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11.
J. Talamoni E. M. Vieira A. M. M. Pucci 《Journal of Radioanalytical and Nuclear Chemistry》1990,145(1):69-79
In the last twenty years the ionizing effects on matter of60Co γ-rays have been widely discussed. However, regarding organic compounds, mainly aromatic ones, results are scarce, particularly
those obtained in alcoholic solution. γ-Radiation is used mainly in industry and medicine, particularly for sterilization
of surgical materials. In this work we studied the chemical and radiolytic stability of products by radiation from quinoline
in isopropanol solution. Doses were from 2×104 to 3×105 Gy and the samples concentration was 1∶1 by volume. We have observed significant effects for high radiation doses. Lower
doses effected the solvent with the production of long polymeric hydrocarbons. Products formed were characterized by capillary
gas chromatography coupled to a mass-selective detector (GC/MSD). We have used a fused silica capillary column 25 m long,
0.2 mm in internal diameter, covered by a 0.33 μm thick film of crosslinked 5% phenyl methyl silicone. 相似文献
12.
Vincenzo Pucci 《Analytica chimica acta》2003,488(1):97-105
Melatonin was determined in pharmaceutical preparations by means of two simple and reliable analytical methods based on micellar electrokinetic chromatography (MEKC) and spectrofluorimetry. The fluorescence emission values were measured at λ=350 nm when exciting at λ=275 nm. The MEKC analysis was achieved using a system consisting of 40 mM SDS in phosphate buffer (20 mM, pH 7.5). The extraction of melatonin from the tablets was achieved by means of a simple one-step dissolution with methanol/water. Both methods were applied for the determination of melatonin in commercial formulations and galenic preparations. The MEKC procedure allows the quantitative determination of melatonin in all pharmaceutical preparations tested. On the contrary, the spectrofluorimetric method is not suitable for tablets which also contain tryptophan; this interference can be eliminated by a suitable liquid-liquid extraction procedure. The results obtained with the two methods are in good agreement and satisfactory in terms of precision and accuracy. 相似文献
13.
The separation and simultaneous determination of caffeine, paracetamol, and acetylsalicylic acid in two analgesic tablet formulations was investigated by capillary electrochromatography (CEC). The effect of mobile phase composition on the separation and peak efficiency of the three analytes was studied and evaluated; in particular, the influence of buffer type, buffer pH, and acetonitrile content of the mobile phase was investigated. The analyses were carried out under optimized separation conditions, using a full-packed silica capillary (75 microm ID; 30.0 cm and 21.5 cm total and effective lengths, respectively) with a 5 microm C8 stationary phase. A mixture of 25 mM ammonium formate at pH 3.0 and acetonitrile (30:70 v/v) was used as the mobile phase. UV detection was at 210 nm. Good linearity was found in the range of 50-200, 20-160, and 4-20 microg/mL for acetylsalicylic acid (r2=0.9988), paracetamol (r2=0.9990) and caffeine (r2=0.9990), respectively. Intermediate precision (RSD interday) as low as 0.1-0.8% was found for retention times, while the RSD values for the peak area ratios (Aanalyte/AIS) were in the range of 1.9-2.9%. The optimized CEC method was applied to the analysis of the studied compounds present in commercial tablets. 相似文献
14.
Dr. Ali Abdulkarim Marvin Nathusius Rainer Bäuerle Dr. Karl-Philipp Strunk Dr. Sebastian Beck Dr. Hans Joachim Räder Prof. Annemarie Pucci Dr. Christian Melzer Daniel Jänsch Dr. Jan Freudenberg Prof. Uwe H. F. Bunz Prof. Klaus Müllen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):281-288
The synthesis of unsubstituted oligo-para-phenylenes ( OPP ) exceeding para-hexaphenylene—in the literature often referred to as p-sexiphenyl—has long remained elusive due to their insolubility. We report the first preparation of unsubstituted para-nonaphenylenes ( 9PP s) by extending our precursor route to poly-para-phenylenes ( PPP ) to a discrete oligomer. Two geometric isomers of methoxylated syn- and anti-cyclohexadienylenes were synthesized, from which 9PP was obtained via thermal aromatization in thin films. 9PP was characterized via optical, infrared and solid-state 13C NMR spectroscopy as well as atomic force microscopy and mass spectrometry, and compared to polymeric analogues. Due to the lack of substitution, para-nonaphenylene, irrespective of the precursor isomer employed, displays pronounced aggregation in the solid state. Intermolecular excitonic coupling leads to formation of H-type aggregates, red-shifting emission of the films to greenish. 9PP allows to study the structure–property relationship of para-phenylene oligomers and polymers, especially since the optical properties of PPP depend on the molecular shape of the precursor. 相似文献
15.
