Comparison of different derivatization approaches for mercury speciation in biological tissues by gas chromatography/inductively coupled plasma mass spectrometry

A novel interface design for coupling gas chromatography and inductively coupled plasma mass spectrometry (GC/ICP-MS) was used to perform mercury speciation in biological tissues. Three derivatization approaches were optimized and compared for this purpose: anhydrous butylation using a Grignard reagent, aqueous ethylation by means of NaEt(4)B and aqueous propylation with NaPr(4)B. The last reagent was synthesized in the laboratory as it is not commercially available. Detection limits obtained by GC/ICP-MS ranged between 100 and 200 fg (as absolute mass) for methylmercury and between 500 and 600 fg for inorganic mercury using a 1 microl injection. Quantification of methyl- and inorganic mercury was carried out by resorting to aqueous calibration, using ethylmercury as internal standard for both propylation and butylation derivatization techniques. For ethylation procedures, a methylpropylmercury solution was used as internal standard. The absence of transmethylation during sample preparation was checked using a 97% enriched (202)Hg inorganic standard. The accuracy of the three derivatization approaches was evaluated by the analysis of the certified reference material DOLT-2 (dogfish liver) from the National Research Council of Canada and certified for methylmercury, with satisfactory results.     

Thermal Cyclodimerization of Aliphatic Secondary C,N-Dilithioallylamine Derivatives

beta-Nitrogen-functionalized vinylic organolithium compounds derived from secondary aliphatic allylamines have been found to undergo upon heating (reflux of THF) either a dimerization or a regio- and stereoselective cyclodimerization reaction affording diamino 1,4-dienes or cis-2,3-disubstituted 4-methylenepyrrolidines, respectively, according to reaction time. In contrast, the corresponding dianions derived from aromatic allylamines underwent protonation by the solvent under analogous thermal treatment. A mechanism accounting for all these results has been proposed, which involves a spontaneous beta-elimination of lithium hydride and an intramolecular nucleophilic cyclization by addition of a lithium amide to an alkene group as critical steps. In addition, experimental evidence is provided about the formation of 3-lithio-1-aza 1,3-dienes as intermediates in these unusual thermal transformations.     

N,N′-双吡咯的合成及其邻位基团效应

2,2-联吡咯是某些天然存在的活性吡咯化合物中关键组成,关于手性联吡咯的研究己有详细的综述报道。近年发现,某些含N-取代氨基的空间阻碍吡咯有明显的生理活性和可贵的药理性质。N,N′-联吡咯中N-N键,很容易发生均裂反应而生成游离基,后     

FORMATION AND DEVELOPMENT OF TAIHU LAKE AND RECENT DEPOSITION

Situated in the Taihu plain between the mouth of the Changjiang River and theHangzhou Bay, the Taihu Lake is a large shallow-water lake in China with a surface area of 2427.8 km~2.The lake bottom mainly consists of loess-like sediment. Some buried and silted up channels and residual depressions can be found at the bottom and a lot of Neolithic cultural relics on the loess-like sediment. This indicated that the Taihu Lake was formed on the alluvial plain charaterized by widely deposited loess-like sediment because of siltation and stagnancy of water, instead of by development from lagoons as reported in the past.Recent deposition including influent-effluent current accumulation, wind-driven current and storm deposition in this lake occurred mainly in the south, the west shore and the midst of the lake.The sedimentary rate in the east Taihu Lake is about 1.7-1.8 mm/a, whereas in the west Taihu Lake it is about 0.41 ram/a, only 23％ of that of the former.     

线粒体和亚线粒体体外代谢及漆酶影响的微量热研究

首次将微量热用于亚细胞层次的研究，测定了鲤鱼肝脏线粒体和亚线粒体代谢的热谱及其漆树漆酶的影响，并用ＭＴＤ方程和演化计算技术对它们的代谢热动力学参数进行了全局优化。     

A kinetic approach to homogeneous Ziegler type polymerization. Steady state

In this paper we present a kinetic approach to the analysis of steady-state homogeneous Ziegler-Natta polymerization activity data. The influence of the number of monomeric species that are coordinated to the active site on the apparent rate law is discussed and the equations are fitted to the experimental results.     

