The potential of reversed-phase HPLC for the determination of distribution coefficient D7.4 of selected 3-hydroxyquinolin-4(1H)-ones (3HQs) as compounds with significant biological activity was studied. Various stationary phases with C18 as well as hexyl-phenyl modification reflect current trends in RP-HPLC development such as higher sorbent silanophilicity, core–shell technology, hybrid and/or charged surface particles. Because of significant peak tailing of 3HQs at physiological pH on reversed-phase sorbents the separations at pH 3 were performed as well. Surprisingly, the pH change did not affect significantly the partition coefficients of 3HQs. Very affordable and common standards such as anisole, acetophenone, benzyl alcohol, brombenzene, ethylbenzoate and trichlorethylene were applied in the described methodology. The best linearity (R2 0.9895) of the correlation between log P and log kw for standards was obtained for hexyl-phenyl sorbent, but this stationary phase was shown to be unsuitable for HPLC separation of 3HQs. The highest linearity (R2 0.9499) of the relationship between log D7.4 determined by the classic shake-flask method and log D determined by means of HPLC for 3HQs was attained with Cortecs C18+ column at pH 7.4. The described methodology with Cortecs C18+ as stationary phase offers fast and accurate estimation of log D7.4 of the tested 3HQs. In an effort to increase the throughput of the HPLC method for log D7.4 determination, we evaluated almost aqueous mobile phase that contained only 3 % of acetonitrile. Although a worse correlation between log D7.4 determined by shake-flask method and HPLC with almost aqueous mobile phase was observed, the described procedure offers a very simple and high-throughput alternative for the estimation of log D7.4.
The delay time of ignition of C2H2-O2-Ar mixtures of various compositions behind reflected shock waves were measured at 980–1300 K and 0.65 ± 0.05 MPa. A kinetic scheme of the ignition of acetylene based on the available rate constants of the key elementary reactions was developed. The scheme satisfactorily describes the experimental data from various works over wide temperature, pressure, and concentration ranges: 980–2400 K, 0.01–1.0 MPa, and 0.5–20.3 vol % acetylene and 1.25–20.4 vol% O2. 相似文献
Thermal stability of titanate nanotubes (Ti-NT) was studied in temperature range from room temperature up to 1000 °C in three different atmospheres—in air, vacuum and helium—and differences were observed. In air, vacuum and helium, the release of adsorbed and crystal water was detected in temperatures up to 200 °C. Transformation of the initial structure to anatase form of TiO2 was found independently of the atmosphere used. But in air the transformation to anatase occurred at lower temperature. The difference between these atmospheres was approximately 100 °C. However, only in air, the transformation to sodium hexatitanate and rutile form of TiO2 occurred at higher temperatures. In vacuum, only the anatase phase was detected up to 800 °C. In helium, the transformation to rutile was observed but not to sodium hexatitanate. The changes of the initial structure of Ti-NT during the elevation of temperature were studied by combination of in situ powder X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis and mass spectroscopy. 相似文献
Journal of Solid State Electrochemistry - The characterization of electrochemically visualized latent fingerprints on steel surfaces is demonstrated. Optimization of electrochemical conditions of... 相似文献
One single crystal based on Th~(4+) and cucurbit[6]uril(CB6) in nitric acid aqueous solutions was synthesized by slow evaporation method. The single crystal was characterized by elemental analysis,single crystal X-ray diffraction, XRD, FT-IR and TGA. The complexed cation of Th~(4+) is a ten coordinated structure, in which the central thorium ion is coordinated by six monodentate water molecules and two bidentate nitrates. While CB6, as a second-sphere ligand, coordinates with the water molecules of [Th(NO_3)_2(H_2 O)_6]~(2+) through the formation of hydrogen bonding. Two other nitrate ions act as the counter anions. Besides, there are two free water molecules in the crystal system. The formation of the Th~(4+)-CB6 complex can contribute to the study of the coordination of CB6 and the extraction of Th~(4+) in HNO_3 system 相似文献
A new cyclopeptide, cyclozanthoxylane A ( 1 ), the lignans cis‐ and trans‐methylpluviatolide, the flavonoid isoquercitrin, along with a mixture of benzoic and cinnamic acid derivatives, were isolated from the MeOH extract of the leaves of Zanthoxylum rigidum (Rutaceae). The structures of the compounds were determined on the basis of 1D‐ and 2D‐NMR, and MS analysis. It is the first time that a natural cyclic peptide has been isolated from the genus Zanthoxylum.相似文献
The ionic imprinted polymer (IIP) of uranyl ion (UO22+) as the template was synthesized by the formation of binary complexes of UO22+ with 2,4-dioxopentan-3-yl methacrylate as functional monomer followed by thermal copolymerization with ethylene glycol dimethacrylate as cross-linking monomer in the presence of 2,2′-azobisisobutyronitrile as initiator and 1,4-dioxane as porogenic solvent. 50 mmol L?1 HCl solution was used to leach out UO22+ ions from the IIP. Similarly, the control polymer was prepared under identical experimental conditions without using UO22+ ions. The above synthesized polymers were characterized by infra-red spectroscopy, thermo-gravimetric analysis and Barrett–Emmett–Teller surface area measurement. The maximum adsorption capacities of IIP and CP in (NH4)4[UO2(CO3)3] solution were 15.3 and 11.2 mg U g?1, respectively. The kinetics of adsorption followed a pseudo-second-order rate equation. The prepared IIP was successfully used to extract uranium from real seawater sample. 相似文献
Double pulse laser induced breakdown spectroscopy in orthogonal configuration was used for the analysis of twelve samples of volcanic glass. Raw material and artifact samples originated from Czech, Slovak, German, Hungarian, Greek, Turkish, and Ukrainian sites. The primary 266 nm laser beam was focused onto a sample area of about 0.1 mm in diameter at the optimised energy of 10 mJ resulting in only very slight sample damage, almost unrecognizable even by a microscope. The secondary 1064 nm laser beam, positioned parallel to the sample surface and focused onto the intersection with the primary beam, induced a spark with enhanced radiation at the optimised energy of 100 mJ. Measurement of emission lines selected on basis of chemical composition, signal intensity, signal-to-background ratio, and minimum interference from the surrounding spectra: Si(I) 288.16 nm, Mg(II) 279.55 nm, 280.27 nm, Mg(I) 285.21 nm, Ca(II) 317.93 nm, Na(I) 589.59 nm, Al(I) 308.22 nm, Fe(II) 259.94 nm, Ti(II) 334.94 nm, Sr(II) 407.77 nm, Ba(II) 455.40 nm, K(I) 769.90 nm, provided experimental data sufficiently sensitive to differentiate the properties of the studied samples. Rare earth elements were not detected even though the double pulse technique is more sensitive than the single pulse variant. Visualisation methods of multidimensional statistical analyses such as radar chart, Chernoff faces, scatterplots, and the Spearman correlation matrix provided successful differentiation of the sample groups and/or particular samples by their origin. 相似文献