Current Developments of Analytical Methodologies for Aflatoxins' Determination in Food during the Last Decade (2013-2022), with a Particular Focus on Nuts and Nut Products.

peer reviewedThis review aims to provide a clear overview of the most important analytical development in aflatoxins analysis during the last decade (2013-2022) with a particular focus on nuts and nuts-related products. Aflatoxins (AFs), a group of mycotoxins produced mainly by certain strains of the genus Aspergillus fungi, are known to impose a serious threat to human health. Indeed, AFs are considered carcinogenic to humans, group 1, by the International Agency for Research on Cancer (IARC). Since these toxins can be found in different food commodities, food control organizations worldwide impose maximum levels of AFs for commodities affected by this threat. Thus, they represent a cumbersome issue in terms of quality control, analytical result reliability, and economical losses. It is, therefore, mandatory for food industries to perform analysis on potentially contaminated commodities before the trade. A full perspective of the whole analytical workflow, considering each crucial step during AFs investigation, namely sampling, sample preparation, separation, and detection, will be presented to the reader, focusing on the main challenges related to the topic. A discussion will be primarily held regarding sample preparation methodologies such as partitioning, solid phase extraction (SPE), and immunoaffinity (IA) related methods. This will be followed by an overview of the leading analytical techniques for the detection of aflatoxins, in particular liquid chromatography (LC) coupled to a fluorescence detector (FLD) and/or mass spectrometry (MS). Moreover, the focus on the analytical procedure will not be specific only to traditional methodologies, such as LC, but also to new direct approaches based on imaging and the ability to detect AFs, reducing the need for sample preparation and separative techniques

