Integration of a contactless conductivity detector into a commercial capillary cassette. Detection of inorganic cations and catecholamines

A contactless conductivity detector integrated into the capillary cassette of Agilent ^3DCE equipment is described. The detector is user-friendly, compact and easily modified. The UV detector of the ^3DCE equipment is available parallel with the contactless conductivity detector increasing the detection power. Two electrolyte solutions, 2-(N-morpholino)ethanesulfonic acid–histidine solution (20 mM, pH 6.0) and ammonium acetate (10 mM, pH 4.0), were used as the separation media for inorganic cations and organic catecholamines, respectively. The detection limit for all metal cations except barium was under 0.5 mg/l, and that for four catecholamines was ca. 10 mg/l. This last value was the same order of magnitude as achieved with parallel UV detection.     

Facile cyanamide-ammonia coupling mediated by cis- and trans-[PtIIL2] centers and giving metal-bound guanidines

Diffusion of ammonia into CH(2)Cl(2) solutions of the dialkylcyanamide complexes cis- or trans-[PtCl(2)(RCN)(2)] (R = NMe(2), NEt(2), NC(5)H(10)) at 20-25 degrees C leads to metal-mediated cyanamide-ammonia coupling to furnish, depending on reaction time, one or another type of novel bisguanidine compound, i.e. the molecular cis- or trans-[PtCl(2){NH=C(NH(2))R}(2)] (cis- and trans-) and the cationic cis- or trans-[Pt(NH(3))(2){NH=C(NH(2))R}(2)](Cl)(2) (cis- and trans-) complexes. Compounds cis- or trans- were converted to cis- or trans-, accordingly, upon prolonged treatment with NH(3) in CH(2)Cl(2). The ammination of the relevant nitrile complexes cis- or trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) in CH(2)Cl(2) solutions affords only the cationic compounds cis- or trans-[Pt(NH(3))(2){NH=C(NH(2))R}(2)](Cl)(2) (cis- and trans-). The formulation of was supported by satisfactory C, H and N elemental analyses, agreeable ESI(+)-MS (or FAB(+)-MS), IR, (1)H and (13)C NMR spectroscopies. The structures of trans-, trans-, cis-, trans-, cis-, and cis- were determined by single-crystal X-ray diffraction disclosing structural features and showing that the ammination gives ligated guanidines and amidines in the E- and Z-forms, respectively, where both correspond to the trans-addition of NH(3) to the nitrile species.     

Oxidation of Pt-bound bis-hydroxylamine as a novel route to unexplored dinitrosoalkane ligated species

The reaction of K 2[PtCl 4] and HO(H)NCMe 2CMe 2N(H)OH.H 2SO 4 ( BHA.H 2SO 4; 2) in a molar ratio 1:2 at 20-25 degrees C in water affords a mixture of [Pt(BHA) 2][PtCl 4] ( 5) and [Pt(BHA-H) 2] ( 6) ( BHA- H = anionic monodeprotonated form of BHA) which, upon heating at 80-85 degrees C for 12 h or on prolonged keeping at 20-25 degrees C for 2 weeks, is subject to a slow transformation giving [PtCl 2(BHA)] ( 7). The latter compound is also obtained from the reaction between K[PtCl 3(Me 2 SO)] and 2. The chlorination of [PtCl 2(BHA)] ( 7) in freshly distilled dry chloroform leads to the selective oxidation of one N(H)OH group yielding [PtCl 2{HO(H) NCMe 2CMe 2 N=O}] ( 13), while the chlorination in water produces the complex [PtCl 2(O= NCMe 2CMe 2 N=O)] ( 14) bearing the unexplored dinitrosoalkane species. Treatment of 14 with 2 equiv of 1,2-bis-(diphenylphosphino)ethane (dppe) in CH 2Cl 2 results in the liberation of the dinitrosoalkane ligand followed by its fast cyclization giving the alpha-dinitrone (3,3,4,4-tetramethyl-1,2-diazete-1,2-dioxide) in solution and the solid [Pt(dppe) 2](Cl) 2. The Pt (II) complexes with hydroxylamino ( intersection)oximes [PtCl 2{HO(H) NC(Me) 2C(R)= NOH}] (R = Me 8; R = Ph 9) upon their oxidation with Cl 2 in CHCl 3 afford the nitrosoalkane derivatives [PtCl 2{O= NCMe 2C(R)= NOH}] (R = Me 16; Ph 17), respectively, while the corresponding chlorination of the bis-chelates [Pt{HO(H) NCMe 2C(R)= NOH} 2] (R = Me 10; Ph 11) gives [Pt{O= NCMe 2C(R)= NO} 2] (R = Me 18; Ph 19). The formulation of 5- 19 is based on C, H, and N microanalyses, IR, 1D ( (1)H, (13)C{ (1)H}, (195)Pt) and 2D ( (1)H, (1)H-COSY, (1)H, (13)C-HSQC) NMR spectroscopies, and X-ray diffraction for five complexes ( 5, 7, and 12- 14).     

