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241.
Occurrence of 2-phenylphenol in food paper packages 总被引:1,自引:0,他引:1
Lenka Votavová Kristýna Hanušová Lukáš Vápenka Jaroslav Dobiáš František Kvasnička 《Central European Journal of Chemistry》2014,12(11):1162-1168
Twenty three paper based packaging materials commercially used for food packaging in the Czech Republic were analysed with regard to 2-phenylphenol (OPP) content using HPLC technique with fluorimetric detection. The HPLC method was modified with the aim to increase its sensitivity. OPP was detected in quantities ranging from 10 mg kg?1 to 527 mg kg?1 in twenty tested samples. The level of OPP in packaging materials was in close correlation to the content of recycled pulp in used paper material. The migration of OPP from two packaging materials comprised of paperboard coated with low density polyethylene (LDPE) into food simulants was determined at 40°C for 10 days. The levels of migration into 3% acetic acid, 10% ethanol and olive oil were below the limit of detection of used analytical procedure. In the case of 95% ethanol, 13% and 21% of OPP present in tested samples were transferred into simulant. The found occurrence of OPP in paper packages does not pose any significant safety risk for food consumer, but OPP could be considered as wide spread contaminant in paper materials. 相似文献
242.
Cover Picture: Elucidating the Structure of Chiral Molecules by using Amplified Vibrational Circular Dichroism: From Theory to Experimental Realization (ChemPhysChem 16/2015)
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Conductometric detectors employed in microseparation methods are designed to primarily match the separation criteria. Consequently, their geometry is seldom optimal from the point of view of conductometry. An unsuitable detection cell geometry is manifested in the dependence of the conductometric cell constant on the frequency of the AC signal applied to the electrodes. Variations in the cell constant value cause changes in the measured signal even if the solution conductivity is constant. By varying the frequency of the AC signal it is thus possible to find an optimal frequency at which the highest detection sensitivity is attained. The optimum frequency depends both on the cell geometry and on the conductivity of the mobile phase solution. 相似文献
245.
Changtong Hao František Tureček 《Journal of the American Society for Mass Spectrometry》2009,20(4):639-651
1,n-Alkanediammonium cations in noncovalent complexes with two dibenzo-18-crown-6-ether (DBCE) ligands undergo an unusual intramolecular
tandem hydrogen atom and proton transfer to the crown ether ligand upon charge reduction by electron capture. Deuterium labeling
established that both migrating hydrogens originated from the ammonium groups. The double hydrogen transfer was found to depend
on the length of the alkane chain connecting the ammonium groups. Ab initio calculations provided structures for select alkanediammonium·dibenzo-18-crown-6-ether
complexes and dissociation products. This first observation of an intra-complex hydrogen transfer is explained by the unusual
electronic properties of the complexes and the substantial hydrogen atom affinity of the aromatic rings in the crown ligand. 相似文献
246.
Kotaro Koike František Mikeš Yoshiyuki Okamoto Yasuhiro Koike 《Journal of polymer science. Part A, Polymer chemistry》2009,47(13):3352-3361
As a novel material of low loss and high thermal stability, a graded index plastic optical fiber (GI POF) comprised of a copolymer of methyl α‐chloro acrylate (MCA) and 2,2,2‐trichloroethyl methacrylate (TCEMA) was prepared and the thermal, mechanical, and optical characteristics were investigated. Although each homopolymer had low loss and desirable high thermal stability, they had crucial disadvantages for the fiber fabrication process. To draw a MCA polymer (PMCA) fiber, it has to be heated above 270 °C. However, the polymer started to decompose at a lower temperature and produced numerous bubbles. In contrast, TCEMA polymer (PTCEMA) is too brittle to roll up during heat drawing. In this study, we succeeded to improve the strong viscoelasticity and the low decomposition temperature of PMCA and the brittleness of PTCEMA by copolymerizing MCA and TCEMA. In addition, the glass transition temperatures (Tg) of the copolymers were in the range of 133–147 °C and the transmittances of the copolymers were much higher than that of PMMA which has been commonly used as a base material of POF. A suitable GI POF was obtained using the MCA and TCEMA copolymer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3352–3361, 2009 相似文献
247.
Lenka Votavová Kristýna Hanušová Lukáš Vápenka Jaroslav Dobiáš František Kvasnička 《Central European Journal of Chemistry》2014,12(12):1304-1305
The original version of the article was published in Cent. Eur. J. Chem. 12(11) (2014) pp. 1162–1168. Unfortunately, the original version of this article contains some mistakes in the Tables 2 and 3. Corrected versions of the tables are presented below. 相似文献
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Visible Photoluminescence in Polysilanes 总被引:1,自引:0,他引:1
Stanislav Nešpůrek František Schauer Andrey Kadashchuk 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):159-168
Summary. The photoluminescence spectrum of poly-(methyl-(phenyl)-silanediyl) shows a strong narrow peak in the UV region which is
of excitonic nature and related to σ*-σ transitions. The broad emission peak in the visible region is related to polymer branching, charge transfer transitions,
and defect electronic states (backbone scission). Chemical substitution of the Si backbone with π-conjugated side groups allows
to generate photoluminescence also in the visible region.
Received June 23, 2000. Accepted (revised) August 7, 2000 相似文献