PROPERTIES OF ADSORBENT MATERIALS AND THEIR APPLICATIONS IN ENVIRONMENTAL AND SUSTAINABLE CHEMISTRY

The separation of the components of large quantities of chemical mixtures into pure forms is at the basis of most industrial processes. These processes often involve the application of energy consumption technologies. The development of economic, effective, safe and rapid separation techniques in many industrial sectors at a large scale is still a challenging issue. Among the different separation techniques, adsorption, a consolidated technology, is still considered to be a reliable and robust method to purify fluids at low cost and with high efficiency. One of the main advantages of adsorption based technologies is that they are capable of removing contaminants in very low concentrations range, an operative condition where most other separation techniques are scarcely efficient due to the small concentration gradients involved. Adsorption base technologies have been successfully employed in many fields and among them in environmental remediation methodologies. The preservation of fresh water as a source of potable water and the safeguard of natural waters as life preservation systems (cultivation of aquatic food and reservoir of evolutionary diversity) has become important objectives. Water pollutants include a wide spectrum of chemicals, they may be organic or inorganic substances. The main objective of this work of thesis is to evaluate the efficiency of different adsorbent materials in the removal of some classes of contaminants from aqueous matrices. The adsorption process was studied to determine both kinetics and thermodynamics properties of the adsorption process. In addition, structural investigation approaches have been adopted to enlighten the mechanisms underlying the process. In the present study, adsorbent materials, different from each other in structure and chemical composition, were selected. They can be categorized in two main classes: (i) silico aluminate synthetic microporous adsorbents (zeolites) and (ii) carbonatic bioadsorbents (scallop shell). Scallop shells, composed of biogenic calcium carbonate, were chosen as bio-adsorbents for the removal of heavy metals from water solution. Mollusc shells represent a waste originating from seafood processing, the features of the shell matrix such as the disposition of the CaCO3 layers and the presence of organic components, make mollusc shells a suitable material for the uptake of metal ions, such as cadmium, lead and nickel, improving the quality of water bodies. Zeolites were instead employed for the adsorption of organic contaminants, in specific for the removal from aqueous solutions of toluene, hexane, chlorobenzene and the metabolite EMA (2- ethyl-6-methylaniline) originating from the degradation of the pesticide metolachlor. Among the many applications in which zeolites are employed, their use as catalysts is one of the most common. This study includes a work on gallium substituted zeolites; gallium was introduced by wet impregnation (adsorption) on three different zeolites and the obtained materials were characterised to determine the nature and structure of the Ga3+ sites. In this case, adsorption has been used to generate a material with interesting characteristics and potential application in the sustainable chemistry field concerning the biomass conversion in platform chemicals.La separazione di grandi quantità di sostanze chimiche da miscele per ottenere prodotti puri è alla base di molti processi industriali. Questi processi spesso comportano l’utilizzo di tecnologie ad alto consumo energetico. Lo sviluppo di tecniche separative economiche, efficaci, sicure e rapide è ancora una sfida per molti settori industriali. Tra le varie tecniche separative, l’adsorbimento è tuttora considerato un metodo robusto e affidabile per la purificazione di fluidi a basso costo e alta efficienza. Uno dei principali vantaggi dei processi di adsorbimento è la loro capacità di rimuovere contaminanti a livelli di concentrazione molto bassi, condizione operativa in cui la maggior parte delle altre tecniche separative sono scarsamente efficienti a causa del basso gradiente di concentrazione coinvolto. Tecnologie basate sull’adsorbimento vengono impiegate con successo in molti campi, tra cui in ambito ambientale in metodologie per la rimediazione e per il trattamento di acque reflue. Il mantenimento della qualità delle acque dolci come risorsa di acqua potabile e la salvaguardia delle acque naturali per il mantenimento di sistemi vitali (acquacoltura e riserva di biodiversità) è diventato un obiettivo importante. I contaminanti presenti nelle acque comprendono una grande varietà di sostanze chimiche, organiche o inorganiche. Il principale obiettivo di questo lavoro di tesi è lo studio dell’efficienza di diversi materiali adsorbenti per la rimozione di alcune classi di contaminanti da matrici acquose. In particolare, sono stati studiati sia gli aspetti cinetici che termodinamici del processo di adsorbimento. Inoltre, sono state eseguite analisi strutturali per valutare i meccanismi coinvolti in questo processo. Nel presente lavoro sono stati selezionati materiali adsorbenti che differiscono tra loro sia nella composizione chimica sia nella struttura. Questi materiali possono essere classificati in due classi: (i) materiali alluminosilicati microporosi sintetici (zeoliti) e (ii) materiali carbonatici (gusci di conchiglie, canestrelli). I gusci di canestrelli, costituiti da calcio carbonato di origine biogenica, sono stati selezionati come bioadsorbenti per la rimozione di metalli pesanti da soluzioni acquose. I gusci di molluschi rappresentano uno scarto dell’industria alimentare, le caratteristiche della matrice della conchiglia, come la disposizione degli strati di CaCO3 e la presenza di componenti organici, rendono le conchiglie dei materiali adatti per l’adsorbimento di ioni metallici, come cadmio, piombo e nickel, per migliorare la qualità delle acque. Le zeoliti sono state invece impiegate per l’adsorbimento di contaminanti organici, nello specifico per la rimozione da soluzioni acquose di toluene, esano, clorobenzene e il metabolita EMA (2-etil- 6-metilanilina) derivante dalla degradazione del pesticida metolachlor. Tra le svariate applicazioni in cui le zeoliti vengono impiegate, il loro utilizzo come catalizzatori è uno dei più comuni. Questo studio include un lavoro riguardo zeoliti sostituite con gallio, ottenute tramite impregnazione umida (adsorbimento) su tre zeoliti aventi diversa struttura e composizione chimica. I materiali così ottenuti sono stati caratterizzati per determinare la natura e struttura dei siti Ga3+. In questo caso, l’adsorbimento è stato impiegato per creare un materiale con particolari caratteristiche per potenziali applicazioni nel campo della chimica sostenibile riguardo la conversione di biomassa in prodotti di vasto impiego industriale

