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91.
Current work has evaluated uncertainty associated to quantification of several organic compounds present in particulate matter of atmospheric aerosols, setting out the stages of analytical procedure that contribute most to the global uncertainty. Several sources of uncertainty have been identified, which were clustered into five main contributions: sampling, extraction, clean-up, derivatization and analysis. A discussion of the main contributions to the overall uncertainty is reported, allowing authors to locate the largest ones and plan future improvements. Combined uncertainties ranged between 10-18% (alkanes), 12-16% (PAHs), 10-18% (alcohols) and 9-21% (acids). The analytical procedure was validated by analysing a standard reference material (SRM1649a, urban dust). Also, the proposed method was applied to the analysis of four samples of particulate matter. 相似文献
92.
Three new compounds bearing furyl, aryl, or thienyl moieties linked to an imidazo-crown ether system (1, 2, and 3) were synthesized and fully characterized by elemental analysis, infrared, UV-vis absorption, and emission spectroscopy, X-ray crystal diffraction, and MALDI-TOF-MS spectrometry. The interaction toward metal ions (Ca(2+), Cu(2+), Ni(2+), and Hg(2+)) and F(-) has been explored in solution by absorption and fluorescence spectroscopy. Mononuclear and binuclear metal complexes using Cu(2+) or Hg(2+) as metal centers have been synthesized and characterized. Compounds 2 and 3 show a noticeable enhancement of the fluorescence intensity in the presence of Ca(2+) and Cu(2+) ions. Moreover compound 3 presents a dual sensory detection way by modification of the fluorimetric and colorimetric properties in the presence of Cu(2+) or Hg(2+). EPR studies in frozen solution and in microcrystalline state of the dinuclear Cu(II)3 complex revealed the presence of an unique Cu(2+) type. 相似文献
93.
de la Pinta N Martín S Urtiaga MK Barandika MG Arriortua MI Lezama L Madariaga G Cortés R 《Inorganic chemistry》2010,49(22):10445-10454
The family of compounds [Mn(dca)(2)(bpa)] (1), [Fe(dca)(2)(bpa)] (2), [Co(dca)(2)(bpa)] (3), [Zn(dca)(2)(bpa)] (4), and [Ni(dca)(bpa)(2)]dca·6H(2)O (5), with dca = dicyanamide and bpa = 1,2-bis(4-pyridyl)ethane, has been synthesized. These compounds have been characterized by single crystal (1, 2, 4, and 5) and powder X-ray diffraction (3), by Fourier transform infrared (FTIR), UV-vis, and electron paramagnetic resonance (EPR) spectroscopies, and by magnetic measurements. Compound 1 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 16.757(6), b = 9.692(3), and c = 13.073(4) ?, and β = 123.02(2)°; Compound 2 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 16.588(5), b = 9.661(3), c = 12.970(5) ?, and β = 123.16(3)°; Compound 4 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 16.519(2), b = 9.643(2), c = 12.943(2) ?, and β = 123.15(1)°; Compound 5 crystallizes in the monoclinic C2/c space group, Z = 4, with a = 18.504(4), b = 19.802(3), and c = 8.6570(18) ?, and β = 99.74(2)°. The compounds 1-4 are isostructural and show a one dimensional (1D) disposition, with the metal(II) ions bridged by double μ(1,5) dca ligands and unusually by a third bridge consisting of the bpa ligand, which adopts a very low torsion angle to accommodate in the structure. This kind of structure is unusual, even considering the voluminous bpa bridge. The compound 5 shows a 3D structure with layers of Ni-bpa joined by single dca bridges. Magnetic susceptibility measurements show antiferromagnetic couplings, increasing for 1-3. Compound 5 shows very slight antiferromagnetic interactions. 相似文献
94.
95.
