1,721,112 research outputs found
Programma Nazionale di Ricerche in AntartideStudio e caratterizzazione di microcostituenti chimici con proprietà complessanti forti nell'ambiente marino dell' Antartide, in relazione al ciclo stagionale di formazione/scioglimento del pack-ice
No full textQuesto progetto di ricerca si propone di studiare e caratterizzare alcuni tra i piu' importanti microcostituenti chimici dell'ambiente marino antartico con forti proprieta' complessanti nei confronti di alcuni metallo ioni, come Cu(II), Cd(II), Mn(II), Zn(II) e Fe(III. Sebbene la concentrazione di questi componenti nelle acque marine sia spesso dell'ordine delle nanomoli/litro, o anche inferiore, essi giocano un ruolo molto importante nel comportamento biogeochimico dei metalli in traccia, ad esempio influenzando la mobilizzazione oppure la precipitazione nei sedimenti, la permanenza nella fase acquosa oppure l'adsorbimento attraverso le membrane biologiche. I complessanti forti verranno caratterizzati dal punto di vista strutturale e termodinamico, tramite l'impiego di idonei metalli 'sonda'. Saranno infine valutate le fonti di tali sostanze complessanti forti e la loro variazione per effetto del processo stagionale di scioglimento/formazione del ghiaccio marino
Towards a zero-blank, preconcentration-free voltammetric method for iron analysis at picomolar concentrations in unbuffered seawater
No full textA method with negligible blank values for the determination of total iron at the ultratrace level in seawater has been optimized and validated exploring for the first time the performance and limitations of Adsorptive Cathodic Stripping Voltammetry (AdCSV) in non-buffered solutions. The method is based on the CSV determination of the Fe-dihydroxynaphthalene (DHN) complex using atmospheric oxygen to catalytically enhance the signal via hydrogen peroxide formation at the electrode/solution interface. The accumulation of hydroxyl ions, the by-product of the hydrogen peroxide formation, increased the pH in the diffusion layer in the absence of buffer bringing it to 9, the optimum for the analytical performance of the method. Voltammograms in UV digested seawater showed no stability or reproducibility drawbacks. The negligible, lower than 5 pM, blank level, is due to the simplicity of the procedure requiring no sample manipulation and a maximum of three reagents only, necessarily the ligand DHN and a base only for those samples previously acidified to raise the pH to circumneutral values (here HCl and NH3 according to common trace metals protocols). These reagents do not require cleaning before use, further simplifying the overall procedure. Analysis of seawater previously acidified at pH ~1.5 with HCl and neutralized with ammonia showed interferences due to the buffering properties of the NH3/NH4Cl couple and the transient formation of a volatile electroactive interference that can be easily removed by simply allowing a set time before analysis. In general, the proposed method features several advantages, including high sample throughput, an excellent limit of detection at 12 pM, minimum sample handling (no preconcentration or change of matrix is required), cost effectiveness and mainly a negligible blank. The method was successfully validated using open ocean consensus samples (SAFe D2 and S)
A viscous film sample chamber for laser ablation inductively coupled plasma - mass spectrometry
No full textContributi fluviali alla contaminazione da elementi in traccia del primo bacino del lago di Como
No full text
Accuracy and precision in speciation analysis: the case of Competitive Ligand Equilibration coupled to Cathodic Stripping Voltammetry detection of the labile fraction
No full text
Modifications of organic and inorganic materials induced by interaction with ultrashort laser pulses
No full text- …