ENTRAPPING OF IBUPROFEN AND ATENOLOL WITHIN Y ZEOLITE: A NEUTRON POWDER CHARACTERIZATION AFTER DRUGS ADSORPTION

Pharmaceuticals products are considered to be among the most common organic wastewater contaminants due to their widespread use and slow natural degradation, which still makes their complete removal from water a challenging task. Due to their unique properties, zeolites have already proved their efficiency as sorbent materials in wastewater treatments. Based on the excellent results obtained, it has been decided to study the removal of two pharmaceutical products (ibuprofen and atenolol) from aqueous solution by organophilic zeolite Y (Si/Al ratio=200). The aim was to determine the zeolite efficiency in adsorption processes of pharmaceutical compounds characterized by high molecular dimensions. Results gained suggest that Y zeolite could be successfully used as sorbent material in water remediation processes from drugs

Heterogeneous sodium decatungstate catalysts for contaminants degradation in aqueous matrix

The ability of decatungstate to photoproduce •OH radicals from water is retained when the polyoxoanion is immobilized on solid supports and can be exploited as a heterogeneous photocatalytic system for advanced oxidation process in water remediation field. Herein, we show that interaction between •OH radicals and drug molecules depends on the physical chemical properties of the chosen support. In particular, it depends on the charge of the molecule at operating pH of 6

Probing the sorption capacity of Y zeolite towards pharmaceutical compounds: a neutron powder diffraction study

No abstract availabl

Insights into adsorption of chlorobenzene in high silica MFI and FAU zeolites gained from chromatographic and diffractometric techniques

In this work, the capability of two commercial high silica zeolites (HSZs), namely ZSM-5 and Y, for the removal of chlorobenzene (CB) from water was investigated by combining chromatographic and diffractometric techniques. The adsorption isotherms and kinetics of CB on ZSM-5 and Y zeolites were determined from batch tests. The adsorption kinetics were very fast; the time to reach equilibrium was less than 10 min. The equilibrium data of CB on the two HSZs showed dissimilarities that are particularly evident in the adsorption data concerning the low concentration range, where Y zeolite is characterized by low adsorption. On the contrary, at higher solution concentrations the adsorption capacity of Y is higher than that of ZSM-5. The crystalline structures of Y and ZSM-5 saturated with CB were investigated by X-ray diffraction (XRD) techniques. Rietveld refinement analyses of XRD data allowed for quantitative probing of the structural modifications of both zeolites after CB adsorption and provided insight into the preferred zeolite adsorption sites in both microporous materials. The refined frameworkâ\u80\u93extraframework bond distances confirm that interactions between the selected organic contaminant and hydrophobic zeolites are mediated via co-adsorbed H2O. The occurrence of H2Oâ\u80\u93CBâ\u80\u93framework oxygen oligomers explains variations in both the unit cell parameters and the shape of the channels, clearly confirming that water plays a very relevant role in controlling the diffusion and adsorption processes in hydrophobic zeolites

