Síntese de aluminas macro-mesoporosas pelo método sol-gel acompanhado de separação de fases

Pós-graduação em Química - IQ

Evaluation of comprehensive two-dimensional gas chromatography coupled to rapid scanning quadrupole mass spectrometry for quantitative analysis

Comprehensive two-dimensional gas chromatography (GC x GC) is a powerful technique that provides excellent separation and identification of analytes in highly complex samples with considerable increase in GC peak capacities. However, since second dimension analyses are very fast, detectors with a rapid acquisition rate are required. Over the last years, quite a number of studies have discussed the potential and limitations of the combination GC x GC with a variety of quadrupole mass spectrometers. The present research focuses on the evaluation of qMS effectiveness at a 10,000-amu/s scan speed and 20-Hz scan frequency for the identification (full scan mode acquisition-TIC) and quantification (extracted ion chromatogram) of target pesticide residues in tomato samples. The following MS parameters have been evaluated: number of data points per peak, mass spectrum quality, peak skewing, and sensitivity. The validated proposed GC x GC/qMS method presented satisfactory results in terms of repeatability (coefficient of variation lower than 15%), accuracy (84-117%), and linearity (ranging from 25 to 500 ng/g), while significant enhancement in sensitivity was observed (a factor of around 10) under scan conditions. (C) 2012 Elsevier B.V. All rights reserved.

Unmanned platform for long-range remote analysis of volatile compounds in air samples

This paper describes a long-range remotely controlled CE system built on an all-terrain vehicle. A four-stroke engine and a set of 12-V batteries were used to provide power to a series of subsystems that include drivers, communication, computers, and a capillary electrophoresis module. This dedicated instrument allows air sampling using a polypropylene porous tube, coupled to a flow system that transports the sample to the inlet of a fused-silica capillary. A hybrid approach was used for the construction of the analytical subsystem combining a conventional fused-silica capillary (used for separation) and a laser machined microfluidic block, made of PMMA. A solid-state cooling approach was also integrated in the CE module to enable controlling the temperature and therefore increasing the useful range of the robot. Although ultimately intended for detection of chemical warfare agents, the proposed system was used to analyze a series of volatile organic acids. As such, the system allowed the separation and detection of formic, acetic, and propionic acids with signal-to-noise ratios of 414, 150, and 115, respectively, after sampling by only 30 s and performing an electrokinetic injection during 2.0 s at 1.0 kV.

A stable liquid-liquid extraction system for clavulanic acid using polymer-based aqueous two-phase systems

The partitioning of Clavulanic Acid (CA) in a novel inexpensive and stable aqueous two-phase system (ATPS) composed by poly(ethylene glycol) (PEG) and sodium polyacrylate (NaPA) has been studied. The aqueous two-phase systems are formed by mixing both polymers with a salt (NaCl or Na2SO4) and an aqueous solution of CA. The stability of CA on the presence of both polymers was investigated and it was observed that these polymers do not degrade the biomolecule. The effect of PEG-molecular size, polymer concentrations on the commercial CA partitioning has been studied, at 25 degrees C. The data showed that commercial CA was preferentially partitioned for the PEG-rich phase with a partition coefficient (K-CA) between 1 and 12 in the PEG/NaPA aqueous two phase systems supplemented with NaCl and Na2SO4. The partition to the PEG phase was increased in the systems with high polymer concentrations. Furthermore, Na2SO4 caused higher CA preference for the PEG-phase than NaCl. The systems having a composition with 10 wt.% of PEG4000, 20 wt.% of NaPA8000 and 6 wt.% of Na2SO4 were selected as the optimal ones in terms of recovery of CA from fermented broth of Streptomyces clavuligerus. The partitioning results (K-CA = 9.15 +/- 1.06) are competitive with commercial extraction methods of CA (K-CA = 11.91 +/- 2.08) which emphasizes that the system PEG/NaPA/Na2SO4 can be used as a new process to CA purification/concentration from fermented broth. (C) 2012 Elsevier B.V. All rights reserved.