Pedro R. Aranda Susana Moyano Luis D. Martinez Irma E. De Vito 《Analytical and bioanalytical chemistry》2010,398(2):1043-1048
A new, simple, and selective method for preconcentration and determination of Cr(VI) in aqueous samples. After adsorption
in “batch mode” on Aliquat 336-AC, determinations were made directly on the solid by X-ray fluorescence spectrometry, which
had the advantage of not requiring the step of elution of the chromium retained. The enrichment factor was calculated considering
that the tablets obtained from 10 mL solution of Cr(VI) (1000 μg L-1) had a final thickness of 0.64 mm and a diameter of 16.7 mm; the volume deposited on the pellet was 0.14 cm3. The preconcentration factor obtained was 71-fold, which was highly satisfactory for chromium trace analysis by XRF. Finally,
the method was successfully applied to the determination of Cr(VI) in drinking water samples. 相似文献
96.
Classification of wines from five Spanish origin denominations by aromatic compound analysis 总被引:1,自引:0,他引:1
Wine is a complex matrix in which aroma compounds play an important role in the characterization of the flavor pattern of a given wine. Twelve volatile compounds were determined in 244 samples of Spanish red wines from different denominations of origin: Rioja, Navarra, Valdepe?as, La Mancha, and Cari?ena. The samples were analyzed by GC using headspace solid-phase microextraction. The concentration (mg/mL) intervals obtained were 3-methyl-butyl acetate (3.9 to 116), 3-methyl-1-butanol (93 to 724), ethyl hexanoate (0.8 to 39), 1-hexanol (0.3 to 6.7), ethyl octanoate (1.4 to 41), diethyl succinate (0.2 to 13), 2-phenyl ethyl acetate (0 to 5.3), hexanoic acid (0 to 8.3), geraniol (0 to 3.0), 2-phenylethanol (1.5 to 56), octanoic acid (0 to 20), and decanoic acid (0 to 3.3). Wines were classified by multivariate statistical methods: principal component analysis, and lineal discriminant analysis. A correct differentiation among wines according to their origin was obtained by lineal discriminant analysis. 相似文献
97.
Mata S Cortijo V Caminati W Alonso JL Sanz ME López JC Blanco S 《The journal of physical chemistry. A》2010,114(43):11393-11398
The Fourier transform microwave spectra of the hydrated forms of the tautomeric pair 2-pyridinone/2-hydroxypyridine (2PO/2HP) have been investigated in a supersonic expansion. Three hydrated species, 2PO-H?O, 2HP-H?O, and 2PO-(H?O)?, have been observed in the rotational spectrum. Each molecular complex was confidently identified by the features of the 1?N quadrupole hyperfine structure of the rotational transitions. The presence of water affects the tautomeric equilibrium -N═C(OH)- ? -NH-C(═O)-, which is shifted to the enol form for the bare molecules 2PO/2HP but to the keto tautomer for the hydrated forms. 相似文献
98.
A problem of decision making under uncertainty in which the choice must be made between two sets of alternatives instead of two single ones is considered. A number of choice rules are proposed and their main properties are investigated, focusing particularly on the generalizations of stochastic dominance and statistical preference. The particular cases where imprecision is present in the utilities or in the beliefs associated to two alternatives are considered. 相似文献
99.
100.
Pharmacokinetics (PK) is a branch of pharmacology dedicated to the study of the time course of drug concentrations, from absorption to excretion from the body. PK dynamic models are often based on homogeneous, multi-compartment assumptions, which allow to identify the PK parameters and further predict the time evolution of drug concentration for a given subject. One key characteristic of these time series is their high variability among patients, which may hamper their correct stratification. In the present work, we address this variability by estimating the PK parameters and simultaneously clustering the corresponding subjects using the time series. We propose an expectation maximization algorithm that clusters subjects based on their PK drug responses, in an unsupervised way, collapsing clusters that are closer than a given threshold. Experimental results show that the proposed algorithm converges fast and leads to meaningful results in synthetic and real scenarios. 相似文献