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951.
The adsorption of HSA onto CHI/ALG multilayer assemblies was assessed in situ using QCM-D. It was found that the behavior of HSA on biomaterials surface can be tuned by adjusting parameters of the polyelectrolyte system such as pH, layer number, crosslinker and polymer terminal layer. Our results confirmed the key role of electrostatic interactions during HSA adsorption, since oppositely charged surfaces were more effective in promoting protein adhesion. QCM-D data revealed that crosslinking (CHI/ALG)(5) CHI films allows HSA to become adsorbed in physiological conditions. Our results suggested that the biological potential of biopolymers and the mild conditions of the LbL technique turn these natural nanoassemblies into a suitable choice to be used as pH-sensitive coatings. 相似文献
952.
Rocío García-Villalba Alegría Carrasco-Pancorbo Ekaterina Nevedomskaya Oleg A. Mayboroda André M. Deelder Antonio Segura-Carretero Alberto Fernández-Gutiérrez 《Analytical and bioanalytical chemistry》2010,398(1):463-475
Olive oil polyphenols have important biological properties which closely depend on their bioavailability; it is, therefore,
essential to understand how polyphenols are absorbed, metabolized, and eliminated from the body. An analytical method based
on rapid-resolution liquid chromatography (RRLC) coupled with mass spectrometric detection with a time-of-flight analyzer
(RRLC–ESI-TOF MS) has been developed for analysis of the main olive oil phenolic compounds and their metabolites in human
urine. Urine samples from ten healthy volunteers were collected before and 2, 4, and 6 h after intake of 50 mL extra-virgin
olive oil. The proposed method includes liquid–liquid extraction with ethyl acetate, which provides extraction recoveries
of the phenolic compounds studied between 35 and 75% from spiked urine samples. Good repeatability was obtained—the relative
standard deviations (RSDs) of peak areas in intra-day and inter-day studies were 4.3 and 6.5%, respectively. Statistical studies
enabled us to discriminate between urine samples before and after intake, and facilitated the search for m/z values enabling this discrimination. Based on the very accurate mass information and the isotopic pattern provided by the
TOF MS analyzer, together with other available information, ten of these biomarkers and more than 50 metabolites, obtained
through phase I and phase II biotransformation reactions, were tentatively identified. Additionally, kinetic studies were
conducted on the metabolites identified as possible biomarkers; for most of the compounds concentrations were maximum in the
first two hours. 相似文献
953.
Núria Serrano José Manuel Díaz-Cruz Cristina Ariño Miquel Esteban 《Analytical and bioanalytical chemistry》2010,396(3):1365-1369
A commercially available screen-printed carbon electrode coated with an ex situ deposited bismuth film (BiSPCE) has been applied
to the determination of Pb(II) and Zn(II) ions in tap water (Barcelona water distribution network) by means of stripping voltammetry
(SV) and stripping chronopotentiometry (SCP). A good reproducibility of the measurements and a satisfactory agreement between
SV and SCP data were observed for both heavy metal ions. Although, in principle, the procedure could be also suited to the
determination of Cd(II), this species was not detected. The results were also consistent with the routine ICP-OES measurements
of the water distribution company, thus confirming the potential usefulness of such BiSPCE disposable devices for the analysis
of heavy metals in natural waters.
相似文献
954.
The influence of various small- and medium-size basis sets used in Hartree-Fock (HF) and density functional theory (DFT)/B3LYP calculations on results of quantum theory of atoms in molecules based (QTAIM-based) analysis of bond parameters is investigated for several single, double, and triple covalent bonds. It is shown that, in general, HF and DFT/B3LYP methods give very similar QTAIM results with respect to the basis set. The smallest 6-31G basis set and DZ-quality basis sets of Dunning type lead to poor results in comparison to those obtained by the most reliable aug-cc-pVTZ. On the contrary, 6-311++G(2df,2pd) and in a somewhat lesser extent 6-311++G(3df,3pd) basis sets give satisfactory values of QTAIM parameters. It is also demonstrated that QTAIM calculations may be sensitive for the method and basis set in the case of multiple and more polarized bonds. 相似文献
955.
