Liquid chromatography with diode-array detection has been used for simultaneous analysis of eight water-soluble synthetic colorants (E102, E104, E110, E122, E124, E129, E131, and E133) in non-alcoholic beverages. The colors were separated in 15 min on a C18 reversed-phase column with a linear mobile phase gradient prepared from tetrabutylammonium hydrogen sulfate, methanol, and deionized water. The analytical characteristics of the separation were evaluated. Good linearity (r2 = 0.9988–0.9999), adequate limits of quantification, and high recovery (from 96.3 to 98.5%) were achieved. The method was used for analysis of 57 samples of soft drinks. The experimental results showed the colorants were present in 34 of the samples, and confirmed the method is sensitive, rapid, precise, and suitable for routine analysis of synthetic organic dyes.
The geometry, frequency, and intensity of the vibrational bands of imidazo[1,2-a]pyridine (which is abbreviated as impy) were
obtained by the density functional theory (DFT) calculations with BLYP, B3LYP, and B3PW91 functionals and 6-31G(d) basis set.
The optimized geometric bond lengths and bond angles are in good agreement with the available X-ray data. The infrared spectrum
of imidazo[1,2-a]pyridine was computed by the DFT method in order to reproduce the vibrational wavenumbers and intensities
with an accuracy, which allows reliable vibrational assignments. Total energy distribution and isotopic shifts have been calculated
in order to help for the perfect assignment of the vibrational modes. The zinc halide complexes Zn(impy)2X2 [X = Cl, Br, and I] have also been synthesized. The compounds were characterized using the elemental analysis, FT-IR spectra,
and quantum chemical calculations. The geometry optimization of Zn(impy)2X2 yields distorted tetrahedral environment around Zn ion. 相似文献
Using the supersymmetric quantum mechanics, we investigate the wave function-sensitive properties of the supersymmetric potentials
which have received a lot of attention in the literature recently. We show that a superdeep potential and its phase-equivalent
shallow-partner potential give very similar rms radius values for the weakly bound systems such as the deuteron and 11Be nuclei. Although the corresponding eigenstates differ in the node-number, our investigation on the 11Be(p, d )10Be single nucleon halo transfer reaction at 35 MeV show that also other physical quantities such as the cross-section angular
distributions calculated using these wave functions reflect the nodal structure rather weakly. This lends support to two nearly
equivalent treatments of the Pauli principle.
Received: 15 May 2000 / Accepted: 14 September 2000 相似文献
In this study, the past investigations of the design criteria of vortex tubes were overviewed and the detailed information
was presented on the design of them. Vortex tubes were classified and the type of them was described. All criteria on the
design of vortex tubes were given in detail using experimental and theoretical results from the past until now. Finally, the
criteria on the design of them are summarized. 相似文献
Most macroeconomic time series are reported on a quarterly basis. However, in many cases, official statistical agencies report annual (or ‘year-on-year’) growth rates rather than the quarterly data themselves. In this paper, we demonstrate how to recover seasonally adjusted quarterly growth rates from annual growth rates that are reported quarterly. As an illustration, we apply the technique to the highly seasonal UK Retail Sales series. Using only the annual growth rates calculated from the underlying data, we find that our procedure generates estimated seasonally adjusted quarterly growth rates that are almost indistinguishable from the ‘true’ seasonally adjusted quarterly growth rates. 相似文献
Calixarenes, which have a great place in supramolecular chemistry, have become the most prominent macrocyclic compounds in synthetic organic chemistry due to their easy synthesis and functionalization. In this study, p-tert-butyl calix[4]arene dihydrazide derivative was synthesized and then reacted with 3-oxo-3,4-dihydro-2 H-benzo[b][1,4] thiazin-2-ylideneacetyl chloride to prepare new calixarene based chromophore compound 4. The structure of the synthesized compound was elucidated by spectroscopic methods such as 1H NMR 13C NMR and FT-IR spectroscopy. Chromogenic and fluorescence properties of compound 4 were evaluated. It was observed from both studies that compound 4 was Co2+ selective and shows fluorescence Switched-off behavior. Stoichiometry, binding constant and the detection limit were calculated. The stoichiometry between compound 4 and Co2+ was found to be 1:1. The binding constant value (K) was calculated as 666.67 M??1 using Benesi–Hildebrand equation, while the detection limit for Co2+ ion was calculated as 0.0465 µM.
Via an oxidation reaction of Cu(I) iodide with pyridine-2,6-dicarboxylic acid (H2L) in DMF three copper(II) complexes, [(CH3)2NH2]2[CuL2] (1), K2[CuL2]?H2L?H2O (2) and [Cu(L)(H2O)]n (3), were synthesized and characterized. The structures of 1–3 were determined by single crystal X-ray diffraction studies. In-situ DMF decomposition produces dimethylamine base under solvothermal conditions and a proton transfer reaction takes place for the complex formation of 1. 3-D networks are stabilized in 1 and 2 via hydrogen bonds. Complex 3 is a 1-D coordination polymer with Cu-O semi-coordination bonds. Thermal decomposition of the complexes results in the corresponding metal oxides. Also, the electrochemical behavior of 1 was determined to be a metal-centered and diffusion-controlled, one-electron reduction process. 相似文献
A switchable solvent-based micro-extraction method for pre-concentration and separation of ultratrace palladium was developed prior to its flame atomic absorption spectrometric detection. Reverse change of hydrophilicity of N,N-dimethylcyclohexylamine (DMA) was achieved by reaction with carbonated water. The hydrophilic bicarbonate salt of the protonated DMA was used as extractant for palladium complexed with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP). Formation of the hydrophobic form of switchable solvent from hydrophilic form of switchable solvent phase was achieved by addition of sodium hydroxide into the extractant-sample solution. The effect of key parameters affected extraction recovery was studied and optimised by using Plackett–Burman design, central composite design and three dimension (3D) surfaces response. The calibration plot was linear in the range 0.015–1.6 mg L?1 of palladium with a correlation coefficient of 0.999. The limit of detections values of palladium for liquid and solid samples were 4.28 μg L?1 and 0.54 µg g?1, respectively. The pre-concentration factor was 37.5. The accuracy was confirmed by determination of palladium in certified reference material. The procedure was also applied for determination of palladium content of real samples as automotive catalytic converter, roadside dust, sea water and river water. 相似文献
Electrochemical behavior of resazurin on HMDE in Britton-Robinson (B-R) buffers (pH 2.0–10.0) was studied using the square-wave
voltammetry (SWV), square-wave adsorptive stripping voltammetry (SWAdSV), and cyclic voltammetry (CV) techniques. The voltammogram
of resazurin in B-R buffer at pH < 4.0 exhibited two cathodic reduction peaks. The voltammetric peaks were obtained at −0.144
V (reversible) and −1.250 V (irreversible) at pH 3.2, and correspond to the reduction of resorufin to dihydroresorufin and
to the catalytic hydrogen wave, respectively. At pH > 4.0, a new irreversible cathodic reduction peak, assigned to the protonation
of N-oxide on the phenoxazin ring, was observed. Electrochemical parameters (Ip/Ep, Ip/v, Ip/pH, Ip/tacc) of the compound were determined. From the voltammetric data, electrochemical reduction mechanisms for all peaks have been
suggested. Maximum peak current for the reversible peak was obtained at pH 4.1. A linear relationship between the current
and concentration was determined, and also the lowest detection limit was found as 3.25 × 10−8 mol L−1 and 1.98 × 10−10 mol L−1 for SWV and SWAdSV, respectively. 相似文献