Recent Advances in the Development of Magnetically Recoverable Metal Nanoparticle Catalysts

The aim of this Account is to provide an overview of our current research activities on the design and modification of superparamagnetic nanomaterials for application in the field of magnetic separation and catalysis. First, an introduction of magnetism and magnetic separation is done. Then, the synthetic strategies that have been developed for generating superparamagnetic nanoparticles spherically coated by silica and other oxides, with a focus on well characterized systems prepared by methods that generate samples of high quality and easy to scale- up, are discussed. A set of magnetically recoverable catalysts prepared in our research group by the unique combination of superparamagnetic supports and metal nanoparticles is highlighted. This Account is concluded with personal remarks and perspectives on this research field.

An integrated approach to evaluate emerging contaminants in drinking water

The chemical stock of emerging contaminants in Brazilian drinking water is of great interest due to the poor water quality at surface water intakes. In addition, little is known about the effect of some contaminants, such as endocrine disrupting chemicals (EDCs), which may be present in both raw and treated water. The aim of this work was to evaluate selected emerging contaminants in Brazilian waters using both chemical and biological analyses. Sampling sites were established in different municipalities based upon raw water quality data. Estrone, 17 beta-estradiol, estriol, 17 alpha-ethinylestradiol, bisphenol A, 4-n-octylphenol and 4-n-nonylphenol were determined in the samples by liquid chromatography-tandem mass spectrometry. A yeast assay using a Saccharomyces cerevisiae bioluminescent bioreporter was used to evaluate the estrogenic activity of the water samples. The first integrated results revealed similarities between the two individual approaches, since higher values for the bioassay were accompanied by significant concentrations of some selected compounds in surface water samples. No estrogenicity was observed for drinking water samples. Our results also indicate that the usual paradigm of evaluating water quality by measuring selected EDCs in a given water sample via chemical analysis, needs to be reviewed since the observed estrogenicity of a water sample is now a better guiding parameter to the selection of samples and substances to be chemically investigated in further analysis. So far, the data bank produced in this work, i.e., the comparison between chemical burden and observed estrogenicity, is not yet sufficiently robust to fully guide this decision. (C) 2011 Elsevier B.V. All rights reserved.

Counter-ion effect on surfactant-DNA gel particles as controlled DNA delivery systems

The ability to entrap drugs within vehicles and subsequently release them has led to new treatments for a number of diseases. Based on an associative phase separation and interfacial diffusion approach, we developed a way to prepare DNA gel particles without adding any kind of cross-linker or organic solvent. Among the various agents studied, cationic surfactants offered particularly efficient control for encapsulation and DNA release from these DNA gel particles. The driving force for this strong association is the electrostatic interaction between the two components, as induced by the entropic increase due to the release of the respective counter-ions. However, little is known about the influence of the respective counter-ions on this surfactant-DNA interaction. Here we examined the effect of different counter-ions on the formation and properties of the DNA gel particles by mixing DNA (either single-(ssDNA) or double-stranded (dsDNA)) with the single chain surfactant dodecyltrimethylammonium (DTA). In particular, we used as counter-ions of this surfactant the hydrogen sulfate and trifluoromethane sulfonate anions and the two halides, chloride and bromide. Effects on the morphology of the particles obtained, the encapsulation of DNA and its release, as well as the haemocompatibility of these particles are presented, using counter-ion structure and DNA conformation as controlling parameters. Analysis of the data indicates that the degree of counter-ion dissociation from the surfactant micelles and the polar/hydrophobic character of the counter-ion are important parameters in the final properties of the particles. The stronger interaction with amphiphiles for ssDNA than for dsDNA suggests the important role of hydrophobic interactions in DNA.

