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An optode for Cu(II), Cd(II), Zn(II) and Hg(II) sensing has been designed by immobilization of dithizone on a triacetylcellulose membrane (mem-DTZ). The sorption of the metal ions on the mem-DTZ has been thoroughly characterized, in particular sorption kinetics, sorption isotherms and profiles as a function of the pH have been studied. Methods to assess the concentrations of the cations, both individually and in a mixture, in unknown samples, have been developed. In particular, UV-vis spectra and digital information of pictures taken by using a common desktop scanner, of the mem-DTZ sensor after equilibration with different solutions, were acquired and they were correlated with the concentration of the metal ions in solutions. For the single analyte determination, the RGB parameters of the pictures were subjected to Principal Component Analysis (PCA); otherwise the UV-vis spectra of a mixture of two cations were elaborated by Partial Least Squares (PLS) Regression. The membrane responds to the divalent cations by changing colour reversibly. The response time of the mem-DTZ is about 1 h for Cd(II), Hg(II) and Zn(II), but longer for Cu(II): more than 10 h are required. The linear interval is in the range of about 10−7 to 10−5 M for all metal ions. The limit of detection (LOD) is around 10−6 M for Cu(II), Cd(II) and Hg(II); for Zn(II) a lower LOD of 10−7 M is obtained. The applicability of mem-DTZ to real samples has been proved by analysis of the four metal cations in a certificate material (Sewage Sludge CC136A), white wine, and drinking water samples.

Successful in vivo chelation treatment of iron(III) overload pathologies requires that a significant fraction of the administered drug actually chelates the toxic metal. Increased mobilization of the iron(III) in experiments on animals or humans, most often evaluated from urinary output, is usually used as an assessment tool for chelation therapy. Alternatively, the efficiency of a drug is estimated by calculating the complexing ability of a chelating agent towards Fe(III). The latter is calculated by the pFe value, defined as the negative logarithm of the concentration of the free metal ion in a solution containing 10 μM total ligand and 1 μM total metal at a physiological pH of 7.4. In theory, pFe has to be calculated taking into account all the complexation equilibria involving the metal and the possible ligands. Nevertheless, complexation reactions in complex systems such as serum and urine may hardly be accurately modelled by computer software. The experimental determination of the bioavailable fraction of iron(III) in biological fluids would therefore be of the utmost relevance in the clinical practice. The efficiency of the therapy could be more easily estimated as well as the course of overload pathologies. In this context, the aim of the present work was the development of a sensor to assess the free iron directly in biological fluids (urine) of patients under treatment with chelating agents. In the proposed device (DFO-MS), the strong iron chelator deferoxamine (DFO) is immobilized on the MCM-41 mesoporous silica. The characterization of the iron(III) sorption on DFO-MS was undertaken, firstly in 0.1 M KNO3, then directly in urine samples, in order to identify the sorption mechanism. The stoichiometry of the reaction in the solid phase was found to be: with an exchange constant (average value) of log βex = 40(1). The application of DFO-MS to assess pFe in SPU (Simulating Pathology Urine) samples was also considered. The results obtained were very promising for a future validation and subsequent application of the sensor in samples of patients undergoing chelation therapy.

