Giuseppe D'Ascenzo

Uniformly sized molecularly imprinted polymers (MIPs) for 17β-estradiol

Molecularly imprinted polymers (MIPs) for 17β-estradiol were prepared following a multistep procedure including swelling and polymerization using polystyrene seeds, 4-vinylpyridine as the functional monomer and ethylene glycol dimethacrylate (EDMA) as crosslinker. Dibutylphthalate (DBF) and toluene were employed as swelling and porogenic compounds. All the samples showed a mono- modal and very narrow diameter distribution with mean diameter values in the 2.0-4.7 μm range. The microspheres prepared in the presence of the template molecule present surface available vinyl pyridine unit content higher than those prepared without the template. The amphiphilic nature of the pre-polymerization complex between vinyl pyridine and 17β-estradiol can be claimed to be responsible for a preferential location of the vinyl pyridine units at the microsphere surface. The ability of molecular recognition depends on the accessibility of interaction sites located on surface of polymeric particles that increases when the ratios EDMA/polystyrene seed and DBF/polystyrene seed increase.

Development of a method based on liquid chromatography–electrospray mass spectrometry for analyzing imidazolinone herbicides in environmental water at part-per-trillion levels

An evaluation was made of the feasibility of using reversed-phase liquid chromatography-mass spectrometry with an electrospray interface (LC-ESI-MS) to measure traces of imidazolinone herbicides in different natural water samples. The imidazolinones are a significant new class of low-use-rate, reduced-environmental-risk herbicides for the protection of a wide variety of agricultural commodities. The procedure used involved passing 0.5, 1, 2 1 of river, ground and drinking water samples, respectively, through a 0.5 g graphitized carbon black (GCB) extraction cartridge. Analytes were eluted from the GCB surface by 8 ml of a methylene chloride-methanol (80:20, v/v) solution acidified with formic acid, 25 mM. Recovery was higher than 89% irrespective of the aqueous matrix in which the analytes were dissolved. A conventional 4.6 mm I.D. reversed-phase LC C18 column operating with a mobile phase flow-rate of 1 ml/min was used to chromatograph the analytes. A flow of 50 microliters/min of the column effluent was diverted to the ESI source. The effects of acid concentration on ESI-MS detector response in the mobile phase were investigated. The effects on the production of diagnostic fragments produced by varying the orifice plate voltage and the response of the MS detector were also evaluated. For the analyte considered, the response of the mass detector was linearly related to the amount of analyte injected between 1 and 50 ng. The limit of detection (signal-to-noise ratio = 3) of the method for the pesticides considered in drinking water samples was estimated to be about 2-5 ng/l.

Determination of arylphenoxypropionic herbicides in water by liquid chromatography–electrospray mass spectrometry

A very sensitive and specific analytical procedure for determining arylphenoxypropionic herbicides in aqueous environmental samples, using pneumatically assisted electrospray (ESI) liquid chromatography-mass spectrometry (LC-MS) is presented. Arylphenoxypropionic acids are a new class of herbicides used for the selective removal of most grass species from any nongrass crop. These herbicides are commercialized as herbicide esters. It has been shown that the ester derivatives undergo fast hydrolysis in the presence of vegetable tissues and soil bacteria, yielding the corresponding free acid. The analytical procedure involves passing 1l of surface or ground water and 2l of drinking-water samples, through a 0.5-g graphitized carbon black (GCB) extraction cartridge. A conventional 4.6-mm I.D. reversed-phase LC C18, operating with a 1 ml/min mobile phase flow-rate, was used for chromatographing the analytes. A flow of 200 microliters/min of the column effluent was diverted to the ESI source. The ESI source was operated in positive-ion mode for neutral pesticides and in negative-ion mode for acid pesticides. For ion-signal optimization, the effect of the concentration of the acid in the mobile phase on the response of the ESI-MS detector was investigated. By evaluating the specificity and sensitivity of the method, the effects of varying the orifice plate voltage on the production of the diagnostic fragment and the response of the MS detector were also investigated. For the analyte considered, the response of the mass detector was linearly related to the amount of the analyte injected between 1 and 200 ng. In all cases, recoveries of the analytes were better than 91%. The limit of detection (signal-to-noise ratio = 3) of the method for the pesticides considered in drinking water samples was estimated to be about 3-10 ng/l.

