The authors report on a novel sorbent (thermally treated natural zeolite; clinoptilolite) for use in dispersive micro-solid phase extraction (D-μ-SPE) of polycyclic aromatic hydrocarbons (PAHs) from water samples. The method was applied to the D-μ-SPE of 16 priority PAHs which then were quantified by gas chromatography with mass spectrometric detection (GC-MS). The method was validated in terms of specificity and selectivity, linearity and linear range, accuracy, precision, uncertainty, limits of detection and quantification. Figures of merit include (a) linear analytical ranges between 2.08 and 208 ppb, and (b) detection limits in the range from 0.01 to 0.92 ppb. The method was successfully applied to the determination of PAHs in river waters.
Graphical abstract Schematic representation of dispersive micro-solid phase extraction (D-μ-SPE) of trace levels of PAHs in water samples by using thermally treated clinoptilolite as sorbent prior to gas chromatography-mass spectrometry analysis (GC-MS).
This work describes the synthesis of compounds [Pt(C=N)(NCMe) 2]ClO 4 (C=N = 7,8-benzoquinolinato (bzq), 2-phenylpyridinato (ppy)) and their use as precursors for the preparation of the cyanido complexes [Pt(C=N)(CN) 2] (-), which were isolated as the potassium, [K(H 2O)][Pt(C=N)(CN) 2] [C=N = bzq ( 3a), ppy ( 4a)], and the tetrabutylammonium, NBu 4[Pt(C=N)(CN) 2] [C=N = bzq ( 5), ppy ( 6)], salts. The difference in the cation has an influence on the solubility, color, and emission properties of these compounds. Compounds 5 and 6 are yellow and soluble in organic solvents, while the potassium salts are also soluble in water and exhibit two forms: the water-containing [K(H 2O)][Pt(C=N)(CN) 2] [C=N = bzq ( 3a), ppy ( 4a)] complexes and the anhydrous ones K[Pt(C=N)(CN) 2] [C=N = bzq ( 3b), ppy ( 4b)], the former being strongly colored [red ( 3a) or purple ( 4a)] and the latter being yellow. Compounds 3a and 4a transform reversibly into the yellow, 3b and 4b, compounds upon desorption/ reabsorption of water molecules from the environment. The red solid, 3a, also exhibits vapochromic behavior when it is exposed to volatile organic compounds, the shortest response times being those observed for methanol and ethanol. UV-vis and emission spectra of all compounds were recorded both in solution and in the solid state. In methanol solution, the difference in the cation causes no differences in the absorption nor in the emission spectra, which is as expected for the monomer species. However, in the solid state, the differences are notable. For both the red ( 3a) and purple ( 4a) compounds, a prominent absorption, which has maxima at about 550 nm and is responsible for their intense colors, as well as a structureless emission at lambda > 700 nm that suffers a significant red-shift upon cooling, are due to (1,3)MMLCT (= metal-metal-to-ligand charge transfer) [dsigma*(Pt) --> pi*(C=N)] transitions characteristic of linear-chain platinum complexes with short Pt...Pt contacts. Time-dependent density-functional theory calculations on complex 5 and the X-ray diffraction study on compound [K(OCMe 2) 2][Pt(ppy)(CN) 2] ( 4c) are also included. 相似文献
We report a systematic investigation of the effects and structural requirements for ion suppression in negative ion mode electrospray ionisation mass spectrometry of a series of carboxylic acids and present a structural model rationalising ion suppression effects. 相似文献
Mn(III)AlPO-5 and Cr(VI)AlPO-5 redox (microporous) catalysts are effective, in the presence of dissolved acetylperoxyborate (APB) under mild conditions (333-373 K), and much superior to the titanosilicate, TS-1 (also a single-site heterogeneous catalyst), in the selective oxidation of primary, secondary, benzylic and other unsaturated alcohols, p-cymene, methyl cyclohexene and other speciality organics which are of value in the fine-chemical and pharmaceutical industries. 相似文献
A Wiener–Hopf operator on a Banach space of functions on is a bounded operator T such that P+S−aTSa = T, a ≥ 0, where Sa is the operator of translation by a. We obtain a representation theorem for the Wiener–Hopf operators on a large class of functions on with values in a separable Hilbert space.
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The title compound, dibromo(3‐hydroxy‐5‐hydroxymethyl‐2‐methyl‐4‐pyridinecarboxaldehyde semicarbazone‐κ3N1,O3,O3′)copper(II), [CuBr2(C9H12N4O3)], consists of discrete complex units with the tridentate pyridoxal semicarbazone ligand as a zwitterion in an almost planar configuration. The CuII ions are in a distorted square‐pyramidal coordination, with the equatorial Br atom at a distance of 2.4017 (6) Å and the apical Br atom at a distance of 2.6860 (6) Å. 相似文献
Employing simplex space-time meshes enlarges the scope of compressible flow simulations. The simultaneous discretization of space and time with simplex elements extends the flexibility of unstructured meshes from space to time. In this work, we adapt a finite element formulation for compressible flows to simplex space-time meshes. The method obtained allows, for example, flow simulation on spatial domains that change topology with time. We demonstrate this with the two-dimensional simulation of compressible flow in a valve that fully closes and opens again. Furthermore, simplex space-time meshes facilitate local temporal refinement. A three-dimensional transient simulation of blow-by past piston rings is run in parallel on 120 cores. The timings point out savings of computation time gained from local temporal refinement in four-dimensional space-time meshes. 相似文献
Non-stationary multisplitting algorithms for the solution of linear systems are studied. Convergence of these algorithms is analyzed when the coefficient matrix of the linear system is hermitian positive definite. Asynchronous versions of these algorithms are considered and their convergence investigated.
Currant fruit extracts were characterized by (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity, 2,2-azinobis-3 ethyl benzothiazoline-6-sulfonic acid cation decolorization activity, total reducing power, cupric ion reducing antioxidant power, and ferric ion reducing antioxidant power (FRAP) assays to evaluate their antioxidant activity. All five antioxidant assays revealed the highest antioxidant activity to be present for the black currants. The highest concentrations of phenolics were present in the black currants (1690?±?10?mg gallic acid equivalents (GAE)/100?g fresh weight), while the lowest value was obtained in the white currants (579?±?5?mg GAE/100?g fresh weight). The correlation between the total phenolic content and antioxidant activity assays was evaluated using regression analysis. A significant positive correlation was obtained between the total phenols and the cupric ion reducing antioxidant power (r?=?0.97, p?0.05), followed by that between the total phenols and FRAP (r?=?0.93, p?0.05). Hierarchical cluster analysis separated these selected fruit species into two statistically significant clusters with black currants as a distinctive cluster. 相似文献
AbstractNew isoquinoline alkaloid hypepontine (1) together with a five known compounds, were identified in Hypecoum ponticum Velen, the partial synonym of Hypecoum procumbens L. The structure of the new substance was elucidated based on spectroscopic evidence. The tertiary and quaternary alkaloid mixtures as well as the isolated alkaloids were evaluated for their antibacterial and antifungal activity. The result revealed that the crude alkaloid mixture containing quaternary isoquinoline alkaloids showed potent antifungal and antibacterial activity. 相似文献