Giorgio Ostacoli

Determination and identification by high-performance liquid chromatography and spectrofluorimetry of twenty-three aromatic sulphonates in natural waters

Abstract A method for detecting and identifying 23 aromatic sulphonates in natural waters was optimized. Samples were pretreated by solid-phase extraction in order to eliminate interferents and to preconcentrate the analytes. Separation of the extracted analytes was accomplished by ion-pair HPLC with fluorimetric detection; the eluent composition and pH were optimized. The detection limits lie in the low μg 1−1 range. Some of the investigated compounds were found in the water of the river Bormida (N.W. Italy). Unknown components were identified from their fluorescence spectra.

Ultraviolet–circular dichroism spectra for structural analysis of copper(II) complexes with aliphatic and aromatic ligands in aqueous solution

An attempt has been made to identify the characteristic positions, and their eventual displacements with changing co-ordination, of the charge-transfer bands involving donor groups located on molecules of biological interest [L-malic acid, N-acetyl-L-aspartic acid, (1R,2R)-cyclohexane-1,2-diamine, L-alanyl-L-alanine, L-γ-glutamyl-L-Iµ-lysine, N-acetyl-L-histidine, β-alanyl-L-histidine and N-benzoylglycyl-L-histidyl-L-leucine] such as carboxylate, alcoholate, amine, deprotonated peptide and imidazole. Information about the species formed in solution was obtained by means of pH-metric readings while ultraviolet–circular dichroism spectra were recorded, at fixed pH values, 298 K and I= 0.1 mol dm–3, for the proton–ligand and proton–copper(II)–ligand systems, in order to evaluate a spectrum for each complex formed in solution. Intraligand and charge-transfer bands were assigned for each spectrum with the aim of relating spectral features to the structure of the species formed in solution.

Pollution of a river basin and its evolution with time studied by multivariate statistical analysis

Abstract A set of quantitative analytical data for 13 rivers belonging to the basin of the Tanaro (Piedmont region, north-western Italy) has been processed by multivariate statistical techniques. The original matrix, which refers to the year 1990, consisted of 20 chemical and physico-chemical variables, determined at 44 sampling sites. The following methods have been used for the treatment of the data: cluster analysis (unsupervised pattern recognition), factor analysis, variable selection by Fisher weights. A comparison has also been made between the data referring to 1990 and to 1978 in order to investigate the evolution of the environmental situation for the Tanaro basin after such a lapse of time. This comparison has been carried out by processing the 3-D matrix which collects the data of the two different periods.

Comparison between microwave and conventional heating procedures in Tessier's extractions of calcium, copper, iron and manganese in a Lagoon sediment

The results of Tessiers extraction of calcium, copper, iron and manganese in sediments using conventional and microwave heating were compared. The metals were determined by atomic absorption spectrometry with flame and electrothermal atomization. Magnesium chloride (extractant of exchangeable fraction) was replaced with ammonium acetate. Sediments collected from the Venice lagoon were analysed. The results showed that microwave heating produces results comparable to those of conventional heating with a much shorter operating time.

Ionic strength dependence of formation constants. Part 4. Potentiometric study of the system Cu2+-Ni2+-citrate

SummaryThe ternary Cu2+-Ni2+-citrate (cit3−) system was investigated potentiometrically in aqueous solution, at different temperatures, 10≤t≤45°C, and ionic strengths, 0.03≤I≤0.8 mol dm−3, using potassium nitrate or tetraethylammonium bromide as background salt. Since the citrate anion forms weak complexes with potassium, the stability constants here reported differ according to whether the potassium association is considered or not. In the presence of both Cu2+ and Ni2+, the mixed metal species, [CuNi(cit)2H−2]4− is formed with citrate in solution, in addition to the various binary complexes. We have obtained the dependence for all the formation constants on ionic strength and temperature. The previous suggestions concerning a general equation for describing the dependence, log β=f(I), are confirmed; from the study of log β=f(T) we have obtained the values of thermodynamic parameters. The dependence of ΔH on ionic strength is discussed.

