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131.
An application of automated on-line HPLC-HRGC is described for direct analysis of edible oils for migrated polymer additives. The sample preparation, separating the additive from the oil triglycerides, is carried out using normal phase HPLC. The fraction of the eluent containing the additive is automatically transferred to a HRGC where a second and final separation of the additive from minor oil components takes place. The method compares well with off-line separation methods. Migration data for Tinuvin 1577 from PET and PC polymers as well as an unspecified experimental polymer is given. The advantages and disadvantages of using different edible oils as food simulants are discussed. 相似文献
132.
Lehmann JF Schrobilgen GJ Christe KO Kornath A Suontamo RJ 《Inorganic chemistry》2004,43(22):6905-6921
The single-crystal X-ray structures of [XF(6)][Sb(2)F(11)] (X = Cl, Br, I) have been determined and represent the first detailed crystallographic study of salts containing the XF(6)(+) cations. The three salts are isomorphous and crystallize in the monoclinic space group P2(1)/n with Z = 4: [ClF(6)][Sb(2)F(11)], a = 11.824(2) A, b = 8.434(2) A, c = 12.088(2) A, beta = 97.783(6) degrees , V = 1194.3(4) A(3), R(1) = 0.0488 at -130 degrees C; [BrF(6)][Sb(2)F(11)], a = 11.931(2) A, b = 8.492(2) A, c = 12.103(2) A, beta = 97.558(4) degrees , V = 1215.5(4) A(3), R(1) = 0.0707 at -130 degrees C; [IF(6)][Sb(2)F(11)], a = 11.844(1) A, b = 8.617(1) A, c = 11.979(2) A, beta = 98.915(2) degrees , V = 1207.8(3) A(3), R(1) = 0.0219 at -173 degrees C. The crystal structure of [IF(6)][Sb(2)F(11)] was also determined at -100 degrees C and was found to crystallize in the monoclinic space group P2(1)/m with Z = 4, a = 11.885(1) A, b = 8.626(1) A, c = 12.000(1) A, beta = 98.44(1), V = 1216.9(2) A(3), R(1) = 0.0635. The XF(6)(+) cations have octahedral geometries with average Cl-F, Br-F, and I-F bond lengths of 1.550(4), 1.666(11) and 1.779(6) [-173 degrees C]/1.774(8) [-100 degrees C] A, respectively. The chemical shifts of the central quadrupolar nuclei, (35,37)Cl, (79,81)Br, and (127)I, were determined for [ClF(6)][AsF(6)] (814 ppm), [BrF(6)][AsF(6)] (2080 ppm), and [IF(6)][Sb(3)F(16)] (3381 ppm) in anhydrous HF solution at 27 degrees C, and spin-inversion-recovery experiments were used to determine the T(1)-relaxation times of (35)Cl (1.32(3) s), (37)Cl (2.58(6) s), (79)Br (24.6(4) ms), (81)Br (35.4(5) ms), and (127)I (6.53(1) ms). Trends among the central halogen chemical shifts and T(1)-relaxation times of XF(6)(+), XO(4)(-), and X(-) are discussed. The isotropic (1)J-coupling constants and reduced coupling constants for the XF(6)(+) cations and isoelectronic hexafluoro species of rows 3-6 are empirically assessed in terms of the relative contributions of the Fermi-contact, spin-dipolar, and spin-orbit mechanisms. Electronic structure calculations using Hartree-Fock, MP2, and local density functional methods were used to determine the energy-minimized gas-phase geometries, atomic charges, and Mayer bond orders of the XF(6)(+) cations. The calculated vibrational frequencies are in accord with the previously published assignments and experimental vibrational frequencies of the XF(6)(+) cations. Bonding trends within the XF(6)(+) cation series have been discussed in terms of natural bond orbital (NBO) analyses, the ligand close-packed (LCP) model, and the electron localization function (ELF). 相似文献
133.
Tam Nga Chiu Fletcher Stephen P. Vogels Christopher M. Westcott Stephen A. Decken Andreas 《Transition Metal Chemistry》2003,28(1):103-109
Dioxomolybdenum(VI) complexes derived from ethyl maltol (2-ethyl-3-hydroxy-4-pyrone) and 1-alkyl-2-ethyl-3-hydroxy-4-pyridin-4(1H)-ones have been prepared and characterized using physical methods including 1H- and 13C-n.m.r. spectroscopy, i.r., elemental analysis, and X-ray diffraction for the pyrone and 3-methylpyridine pyridinone derivatives. The octahedral complexes have the general formula cis-MoO2L2 where L = the deprotonated pyrone or pyridinone ligand. 相似文献
134.
