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11.
A novel methodology in on-line pyrolysis-gas chromatography (Py-GC) for the fast analysis of fatty acids in vegetable oils with minimal sample treatment and the use of non-toxic reagents is described. Pyrolysis at 500 degrees C for 10 s of sub-microgram quantity of vegetable oil dissolved in dimethyl carbonate (DMC) and in the presence of nanopowder titanium silicon oxide resulted in the production of fatty acid methyl esters (FAMEs) as unique products. Pyrolysis performed by means of a resistively heated filament pyrolyser interfaced to a GC-MS apparatus enabled the direct analysis of evolved FAMEs. The DMC/Py-GC-MS analysis was tested on soybean, coconut, linseed, walnut and olive oil and the results compared to the classical BF(3)-methanol as reference methodology. The DMC method exhibited a lower precision and was biased towards lower levels of polyunsaturated fatty acids (PUFA) in comparison to the BF(3)-methanol method, but was more advantageous in terms of reduced sample treatment, waste generation and risk factors of employed chemicals. 相似文献
12.
AISI 304 Stainless Steel is widely used in different industrial fields because of its mechanical and corrosion properties.
However, its tendency to corrosion in presence of halide ions limits the applications. One strategy to improve the corrosion
resistance is the use of coatings barriers containing corrosion inhibitors in their formulation. The lanthanides present attractive
green and corrosion properties for the substitution of chromates, which are the most common substances used as corrosion protection.
However, these compounds are highly toxic, and an intense effort is being undertaken to replace them. Cerium is a good alternative
because of its relatively low cost and abundance. It fulfils the basics requirements for being considered an alternative inhibitor:
the ions form insoluble hydroxides and they present low toxicity. Inorganic and hybrid sol-gel coatings have been developed
to increase the corrosion resistance of metals and they provide an excellent vehicle for the incorporation of secondary phases
including particles and metal ions as cerium ions.
The aim of this work was to study the influence of the incorporation of cerium ions in hybrid silica sol-gel coatings deposited
on AISI 304 stainless steel as substrate as a potential replacement of chromate treatments. This system should combine the
barrier protection effect of silica coating with the corrosion inhibitor effect of the cerium ions inside the coatings. After
7 days of immersion in NaCl, coated substrates showed lower current densities than the bare steel, although the coatings produced
from Ce (III) salts experience a slight weakening in time and those obtained from Ce (IV) chemicals evidence an enhance in
the coating performance, probably due to the plugging of corrosion products in the defective areas of the film. 相似文献
13.
Buneva VN Kanyshkova TG Vlassov AV Semenov DV Khlimankov DYu Breusova LR Nevinsky GA 《Applied biochemistry and biotechnology》1998,75(1):63-76
Various catalytically active antibodies (Abs), or abzymes, have been detected recently in the sera of patients with autoimmune
pathologies, in whom their presence is probably associated with autoimmunization. Normal humans are generally not considered
to have abzymes, since no obvious immunizing factors are present. Here is shown by different methods that IgG from the milk
of normal females possesses both DNase and RNase activities. The activities were also present in the IgG F(ab′)2 and Fab fragments.
Affinity modification of IgG by the chemically reactive derivative of an oligonucleotide led to preferential modification
of the L chain of IgG. After separation of the subunits by sodium dodecyl sulfate electrophoresis in a gel containing DNA,
an in-gel assay showed DNase activity in the L chain. The L chain separated by affinity chromatography on DNA-cellulose was
catalytically active. These findings speak in favor of the generation of cat alytic Abs by the immune system of healthy mothers.
It is known that the treatment of adults with DNases and RNases offers protection from viral and bacterial diseases. Since
breast milk protects the infants from infec tions until the immune system is developed, this raises the possibility that catalytic
Abs like nucleases, may possess a protective role. 相似文献
14.
Meerovich IG Jerdeva V Derkacheva VM Meerovich GA Lukyanets EA Kogan EA Savitsky AP 《Journal of photochemistry and photobiology. B, Biology》2005,80(1):57-64
The photodynamic activity of dibiotinylated aluminum sulfophthalocyanine was studied in vitro and in vivo. Dibiotinylated aluminum sulfophthalocyanine provided enhanced phototoxic action on OAT-75 cell monolayers as compared with the parent drug. Photodynamic therapy of mice with Ehrlich carcinoma using dibiotinylated aluminum sulfophthalocyanine (0.25 mg/kg) resulted in enhanced inhibition of tumor growth, pronounced vascular damage (thrombosis and destruction of vascular walls) and eventual tumor necrosis. 相似文献
15.
Maria Teresa Cocco Cenzo Congiu Valentina Onnis Angela Maria Bernard Pier Paolo Piras 《Journal of heterocyclic chemistry》1997,34(4):1347-1350
A simple approach to the fluorinated 1,5-benzoxazepine ring system is described. By reacting commercially accessible aminophenols 1 and the trifluoroacetylvinyl ether 2, high yields of enaminones 3 were obtained. Functionalization of methyl group of compounds 3 gave rise to dieneamines 4 that were cyclized in acidic environment to benzoxazepine derivatives 5. 相似文献
16.
