Annali di chimica最新文献

Quantitative structure–property relationship (QSPR) analysis has been carried out to a series of fatty, amino and dicarboxylic acids to model their GC retention times. A genetic partial least square method (GAPLS) was applied as a variable selection tool. Modeling of retention times of these compounds as a function of the theoretically derived descriptors was established by multiple linear regression (MLR) and artificial neural network (ANN). The neural network employed here is a connected back-propagation system with a 3-4-1 architecture. Three topological indices for these compounds, namely, mean information index on atomic composition (AAC), average connectivity index chi-0 (X0A) and total information index of atomic composition (IAC) taken as inputs for the regression models. The results indicate that the GA is a very effective variable selection approach for QSPR analysis. The comparison of the two regression methods used showed that ANN has better prediction ability than MLR. The statistical figure of merits of the two models showed the successful modeling of the retention times with molecular descriptors.

The compound URB754 was recently identified as a potent inhibitor of the endocannabinoid-deactivating enzyme monoacylglycerol lipase (MGL) by screening of a commercial chemical library. Based on HPLC/MS, NMR and EI/MS analyses, the present paper shows that the MGL-inhibitory activity attributed to URB754 is in fact due to a chemical impurity present in the commercial sample, identified as bis(methylthio)mercurane. Although this organomercurial compound is highly potent at inhibiting MGL (IC₅₀ = 11.9±1.1 nM), its biological use is prohibited by its toxicity and target promiscuity.

A simple, selective and sensitized spectrophotometric method for determination of trace amounts of Fe³⁺ ion in tap and waste water solutions has been described. The spectrophotometric determination of Fe³⁺ ion using Ferron in the presence of N,N-Dodecytrimethylammonium bromide (DTAB) has been carried out. The Beer's law is obeyed over the concentration range of 0.05-2.6 μg mL^-1 of Fe³⁺ ion with the relative standard deviation (RSD %) <0.2 % and the molar absorptivity of complexes in pH 3.5 is 3.8×10³ L mol^-1 cm^-1.

Potentiometric pH titration has been used for prediction of protonation constants of ferron, and evaluating its stoichiometry and respective stability constant with Fe³⁺ ion. As it is obvious the most likely species of ferron alone and its complexes are LH (log=7.64), LH₂ (logK=10.52), LH₃ (logK=11.74) and ML₂ (logβ= 23.68), ML₃ (logβ= 23.68), ML₃H (logβ= 23.68), ML₃H₂ (logβ= 23.68) and ML(OH)₂ (logβ=23.68) respectively.

Mercury ion-selective electrodes (ISEs) were prepared with a polymeric membrane based on heterocyclic systems: 2-methylsulfanyl-4-(4-nitro-phenyl)-1-p-tolyl-1H-imidazole (I) and 2,4-diphenyl-1-p-tolyl-1H-imidazole (II) as the ionophores. Several ISEs were conditioned and tested for the selection of common ions. The electrodes based on these ionophores showed a good potentiometric response for Hg²⁺ ions over a wide concentration range of 5.0×10^-5-1.0×10^-1M with near-Nernstian slopes. Stable potentiometric signals were obtained within a short time period of 20 s. The detection limits, the working pH range of the electrodes were 1.0×10^-5 M and 1.6-4.4 respectively. The electrodes showed better selectivity for Hg²⁺ ions over many of the alkali, alkaline-earth and heavy metal ions. Also sharp end points were obtained when these sensors were used as indicator electrodes for the potentiometric titration of Hg²⁺ ions with iodide ions.

An analytical methodology was developed for the determination of 21 trace elements in suspended particulate matter (PM) using a microwave digestion procedure associated with an inductively coupled plasma mass spectrometry (ICP-MS). The dynamic reaction cell (DRC) of the instrument was carefully optimized to eliminate polyatomic species causing spectral interferences for three specified elements (Cr, Fe, Mn). With this method, the detection limits based on the analysis of seven quartz fibre filters (QFF) considering a one-week sample (250 ^m3) varied between 0.2 and 650 pg m^-3 for trace elements and between 2.1 and 5.6 ng m^-3 for major elements (Fe, Ti, Zn). The recovery of the analytes was tested with NIST SRM 1648 urban dust within 10 % of the certified values only for 3-4 mg of material. The first results were discussed for a field campaign which was carried out simultaneously in the heaviest traffic road tunnel of the centre of Nice and near the landing-taking-off runways in the international airport of Nice Côte d'Azur. The behaviour of some combustion tracers was especially studied.

A study to obtain more knowledge on funeral set in Greek age, (5^th Century, b.C.) was carried out on thirteen ancient unguentaria, small vessels used as containers of balms or ointments, founded in two different Sicilian necropolis: Adranon and Hymera. Every find was subjected to three extractions by increasing polarity solvents. All crude extracts, unsaponifiables and methyl esters of saponifiable fraction were analysed by GC-MS. Analysis showed difference between two groups of finds: the unguentaria from Adranon show abundant traces of lipids used in balm making, while those from Hymera resulted empty and buried for ritual purpose. Even if in the two towns, flourished in the same period, adopted probably different funerary uses.

Ceramic and glass are some of the more recent engineering materials and those that are most resistant to environmental conditions. They belong to advanced materials in that they are being developed for the aerospace and electronics industries. In the last decade, a new class of ceramic materials has been the focus of particular attention. The materials were produced with natural, renewable resources (wood or wood-based products). In this work, we have synthesised a new biomorphic ceramic material from oak wood and Si infiltration. After the material characterization, we have optimized the dissolution of the sample by acid attack in an oven under microwave irradiation. Experimental designs were used as a multivariate strategy for the evaluation of the effects of varying several variables at the same time. The optimization was performed in two steps using factorial design for preliminary evaluation and a Draper-Lin design for determination of the critical experimental conditions. Five variables (time, power, volume of HNO₃, volume H₂SO₄ and volume of HF) were considered as factors and as a response the concentration of different metal ions in the optimization process. Interactions between analytical factors and their optimal levels were investigated using a Draper-Lin design.