A tandem mass spectrometric investigation of hydroxy-aromatic constituents in coal liquids

Preasphaltene fractions of exinite and vitrinite macerals, liquefied in tetralin, were examined by chemical ionization mass spectrometry/mass spectrometry for phenolic constituents. Recognition was based on dehydration of the protonated molecule with confirmation from daughter spectra, which in some cases could be compared with the spectra of authentic compounds. Rapid screening for homologous compounds was achieved by employing parent scans. Twelve homologous series of hydroxyaromatic compounds were identified, including phenols, naphthols, indenols, indanols, and some dihydroxy compounds. Many of the alkylated species have not been previously reported in coal liquids. While tanden mass spectrometry is an effective means of encountering new compounds, it does not provide the isomer selectivity of chromatographic methods to which it is complementary.     

Reversible oxidative addition of a diaryl diselenide to a diorganopalladium(II) complex, carbon-selenium bond formation at palladium(IV), and structural studies of palladium(II) and platinum(IV) selenolates

Methyl(4-methoxyphenyl)(2,2^′-bipyridine)palladium(II) (1) reacts with bis(4-chlorophenyl) diselenide in dichloromethane to form an equilibrium with the Pd(IV) complex Pd(SeC₆H₄Cl)₂Me(C₆H₄OMe)(bpy) (2) for which the forward reaction exhibits ΔH=−130±12 kJ mol⁻¹ and ΔS=−472±49 J K⁻¹ mol⁻¹, and with K=754±145 at −25 °C. The Pd(IV) complex is isolable at −40 °C, and when the equilibrium mixture is kept at −25 °C, a temperature at which the Pd(II) complex is stable, selective reductive elimination of Me-SeC₆H₄Cl occurs very slowly from the Pd(IV) complex to form Pd(SeC₆H₄Cl)(C₆H₄OMe)(bpy) (3). In contrast, (ClC₆H₄Se)₂ reacts with PdMe₂(dmpe) (4) [dmpe=1,2-bis(dimethylphosphino)ethane] to form Pd(SeC₆H₄Cl)Me(dmpe) (5) and Me-SeC₆H₄Cl. A second equivalent of (ClC₆H₄Se)₂ reacts with 5 to cleave the second Pd-Me bond to give Pd(SeC₆H₄Cl)₂(dmpe) (6) and Me-SeC₆H₄Cl. Similarly, PdMeTol(dmpe) (7) (Tol=4-tolyl) forms predominantly Pd(SeC₆H₄Cl)Tol(dmpe) (8) together with some Pd(SeC₆H₄Cl)Me(dmpe) (5), and 8 reacts with (ClC₆H₄Se)₂ to form Pd(SeC₆H₄Cl)₂(dmpe) (6) and Tol-SeC₆H₄Cl. Bis(4-chlorophenyl) diselenide reacts with PtTol₂(bpy) (9) (Tol=4-tolyl) to form Pt(SeC₆H₄Cl)₂Tol₂(bpy) (10) which, together with 2, has a trans-configuration for the selenolate ligands. X-ray structural studies of octahedral 10 as the solvate 10 · 3CHCl₃ and square planar 5 are reported.     

Increasing the kinase specificity of k252a by protein surface recognition

[reaction: see text] Here we describe a miniature protein (1) that presents the cAMP-dependent protein kinase (PKA) recognition epitope found within the heat-stable Protein Kinase Inhibitor protein (PKI) and a miniature protein conjugate (1-K252a) in which 1 is joined covalently to the high-affinity but nonselective kinase inhibitor K252a. Miniature protein 1 recognizes PKA with an affinity that rivals that of PKI and, in the context of 1-K252a, leads to a dramatic increase in kinase specificity.     

Quantitative analysis of PET microplastics in environmental model samples using quantitative 1H-NMR spectroscopy: validation of an optimized and consistent sample clean-up method

Identification and quantification of microplastics (MP) in environmental samples is crucial for understanding the risk and distribution of MP in the environment. Currently, quantification of MP particles in environmental samples and the comparability of different matrices is a major research topic. Research also focusses on sample preparation, since environmental samples must be free of inorganic and organic matrix components for the MP analysis. Therefore, we would like to propose a new method that allows the comparison of the results of MP analysis from different environmental matrices and gives a MP concentration in mass of MP particles per gram of environmental sample. This is possible by developing and validating an optimized and consistent sample preparation scheme for quantitative analysis of MP particles in environmental model samples in conjunction with quantitative ¹H-NMR spectroscopy (qNMR). We evaluated for the first time the effects of different environmental matrices on identification and quantification of polyethylene terephthalate (PET) fibers using the qNMR method. Furthermore, high recovery rates were obtained from spiked environmental model samples (without matrix ~ 90%, sediment ~ 97%, freshwater ~ 94%, aquatic biofilm ~ 95%, and invertebrate matrix ~ 72%), demonstrating the high analytical potential of the method.