The formation of sparingly soluble species of Ca2+ with carboxylic ligands: speciation and thermoanalysis

This work reports the results of studies into the solubility and thermal decomposition of various sparingly soluble complexes of calcium with two isomeric benzene tricarboxylates, and with benzene penta- and hexa-carboxylates. The dependence of their solubility on ionic strength and, for the calcium benzene hexacarboxylate, the dependence of solubility on Na(+) concentration in solution were studied. Comparison between structure and solubility of the calcium insoluble compounds here and previously studied, is also reported. In order to perform solubility calculations, we determined also the formation constants of trimellitic and trimesic anions with H(+), Na(+) and Ca(2+) potentiometrically (H(+)-ISE), since these are not reported in literature. All solid compounds were characterised by TG-FTIR measurements, and comparable behaviours in thermal decomposition as a function of ligand structure were found.

Studies on polyfunctional O-ligands. Solubility and thermal stability of 1,2,4,5-benzenetetracarboxylate complexes with alkali and alkaline earth metal ions

Abstract A solubility and thermoanalytical study of alkali and alkaline earth solid complexes of pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid, H 4 L) is reported. The insoluble Na + species is Na 2 LH 2 . K + , Rb + and Cs + form MLH 3 . The stoichiometry of precipitation of H 4 L with Ca 2+ , Ba 2+ and Sr 2+ depends on pH: at pH 2 is formed; in the range 4 2 and M 2 L; and at pH > 4.5, only M 2 L is formed. The p K s0 of all the species were determined. The insoluble compounds were also characterized by thermogravimetric analysis.

Grana Padano cheese : thermoanalytical techniques applied to the study of ripening

Abstract In the present work, modifications of water–matrix interactions in Grana Padano (GP) cheese were studied using thermogravimetric techniques in order to provide an index of ripening. These techniques represent a simple and rapid method for determining water content and for monitoring its behaviour in ripening GP cheese. It is possible to evaluate the quantity of water present in the matrix, as well as the different types of water bound to it both qualitatively and quantitatively. Samples of traditional GP cheese produced in the winter season (same day), and collected at different ripening stages (5,10,14,19 months), were investigated. When statistical models of the STARMAX (Space Time Autoregressive Moving Average eXogenous variables) class, augmented with surface trends, were fitted to thermoanalytical data, valuable insights into the chemical nature of the ripening were acheived with good predictive performances.

Potentiometric determination of bile phosphates using a lead selective electrode.

A potentiometric method based on phosphate precipitation with Pb2+ and on a lead ion selective electrode is applied to the determination of bile phosphates. The method is rapid and simple and does not require extensive sample pretreatment.

Evolution of paper chromatography: from Runge's perceptions to Tswett's adsorption

SummaryThe historical development of paper chromatography is reviewed from the work of Runge up to the contribution of Tswett. The type of support, the path of substances and the forces responsible for the phenomenon are discussed in detail.

Differential scanning calorimetry as a tool for obtaining quantitative data on thin layer chromatrography

Abstract An analytical method for the quantitative determination of some aminoacids is proposed. The analysis is carried out in two steps. The first is based on a thin layer chromatographic separation (TLC) which is realized on alumina and allows the aminoacids to be separated. The second is based on an application of differential scanning calorimetry (DSC), by which it is possible to characterize and determine the amount of the compound contained in each spot, after having removed from the plate the layer corresponding to the spot. This is put in the sample capsule of the differential scanning calorimeter, while the reference capsule is filled with an identical weight of the sample-free aluminium oxide from the same TLC plate. The DSC signal is proportional to the quantity of the sample present in the spot.

Thermal properties of some complexes of nickel(II) with pyridine-2-aldoxyme

Abstract The thermal properties of some complexes of the Ni(II) with the pyridine-2-aldoxyme (PaOH), where the ligand appears either as ion (PaO − ) or as a neutral molecule, were determined using TG, DTA, HTRS and DRS techniques. The thermal stability, as determined by procedural decomposition temperatures, was The thermal stability is discussed in terms of the intermolecular bonds of the solid lattice and of the electronegativity of the ligands. The thermal decomposition mechanism of the [Ni(PaOH) 2 Cl 2 ] is also examined.