Maciej Jabłoński 《Central European Journal of Chemistry》2010,8(1):149-154
Enriched titanium raw materials with high titanium content called titanium slags are received by the electrothermal reduction
of ilmenite. Titanium slags are most frequently used in the titanium dioxide industry. The reaction of titanium slags with
sulphuric acid is strongly exothermic and creates danger of thermal explosion. Kinetics of this reaction depends on the parameters
such as temperature of initiation, sulphuric acid concentration and dimension of particles of titanium slag. The reaction
of titanium slag with sulphuric acid was investigated at non-isothermal conditions in a special construction calorimeter.
The observed thermal power changes in the calorimeter (“calorimeter run”), are the basis for estimation of reaction kinetics.
A proposed model describing the thermal power changes and taking into account the moment of initiation of reaction is presented.
The calorimetric investigations showed, that reaction rate of titanium slags with sulphuric acid depends on initial temperature
of reaction, size of particles of titanium raw material and sulphuric acid concentration. 相似文献
956.
E. Mateus R.C. Barata Jitka Zrostlíková M.D.R. Gomes da Silva M.R. Paiva 《Journal of chromatography. A》2010,1217(11):1845-1855
The chemical composition of the needles of P. pinea, P. pinaster, P. halepensis, P. nigra, P. brutia, P. patula, P. radiata, P. taeda, P. elliotti, P. kesiya, P. sylvestris and P. eldarica was investigated. Headspace solid-phase microextraction and steam distillation extraction were used to collect the volatile fractions. Samples were analyzed using one-dimensional gas chromatography (1D-GC) and comprehensive two-dimensional gas chromatography (GC × GC) associated with a quadrupole and a time-of-flight mass detectors. Results showed that the analytical capabilities of 1D-GC are partially limited by the separation power of the columns. The higher sensibility and the absence of peak skewing of the time-of-flight mass analyzer, with the use of automated peak finding and deconvolution algorithms, allowed for the detection of trace components with qualitative full spectra and the extraction of true mass spectra from coeluting compounds, promoting their reliable identification and thus significantly improving results obtained by 1D-GC/MS, when using a quadrupole mass analyzer. The use of GC × GC resulted in enhanced separation efficiency and increased signal to noise ratio (sensitivity) of the analytes, maximizing mass spectra quality and improving compound detection and identification. This work shows the use of 1D-GC/ToFMS for the analysis of pine needles volatiles, achieving the detection of 177 compounds, that is more than twice the number previously identified by standard 1D-GC/MS. The analysis by GC × GC for the same sample allowed the detection of 212 compounds. The enantioselective GC × GC analysis performed for all the Pinus spp. under study achieved the detection of 422 different compounds. Cross-over phenomena according to operational conditions are highlighted and discussed. 相似文献
957.
Fátima C.M. Portugal Moisés L. Pinto João Pires J.M.F. Nogueira 《Journal of chromatography. A》2010,1217(23):3707-3710
Polyurethane (PU) foams were applied for stir bar sorptive extraction of five triazinic metabolites (desethyl-2-hydroxyatrazine, desisopropylatrazine, desethylatrazine, 2-hydroxyatrazine and desethylterbuthylazine) in water matrices, followed by liquid desorption and high performance liquid chromatography with diode array detection (SBSE(PU)-LD/HPLC-DAD). The optimum conditions for SBSE(PU)-LD were 5 h of extraction (1000 rpm) and 5% (v/v) of methanol for the analysis of desethyl-2-hydroxyatrazine and 2-hydroxyatrazine, 15% (w/v) of sodium chloride for the remaining compounds and acetonitrile as back-extraction solvent (5 mL) under ultrasonic treatment (60 min). The methodology provided recoveries up to 26.3%, remarkable precision (RSD < 2.4%), excellent linear dynamic ranges between 5.0 and 122.1 μg/L (r2 > 0.9993) and convenient detection limits (0.4-1.3 μg/L). The proposed method was applied in the analysis of triazinic metabolites in tap, river and ground waters, with remarkable performance and negligible matrix effects. The comparison of the recoveries obtained by PU and commercial stir bars was also performed, where the yields achieved with the former were up to ten times higher proving that PU is appropriate for analysis at trace level of this type of polar compounds in water matrices. 相似文献
958.
959.
