Determination of biogenic halogenated methyl-phenyl ethers (halogenated anisoles) in the picogram m -3 range in air

Halogenated anisoles (methyl-phenyl ethers) appear to be ubiquitous organic trace compounds in the environment. An analytical method is presented for analyzing the altogether 134 congeners of chloro-, bromo- and mixed bromochloro-anisoles on an isomer-specific basis in air. High volume sampling (20 m³ per hour) is carried out by adsorption, using a mixture of silica gel 60 and ENVI-Carb. The preseparation of the anisoles is achieved by NP-LC on Florisil (a magnesium silicate). The interference by volatile n-alkyl nitrates in the electron-capture detection can be avoided by a LC-preseparation on a carboneous phase. The isomer-specific separation and detection is performed by HRGC-ECD and HRGC-MS-SIM. A structure-specific systematic numbering of the 134 congeners of the chloro-, bromo- and bromochloro-anisoles is suggested. The retention data are given of 16 chloroanisoles, 10 bromoanisoles and 27 bromo-chloroanisoles on three stationary phases with different polarity.     

稀土添加剂对镍,铜刷镀层质量的影响

通过在刷镀镀液中加入稀土添加剂，研究稀土对刷镀层质量的影响。实验结果表明，稀土起到平整、光亮、细化镀层晶粒、减少镀层应力的作用，并增强镀层结合力，提高镀层的耐磨性、耐蚀性。     

关于Szász-Mirakjan—Durrmeyer算子在Besov空间上的逼近阶

本文主要给出了Ｓｚａｓｚ－Ｍｉｒａｋｊａｎ－Ｄｕｒｒｍｅｙｅｒ算子在Ｂｅｓｏｖ空间上逼近阶的特征刻划     

S-convex,monotone, and positive interpolation with rational bicubic splines of C2-continuity

In this paper we deal with shape preserving interpolation of data sets given on rectangular grids. The aim is to show that there exist spline interpolants of the continuity classC ² which areS-convex, monotone, or positive if the data sets have these properties. This is done by using particular rational bicubic splines defined on the grids introduced by the data. Interpolants of the desired type can be constructed by a simple search procedure.     

Ionization of hydrogen and deuterium atoms in thermal energy collisions with state-selected Ne(3s 3 P 2,3 P 0) metastable atoms

High resolution energy spectra of electrons and ions resulting from thermal energy collisions of hydrogen and deuterium atoms with state-selected metastable Ne(Ne(3s ³ P ₂,³ P ₀) atoms are reported. The electron spectra for Ne(³ P ₂)+H(D) are very broad: The high energy part due to formation of NeH⁺ (NeD⁺) bound states (associative ionization), amounts to about 30% of the ionizing events, whereas the dominant part of the spectrum including a prominent low-energy peak is due to Penning ionization out of a strongly-attractive entrance potential curve. Comparison of the spectra with quantum mechanical fit calculations yields fairly accurate information on this potential, in particular its well depthD _e [Ne(³ P ₂)?H,D]= 2.0(1) eV. The spectra for Ne(³ P ₀)+H, D are comparatively narrow with much lower cross sections than the one for the Ne(³ P ₂) state. The corresponding entrance channel is a weakly bound van der Waals molecule with a well depth below 0.1 eV. A perturbation calculation of the Ne(3s)+H(1s) potential energy curves at large distances explains the observed difference between the Ne(³ P ₂)+H(D) and Ne(³ P ₀)+H(D) systems. Symmetry arguments are given that the major contribution to the Ne(³ P ₂)+H(D) spectra is due to the² Σ potential.     

Synthesen in der Pyridazin-Reihe, 10. Mitt.: Über einige Reaktionen mit Pyridazonyl-4-essigsäuren

Zusammenfassung Es wird über einige Reaktionen an der Methylen-Gruppe der Pyridazonyl-4-essigsäuren berichtet, so die Crotonisierung und die Reaktion nachJapp—Klingemann. Weiter wurden auch Hydrazide erhalten und aus diesen die entsprechenden substituierten 1,3,4-Oxdiazole hergestellt.

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Some reactions on the reactive methylene group of 4-carboxymethyl pyridazines are reported, e. g. the condensation with aldehydes and theJapp—Klingemann reaction. Furthermore, the corresponding hydrazides were prepared and these were used for the preparation of 1,3,4-oxadiazole derivatives.

     

High-performance size-exclusion chromatography with crosslinked polystyrene. Separation of polymers and oligomers using LiChrogel PS

Summary A new series of polystyrene-divinyl benzene PS/DVB-based microparticulate packings for size-exclusion chromatography [SEC] is presented. These gel-based packings are characterized by mechanical stability, minimal interaction with solutes and ability to handle a wide variety and size range of polymers and low relative molecular mass samples. Combinations of different pore sizes are discussed and separations of standard polymers and commercial products are shown.     

Modified polystyrene,stationary phases for the separation of different aromatic hydrocarbon types by HPLC

Summary One possible method of characterizing chemicall-modified stationary phases is to describe their chromatographic properties. In this study we investigated several chemically-modifiedpolystyrene-divinylbenzene packings for the separation of nitroarenes, polycyclic aromatic hydrocarbons and aminosubstituted aromatic hydrocarbons. Chromatography was carried out on commercially available polymer stationary phases, for example C-18 or vinylpyridine modified polystyrene. In addition, a chemically-immobilized polymer packing was prepared by introducing nitrogroups, which were established by elemental analysis and infrared spectroscopy.