Orfeo Zerbinati

Photocatalytic degradation of bentazon by TiO2 particles

The degradation of 3-isopropy1–2,1,3-benzothiadiazin-4-one-2,2-dioxide, the herbicide bentazon, by AMI simulated sunlight has been investigated in the presence of aqueous suspensions of TiO2. The half-life of the degradation process is ca. 30 minutes at pH=2 and ca. 4 minutes at pH=7 in the presence of 0.5 g L−1 of TiO2. The near quantitative recovery of sulfate ions and CO2 as well as the variation with time of dissolved and adsorbed organic carbon suggest that the process leads to complete mineralization of the herbicide. The process is extremely efficient even at very low concentration: in fact irradiation of 20 ppb of bentazon in the presence of 50 ppm TiO2 allows to recover < 0.1 ppb after 10 minutes.

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.

Fate of aromatic sulfonates in fluvial environment

Abstract Water samples of the Italian river Bormida, which is polluted by the wastes of the production of azo-dyestuff intermediates, were analysed by FAB/MS and the resulting data were compared to those obtained by HPLC. The presence of sulfonated derivatives of naphthalene was confirmed but, in addition, several sulfonated compounds having molecular mass other than those of naphthalenesulfonates (NS) were also found. Those compounds were suspected of originating from oxidative degradation of NSs. Laboratory tests showed that some NSs indeed can undergo oxidative degradation under physico-chemical conditions similar to those occurring in a river. In particular, the dark-coloured degradation products of 1-hydroxy-2-naphthalenesulfonic acid appeared similar to an unknown compound found in the river water.

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.

Optimization of the cyclodextrin-assisted capillary electrophoresis separation of the enantiomers of phenoxyacid herbicides.

An ethylcarbonate derivative of beta-cyclodextrin (beta-CD) with three substituents per molecule, hydroxypropyl-beta-CD and native alpha-CD have been tested as resolving agents in the capillary zone electrophoresis (CZE) separation of the four enantiomers of the herbicides mecoprop and dichlorprop. The performances of the three compounds have been quantified by means of two-levels full factorial design and the inclusion constants were calculated from CZE migration time data. Possible structure of inclusion complexes have been proposed, on the basis of molecular mechanics simulations.

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.

Analysis of chiral carboxylic acids in wine by high-performance liquid chromatography with coupled UV and circular dichroism detection

Abstract A circular dichroism (CD) spectrophotometer, equipped with a flow cell, and a UV detector were connected in series and were used for coupled UV-CD detection of optically active carboxylic acids. The limits of detection and the linear range for the enantiomers of tartaric, malic, lactic and ascorbic acids are reported. Several wines were analysed and CD detection proved to be sensitive enough for accurate determinations. The combined UV-CD detection was helpful for identifying the peaks and allowed the calculation of enantiomeric ratios.

New derivatives of cyclodextrins as chiral selectors for the capillary electrophoretic separation of dichlorprop enantiomers

Abstract α-, β- and γ-cyclodextrins (CDs), as well as some of their chemical derivatives, have been tested as chiral resolving agents for the capillary zone electrophoretic resolution of the racemic herbicide dichlorprop, (±)-2-(2,4-dichlorophenoxy)propionic acid, of which only the (+)-isomer is herbicidally active. The complexation constants of the herbicide enantiomers with the cyclodextrin host molecules have been calculated from the electrophoretic migration time data at variable cyclodextrin concentration. The experimental results showed that several of the investigated CDs allowed dichlorprop enantiomer resolution. In particular, a newly synthesised ethylcarbonate derivative of β-CD showed the best enantiomer resolution properties among the tested compounds, while the remaining ones showed inferior or no performances at all. The calculated inclusion constants allowed identification of the best conditions for enantioresolution, and an explanation of the different complexation properties of the investigated compounds has been proposed on the basis of molecular modeling.