Adriano Vanni

A molecular imprinted polymer with recognition properties towards the carcinogenic mycotoxin ochratoxin A

A molecularly imprinted polymer which recognises the mycotoxin ochratoxin A was prepared using the mimic N-(4-chloro-1-hydroxy-2-naphthoylamido)-(L) -phenylalanine as a template. The polymer was obtained by dissolving the template, methacrylic acid and ethylendimethacrylate in chloroform and polymerising the mixture by thermal treatment at 60 °C. The monolith obtained was crushed, sieved to 30–90 μm and extensively washed till the template could no longer be found in the washing solution. The binding properties towards the template, ochratoxin A and several related molecules were measured by eluting with acetonitrile and chloroform a HPLC column packed with the imprinted polymer. The experimental results show that the polymer recognises not only the template well, but also the ochratoxin A. The specific molecular recognition effect is due to hydrogen bond interactions but in order to assure the full recognition effect adjunctive steric factors are necessary. The magnitude of these interactions can be controlled by the use of limited amounts of acetic acid in the mobile phase.From the measurement of the relative selectivity it was found that only the simultaneous presence of the carboxyl, the phenolic hydroxyl and certain peculiar substructures such as the chlorine atom assures the whole recognition of the template.

Chromatographic characterization of molecularly imprinted polymers binding the herbicide 2,4,5-trichlorophenoxyacetic acid

Two polymers binding the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were prepared by utilising the technique of the non-covalent molecular imprinting polymerisation in an aqueous medium. The polymers obtained were packed in HPLC columns and the effects of the mobile phase composition on the retention of the imprinting molecule and the selectivity of the stationary phases towards several analogous structures were studied by liquid chromatography. The columns showed a good level of selectivity towards the template and strictly related molecules. It was found that the molecular recognition mechanism acting on the columns was dependent on a combination of ion pair and hydrophobic interactions.

Chromatographic characterization of a molecularly imprinted polymer binding theophylline in aqueous buffers

Abstract A theophylline-binding polymer was prepared utilizing the technique of non-covalent molecular imprinting polymerization. The polymer obtained was packed in a high-performance liquid chromatography (HPLC) column, and the molecular recognition mechanism regulating the binding behavior was studied by frontal and zonal chromatography, determining the effects of pH and methanol on the affinity constant and concentration of the binding sites. The values of binding capacity found show thet ability of the imprinted polymer to bind theophylline in aqueous buffer, even if with reduced affinity with respect to the values reported in literature for the same polymer in an organic medium. Hydrogen bonding was confirmed as leading interaction in the recognition mechanism.

Chromatographic characterization of a molecular imprinted polymer binding cortisol

A cortisol-binding polymer was prepared by utilising a non-covalent molecular imprinting polymerisation technique. The obtained polymer was packed in a high-performance liquid chromatography (HPLC) column; the selectivity was studied by liquid chromatography, eluting cortisol, cortisone, corticosterone, progesterone, 11-ketoprogesterone, 11alpha-hydroxyprogesterone, 17alpha-hydroxyprogesterone, cortisol 21-hemisuccinate, and cortisol 21-acetate with chloroform, containing 0.5% (v/v) acetic acid, as mobile phase. The mechanism of molecular imprinting was confirmed and a good selectivity for cortisol, with limited recognition for cortisone and 11alpha-hydroxyprogesterone, was found.

Soil sorption of heavy metals as influenced by sewage sludge addition

Abstract In this paper it was evaluated how the sorption process of heavy metals (Zn, Cu and Pb) by soil is influenced by the presence of sewage sludge. Results obtained both from sorption experiments and analytical characterization of a sewage sludge estract, showed that confounds of an organic nature deriving from the sludge adsorb on the soil at first, offering new adsorbing sites to heavy metals, increasing the soil sorption ability. However this sorption capacity is inversely related to the amount of metal sorbed, as evidentiated by the Kd graphs, so that only “low metal”; sludges will be able to provide new sorbing sites in addition to the ones supplied by the soil.

Determination and identification of metabolites of the fungicides Iprodione and Procymidone in compost.

The main metabolites formed from Iprodione and Procymidone during the composting process have been isolated and identified by HPLC-DAD-MSD. After addition of the fungicides to the composting pile, we monitored the reaction of the two analytes and the formation of their degradation products for eight months. We verified the nature of the metabolites by comparison with those hypothesised in the literature and by comparison with the behaviour of an abiotic process in aqueous acetonitrile pH 6 and at 35 degrees C. After taking into account the different kinetic behaviours of the fungicides on degradation in compost and hydro-organic solution, breakdown pathways are proposed for biodegradation.

Effect of a sewage sludge extract on the sorption process of cadmium and nickel by soil

Abstract Studies about heavy metals interactions with soils have received increasing attention due to land addition of different kinds of sewage sludge. Of particular importance in this field is the sorption process of heavy metals which influences their mobility, determining their distribution between the liquid and the solid phase of the soil. In this work, heavy metals (Ni and Cd) sorption was carried out on a sandy‐loam soil with and without a sewage sludge extract (CO2‐H2O solution at pH 3.8) to evaluate the effects of ligand species present in the sludge in the process of retaining heavy metals. The addition of sewage sludge extract, did not reduced the sorption, but rather increased the amount of heavy metals retained by the soil. The effect could be ascribable, at the pH of the experiment, to a preliminary sorption of organic ligands on to soil with the creation of new sorbing surfaces. The sewage sludge extract was, then characterized by elemental analysis, thermogravimetric, NMR and IR technique...

Determination of presence of fungicides by their common metabolite, 3,5-DCA, in compost.

This paper describes the determination of 3,5-DCA in commercial composts, a common metabolite in a class of fungicides, and dicarboximides (Vinclozolin, Chlozolinate, Iprodione, Procymidone) which are commonly used in agriculture. The extracts, obtained in acetonitrile by sonication, are analysed by HPLC/DAD without clean-up. This method has shown several advantages: reduced manipulation of samples, good recovery (80-90%) and good reproducibility (RSD% <7). The limit of detection (DL) of the analytical method has been estimated as 15 microg/kg for the common metabolite, and 35-145 microg/kg for the four fungicides in the matrices.

Catalytic and spectroscopic characterisation of a copper-substituted alcohol dehydrogenase from yeast

Yeast alcohol dehydrogenase (Y-ADH) is widely studied for its biotechnological importance and various attempts to improve its catalytic properties have been made. In this paper, a catalytically active metal-substituted Y-ADH was prepared in vitro by substituting one zinc atom with copper. EPR and Raman spectroscopy suggest that copper maintains the same co-ordination geometry as zinc in native Y-ADH. The active Cu-ADH shows lower substrate affinity and lower specific activity (SA) than native ADH, but greater than a previously obtained Co-ADH. Furthermore, Cu-ADH maintains its catalytic efficiency in a wider pH range than native enzyme.

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.