A model of nonequilibrium charge recombination from an excited adiabatic state of a donor-acceptor complex induced by the nonadiabatic interaction operator is considered. The decay of the excited state population prepared by a short laser pulse is shown to be highly nonexponential. The influence of the excitation pulse carrier frequency on the ultrafast charge recombination dynamics of excited donor-acceptor complexes is explored. The charge recombination rate constant is found to decrease with increasing excitation frequency. The variation of the excitation pulse carrier frequency within the charge transfer absorption band of the complex can alter the effective charge recombination rate by up to a factor 2. The magnitude of this spectral effect decreases strongly with increasing electronic coupling. 相似文献
17.
Mezzache S Afonso C Pepe C Karoyan P Fournier F Tabet JC 《Rapid communications in mass spectrometry : RCM》2003,17(14):1626-1632
The proton affinities of proline, cis-3-methylproline and cis-3-ethylproline have been measured by the kinetic method using an ion trap instrument; the values obtained are 936, 940.5, and 943 kJ mol(-1), respectively. The experimental values are consistent with those obtained by high-level ab initio calculations (B3LYP/6-31+G*//B3LYP/6-31G* and B3P86/6-31+G*//B3LYP/6-31G*). Several conformations of neutral and protonated proline were considered, in particular the endo and exo ring structure and the position of the carboxyl group. These results show the importance of the position of the hydrogen atom of the carboxyl group in determining the most stable protonated proline structure. 相似文献
18.
Dimethyl carbonate (DMC) was investigated as a mild, harmless and odorless reagent for pyrolytic methylation of fatty acids. Soybean oil was selected as test material for its high content of (poly)unsaturated fatty acids. Pyrolyses were performed at 500, 700 and 900 degrees C by means of a heated platinum filament pyrolyser on-line and off-line to the GC-MS apparatus. Methyl esters of palmitic, linoleic, oleic and stearic acid were formed as prominent products from off-line pyrolysis of soybean oil in the presence of DMC and zeolite 13X. Fatty acid methyl esters (FAMEs) were not observed at important levels in the absence of zeolite, while on-line Py-GC-MS experiments resulted principally in the formation of free fatty acids and hydrocarbons. The FAME profiles obtained from the DMC/zeolite off-line pyrolysis were compared to those resulting from tetramethylammonium hydroxide (TMAH) thermochemolysis and BF3-methanol procedure. The observed differences between pyrolysis and methanolysis methods were principally attributed to the thermal degradation of unsaturated fatty acids. The effectiveness of the DMC/zeolite pyrolytic methylation was further demonstrated by the analysis of tripalmitine and soybean seeds. 相似文献
19.
MITIC Snezana ZIVANOVIC Valentina OBRADOVIC Mirjana TOSIC Snezana PAVLOVIC Aleksandra 《中国化学》2007,25(4):531-534
The kinetic method for the determination of phosphate microamounts was described. The developed method is based on catalytic effect of phosphate on sodium pyrogallol-5-sulphonate (PS) by dissolved oxygen. The reaction was followed spectrophotometrically by measuring the rate of change in the values of the absorbance of the oxidation product at 437 nm. The optimum reaction conditions are PS (0.44×10^-3 mol·L^-1) and HClO4 (3.6×10^-6 mol·L^-1) at 25 ℃. Following this procedure, phosphate can be determined with a linear calibration graph up to 0.23 μg·mL^-1. The interference effect of several species was also investigated and it was found that the most common cations and anions did not interfere with the determination. The developed procedure was successfully applied to the determination of phosphate in natural waters and soil. 相似文献
20.
Angelini N Micali N Mineo P Scamporrino E Villari V Vitalini D 《The journal of physical chemistry. B》2005,109(39):18645-18651
Changes in the UV-vis spectra and induced circular dichroism (ICD) signals observed, in correspondence with the porphyrin Soret region, for aqueous solutions of achiral 5,10,15,20-tetrakis{p-[omega-methoxy poly(oxy-ethylene)]phenyl}porphyrin cobalt (II) (Co-P) and aromatic alpha-L-amino acids (Trp and Phe) give direct evidence for the coordination between the Co-P and amino acids. Considering that Co-P, besides the Co atom (one-fixation-point system), does not contain in the molecule active ligand groups and that no ICD signals have been observed in the case of Co-P/Ala, it has been concluded that hydrophobic interactions or stacking interactions between the aromatic rings of the porphyrin and those of Trp or Phe, acting as further amino acid (AA) fixation points, can strongly reduce the mobility of the chiral guest, thus permitting the generation of ICD signals. The effects of changes of both pH (in the range 2-9) and amino acid structure on the ICD phenomenon have also been investigated. In particular, the following have been observed: (i) strong ICD signals for all of the Co-P/N-acetyl amino acid aqueous solutions at pH 7, (ii) an unexpected ICD band with a bisignate form for the Co-P/Ala solution at pH 9 after long aging, and (iii) an opposite ICD signal when alpha-D-Phe and alpha-D-Trp enantiomers have been used. The data reported in this paper show how the binding mechanism between receptor and AAs changes by modulating properly the pH or the molecular structures and indicate that in these aqueous solutions the coordination Co-N is not the fundamental mechanism giving rise to the formation of the complexes and that the binding can be driven by hydrophobic interactions. These occurrences, through the analysis of the spectroscopic response (and, in particular, the form of the ICD band), can allow the recognition of AAs. 相似文献