Treatment of delocalized electron transfer in periodic and embedded cluster DFT calculations: The case of Cu on ZnO (10 0)

We assess the consequences of the interface model—embedded‐cluster or periodic‐slab model—on the ability of DFT calculations to describe charge transfer (CT) in a particularly challenging case where periodic‐slab calculations indicate a delocalized charge‐transfer state. Our example is Cu atom adsorption on ZnO(10 0), and in fact the periodic slab calculations indicate three types of CT depending on the adsorption site: full CT, partial CT, and no CT. Interestingly, when full CT occurs in the periodic calculations, the calculated Cu atom adsorption energy depends on the underlying ZnO substrate supercell size, since when the electron enters the ZnO it delocalizes over as many atoms as possible. In the embedded‐cluster calculations, the electron transferred to the ZnO delocalizes over the entire cluster region, and as a result the calculated Cu atom adsorption energy does not agree with the value obtained using a large periodic supercell, but instead to the adsorption energy obtained for a periodic supercell of roughly the same size as the embedded cluster. Different density functionals (of GGA and hybrid types) and basis sets (local atom‐centered and plane‐waves) were assessed, and we show that embedded clusters can be used to model Cu adsorption on ZnO(10 0), as long as care is taken to account for the effects of CT. © 2015 Wiley Periodicals, Inc.     

The Mellin transform of the square of Riemann's zeta-function

The meromorphic continuation of the function. can be established by a method of Y. Motohashi. We show this by an alternative argument revealing the close afinity of this function with 2 (s).     

Nickel complexes of carboxylate-containing polydentate ligands as models for the active site of urease

Two new carboxylate-containing polydentate ligands have been synthesized, the symmetric ligand 2,6-bis[N-(N-(carboxylmethyl)-N-((1-methylimidazol)methyl)amine)methyl]-4-methylphenolate (BCIMP) and the corresponding asymmetric ligand 2-(N-isopropyl-N-((1-aminomethyl)-4-methylphenol (ICIMP). The ligands have been used to prepare model complexes for the active site of the dinuclear nickel enzyme urease, viz. [Ni(2)(BCIMP)Ac(2)](-) (6), [Ni(2)(BCIMP)(Ph(2)Ac)(2)](-) (7), [Ni(2)(ICIMP)(Ph(2)Ac)(2)] (14), [Ni(4)(ICIMP)(2)(Ph(2)Ac)(2)][ClO(4)](2) (15), [Ni(4)(ICIMP)(2)(Ph(2)Ac)(2)(DMF)(2)][ClO(4)](2) (16), and [Ni(4)(ICIMP)(2)(Ph(2)Ac)(2)(urea)(H(2)O)][ClO(4)](2) (17), where the latter complex contains urea coordinated in a unidentate fashion through the carbonyl oxygen. The N(2)O-N(2)O(2) donor set of ICIMP provides a good framework for the preparation of urease models, but in some cases tetranuclear nickel complexes are formed due to coordination of the carboxylate moiety of one dinickel-ICIMP unit to one or both of the nickels of a second Ni(2) unit. Reactivity and kinetics studies of 7 and 15 show that these model complexes catalyze hydrolysis of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) at basic pH. In this assay, complexes based on the asymmetric ligand ICIMP exhibit a significantly faster rate of hydrolysis than the corresponding BCIMP complexes. Magnetic measurements indicate that there are weak antiferromagnetic interactions between the nickel ions in complex 16.     

Determination of organic acids in aerosol particles from a coniferous forest by liquid chromatography-mass spectrometry

LC-MS methods with use of ion-trap and time-of-flight mass spectrometers were developed for the determination of organic acids in aerosol samples collected by a high-volume sampler in a Finnish coniferous forest. Comparison was made of the composition of samples collected during atmospheric formation of new aerosol particles and on days when this formation did not occur. A dynamic sonication-assisted solvent extraction system was developed for fast and quantitative extraction of the filter samples. Several organic acids, including pinonic acid, pinic acid, and homologous series of n-alkanoic acids, n-alkenoic acids, and aliphatic dicarboxylic acids, were identified. In samples collected between 08:00 and 16:00 hours the concentration of pinonic acid ranged from 0.5 ng m(-3) to 3.7 ng m(-3) and that of pinic acid from 0.2 ng m(-3) to 1.5 ng m(-3). For most of the compounds identified, the trends in concentration could be explained by the differences in temperature during collection. However, concentrations of short-chain n-alkanoic acids were clearly higher on the days when new aerosol particle formation occurred.     

Simulation model for anisotropic fibrous materials

Paper and paper–based materials such as cardboard are used in a wide variety of applications and in the development of new applications such as boxes an accurate simulation model is of major importance. Industrially made paper material typically has an orthotropic fibrous structure, due to the manufacturing process, where the fibers tend to align in the direction of motion in the machine. In this work a plasticity–based material model allowing for finite strains is developed. The model is suitable for materials with an anisotropic fibrous structure such as paper. The general framework is based on separate mappings describing the deformations of the continuum and the substructure and a multiplicative split of these mappings into elastic and plastic parts. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Density functional theory study of ω phase in steel with varied alloying elements

The presence of a long-abandoned hexagonal omega (ω) phase in steel samples is recently gaining momentum owing to the advances in transmission electron microscopy (TEM) measurements, even though it is already reported in other transition-metal alloys. The stabilization of this metastable phase is mainly investigated in presence of C, even though the formation of the ω phase is attributed to the combined effect of many factors, one among which is the enrichment of solute elements such as Al, Mn, Si, C, and Cr in the nanometer-sized regimes. The present study investigates the effect of the above alloying elements in ω-Fe using density functional theory (DFT) calculations. It is seen that the magnetic states of the atoms play a major role in the stability of ω-Fe. Cohesive energy calculations show that the alloying elements affect the energetics and stabilization of ω-Fe. Further, density of states calculations reveal the variation in d-band occupancy in the presence of alloying elements, which in turn affects the cohesive energy. Phonon band structure calculations show that only ω-Fe with substitutional C shows positive frequencies and hence possess thermodynamic stability. Finally, we confirm the existence of ω-Fe using TEM measurements of a steel sample containing the same alloying elements. Our results can shed light on the stabilization of the ω in other transition-metal alloys as well, in the presence of minor alloying elements.