Purification of bromelain from pineapple wastes by ethanol precipitation

Bromelain is an aqueous extract of pineapple that contains a complex mixture of proteases and non-protease components. These enzymes perform an important role in proteolytic modulation of the cellular matrix in numerous physiologic processes, including anti-inflammatory, anti-thrombotic and fibrinolytic functions. Due to the scale of global production of pineapple (Ananas comosus L.), and the high percentage of waste generated in their cultivation and processing, several studies have been conducted on the recovery of bromelain. The aim of this study was to purify bromelain from pineapple wastes using an easy-to-scale-up process of precipitation by ethanol. The results showed that bromelain was recovered by using ethanol at concentrations of 30% and 70%, in which a purification factor of 2.28 fold was achieved, and yielded more than 98% of the total enzymatic activity. This enzyme proved to be susceptible to denaturation after the lyophilization process. However, by using 10% (w/v) glucose as a cryoprotector, it was possible to preserve 90% of the original enzymatic activity. The efficiency of the purification process was confirmed by SDS-PAGE, and native-PAGE electrophoresis, fluorimetry, circular dichroism and FTIR analyzes, showing that this method could be used to obtain highly purified and structurally stable bromelain. (C) 2012 Elsevier B.V. All rights reserved.

Synthesis of supported metal nanoparticle catalysts using ligand assisted methods

The synthesis and characterization methods of metal nanoparticles (NPs) have advanced greatly in the last few decades, allowing an increasing understanding of structure-property-performance relationships. However, the role played by the ligands used as stabilizers for metal NPs synthesis or for NPs immobilization on solid supports has been underestimated. Here, we highlight some recent progress in the preparation of supported metal NPs with the assistance of ligands in solution or grafted on solid supports, a modified deposition-reduction method, with special attention to the effects on NPs size, metal-support interactions and, more importantly, catalytic activities. After presenting the general strategies in metal NP synthesis assisted by ligands grafted on solid supports, we highlight some recent progress in the deposition of pre-formed colloidal NPs on functionalized solids. Another important aspect that will be reviewed is related to the separation and recovery of NPs. Finally, we will outline our personal understanding and perspectives on the use of supported metal NPs prepared through ligand-assisted methods.

Recent advances in the development of magnetically recoverable metal nanoparticle catalysts

The aim of this Account is to provide an overview of our current research activities on the design and modification of superparamagnetic nanomaterials for application in the field of magnetic separation and catalysis. First, an introduction of magnetism and magnetic separation is done. Then, the synthetic strategies that have been developed for generating superparamagnetic nanoparticles spherically coated by silica and other oxides, with a focus on well characterized systems prepared by methods that generate samples of high quality and easy to scale-up, are discussed. A set of magnetically recoverable catalysts prepared in our research group by the unique combination of superparamagnetic supports and metal nanoparticles is highlighted. This Account is concluded with personal remarks and perspectives on this research field.

Children's discomfort in assessments using different methods for approximal caries detection

Because discomfort caused by different approximal caries detection methods can influence their performance, the assessment of this discomfort is important. Thus, this study aimed to evaluate the discomfort reported by children after the use of different diagnostic methods to detect approximal caries lesions in primary teeth: visual inspection, bitewing radiography, laser fluorescence (DIAGNOdent pen - LFpen) and temporary separation with orthodontic rubbers. Seventy-six children aged 4 to 12 years were examined using these methods. Their discomfort was assessed using the Wong-Baker scale and compared among the methods. Visual inspection caused less discomfort than did other methods. Radiography and the LFpen presented similar levels of discomfort. Older children reported higher discomfort using temporary separation, whereas younger children reported less discomfort with the LFpen. In conclusion, radiographic, temporary separation and LFpen methods provoke higher discomfort than visual inspection.

Assessment of the presence of pharmaceutical compounds in seawater samples from coastal area of Gran Canaria Island (Spain)

[EN]This study presents the evaluation of seven pharmaceutical compounds belonging to different commonly used therapeutic classes in seawater samples from coastal areas of Gran Canaria Island. The target compounds include atenolol (antihypertensive), acetaminophen (analgesic), norfloxacin and ciprofloxacin (antibiotics), carbamazepine (antiepileptic) and ketoprofen and diclofenac (anti-inflammatory). Solid phase extraction (SPE) was used for the extraction and preconcentration of the samples, and liquid chromatography tandem mass spectrometry (LC-MS/MS) was used for the determination of the compounds. Under optimal conditions, the recoveries obtained were in the range of 78.3% to 98.2%, and the relative standard deviations were less than 11.8%. The detection and quantification limits of the method were in the ranges of 0.1–2.8 and 0.3–9.3 ng·L−1, respectively. The developed method was applied to evaluate the presence of these pharmaceutical compounds in seawater from four outfalls in Gran Canaria Island (Spain) during one year. Ciprofloxacin and norfloxacin were found in a large number of samples in a concentration range of 9.0–3551.7 ng·L−1. Low levels of diclofenac, acetaminophen and ketoprofen were found sporadically.

