Questa tesi descrive lo sviluppo di un elettrodo modificato con un polimero isolante per la determinazione indiretta del radicale OH. I polimeri testati sono stati polifenolo, polipirrolo e ...polipirrolo sovraoossidato ed il primo è risultato quello con le migliori prestazioni. Il film di modificante è stato depositato per elettropolimerizzazione del fenolo in ambiente acido, su un elettrodo di carbone vetroso (GC) ed è risultato isolante e perfettamente adeso al GC, impedendo il trasferimento di carica alle più comuni sonde redox. L’attacco dei radicali OH, generati dalla reazione di Fenton o dalla fotolisi di H2O2, rimuove parzialmente il polimero dal GC, ripristinando parzialmente il comportamento conduttore dell’elettrodo. L’entità della degradazione del film polifenolico è stata valutata sfruttando la corrente relativa alla sonda redox Ru(NH3)63+, che rappresenta il segnale analitico per la determinazione del radicale OH. L’elettrodo è stato impiegato per stimare le prestazioni di foto catalizzatori a base di nanoparticelle di TiO2, ottenendo risultati correlati a quelli ricavati da un metodo HPLC. Inoltre esso è stato usato per sviluppare una nuova procedura per la determinazione della capacità di scavenging verso i radicali OH, che è stata applicata all’analisi di composti puri e campioni reali. I risultati erano confrontabili con quelli determinati con metodiche standardizzate, comunemente impiegate per la determinazione della capacità antiossidante. Inoltre è stato condotto uno studio riguardante la modifica di un elettrodo di platino con un idrossido misto a strati a base di cobalto e alluminio (LDH). In particolare si sono valutati gli effetti di diversi pretrattamenti del Pt sulle caratteristiche e prestazioni elettrocatalitiche del film di LDH nei confronti dell’ossidazione di anilina, fenolo e acido salicilico. Questi composti possono essere impiegati come molecole sonda per la determinazione del radicale OH e rivestono interesse da un punto di vista elettroanalitico perché portano facilmente alla passivazione della superficie di Pt.
The development of a cheap modified electrode for the indirect detection of OH radical is described. The method is based on the attack of OH radicals on the modifier and the quantification of its degradation is evaluated by electroanalytical approaches. Polyphenol, polypyrrole and overoxidized polypyrrole were tested as modifiers for the determination and, from our experiments, polyphenol resulted the best one. The modified electrode was prepared by electropolymerization of phenol in acid environment on glassy carbon (GC). The film perfectly covered the GC surface and inhibited the charge transfer of many redox species. The attack of OH radicals generated by Fenton reaction or H2O2 photolysis partly removed the polymer from GC and the conductor behavior of the electrode was partially restored. The degree of degradation of the polyphenol is the analytical signal and was quantified by cyclic voltammetry and chronoamperometry, using the redox probe Ru(NH3)63+. The electrode was used to evaluate the performances of different photocatalysts based on TiO2 nanoparticles and the results were successfully compared with those obtained from a more traditional HPLC method. A new procedure for the determination of the scavenging activity towards OH radicals was developed using the polyphenol modified GC. The results obtained for pure compounds and real samples were comparable to those from standardized methods which are widely employed to estimate the antioxidant capacity. Furthermore, the modification of a Pt electrode with a double layered hydroxide, based on Co and Al, (LDH) was deeply investigated. In particular, we studied the effects of different pretreatments of Pt surface on the characteristics and performances of the LDH film towards the electrocatalytic oxidation of aniline, phenol and salicylic acid. These compounds can be used as probe molecules for hydroxyl radical detection and are very interesting from an electroanalytical point of view since they lead to Pt passivation.
Off-line TMAH-GC/MS and NMR characterization of humic substances extracted from river sediments of northwestern So Paulo under different soil uses Tadini, Amanda Maria; Glaucia PantanoauthorDepartamento de Qumica e Cincias Ambientais, Instituto de Biocincias, Letras e Cincias Exatas, Universidade Estadual Paulista Jlio de Mesquita Filho, R. Cristvo Colombo 2265, 15054-000 So Jos do Rio Preto, SP, Brazil; Ana Lcia de ToffoliauthorDepartamento de Qumica e Cincias Ambientais, Instituto de Biocincias, Letras e Cincias Exatas, Universidade Estadual Paulista Jlio de Mesquita Filho, R. Cristvo Colombo 2265, 15054-000 So Jos do Rio Preto, SP, Brazil ...