大区域取向对非晶态聚对苯二甲酸乙二酯结晶的影响

ffects of the chain orientation in the global sense on the solvent induced crystallization (SINC),diffusion velocity of toluol into poly(ethylene terephtlialate)(PET)and crystallization morphology were:studied by using density measurement and SEM.It has been shown that the SINC and diffusion velocity of toluol into PET increase with increasing degree of chain orientation in global sense,and the chain orientatioll can be essentially remained during SINC.     

An Investigation of Inclusion Complexes of Cyclodextrins with Phenylurea Herbicides by Photochemically-Induced Fluorescence. Analytical Applications

The effect of -cyclodextrin (-CD) and hydroxypropyl--cyclodextrin (HP--CD) upon the photochemically-induced fluorescence (PIF) properties of four phenylurea herbicides, including linuron, diuron, isoproturon and neburon has been studied. Photochemical conversion of these nonfluorescent herbicides into strongly fluorescent photoproducts was shown to occur in -CD and HP--CD aqueous media. The influence of pH, UV irradiation time and photoproduct stability on the fluorescence intensity was also investigated. In addition, the stoichiometry and formation constants of the complexes formed between herbicides and -cyclodextrin (-CD) or 2-hydroxypropyl--cyclodextrin (HP--CD) were determined. The formation constant values, ranging from 184 ± 40 to 1498 ± 245 M^-1, were calculated by applying the iterative nonlinear regression (NLR) approach to the PIF data. Linear calibrations graphs were established in the interval 1–12 g/mL, for diuron, linuron and neburon. The IUPAC limits of detection ranged between 580 and 700 ng/mL, according to the compound. Application to the analysis of phenylurea herbicides in spiked river water was also described.     

XPS spectra of some transition metal and alkaline earth monochalcogenides

The first-row transition-metal monosulfides and alkaline-earth chalcogenides were studied by means of X-ray photoelectron spectroscopy. It is shown that the bonding in the alkaline earth compounds is relatively ionic with XPS evidence for significant charge separation. On the other hand, transition metal sulfides, with the exception of MnS, appear to be principally metallic with little or no charge separation. Values for the inner orbital binding energy shifts are reported for a large number of monochalcogenides.     

Polarized basis sets of Slater-type orbitals: H to Ne atoms

We present three Slater-type atomic orbital (STO) valence basis (VB) sets for the first and second row atoms, referred to as the VB1, VB2, and VB3 bases. The smallest VB1 basis has the following structure: [3, 1] for the H and He atoms, [5, 1] for Li and Be, and [5, 3, 1] for the B to Ne series. For the VB2 and VB3 bases, both the number of shells and the number of functions per shell are successively increased by one with respect to VB1. With the exception of the H and Li atoms, the exponents for the VB1 bases were obtained by minimizing the sum of the Hartree-Fock (HF) and frozen-core singles and doubles configuration interaction (CISD FC) energies of the respective atoms in their ground state. For H and Li, we minimized the sum of the HF and CISD FC energies of the corresponding diatoms (i.e., of H(2) or Li(2)) plus the ground-state energy of the atom. In the case of the VB2 basis sets, the sum that was minimized also included the energies of the positive and negative ions, and for the VB3 bases, the energies of a few lowest lying excited states of the atom. To account for the core correlations, the VBx (x = 1, 2, and 3) basis sets for the Li to Ne series were enlarged by one function per shell. The exponents of these extended (core-valence, CV) basis sets, referred to, respectively, as the CVBx (x = 1, 2, and 3) bases, were optimized by relying on the same criteria as in the case of the VBx (x = 1, 2, and 3) bases, except that the full CISD rather than CISD FC energies were employed. We show that these polarized STO basis sets provide good HF and CI energies for the ground and excited states of the atoms considered, as well as for the corresponding ions.