1,720,987 research outputs found
Tecnica SdFFF ed estrazione selettiva
No full textLa Sedimentation Field Flow Fractionation (SdFFF) è una tecnica
separativa ad alta risoluzione di ampia applicazione nella caratterizzazione dei sistemi dispersi. Campioni di materiale particolato sospeso nel fiume Po e di particolato atmosferico, raccolto nell’area urbana di Ferrara ed opportunamente trattato, sono esempi di possibili applicazioni della tecnica SdFFF, accoppiata a tecniche spettroscopiche, per la separazione
dimensionale di colloidi ambientali e della determinazione di alcuni metalli
Chiral ligand exchange chromatography on an RP HPLC column coated with a new chiral selector derived from L-spinacine
No full textA commercial reversed-phase (RP) C18 HPLC column has been dynamically coated with the
chiral selector N<n-decyI-L-spinacine and then loaded with copper(ll) ions. Several racemic
mixtures of underivatized amino acids and oligopeptides were resolved on the column by chiral
ligand-exchange chromatography. The most important experimental conditions affecting
column efficiency, retention, and selectivity (temperature and mobile phase flow rate and
composition) were extensively investigated
‐spinacine
No full textIncreasing attention has been devoted in the last decades to chiral chromatography, principally to the HPLC techniques using a chiral stationary phase. Many chiral HPLC columns are commercially available, but, unfortunately, they are most often rather expensive. A cheap alternative to the commercial chiral columns is the dynamic-coating procedure of a standard achiral stationary phase with a chiral selector containing both a chiral domain and a chain or a group able to tightly (but non- covalently) bind the achiral support. This is the case of Nτ-decyl-L-spinacine, already successfully employed to dynamically cover a reversed-phase column in order to separate racemic mixtures of amino acids through the Ligand–Exchange mechanism. In the present work, the same chiral selector is employed to separate racemic mixtures of amino acids and oligopeptides, in the absence of metal ions: no coordination complex is formed, but only electrostatic and weak non-bonding interactions, between the chiral phase and the analytes, are responsible for the observed enantioselectivity. The new method is simpler than the previous one, very effective in the case of aromatic amino acids and oligopeptides and also suitable for preparative purposes
Caratterizzazione di materiale particolato di interesse ambientale mediante tecnica combinata SdFFF-ETAAS
No full textAtmospheric particulate matter: dimensional and elemental characterization
No full textAn integrated analytical approach , based on the employement of separative techniques, the gravitational sedimentation and the Sedimentation Field Flow Fractionation (SdFFF), combined with the identificative Inductive Coupled Plasma –Atomic Emission Spectroscopy (ICP-AES) technique, is presented for the elemental and dimensional characterization of atmospheric fine aerosols and, in particular, for its submicronic fraction, obtained by gravitational sedimentation (operational cut-off <2 micron). The natural sample particle matter <10 micron (PM10), was transferred from collection filters into slurry aqueous solution, via ultrasonic agitation. The direct slurry sample analysis by ICP-AES, evaluated to be accurate enough for the investigation of heavy metal occurrence, was shown able to provide prompt analytical answer, thanks to its instrumental multi-elemental performances, either for the total PM10 sample and relative sub-samples, obtained by gravitational sedimentation. The considered heavy metals of environmental interest were Cd, Cr, Cu, Ni, Mn and Pb. The SdFFF fractionation was applied to the sub-sample <2 micron to determine the particle size distribution. The collected fractions were analyzed by Scanning Electron Microscopy (SEM)
Field Flow Fractionation techniques applied to the analysis of aquatic colloids and sediments
No full textThermodynamic and spectroscopic investigation on Copper complexes with oligopeptides containing two Histidine residues
No full textSynthesis of glycil-L-spinacine and study of its protonation and Cu(II) complex-formation equilibria, in aqueous solution
No full textA new dipeptide, glycil-L-spinacine, has been synthesised and fully characterised. Protonation constants have been determined and binary Cu(II) complex formation equilibria investigated in an aqueous solution (25 °C, I = 0.1 mol dm-3, KNO3) using the potentiometric and spectrophotometric techniques. Mononuclear and binuclear complex species have been found to form. Binding sites and structure hypotheses are discussed on the basis of available experimental and literature data
Copper and nickel complex-formation equilibria with Lys-Gly-His-Lys, a fragment of the matricellular protein SPARC
No full textComplex-formation equilibria of the tetrapeptide Lys-Gly-His-Lys with the Cu(II) and the Ni(II) ions have been studied in aqueous solution, at I=0.1 mol dm-3 (KNO3) and T=25 C. Protonation and complex-formation constants have been
potentiometrically determined. The structure of the main complex species is discussed on the basis of thermodynamic data obtained
by direct calorimetry as well as the CD, ESR and electronic spectra. The participation of two amide nitrogens in complex-formation
is suggested for both the metal ions, while no evidence supports the participation of the NH2 side groups of Lys residues in
coordination
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