2015
Journal Article
The ability of Trichoderma harzianum (strain OMG-08) as plant growth promoting fungus (PGPF), was tested on Zea mays plants grown in soil pots added with different inorganic (triple superphosphate ...and rock phosphate) and organic (cow and horse manure composts) P fertilizers. The effect of treatments was evaluated by following the variations of plants dry biomass and nutrient content, as well as the metabolic changes in plant leaves by both GC-MS and NMR spectroscopy. A synergic effect was observed in treatments with both composts and fungus inoculation, in which not only plant growth and P uptake were enhanced, but also the expression of different metabolites related to an improved photosynthetic activity. Conversely, the combination of Trichoderma with inorganic fertilizers was less effective and even showed a reduction of plants shoot biomass and N content. The corresponding plant metabolome revealed metabolic compounds typical of biotic or abiotic stresses, which may be attributed to a reduced capacity of inorganic fertilizers to provide a sufficient P availability during plant growth. Our findings also indicate that the molecular composition of compost differentiated the Trichoderma activity in sustaining plant growth. The positive effects of the combined Trichoderma and compost treatment suggest that it may become an alternative to the phosphorus mineral fertilization.
In this study, the trend of VOCs of dietary fiber samples, coming from three different watermelon cultivars
L. (variety
, and
) was investigated. This foodstuff, obtained as a by-product of residual ...agri-food production, has gained increasing attention because of its many bioactive components and high dietary fiber content. The result is a fibrous material for specific applications in food manufacturing, such as corrector for some functional and technological properties. In this study, a method based on headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to characterize the aromatic profiles of the dried raw materials. Therefore, the VOCs of the samples of the three cultivars were investigated. Experimental results have shown that watermelon fibers generate VOCs, which can be grouped into six common classes of analytes. The different distributions of the identified compounds made it possible to effectively differentiate the three cultivars studied based on their peculiar aroma profiles. In particular,
fiber is distinguished by the high content of terpenes,
by the presence of aldehydes generated as fatty acid metabolites, and
by the higher content of acetyl esters.
In this study, the trend of Volatile Organic Compounds (VOCs) in dietary fiber samples from the winter melon (Cucumis Melo var. Inodorus, Yellow Canary type) were investigated. This foodstuff, ...obtained as a by-product of agri-food production, has gained increasing attention and is characterized by many bioactive components and a high dietary-fiber content. As regards fiber, it is poorly colored, but it may be whitened by applying a bleaching treatment with H2O2. The result is a fibrous material for specific applications in food manufacturing, for example, as a corrector for some functional and technological properties. This treatment is healthy and safe for consumers and widely applied in industrial food processes. In this study, a method based on headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC-MS) was applied for the characterization of the aromatic profile of the dried raw materials. Furthermore, VOC variation was investigated as function of the bleaching treatment with H2O2. The bleached samples were also analyzed after a long storage period (24 months), to assess their stability over time. As a result, the VOC fraction of the fresh raw fiber showed nine classes of analytes; these were restricted to seven for the bleached fiber at t0 time, and further reduced to four classes at the age of 24 months. Alcohols were the main group detected in the fresh raw sample (33.8 % of the total chromatogram area), with 2,3-butanediol isomers as the main compounds. These analytes decreased with time. An opposite trend was observed for the acids (9.7% at t0), which increased with time and became the most important class in the 24-month aged and bleached sample (57.3%).
Abstract
Bei der molekulare Charakterisierung von organischen Materialien in Proben von Kunstwerken und historischen Objekten wird traditionell die qualitative und quantitative Analyse mittels HPLC ...und GC durchgeführt. Heutige Ansätze, basierend auf analytischer Pyrolyse, ermöglichen die Analyse von Proben ohne chemische Vorbehandlung. Die Pyrolyse, die bisher oft als Screening‐Methode angesehen wurde, birgt bisher unerkannte Möglichkeiten dank jüngster Entwicklungen in der instrumentellen Analytik. Organische Materialien makromolekularer Natur oder solche, die während des Trocknens und Alterns polymerisieren, können nun besser untersucht werden. Farbschichten und archäologische organische Substanzen beinhalten oft als Hauptbestandteil unlösliche und chemisch nicht‐hydrolisierbare Bestandteile, die durch GC und HPLC nicht zugänglich sind. Bis zum heutigen Tage haben sich die wissenschaftlichen Untersuchungen organischer Bestandteile von Kunstgegenständen und historischen Objekten vor allem auf die löslichen Nebenbestandteile beschränkt. Dieser Kurzaufsatz präsentiert die jüngsten Fortschritte bei qualitativen und semiquantitativen Analysen von organischen Materialien in Kulturgütern, basierend auf analytischer Pyrolyse gekoppelt mit Massenspektrometrie.
