradient gel SDS-PAGE could separate PEG-UHC into seven gel bands; however, most of the gel bands were smeared or blurred, and the separation of PEG-UHC samples by iCIEF was significantly better than that by 3–8% gradient gel SDS-PAGE. Under denatured conditions, iCIEF separated 12 pI peaks, and could also accurately quantify the relative monomer PEG-UHC content. More than 85% of the total monomeric PEG-UHC was conjugated with 7–12 PEG molecules; of this 85%, approximately 40% was conjugated with 9–10 PEG molecules. These results demonstrated that iCIEF exhibits good potential for determining the PEGylation homogeneity of PEGylated protein drugs. 相似文献
The unprecedented title reaction between glycine derivatives and indoles, as well as the auto‐oxidative Povarov/aromatization tandem reaction of glycine derivatives with olefins are described. The reactions were performed in the absence of redox‐active catalysts and chemical oxidants under mild reaction conditions. Only simple organic solvents and air (or O2) were required. 相似文献
A pyridoxal-based chemosensor was synthesized by reacting hydrazine hydrate and pyridoxal hydrochloride in ethanol and characterized by NMR and ESI-MS.The optical properties of the compound were investigated in a methanol:HEPES solution.The compound displayed selectivity for Cu2+,as evidenced by a colorless to yellow color change,which was characterized using UV–vis spectroscopy.The fluorescence of the compound can be quenched only by Cu2+,accompanying by a color change from blue to colorless.Furthermore,it can be used in bioimaging. 相似文献
As a kind of photoluminescent material, CuI complexes have many advantages such as adjustable emission, variable structures, and low cost, attracting attention in many fields. In this work, two novel two-coordinate CuI-N-heterocyclic carbene complexes were synthesized, and they exhibit unique dual emission properties, fluorescence and phosphorescence. The crystal structure, packing mode, and photophysical properties under different conditions were systematically studied, proving the emissive mechanism to be the locally excited state of the carbazole group. Based on this mechanism, ultralong room-temperature phosphorescence (RTP) with a lifetime of 140 ms is achieved by selective deuteration of the carbazole group. These results deepen the understanding of the luminescence mechanism and design strategy for two-coordinate CuI complexes, and prove their potential in applications as ultralong RTP materials. 相似文献