A method for the determination of the total metal ion concentration in samples of unknown composition after separation on a chelating resin was applied to the determination of aluminium(III) concentration in real freshwater samples, using Chelex 100 as a sorbing resin. The method, called chelating resin titration, was previously tested on synthetic samples, and allows also the evaluation of the side reaction coefficient [αM(I)] of the metal ion in the presence of the resin, which is useful for the study of metal speciation. To obtain this information, the sorption equilibria of aluminium(III) on Chelex 100 under the experimental conditions must be exactly known. These equilibria were investigated according to a previously reported method, based on the determination of the sorption curves of aluminium on Chelex 100 from solutions of known composition, sometimes containing chelating substances. It was found that the sorption of aluminium on Chelex 100 takes place by formation of three species, AlL, AlL(OH) and Al(OH)3. The corresponding exchange coefficients were determined. Despite the fact that Chelex 100 sorbs aluminium(III) strongly, it was found that the sorption from fresh waters was not quantitative, which was ascribed to the strong complexation of aluminium in the samples considered. The values of αM(I) of aluminium in some freshwater samples at natural pH and acidified up to pH 3 were determined. They were found to be much higher than those ascribable to hydrolysis or to inorganic and organic ligands present in natural waters, being for instance 1012.1 at pH 7.48 and 107.5 at pH 4.88. A similar determination carried out in a 10–3 mol kg–1 sodium chloride solution containing a known amount of aluminium at pH ≈ 8 gave log αM(I) = 14, completely ascribable to hydrolysis, showing that an accurate evaluation can be obtained by the proposed method.

The synthesis and the physico-chemical characterisation of a novel solid phase, designed for iron(iii) sorption, are presented. The solid (indicated in the following as DFO-SAMMS) is made with a hydroxamate siderophore, the deferoxamine (DFO), covalently bound on a self-assembled monolayer on mesoporous silica (SAMMS). The data demonstrate that the DFO molecules are bound to the solid material, grafted on the surface and do not enter the silica pores. A new one-pot synthesis is presented in which DFO is dissolved in DMSO, and left to react with GPTMS with stirring overnight. In the same mixture, SAMMS is added to get the final product. The optimisation of experimental conditions of this novel one-pot synthesis is presented, with results indicating that a temperature of 90 °C, for the reaction between DFO and GPTMS, and the use of MCM-41 silica are the most convenient conditions. The kinetics of sorption reveals that the iron uptake is relatively fast, around 100 min at pH = 2.5, and from the sorption profile of iron(iii), the estimated capacity of the product obtained under optimized conditions was higher than 0.3 mmol g(-1). The results found in the present research are very promising for application in real biological samples.

A method for determining iodate and iodine(+1) in aqueous solutions is proposed. The assay is similar to a previously described method for the determination of iodide and iodine(0), which were titrated with standard iodate in hydrochloric acid solution. A sample solution made 0.5–1.5 M in hydrochloric acid is titrated with a standard iodide solution and monitored spectrophotometrically at 230 nm. The species involved have strong absorbances that are well differentiated at this wavelength. By combining the two titrations it is possible to resolve any mixture of species of iodine in different oxidation states. The precision of the method (standard deviation) is the same both when determining a single species (IO–3, I+, I2 or I–) and a mixture, and is equal to 2 × 10–7M. Chloride and bromide, even at very high concentrations, do not interfere.

1-(Tetrazolylazo)-2-hydroxynaphthalene-3,6-disulphonic acid (T-azo-R), 2-(tetrazolylazo)-1,8-dihydroxynaphthalene-3,6-disulphonic acid (T-azo-C), 1-(thiazolylazo)-2-hydroxynaphthalene-3,6-disulphonic acid (3,6-disulpho-TAN) and 2-(thiazolylazo)-1,8-dihydroxynaphthalene-3,6-disulphonic acid (TAAC) have been investigated as spectrophotometric reagents for palladium(II). Stable water-soluble complexes are formed, even in 1 M perchloric acid, and at this acidity the considered reagents are specific for palladium(II). A number of donor anions interfere in the palladium(II) determination, mainly by competing with the azo dyes for complexation with the metal ion. The first three reagents were found to form 1:1 (metal to ligand) complexes, while the last forms a 1:2 complex, with a molar absorptivity more than twice that of the others. In all instances the spectra of the complexes are well resolved with respect to those of the free ligands. Concentrations of palladium(II) ranging from 2 × 10–6 to 1.5 × 10–4M can be determined spectrophotometrically. The accuracy (relative difference between the known and the found concentration) is 1% at a concentration of 2 × 10–5M.