Ingegnerizzazione e design di nanoparticelle core-shell di magnetite/silice

In the past decade the study of superparamagnetic nanoparticles has been intensively developed for many biomedical applications such as magnetically assisted drug delivery, MRI contrast agents, cells separation and hyperthermia therapy. All of these applications require nanoparticles with high magnetization, equipped also with a suitable surface coating which has to be non-toxic and biocompatible. In this master thesis, the silica coating of commercially available magnetic nanoparticles was investigated. Silica is a versatile material with many intrinsic features, such as hydrophilicity, low toxicity, proper design and derivatization yields particularly stable colloids even in physiological conditions. The coating process was applied to commercial magnetite particles dispersed in an aqueous solution. The formation of silica coated magnetite nanoparticles was performed following two main strategies: the Stöber process, in which the silica coating of the nanoparticle was directly formed by hydrolysis and condensation of suitable precursor in water-alcoholic mixtures; and the reverse microemulsions method in which inverse micelles were used to confine the hydrolysis and condensation reactions that bring to the nanoparticles formation. Between these two methods, the reverse microemulsions one resulted the most versatile and reliable because of the high control level upon monodispersity, silica shell thickness and overall particle size. Moving from low to high concentration, within the microemulsion region a gradual shift from larger particles to smaller one was detected. By increasing the amount of silica precursor the silica shell can also be tuned. Fluorescent dyes have also been incorporated within the silica shell by linking with the silica matrix. The structure of studied nanoparticles was investigated by using transmission electron microscope (TEM) and dynamic light scattering (DLS). These techniques have been used to monitor the syntetic procedures and for the final characterization of silica coated and silica dye doped nanoparticles. Finally, field dependent magnetization measurements showed the magnetic properties of core-shell nanoparticles were preserved. Due to a very well defined structure that combines magnetic and luminescent properties together with the possibility of further functionalization, these multifunctional nanoparticles are potentially useful platforms in biomedical fields such as labeling and imaging.

Entwicklung einer Online-Kopplung der Gelelektrophorese mit der induktiv gekoppelten Plasma-Massenspektrometrie und deren Anwendung in der Bioanalytik

