Vincenzo Zelano

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.

Ionic strength dependence of formation constants—XVIII. The hydrolysis of iron(III) in aqueous KNO3 solutions☆

The hydrolysis of iron(III) was studied potentiometrically at different ionic strengths in KNO(3) aqueous solutions, at 25 degrees C, to determine the dependence of hydrolysis constants on ionic strength (nitrate media), to check the existence of nitrate-ferric ion interactions, and to confirm the formation of high polymeric species. Under the experimental conditions 0.03 I (KNO(3)) 1M, 0.3 C 12 mM, the species Fe(OH)(2+), Fe(2)(OH)(4+)(2), Fe(OH)(+)(2) and Fe(12)(OH)(2+)(34) were found, and the hydrolysis constants log beta(11) = 2.20, log beta(12) = -2.91, log beta(22) = -5.7, log beta(12,34) = -48.9 (I = 0M) were calculated. The ionic strength dependence of hydrolysis constants is quite close to that found for several protonation and metal complex formation constants reported elsewhere.

CYTOGENETIC CHARACTERISTICS OF A POPULATION OF CHIRONOMUS RIPARIUS MEIGEN 1804 (DIPTERA, CHIRONOMIDAE) FROM A POLLUTED PO RIVER STATION

A population of Chironomus riparius from a Po river station near Moncalieri (a trace-metal polluted station) was studied. In this population was established a great variability of band structure of polytene chromosomes as well as paracentric heterozygous inversions, deletions, deficiencies, partial breaks, diploid chromosome fragments, and changes in functional activity and appearance of heterochromatin. In arms A through F, some bands had an increased size compared to the standard chromosomic map. Some bands appeared in a heterozygous or normal homozygous state or were amplified. In all arms, many condensed stable bands appeared in the decondensed state when compared to the standard map. Asynaptic zones in arms E and G as well as heterozygous Balbiani rings and NORs were established. Very often the 4th chromosome was almost completely heteropycnotic and looded like a ‘pompon’ chromosome. For the first time in this species, a high frequency of ectopic pairings of different arms was observed. Telomeric regions involved in ectopic pairings had a granular appearance, as did some centromeres. The hypothesis is advanced that such a high frequency of structural rearrangements could be correlated with genomic distribution of specific mobile elements.

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.

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.

Selective recovery of uranium(VI) from aqueous acid solutions using micellar ultrafiltration

Preconcentration and removal of uranyl ions from aqueous solutions were achieved by using micellar-enhanced ultrafiltration with complexing micellar aggregates composed of Triton X-100 and different hydrophobic ligands. Derivatives of 4-aminosalicylic acid (PAS) and of 1-(2-pyridylazo)-2-naphthol (PAN) having tuned alkyl chains were used as suitable chelating agents. The selective recovery of uranyl from acid samples containing also SrII and CdII is possible using the multi-step ultrafiltration approach with the PAN derivatives, whereas effective uranyl retention can be obtained with salicylates only in neutral to basic media.

A study on the reproducibility of Tessier's extractions in a fluvial sediment and a comparison between different dissolution procedures in a reference material

Abstract The reproducibility of Tessiers extractions and the total content of cadmium, chromium, copper, iron, manganese, lead, zinc and calcium in a river sediment have been evaluated. The metals were determined with AAS in flame and in graphite furnaces. The accuracy of the dissolution procedures was evaluated using a reference material (RM) BCR 145; none of the methods applied proved optimal for all the metals determined. The concentrations of metals extracted by the various reagents were characterized by good reproducibility on species bonded to the carbonates, to iron and manganese oxides and in the residual; precision was lower in the other cases. The sequential extractions also showed a satisfactory mass balance.

Chemical relevance of the copper(II)-L-carnosine system in aqueous solution : a thermodynamic and spectrophotometric study

Abstract The copper(II)— l -carnosine (L − ) system has been re-investigated in aqueous solution, at I = 0.1 mol dm −1 , different temperatures (5⩽ t ⩽45°C) and with metal to ligand ratios ranging from 3:1 to 1:3. Both potentiometry and visible spectrophotometry were employed. From an overall consideration of all experiments, [CuLH] 2+ , [CuL] + , [CuLH −1 ]°, [Cu 2 L 2 H −2 ]° and [Cu 2 LH −1 ] 2+ were recognized as the species which provide the best interpretation of experimental data. The complex formation constants, determined at different temperatures, allowed us to obtain reliable values of Δ H ° and good estimates of Δ C ° p . From visible spectrophotometric measurements, carried out at different pH and metal to ligand ratios, it was possible to calculate the electronic spectrum of each complex formed in solution. A structure is also proposed for each species, on the basis of thermodynamic and spectral results.

Response to metal stress of Nicotiana langsdorffii plants wild-type and transgenic for the rat glucocorticoid receptor gene

Recently our findings have shown that the integration of the gene coding for the rat gluco-corticoid receptor (GR receptor) in Nicotiana langsdorffii plants induced morphophysiological effects in transgenic plants through the modification of their hormonal pattern. Phytohormones play a key role in plant responses to many different biotic and abiotic stresses since a modified hormonal profile up-regulates the activation of secondary metabolites involved in the response to stress. In this work transgenic GR plants and isogenic wild type genotypes were exposed to metal stress by treating them with 30ppm cadmium(II) or 50ppm chromium(VI). Hormonal patterns along with changes in key response related metabolites were then monitored and compared. Heavy metal up-take was found to be lower in the GR plants. The transgenic plants exhibited higher values of S-abscisic acid (S-ABA) and 3-indole acetic acid (IAA), salicylic acid and total polyphenols, chlorogenic acid and antiradical activity, compared to the untransformed wild type plants. Both Cd and Cr treatments led to an increase in hormone concentrations and secondary metabolites only in wild type plants. Analysis of the results suggests that the stress responses due to changes in the plants hormonal system may derive from the interaction between the GR receptor and phytosteroids, which are known to play a key role in plant physiology and development.

Acid-base properties of a river sediment: Applicability of potentiometric titrations

Abstract The application of potentiometric titrations to the study of the acid-base properties of a river sediment was investigated. A set of alkalimetric titrations were performed on suspensions containing different sediment-solution ratios and EMF measurements were elaborated by a suitable computer program. After the optimisation of the titration procedure, it was possible to refine conditional acid constants. For the considered sediment it was possible to calculate three protonation constants. Comparing calculated pKa with those reported in literature for the characterisation of humic and fulvic material of various origins and for inorganic hydrous oxides, it appears that calculated values are in the range indicated for the assignment of the constants to organic and inorganic titratable groups that can be present on the surface of a natural sediment.