Determination of acetone, 2-butanone, diethyl ketone and BTX using HSCC-UV-IMS

A combination of a custom-designed ion mobility spectrometer (IMS) with a UV ionization source and a high speed capillary column (HSCC) has been developed as an analytical device for the sensitive detection of volatile organic compounds (VOCs), e.g. 2-propanone (acetone), 2-butanone and 3-pentanone (diethyl ketone) in the gas phase. A fast separation of the three selected substances and benzene, toluene and m-xylene (BTX) - all of which occur in human breath - has been achieved within less than four minutes at a carrier gas flow rate of 4.5 mL x min(-1). Multi-dimensional correlations presented support the interpretation of the acquired spectra of mixtures. Method detection limits were 2.7 microg x L(-1) for acetone and 2-butanone and 3.0 microg x L(-1) for diethyl ketone in nitrogen, respectively. The assay linear dynamic range is 4-320 microg x L(-1).     

Rhodium-catalyzed asymmetric hydrogenation of functionalized olefins using monodentate spiro phosphoramidite ligands

Novel chiral monodentate phosphorus ligands, SIPHOS, were conveniently synthesized from 1,1'-spirobiindane-7,7'-diol. The Rh complexes of SIPHOS can catalyze the hydrogenation of alpha-dehydroamino esters in mild conditions, providing alpha-amino acid derivatives in up to 99% ee. Enamides and beta-dehydroamino esters can also be hydrogenated in good to excellent enantioselectivities (up to 99% and 94% ee, respectively). The SIPHOS ligand with smaller alkyl groups on the N-atom afforded higher enantioselectivity. The X-ray analysis of single crystal showed that the structure of Rh/SIPHOS catalyst is [Rh(COD)((S)-SIPHOS-Me)(2)](+), which clarified the configuration of the catalyst with the monodentate chiral phosphorus ligand in Rh-catalyzed asymmetric hydrogenation. A positive nonlinear effect in the relationship of the optical purities of ligand and product was observed in the hydrogenation of dehydroamino acid derivatives. The kinetic study of hydrogenation showed that the reaction is zero order in the concentration of substrate and first order in the concentration of Rh catalyst and the hydrogenation pressure. The rate of hydrogenation decreased when the Rh/L ratio changed from 1:1 to 1:4.     

Chromatographic evaluation of perphenylcarbamoylated β-cyclodextrin bonded stationary phase for micro-high performance liquid chromatography and pressurized capillary electrochromatography

Application of mono (6^A-N-ethylenediamine-6^A-deoxy) perphenylcarbamoylated β-cyclodextrin (β-CD) bonded stationary phase (CSP) in micro-high performance liquid chromatography (micro-HPLC) and pressurized capillary electrochromatography (p-CEC) was firstly presented. A series of racemic α-amidophosphonates were resolved in reversed- and normal-phase modes on this CSP. The investigated chromatographic parameters include retention factor (k′), separation factor (α) and resolution (Rs) of solutes. In addition, the structural variation of the solutes and the experimental factors affecting chiral separations have been examined, including the percentage of alcohol modifier, the linear velocity (u) of the mobile phase, electrical field strength, etc. Baseline separation was achieved for most of the entities. Hydrophobic interaction, steric effect and π-π interaction contribute to the possible mechanism. Comparative results indicate that higher Rs value up to 3.1 was found in micro-HPLC, higher efficiency up to 29,970 in p-CEC.     

C–H· π Interaction and N·H–O Hydrogen Bonding in the Chair-like p-tert-Butylcalix[8]arene Complex Including Four Pyridine Molecules

Crystal structure analysis shows that the p-tert-butylcalix[8]arene host and its four pyridine guests sit around an inversion center in the P2₁/c crystal lattice. The monoclinic cell parameters and its volume are: a = 19.617(4), b = 9.912(2), c = 25.178(5) , = 101.03(3)°, V =4805.27(17) ³. For Z = 2 and Mw = 1614.18, the calculated density Dcalc = 1.116 g/cm³. A host calixarene molecule includes four pyridine guests in two different ways: by hydrogen bonding and by possible C–H· interaction between the molecules. The hydrogen bonding drives the host macrocycle into a chair-like conformation.     

Ba-K-Bi-O和Ba-K-Pb-O氧化物的碘量滴定

本文提出了碘量法滴定Ba－K－Bi-O和Ba－K－Pb－O氧化物中Ba和Pb的名义价态，然后据此计算这些氧化物中K和Ba含量的方法。该法适用于正常条件下合成的具有ABO3型钙钛矿结构的Ba－K－Bi-O和Ba－K－Pb－O晶体。用本法的滴定结果表明，Tc为31K的Ba－K－Bi-O超导体的K含量为0．4，当K含量减少时，Tc随之下降。     

SYNTHESIS AND CHARACTERIZATION OF A NEW POLYSILOXANE CONTAINING N,N’-BIS(DIPHENYLSILYL)TETRAPHENYLCYCLODISILAZANE

A new kind of polysiloxane containing N,N'-bis(diphenylsilyl)tetraphenylcyclodisilazane was prepared by anionicnon-equilibrium polymerization with a "seed solution" as initiator. The monomer, N,N'-bis(hydroxydiphenylsilyl)-tetraphenyl-cyclodisilazane (BHPTPC), was synthesized via the hydrolysis of N,N'-bis(chlorodiphenylsilyl)tetraphenyl-cyclodisilazane (BCPTPC). A new method for the preparation of BCPTPC is also reported here with high yield and simplermanipulation. The synthesized polysiloxane containing N,N'-bis(diphenylsilyl)tetraphenylcyclodisilazane was characterized by ~1H-NMR, ~(29)Si-NMR, gel permeation chromatography (GPC) and intrinsic viscosity.     

Electrodeposition and stripping process by long optical pathlength potential-step transmission chronoabsorptometry

Based on the transmittance-averaged rather than absorbance-averaged model of long optical pathlength transmission spectroelectrochemistry, a reasonable theoretical model for potential-step electrodeposition and stripping process has been developed. It can accurately predict the stripping-chronoabsorptometric waveform with a peak absorbance with respect to the time rather than that with no peak but only a theoretical maximum absorbance at the initial stage of the stripping process. Cu(II) in NH(3) . H(2)ONH(4)Cl supporting electrolyte is utilized to verify the theory. With this anodic stripping spectroelectrochemical method, a detection limit of ca 0.01mM without stirring or ca 0.002mM under stirring during deposition can be achieved. An application in the analysis of copper in practical samples is presented.     

Microkinetics of H2S Removal by Zinc Oxide in the Presence of Moist Gas Atmosphere

The microkinetics os H2S removeal by ZnO desulfurization in H2O-CO2-N2,H2O-CO-N2 and H2O-O2-N2 gas mixtures was studied by thermogravimetric andlysis.Experiments were carried out with 100-120 mesh ZnO powder at temperatures from 473K to 563K.The results show that the kinetic behaviors of desulfurization could all be described by an improved shrinking-core model.The activation energies of the reaction and the diffusion in different gas atmospheres were estimated.