Javier A. Cabeza Prof. Ignacio del Río Prof. Enrique Pérez‐Carreño Prof. Vanessa Pruneda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(18):5425-5436
The cationic cluster complexes [Ru3(μ‐H)(μ‐κ2N,C‐L1 Me)(CO)10]+ ( 1 +; HL1 Me=N‐methylpyrazinium), [Ru3(μ‐H)(μ‐κ2N,C‐L2 Me)(CO)10]+ ( 2 +; HL2 Me=N‐methylquinoxalinium), and [Ru3(μ‐H)(μ‐κ2‐N,C‐L3 Me)(CO)10]+ ( 3 +; HL3 Me=N‐methyl‐1,5‐naphthyridinium), which contain cationic N‐heterocyclic ligands, undergo one‐electron reduction processes to become short lived, ligand‐centered, trinuclear, radical species ( 1 – 3 ) that end in the formation of an intermolecular C? C bond between the ligands of two such radicals, thus leading to neutral hexanuclear derivatives. These dimerization processes are selective, in the sense that they only occur through the exo face of the bridging ligands of trinuclear enantiomers of the same configuration, as they only afford hexanuclear dimers with rac structures (C2 symmetry). The following are the dimeric products that have been isolated by using cobaltocene as reducing agent: [Ru6(μ‐H)2{μ6‐κ4N2,C2‐(L1 Me)2}(CO)18] ( 5 ; from 1 +), [Ru6(μ‐H)2{μ6‐κ4N2,C2‐(L2 Me)2}(CO)18] ( 6 ; from 2 +), and [Ru6(μ‐H)2{μ4‐κ8N2,C6‐(L3 Me)2}(CO)18] ( 7 ; from 3 +). The structures of the final hexanuclear products depend on the N‐heterocyclic ligand attached to the starting materials. Thus, although both trinuclear subunits of 5 and 6 are face‐capped by their bridging ligands, the coordination mode of the ligand of 5 is different from that of the ligand of 6 . The trinuclear subunits of 7 are edge‐bridged by its bridging ligand. In the presence of moisture, the reduction of 3 + with cobaltocene also affords a trinuclear derivative, [Ru3(μ‐H)(μ‐κ2N,C‐L3′ Me)(CO)10] ( 8 ), whose bridging ligand (L3′ Me) results from the formal substitution of an oxygen atom for the hydrogen atom (as a proton) that in 3 + is attached to the C6 carbon atom of its heterocyclic ligand. The results have been rationalized with the help of electrochemical measurements and DFT calculations, which have also shed light on the nature of the odd‐electron species, 1 – 3 , and on the regioselectivity of their dimerization processes. It seems that the sort of coupling reactions described herein requires cationic complexes with ligand‐based LUMOs. 相似文献
960.
Ricardo J. N. Bettencourt da Silva Maria Filomena G. F. C. Camões 《Accreditation and quality assurance》2010,15(12):691-704
The dispersion of results from proficiency tests for the analysis of pesticide residues in foodstuffs suggests that improvements
in the compatibility of measurement results are needed. Currently observed divergences can make the evaluation conclusion
on foodstuffs compliance with certain legislation dependent on the consulted laboratory. This work discusses the origin and
impact of this lack of compatibility, following the metrological concepts presented at the latest version of the “International
Vocabulary of Metrology” (VIM3), thus allowing for a clear diagnostic of the problem. The reporting of results from different
measurement methods uncorrected for the observed analyte recovery makes them traceable to different “operationally defined
measurement procedures” (VIM3) and, therefore, not comparable. When results from different measurement methods are reported
corrected for analyte recovery, R, and R is different for spiked and incurred residues, measurement results may be not compatible if this effect is not considered
on the uncertainty budget. This discussion is illustrated with metrological models for any possible combination of “measurement
performance” and “maximum residue level”. These models are complemented with experimental data of the analysis of pesticide
residues in a sample of ginseng powder from a proficiency test. The adopted experimental design allowed the identification
of additional threats to metrological compatibility in this field. Solutions to the faced problem are discussed for practicability
and impact on regulatory issues. The use of a universal “reference measurement procedure” proves to be the most feasible way
of ensuring comparability of measurements in this field. 相似文献