Andreas Hofer 《Fresenius' Journal of Analytical Chemistry》1968,240(4):229-232
Zusammenfassung Spuren Zinn(IV) können von gro\en Mengen Nickel durch Extraktion mit einer Lösung von Amberlite LA-2 in Xylol getrennt werden. Nach Rückextraktion in verdünnte SalpetersÄure wird Zinn(IV) spektralphotometrisch mit Phenylfluoron als Reagens bestimmt. Die Methode ist für die Bestimmung geringer Zinngehalte in Nickel hoher Reinheit geeignet.
Herrn Univ.-Prof. Dr. W. Leithe danke ich für wertvolle Anregungen und Hinweise, der Direktion der österreichischen Stickstoffwerke A.G. für die Erlaubnis zur Veröffentlichung. 相似文献
Separation of trace amounts of tin from nickel of high purity using amberlite LA-2 and their determination with phenylfluorone
Traces of tin can be separated from large amounts of nickel by extraction with a solution of Amberlite LA-2 in xylene. After back-extraction into diluted nitric acid tin is determined spectrophotometrically using phenylfluorone as reagent. The method is suitable for the determination of low tin contents in nickel of high purity.
Herrn Univ.-Prof. Dr. W. Leithe danke ich für wertvolle Anregungen und Hinweise, der Direktion der österreichischen Stickstoffwerke A.G. für die Erlaubnis zur Veröffentlichung. 相似文献
135.
Andreas G. Galinos Spyros P. Perlepes Theodore F. Zafiropoulos Panayiotis V. Ioannou John K. Kouinis 《Monatshefte für Chemie / Chemical Monthly》1981,112(10):1113-1121
The preparation and some properties of the cobalt(II) complexes Co(LH2)Cl2·2H2O, Co(LH2(NCS)2 and CoL·H2O (whereLH2=N,N-(dipicolyl)-1,8-naphthylenediamine) are reported. On the basis of magnetic moments, visible reflectance and IR data, the structure is proposed to be pseudo-octahedral for Co(LH2)Cl2·2 H2O, pseudo-tetrahedral for Co(LH2)(NCS)2 and square planar for CoL·H2O.
Deprotonierte und Nicht-deprotonierte Co(II)-Komplexe des vierzähnigen Bisamid-Liganden N,N-(Dipicolyl)-1,8-naphthyldiamin. Drei verschiedene Koordinationstypen
Zusammenfassung Es werden die Darstellung und einige Eigenschaften der Kobalt(II)-Komplexe Co(LH2)Cl2·2 H2O, Co(LH2)(NCS)2 und CoL·H2O [LH2=N,N-(dipicolyl)-1,8-naphthylendiamin] diskutiert. Auf der Grundlage von magnetischen Momenten, von Daten der sichtbaren Reflektions-und IR-Spektren wird eine pseudooctaedrische Struktur für Co(LH2)Cl2·2H2O, eine pseudotetraedrische für Co(LH2)(NCS)2 und eine planar-quadratische für CoL·H2O vorgeschlagen.相似文献
136.
Stasch A Roesky HW Vidovic D Magull J Schmidt HG Noltemeyer M 《Inorganic chemistry》2004,43(12):3625-3630
The carbaalane halogen derivatives [(AlX)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (X = F (9), Cl (7), Br (10), I (11)) were prepared in toluene from [(AlH)(6)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (6) and BF(3).OEt(2), BX(3) (X = Br, I), Me(3)SnF, and Me(3)SiX (X = Cl, Br, I), respectively. A partially halogenated product [(AlH)(2)(AlX)(4)(AlNMe(3))(2)(CCH(2)CH(2)SiMe(3))(6)] (12) (X = Cl (approximately 40%), Br (approximately 60%)) was obtained from 5 and impure BBr(3). [(AlH)(6)(AlNMe(3))(2)(CCH(2)Ph)(6)] (5) was converted to [(AlX)(6)(AlNMe(3))(2)(CCH(2)Ph)(6)] (X = F (13), Cl (14), Br (15), I (16)) using BF(3).OEt(2) and Me(3)SiX (X = Cl, Br, I), respectively. The X-ray single-crystal structures of 11.C(6)H(6), 12.3C(7)H(8), 13.6C(7)H(8), and 15.4C(7)H(8) were determined. Compounds 7 and 9-11 are soluble in benzene/toluene and could be well characterized by NMR spectroscopy and MS (EI) spectrometry. The results demonstrate the facile substitution of the hydridic hydrogen atoms in 5 and 6 by the halides with different reagents. 相似文献
137.