Die Elementmassenspektrometrie wurde in den letzten Jahren sehr erfolgreich zur Aufklärung verschiedener Fragestellungen in der Bioanalytik eingesetzt. Hierbei spielen vor allem Kopplungstechniken von Trennmethoden wie der Flüssigchromatographie (LC) oder der Kapillarelektrophorese (CE) mit der induktiv gekoppelten Plasma-Massenspektrometrie (ICP-MS) als Multielementdetektor mit hervorragenden Quantifizierungseigenschaften eine entscheidende Rolle bei der Untersuchung von Biopolymeren und deren Wechselwirkung mit verschiedenen Metallen. So wurden beispielsweise verschiedene Methoden für die Trennung und Detektion von Metalloproteinen oder DNA-Metall-Addukten in unterschiedlichen Probenmaterialien entwickelt. Die traditionelle und leistungsstärkste Trennmethode für Biopolymere aller Art, die Gelelektrophorese, wurde jedoch bislang nicht in einem Online-Verfahren an die ICP-MS gekoppelt, um solche Fragestellungen zu bearbeiten. Verschiedene Versuche auf der Basis der Laserablation wurden in diese Richtung unternommen, wobei diese Techniken als sehr umständlich und zeitaufwändig anzusehen sind. In dieser Arbeit wird erstmals die technische Realisierung einer Online-Kopplung der Gelelektrophorese mit der ICP-MS beschrieben. Das System basiert auf einem Prinzip aus der präparativen Gelelektrophorese, in welcher eine kontinuierliche Elution der getrennten Komponenten aus dem Gel während der laufenden Elektrophorese durchgeführt wird. Die eluierten Komponenten werden mit dem Elutionspuffer direkt in das Zerstäubersystem des ICP-MS geführt. Die ersten Untersuchungen wurden am Beispiel der Fragemente von doppelsträngiger DNA (dsDNA) durchgeführt. Kommerziell erhältliche Standardlösungen wurden mit der Online-GE-ICP-MS mittels Detektion von 31P an einem hochauflösenden Massenspektrometer mit einer Massenauflösung von 4000 analysiert. Die Trennbedingungen (z.B. pH-Wert oder Ionenstärke der Pufferlösungen) wurden für die Trennung von dsDNA-Fragementen in Agarosegelen optimiert und auf verschiedene dsDNA-Fragmente angewandt. In einem nächsten Schritt wurden die Quantifizierungsmöglichkeiten für Biopolymere untersucht. Sehr kleine Mengen an dsDNA konnten mit einer Präzision von weniger als 3% quantifiziert werden. Hierfür kamen verschiedene Möglichkeiten der externen Kalibration zum Einsatz, wie der Kalibration mit einem Phosphat-Standard oder einem kommerziell erhältlichen quantitativen dsDNA-Standard. Um das Potenzial der entwickelten Methode für die Untersuchung von Biopolymer-Metall-Wechselwirkungen zu demonstrieren, wurden Oligonukleotide mit Cisplatin unter physiologischen Bedingungen inkubiert und die Reaktionsprodukte mit der Online-GE-ICP-MS mittels 31P- und 195Pt-Detektion untersucht. Verschiedene Cisplatin-Oligonukleotid-Addukte konnten auf diese Weise beobachtet werden, was zur Identifizierung die Anwendung der MALDI-TOF-MS als komplementärer Form der Massenspektrometrie notwendig machte. Abschließend wurde die Isotopenverdünnungsanalyse zum Zweck der Quantifizierung herangezogen.

I controlli sulla tutela interinale della crisi della famiglia

La tesi affronta il tema dei controlli avverso i provvedimenti nell’interesse della prole e dei coniugi resi nell’ambito dei procedimenti di separazione e di divorzio, dapprima fornendo un inquadramento storico della problematica, attraverso la disamina delle posizioni dottrinali e giurisprudenziali formatesi con riferimento alla natura ed al regime impugnatorio di tali provvedimenti dall’entrata in vigore del codice di rito del 1865 ad oggi, dopodiché analizzando le numerose questioni interpretative cui l’attuale quadro normativo, risultante dalla stratificazione legislativa operata dalla L. 14 maggio 2005, n. 80 e dalla L. 8 febbraio 2006, n. 54, dà origine. In particolare la tesi, dopo aver delineato la struttura del reclamo di cui all’art. 708 c.p.c., cercando di fornire una soluzione ai dubbi che la scarna disciplina contenuta nella menzionata norma solleva, si occupa dei rapporti tra gli istituti del reclamo alla Corte d’appello e della revoca e modifica ad opera del giudice istruttore, riepilogando le varie teorie elaborate dalla dottrina e dalla giurisprudenza sul tema e cercando di individuare quale sia l’ambito di applicazione di ciascuno strumento di controllo. La tesi affronta poi, a fronte della mancata previsione di una forma di riesame avanti ad un organo superiore avverso i provvedimenti resi dal giudice istruttore ai sensi dell’art. 709, ultimo comma, c.p.c., la questione della reclamabilità di tali provvedimenti, cercando di individuare quale sia lo strumento più idoneo cui fare ricorso per colmare la lacuna che si dovesse ritenere esistente nel dato normativo. Il lavoro si conclude con la disamina, in una prospettiva de iure condendo, dei progetti di riforma che sono stati elaborati con riferimento al tema dei controlli avverso i provvedimenti temporanei e urgenti.