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Speciation of Cr(III) and Cr(VI) in surface waters with a Chelex-100 resin column and their quantitative determination using inductively coupled plasma mass spectrometry and instrumental neutron activation analysis

Inorganic Cr(III) and Cr(VI) have contrasting biological, geochemical and toxicology effects. Cr(III) is considered as an essential species for the proper functioning of living organisms but Cr(VI) is toxic for the biological systems. An off-line speciation method using Chelex-100 has been practiced for speciation to Cr(III) and Cr(VI) from surface waters of rivers. The underlying principal of this separation method is based on the ability of cationic Cr(III) to be retained by the resin Chelex-100 while the anionic Cr(VI) remained in the sample matrices. The efficiency of this technique was improved by studying the effect of resin pH. Quantitative determination using inductively coupled plasma-mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA) was carried out after the separation to determine the total Cr and Cr(VI) in the liquid matrices. The precision and the accuracy of the quantitative analysis were evaluated by using standard reference material NRCC CASS-2 Intercomparison of INAA and ICP-MS results were determined. The quantity of inorganic Cr(III) and Cr(VI) in the surface water of rivers in the vicinity of industrial areas was investigated together with the determination of the physical properties of the water rivers during sampling.     

Interactions in aqueous nonelectrolyte systems. Gibbs energy of interaction of the ether group with the hydroxyl group and the amide group

Freezing temperatures of dilute aqueous solutions of equimolar mixtures of 1,3,5-trioxane with myo-inositol, d-mannitol, cyclohexanol, formamide, and acetamide, and 1,4-dioxane with myo-inositol, d-mannitol, formamide, and acetamide have been measured. These data yield pairwise Gibbs energies of interactions between the molecules in an aqueous solution. Using the group additivity principle, the results also yield the pairwise functional group Gibbs energies of interaction for the ether group with the hydroxyl and amide group. These results have been combined with all available data from the literature to yield the Gibbs energy and enthalpy of interaction of amides, ethers, alcohols, and saccharides in aqueous solution.To whom correspondence should be addressed.     

Determination of low concentrations of chlorite and chlorate ions by using a flow-injection system

A flow-injection method is reported for the determination of chlorite ion and chlorite and chlorate ions in mixtures at the submilligram per liter level in drinking water. The chlorite ion concentration is selectively determined by using its reaction with iodide ion at pH 2, which liberates iodine. Both species react with iodide ion in6 M HCl to produce iodine, the concentration of which is measured spectrophotmetricaly at 370 nm. The individual species are determined using multiplel regression. The method exhibits a linear range from 2 to 150 μM (0.1–10.1 mg l^-1) for chlorite ion and from 2 to μM (0.1–8.3 mg l^-1 for chlorate ion, with relative standard deviations of 0.4 and 1.2%, respectively.     

Polypeptide-templated synthesis of hexagonal silica platelets

Several studies have demonstrated the use of biomimetic approaches in the synthesis of a variety of inorganic materials. Poly-L-lysine (PLL) promotes the precipitation of silica from a silicic acid solution within minutes. The molecular weight of PLL was found to affect the morphology of the resulting silica precipitate. Larger-molecular weight PLL produced hexagonal silica platelets, whereas spherical silica particles were obtained using low-molecular weight PLL. Here we report on the polypeptide secondary-structure transition that occurs during the silicification reaction. The formation of the hexagonal silica platelets is attributed to the PLL helical chains that are formed in the presence of monosilicic acid and phosphate ions. Hexagonal PLL crystals can also serve as templates in directing the growth of the silica in a manner that generates a largely mesoporous silica phase that is oriented with respect to the protein crystal template.     

Anionic triazine systems

The synthesis of TAS+ C3N3F4- (1) (TAS+ = (Me2N)3S+) and the reactions of 1 with Me3SiOSiMe3 and Me3SiCF3 to give TAS+ C3N3F2O- (2) and TAS+[(NCF)(NCCF3)(NC(CF3)(2)]- (4) are reported. An isomer of 4, TAS+[(NCCF3)2(NCFCF3)]-, compound 6, was obtained by fluoride ion addition to (CF3CN)3. From the reactions with Me3SiNMe2 neutral fluoroamino triazines C3N3Fn(NMe2)(n-1) (n = 1, 2) were isolated. Possible reaction pathways are discussed, the X-ray structures of 1, 2, 4 and 6 were determined.