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41.
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Summary The potentiality of a porous graphitized carbon stationary phase was assessed for ceramide analysis in nonaqueous reversed
phase chromatography with an evaporative light scattering detection. The influence of the nature of the mobile phase was first
performed under isoeluotropic isocratic conditions. Eight mobile phase compositions in the presence or absence of triethylamine/formic
acid were tested with a set of structurally relevant ceramides. Values obtained under these conditions for the peak heights,
retention factors, plate numbers, asymmetry factors, relative retentions and Time-Corrected Calibrated Normalised Resolution
Product were analysed by Principal Component Analysis. Principal Component Analysis was effective in attributing relationships
between the chromatographic behaviour and analytical conditions. The relationship between the increase of the detector response
and the presence of triethylamine/formic acid has been confirmed, and the main change of selectivity has been attributed to
interactions provided by the weak solvent of the mobile phase. These conclusions have allowed the development of gradient
conditions for the analysis of complex ceramide mixtures on porous graphitized carbon column. 相似文献
43.
Zachary R. Jones Maksim Y. Livshits Frankie D. White Elodie Dalodire Maryline G. Ferrier Laura M. Lilley Karah E. Knope Stosh A. Kozimor Veronika Mocko Brian L. Scott Benjamin W. Stein Jennifer N. Wacker David H. Woen 《Chemical science》2021,12(15):5638
The positive impact of having access to well-defined starting materials for applied actinide technologies – and for technologies based on other elements – cannot be overstated. Of numerous relevant 5f-element starting materials, those in complexing aqueous media find widespread use. Consider acetic acid/acetate buffered solutions as an example. These solutions provide entry into diverse technologies, from small-scale production of actinide metal to preparing radiolabeled chelates for medical applications. However, like so many aqueous solutions that contain actinides and complexing agents, 5f-element speciation in acetic acid/acetate cocktails is poorly defined. Herein, we address this problem and characterize Ac3+ and Cm3+ speciation as a function of increasing acetic acid/acetate concentrations (0.1 to 15 M, pH = 5.5). Results obtained via X-ray absorption and optical spectroscopy show the aquo ion dominated in dilute acetic acid/acetate solutions (0.1 M). Increasing acetic acid/acetate concentrations to 15 M increased complexation and revealed divergent reactivity between early and late actinides. A neutral Ac(H2O)6(1)(O2CMe)3(1) compound was the major species in solution for the large Ac3+. In contrast, smaller Cm3+ preferred forming an anion. There were approximately four bound O2CMe1− ligands and one to two inner sphere H2O ligands. The conclusion that increasing acetic acid/acetate concentrations increased acetate complexation was corroborated by characterizing (NH4)2M(O2CMe)5 (M = Eu3+, Am3+ and Cm3+) using single crystal X-ray diffraction and optical spectroscopy (absorption, emission, excitation, and excited state lifetime measurements).Actinide complexation from aqueous acetic acid/acetate buffered solutions is described. The number of water ligands was directly correlated with the acetate concentration and characterized by X-ray absorption and optical spectroscopy. 相似文献
44.
Manon Chaumontet 《Tetrahedron letters》2006,47(7):1113-1116
The first members of two new families of arabinosyltransferase inhibitors, derived from previously reported hybrid compounds covalently associating an iminoalditol with an α-d-arabinofuranoside, have been prepared. In place of the arabinofuranoside moiety, they incorporate in their structure a suitably substituted tetrahydrofuran (C-glycoside family) or a cyclopentane (carba-sugar family) for mimicking the α-d-arabinofuranoside ring. 相似文献
45.
Marine Guy Manon Mathieu Ioannis P. Anastopoulos María G. Martínez Frdric Rousseau Guilherme L. Dotto Helinando P. de Oliveira Eder C. Lima Mikael Thyrel Sylvia H. Larsson Glaydson S. dos Reis 《Molecules (Basel, Switzerland)》2022,27(2)
In this work, Norway spruce bark was used as a precursor to prepare activated biochars (BCs) via chemical activation with potassium hydroxide (KOH) as a chemical activator. A Box–Behnken design (BBD) was conducted to evaluate and identify the optimal conditions to reach high specific surface area and high mass yield of BC samples. The studied BC preparation parameters and their levels were as follows: pyrolysis temperature (700, 800, and 900 °C), holding time (1, 2, and 3 h), and ratio of the biomass: chemical activator of 1: 1, 1.5, and 2. The planned BBD yielded BC with extremely high SSA values, up to 2209 m2·g−1. In addition, the BCs were physiochemically characterized, and the results indicated that the BCs exhibited disordered carbon structures and presented a high quantity of O-bearing functional groups on their surfaces, which might improve their adsorption performance towards organic pollutant removal. The BC with the highest SSA value was then employed as an adsorbent to remove Evans blue dye (EB) and colorful effluents. The kinetic study followed a general-order (GO) model, as the most suitable model to describe the experimental data, while the Redlich–Peterson model fitted the equilibrium data better. The EB adsorption capacity was 396.1 mg·g−1. The employment of the BC in the treatment of synthetic effluents, with several dyes and other organic and inorganic compounds, returned a high percentage of removal degree up to 87.7%. Desorption and cyclability tests showed that the biochar can be efficiently regenerated, maintaining an adsorption capacity of 75% after 4 adsorption–desorption cycles. The results of this work pointed out that Norway spruce bark indeed is a promising precursor for producing biochars with very promising properties. 相似文献
46.
47.
Degenerate four wave mixing is produced by the single pulse of a mode locked laser (duration 25 ps). The intensities are measured. The feasibility of image reconstruction is proved, and methods for time measurements (pulse durations, relaxation times) are proposed. 相似文献
48.
49.