Ange Polidori Bernard Pucci Leila Zarif Jean G. Riess Andr A. Pavia 《Macromolecular rapid communications》1996,17(4):229-238
Sugar-derived surfactants bearing a polymerizable acryloyl moiety on one of the branches of the double-chain hydrophobic tail were prepared. The non–ionic hydrophilic head and the biantennary hydrophobic tail were built on, respectively, an aspartic acid and a tris(hydroxymethyl)aminomethane core. Ultraviolet irradiation of aqueous dispersions of these surfactants above their transition phase temperature (Tc) was achieved. The morphology of self-assemblies produced in such a way were investigated by transmission electron microscopy. TEM photographs revealed that irradiation leads to the formation of unilamellar vesicles. Neither fibers nor tubules were detected in contrast to what was observed before polymerization. 相似文献
16.
Stationary phases for capillary electrochromatography with a longitudinal gradient of functionalities have been prepared via photoinitiated grafting of polymer chains onto the pore surface of a porous polymer monolith. In order to achieve the desired retention and electroosmotic flow, the hydrophobic poly(butyl methacrylate-co-ethylene dimethacrylate) monolith with optimized porous properties was grafted with a layer of ionizable polymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid). A moving shutter and a neutral density filter were used to control the dose of UV light received at different locations along the monolith in order to create the longitudinal gradient of functionalities. Formation of the desired gradients was confirmed using electron probe microanalysis of different locations along the column. The preparation technique significantly affects performance in the CEC mode as demonstrated on the separations of a model mixture using columns both with homogeneous distribution of grafts and with a gradient of functionality. Columns grafted with the gradient of functionalities were found superior to those functionalized uniformly. A comparison of the performance of the gradient column with another containing evenly distributed functionalities showed the performance benefits of the "gradient" column. 相似文献
17.
B. Apicella A. Carpentieri R. Barbella P. Pucci 《Proceedings of the Combustion Institute》2007,31(1):547-553
Mass spectrometric analysis by laser desorption-time of flight-mass spectrometry (LDI-TOF-MS) was exploited to extend the detection of flame-formed polycyclic aromatic hydrocarbons (PAH) up to the mass limit of the first soot particles (>2000 Da) in the soot formation region of a premixed fuel-rich (C/O = 1) ethylene flame. The typical decreasing intensity of PAH ion peaks with increasing mass was found in the mass range m/z 500-1700 although a slight enrichment in the heavier part of PAH could be observed to occur along the flame axis. The separation by means of size exclusion chromatography (SEC) into two different classes of PAH followed by UV-visible spectroscopy corroborated the mass spectral identification of large mass PAH. Critical examination of mass spectral features and SEC separation was the starting point for speculation about the changes occurring in PAH growth from planar to concave structures which could be important for soot inception mechanisms. 相似文献
18.
Iolinda Aiello Mauro Ghedini Annarita Grisolia Daniela Pucci Oriano Francescangeli 《Liquid crystals》2005,32(6):763-769
New Ni(II) and UO2(II) metallomesogens obtained from mesomorphic N,N'-salicyliden(3,3'-diamine-N-methyldipropylamine) ligands containing a pentadentate N3O2 chelating cavity and bearing two or four lateral substituents, are isolated and fully characterized. Some of the synthesized nickel and dioxouranium complexes show a SmC mesophase. To the best of our knowledge, these species are the first pentacoordinated Ni(II) and heptacoordinated UO2(II) metallomesogens to be reported. 相似文献
19.
Kanishka Perera Patrizia Pucci Csaba Varga 《NoDEA : Nonlinear Differential Equations and Applications》2014,21(3):441-451
We consider a nonlinear eigenvalue problem under Robin boundary conditions in a domain with (possibly noncompact) smooth boundary. The problem involves a weighted p–Laplacian operator and subcritical nonlinearities satisfying Ambrosetti–Rabinowitz type conditions. Using Morse theory and a cohomological local splitting as in Degiovanni et al. (Commun Contemp Math 12:475–486, 2010), we prove the existence of a nontrivial weak solution for all (real) values of the eigenvalue parameter. Our result is new even in the semilinear case p = 2 and complements some recent results obtained in Autuori et al. (Adv Anal Equ 18:1–48, 2013). 相似文献
20.
We report on the in situ observation of temperature-driven drastic morphology evolution and surface pre-melting of the Bi(0 0 1) nanofilm deposited on the Si(1 1 1)-7 × 7 surface by use of spot-profile-analyzing low-energy electron diffraction (SPA-LEED). Surface step density of the single-crystalline, epitaxial Bi(0 0 1) film decreases above 350 K in a critical manner. On annealed Bi(0 0 1) films, we have detected surface pre-melting with a transition temperature of 350 K, which yields reversible diffraction intensity drop in addition to the harmonic Debye-Waller behavior. The observed surface flattening of the as-deposited film is driven by the increased amount of mobile adatoms created through the surface pre-melting. 相似文献