1,721,081 research outputs found
A simplex-optimized chromatographic separation of fourteen cosmetic preservatives: Analysis of commercial products
No full textIon-interaction RP-HPLC separation of inorganic anions on porous graphitized carbon stationary phase. Comparison with ODS stationary phase
No full textHPLC-DAD-MSn to investigate the photodegradation pathway of nicosulfuron in aqueous solution
No full textThe environmental interest of sulfonylurea herbicides was derived from the possibility of diffusion and penetration of these herbicides in the deepest layers of the ground, in particular in sandy or clay-poor soils, up to the ground waters; another interest of the study is their natural degradation pathway which leads to the formation of new species that are potentially more toxic and stable than the precursor herbicides. In this case, a lower persistence in the environment unfortunately does not correspond to a lower toxicity: hence, the importance of the identification of the species can be potentially formed. Here, nicosulfuron, a typical sulfonylurea herbicide, is considered in order to outline the environmental fate of the molecules generating from the simulation of one of the natural processes that can occur, i.e. photoinduced degradation. Aqueous nicosolfuron solutions underwent a simulated sun irradiation: the new species formed during the degradation process were identified by HPLC-DAD-MS/MS and a degradation pathway was proposed. The effect of temperature and the contribution of the hydrolysis were also evaluated. The use of ESI in both positive ion (PI) and negative ion (NI) mode and APCI in PI mode permits to obtain integrated information about the transformation products that can form; moreover, a study of the total ion chromatogram followed by the extraction of the SIM chromatograms of the most intense m/z signals made possible the identification of five possible photodegradation transformation products
A new approach to the statistical treatment of 2D-maps in proteomics using fuzzy logic
No full textA new approach to the statistical treatment of 2D-maps has been developed. This method is based on the use of fuzzy logic and allows to take into consideration the typical low reproducibility of 2D-maps. In this approach the signal corresponding to the presence of proteins on the 2D-maps is substituted with probability functions, centred on the signal itself. The standard deviation of the bi-dimensional gaussian probability function employed to blur the signal allows to assign different uncertainties to the two electrophoretic dimensions. The effect of changing the standard deviation and the digitalisation resolution are investigated
Rationalization of liquid assisted grinding intercalation yields of organic molecules into layered double hydroxides by multivariate analysis
No full textThe Liquid Assisted Grinding (LAG) method for the fast and facile preparation of organic-intercalated Layered Double Hydroxide (LDH) nanocomposites allowing the production of low cost, stable and efficient functional materials, is here employed to rationalize the features of the organic compounds that most likely undergo easy intercalation. LAG method was exploited to determine in a short time which molecules can be successfully intercalated into LDH. A straightforward rationalization of the intercalation yield results was not possible since no individual feature (such as bulkiness or pK(a)) could alone describe the intercalation behaviour of the whole set of molecules. Therefore, Principal Component Analysis (PCA) together with the use of molecular descriptors to classify molecules, were mutuated from the chemometric approach, widely used in analytical chemistry and applied successfully, for the first time, to a novel area of materials science. A set of molecular descriptors were chosen to cover different features of the molecule (physicochemical, topological, geometrical etc.) and then screened by statistical methods to understand which descriptors affected the intercalation yield. Then PCA allowed us to highlight the presence of various mechanisms, involved in the LAG intercalation and to separate the samples along PC3 as a function of yield. Finally, the classification tree method allowed us to understand the various mechanisms of intercalation and to classify molecules in groups, related to their yield. These groups can be used to estimate the expected yield as a function of the molecular descriptors. The molecules more apt to LAG have medium-low molecular weight, high flexibility and low refractivity. Conversely large and hydrophobic molecules and, surprisingly, small but rigid molecules have a small success rate concerning LAG intercalation. The behaviour of this last class of molecules, that should be in principle easily intercalated by LAG but which was identified by the present study as a difficult case, was thus tested using two molecules and the prediction of the chemometric study was confirmed
Sorption and desorption behaviour of chloroanilines and chlorophenols on montmorrillonite and kaolinite
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