EXPLORING THE EFFECT OF TEMPERATURE ON GA-DOPED ZEOLITE CATALYSTS BY IN SITU SYNCHROTRON X-RAY POWDER DIFFRACTION

Gallium-containing zeolites have been extensively investigated due to their unique catalytic performances in light hydrocarbon aromatization. Newest applications concern the conversion of biomass into biofuels and bio-based chemicals. These Ga-doped catalysts can be prepared by post synthesis methods, including impregnation, ion exchange or Chemical Vapor Deposition (CVD). The complex mechanism of galliation by post synthesis treatment is suitable to introduce gallium into both tetrahedrally coordinated framework and interstitial non-framework positions. Brønsted acidity within zeolites is generated when tetravalent Si4+ is replaced with trivalent Ga3+. Oxo cations GaO+ on exchange positions of the framework behave as Lewis acids. Non-framework gallium is the source of Lewis acidity. Thermal treatments cause the migration of Ga3+ to extraframework positions and its progressive aggregation in form of isolated, dimeric and polymeric species up to oxide nanoparticles. This migration leads to the appearance of a different type of acid sites of Lewis nature. As a consequence, after this treatment Ga-zeolites can possess both Brønsted and Lewis acid sites, working separately or in a synergistic way in acid catalyzed reactions. In spite of the growing interest on the nature of gallium species in Ga-catalysts, there is a lack of in situ studies of Ga-zeolite systems at the high temperature range, where they exhibit their catalytic activity. To predict catalysts behaviour at non-ambient conditions is mandatory to improve their effectiveness and prevent from a possible deactivation, which is still a challenging task. To ensure the long-term stability during catalytic reactions, detailed information about catalyst modifications upon thermal treatment are required. In particular, a better understanding of extraframework metal cations nature and the way they contribute to catalytic reactions is of primary importance to support the design of high-performing Ga-zeolite catalysts, at whose request in the industrial field is continuously growing. In spite of that, the particular role of the framework and non-framework gallium is still very controversial. As a result, the nature of the catalytically active sites in Ga-zeolites as well as the possible cooperative effects (framework and non-framework gallium) and the evaluation of their stability under operating conditions remain debatable

Adsorption of p-hydroxybenzaldehyde onto zeolites for water remediation: evaluation of the competition between contaminant and natural organic substances

Toluene is a hydrocarbon belonging to the BTEX class (Benzene, Toluene, Ethylbenzene, Xylene) which is frequently detected in all environmental compartments due to its wide use as solvent, antiknock agent in gasoline, and for the production of benzene. In this study we tested the efficiency of zeolites as eco-compatible adsorbent material for the removal of the organic contaminant toluene from aqueous matrices containing the natural component p-hydroxybenzaldehyde (p-HBA). p-HBA is one of the monomers of humic acids derived from the biodegradation of lignin, these substances are commonly found in surface and ground waters and, due to their dimensions similar to the zeolites pore size, could interfere in the adsorption of organic pollutants. Regarding the adsorption of the contaminant (TOL) from the aqueous matrix containing the natural humic acids monomer (p-HBA), it resulted that this latter does not show competitive behavior: the adsorption of TOL was slightly affected by the presence of p-HBA

Study of the adsorption of the amino acid L-lysine onto microporous materials

Zeolites are aluminosilicate minerals composed of [SiO4]4- and [AlO4]5- tetrahedral units linked through the oxygen atoms creating a regular crystalline structure with microporous cavities that confer a high superficial area. The physico-chemical properties of zeolites depend strongly on the composition of their framework, in particular the hydrophilic/hydrophobic behaviour is affected by the SiO2/Al2O3 ratio (SAR). Moreover, the different shapes and dimensions of the internal channels and cages influence the adsorption selectivity towards host molecules. The ability of zeolites to adsorb biologically active biomolecules such as amino acids is of particular interest in industrial biotechnology due to the fact that these adsorbent materials could be used as solid solvents to stabilize the different charged forms of the amino acids. In addition, these materials can also be employed in enrichment and separation processes of amino acids from complex mixtures. In the present study the adsorption of the amino acid L-lysine onto zeolites L and ZSM-5 from aqueous solutions was evaluated. Zeolites presenting different framework structures were selected in order to evaluate the effect of the intra-crystalline characteristics of the material. Moreover, different SAR values were considered to determine the adsorption behaviour according to this factor

Adsorption of L-lysine on L and ZSM-5 zeolites

Zeolites are aluminosilicate minerals characterized by a regular crystalline structure with microporous cavities that confer a high superficial area. The physico-chemical properties of zeolites depend strongly on the composition of their framework, in particular, the hydrophilic/hydrophobic behaviour is affected by the SiO2/Al2O3 ratio (SAR). The ability of zeolites to adsorb amino acids is of particular relevance in industrial biotechnology due to the fact that these adsorbent materials could be used as solid solvents to stabilize the different charged forms of the amino acids. Moreover, these materials can also be employed in enrichment and separation of amino acids from complex mixtures. In this work we evaluated the adsorption behaviour of zeolite L and ZSM-5 towards the amino acid L-lysine