The scheme of ‘through-space’ and ‘through-bond’ interaction of (semi)localized orbitals, originally proposed by Hoffmann, is reexamined in terms of SCF many-electron treatments. It is shown that the two types of interaction can be characterized by examining the corresponding off-diagonal matrix elements of the Hartree-Fock matrices of the localized or the symmetry adapted localized orbitals and of the partially diagonalized Hartree-Fock matrices referring to ‘precanonical orbitals’. The procedure outlined is applied to three practical examples using the semiempirical many-electron treatments SPINDO, MINDO/2 and CNDO/2:
- a A reassessment of ‘through-space’ and ‘through-bond’ interaction in norbornadiene indicates, that the latter type of interaction is also of importance for the orbital based mainly on the antisymmetric combination of the localized x-orbitals. The differences in the predictions derived from the three models are critically examined.
- b The competition between ‘through-space’ and ‘through-bond’ interaction in the series of bicyclic dienes from norbornadiene to bicyclo[4.2.2]-dcca-7,9-diene and in cyclohexa-1,4-diene, i. e. their dependence on the dihedral angle UI is reexamined. It is found that the rationalization for the orbital crossing near ω = 130° deduccd from PE. spectroscopic data can not be as simple as originally suggested and that the relay’ orbitals responsible for ‘through-bond interaction affecting both the symmetric and the antisymmetric combination of the π-orbitals extend over the whole CC-σ-system of the six membered ring.
- c ‘Through-bond’ interaction of the two lone pair orbitals in 1,4-diazabicyclo[2.2.2]octane is found to be large for their symmetric and the antisymmetric linear combination.
138.
139.
The influence of Joule heating on electroosmotic flow velocity, the retention factor of neutral analytes, and separation efficiency in capillary electrochromatography was investigated theoretically and experimentally. A plot of electrical current against the applied electrical field strength was used to evaluate the Joule heating effect. When the mobile phase concentration of Tris buffer exceeded 5.0 mM in the studied capillary electrochromatography systems using particulate and monolithic columns (with an accompanying power level of heat dissipation higher than 0.35 W/m), the Joule heating effect became clearly noticeable. Theoretical models for describing the variation of electroosmotic flow velocity with increasing applied field strength and the change of retention factors for neutral analytes with electrical field strength at higher Tris buffer concentrations were analyzed to explain consequences of Joule heating in capillary electrochromatography. Qualitative agreement between experimental data and implications of the theoretical model analysis was observed. The decrease of separation efficiency in capillary electrochromatography with macroporous octadecylsilica particles at high buffer concentration can be also attributed to Joule heating mainly via the increased axial diffusion of the analyte molecules and dispersion of solute bands by a nonuniform electroosmotic flow profile over the column cross-section. However, within a moderate temperature range, the contribution of the macroscopic velocity profile in the column arising from radial temperature gradients is insignificant. 相似文献
140.
Heydenreich M Koch A Kovács J Tóth G Kleinpeter E 《Magnetic resonance in chemistry : MRC》2004,42(8):667-670
3J(C,H) coupling constants via a sulfur atom in two series of compounds, both including a sulfide, a sulfoxide and a sulfone, were detected experimentally and calculated by quantum mechanical methods. In the first series (1-3) the coupling between a hydrogen, bonded to an sp3 carbon, and an sp2 carbon is treated; the second series (4-6) deals with the coupling between a hydrogen, bonded to an sp3 carbon, and an sp3 carbon. Different pulse sequences (broadband HMBC, SelJres, 1D HSQMBC, J-HMBC-2, selective J-resolved long-range experiment and IMPEACH-MBC) proved to be useful in determining the long-range 3J(C,H) coupling constants. However, the dynamic behaviour of two of the compounds (4 and 6) led to weighted averages of the two coupling constants expected (concerning equatorial and axial positions of the corresponding hydrogens). DFT calculations proved to be useful to calculate not only the 3J(C,H) coupling constants but also the different contributions of FC, PSO, DSO and SD terms; the calculation of the Fermi contact term (FC) was found to be sufficient for the correct estimation of 3J(C,H) coupling constants. 相似文献