Some complexes of azide ion with metal ions in solution

Abstract Spectrophotometric measurements made in aqueous solutions containing Cu++ and N3− ions, show the formation of the complex ion CuN3+. The stability constant of this complex has been determined, and its value is 2.3 × 102 at ionic strength 0.20, and 2.8 × 102 at ionic strength 0.10. The value of pK, extrapolated to zero ionic strength, lies in the range of −2.9 and −3.0. (Temperature 20°C). Spectrophotometric titrations in mixtures of 2-ethoxy-ethanol and water, seem to reveal the presence of higher complexes, like those, whose salts have been already prepared in the solid state by Straumanis and Cirulis. Informations about some preliminary measurements with solutions of Co++ and N3− ions, as well as of Ni++ and N3− ions, are also given.

Determination of aromatic sulphonates in surface waters by high-performance liquid chromatography with coupled fluorescence and UV detection

An HPLC procedure for determining anthraquinonesulphonates in the presence of both benzene- and naphthalensulphonates in river water was developed. Enrichment of analytes was accomplished by means of solid-phase extraction, based on an RP-18 reversed-phase silica cartridge coated with an aliphatic amine. The analytes were separated by ion-pair chromatography with coupled fluorescence and UV detection, which resulted in a convenient way to discriminate derivatives of benzene and of naphthalene from those of anthraquinone. The peaks of anthraquinonesulphonates were identified by measuring the ratio of their absorbances at two different wavelengths. Four of the target analytes were found in water from the river Bormida (Italy).

Sulfonated derivatives of naphthalene in water samples of an Italian river

Abstract Naphthalenesulfonates were found in water samples of the Italian river Bormida. Samples were collected at increasing distances from the point of emission of pollutants, and their analyses showed that these compounds can persist in river water and that they can propagate for considerable distances.

Mixed metal complexes in solution. Thermodynamic and spectrophotometric study of copper(II)-citrate heterobinuclear complexes with nickel(II), zinc(II) or cadmium(II) in aqueous solution

SummaryA thermodynamic study of CuII−MII-citrate (MII=NiII, ZnII or CdII) ternary systems has been performed by means of potentiometric measurements of hydrogen ion concentration at different temperatures (10, 25, 35 and 45°C) and at I=0.1 mol dm−3 (KNO3).The different binary and ternary systems involved have been further characterized by visible spectra and by calculating the spectra (ε versus λ) of all the CuII complexes.The thermodynamic data suggest strong entropic stabilization for the species under discussion. As regards the visible spectral characteristics of CuII(d-d transitions), the substitution of one CuII ion in the dimer [Cu2(cit)2H−2]4− by NiII or ZnII to form heterobinuclear [CuM(cit)2H−2]4− complexes, gives rise to a change in the visible spectrum.

Thermodynamic and spectroscopic study of copper(II)–glycyl-L-histidylglycine complexes in aqueous solution

The complexes formed in aqueous solution by copper(II) with glycyl-L-histidylglycine (L–) have been extensively studied, by using potentiometry, calorimetry, visible spectrophotometry and circular dichroism techniques, with the aim of elucidating their type and probable structure. Only monomeric species are formed in the acidic range of pH ([CuL]+, [CuLH–1], [CuL2] and [CuL2H–1]–), while at higher pH (>8) polynuclear [Cu4L4H–6]4– is formed in addition to [CuLH–2]–. The interpretation of all the experimental data is strongly consistent with a structure involving three nitrogen atoms co-ordinated to copper(II) for [CuLH–1] and [CuL]+ and with the participation of a fourth nitrogen atom in [CuLH–2]– and [Cu4L4H–8]4–. In the tetrameric species very probably there is a dissociation of the N(1)-pyrrole hydrogen ion, with consequent formation of imidazolate bridges.