Les résines végétales sont des sécrétions de végétaux qui ont été utilisées par l’homme de l’Antiquité à nos jours dans de nombreuses applications (pharmaceutique, cosmétique et artistique). Ces ...exsudats sont composés majoritairement de terpènes. L'identification et la quantification de l'ensemble de ces composés dans les extraits végétaux reste un défi du fait de leur très grande diversité structurale. L’objectif de ce travail a été de développer de nouvelles approches analytiques pour identifier et quantifier les composés terpéniques présents dans ce matériel végétal afin d’en assurer le contrôle qualité et la certification. Deux méthodes séparatives ont été sélectionnées: la TLC et la GC. Pour ces deux techniques on s’est intéressé à toutes les potentialités de leur couplage avec la spectrométrie de masse. Le développement en TLC-1D et TLC-2D a permis le « screening » rapide des résines végétales et la faisabilité du couplage avec le MALDI-TOF-MS a été mise en évidence pour l’identification des marqueurs majoritaires (acides triterpéniques). La GC a permis une caractérisation plus aboutie des résines en mettant en place une méthode d’analyse exhaustive des terpènes des plus volatils au non-volatils. L’optimisation des différentes étapes de la méthodologie GC-MS s’est effectuée en se basant sur la méthode des plans d’expérience ainsi que sur des analyses statistiques tels que l’ACP et la CAH. Dans un souci d’apporter des éléments plus précis pour distinguer les résines les plus proches, la quantification de leurs marqueurs majoritaires a été établie après une validation complète de la méthode GC. L’ensemble de ce travail a permis de développer des outils pour une caractérisation rapide des extraits de résines permettant de différencier les espèces même les plus proches.
Resins are hydrocarbon secretions of many plants and well known for their protective benefits. They have been used as raw materials for a wide range of applications (pharmaceutic, cosmetic and artistic). Plant resins are complex mixtures of organic substances mainly terpenoid compounds which constitute the most abundant and structurally diverse group of plant secondary metabolites. The chemical characterization of this material results in long and difficult separation due to the wide range of polarity and volatility of its constituents. The aim of this work was to develop new analytical approaches to improve the identification of resins certifying their origin and ensuring the quality control. For that purpose two analytical methods were selected: TLC and GC approaches hyphenated to mass spectrometry. TLC-1D and TLC-2D allow a rapid screening and first visual differences of resins. The innovating TLC coupling to MALDI-TOF-MS gives a clear identification of major markers (triterpenic acids). In order to have complementary information about the composition of resins, a gas chromatography-mass spectrometry (GC-MS) method was developed to analyze volatile to non-volatile compounds. The various stages of optimization were based on experimental design and statistical (PCA and HAC) approaches. For closely related resins, a quantitative approach was investigated based on a complete validation for major markers. This work allows the development of two complementary techniques that give a powerful approach for fast and reliable differentiation of various resins even the closest ones.
Objective: To verify the correlation between the percentage body fat (%body fat) evaluated by the Body Adiposity Index (BAI) and %body fat evaluated by dual-energy X-ray absorptiometry (DXA) in ...elderly women. Materials and Methods: Cross-sectional study with elderly women submitted to bone densitometry at an imaging clinic in the Northwest part of Rio Grande do Sul (RS) state in Brazil. Sociodemographic data were evaluated through a questionnaire, which was structured by the researchers. The %body fat was evaluated by DXA and BAI. For the BAI calculation, stature was measured using a stadiometer coupled with a scale. Hip circumference was measured with a tape measure at the most protruding part of the hip. The BAI was calculated through an equation (BAI = Hip / (height x √height) - 18. Results: Two hundred and five elderly women, aging 67.3 ± 5.8 years old, participated in this study. There was a higher prevalence of women with partners (61.5%), retired (90.2%) and with schooling between 4 and 8 years (47.3%). Regarding adiposity, the mean %body fat demonstrated by BAI was 34%, and 40.59% according to the DXA results. The Pearson's correlation was significant and high r=0.714 (p <0.001) and the Intraclass Correlation Coefficient was 0.649 (95% CI, -0.106 – 0.852) (p<0.001), being considered strong. Conclusion: In this study, the BAI obtained the elderly women in southern Brazil showed a high correlation with the % body fat measured by DXA and can be used as a complementary index to assess the adiposity of this population.
Obiettivo: Verificare la correlazione tra la percentuale di grasso corporeo (%BF) valutata dal Body Adipity Index (BAI) con la %BF valutata mediante assorbimetria a raggi X a doppia emissione (DXA) nelle donne anziane. Materiali e metodi: uno studio trasversale con donne anziane sottoposte a densitometria ossea in una clinica di imaging nel nord-ovest del Rio Grande do Sul. I dati sociodemografici sono stati valutati utilizzando un questionario strutturato dai ricercatori. %BC è stato valutato da DXA e IAC. Per calcolare l'IAC, l'altezza è stata misurata utilizzando uno stadiometro su scala antropometrica. La circonferenza dell'anca (HC) è stata misurata con un metro a nastro nella parte più sporgente dell'anca. La IAC è stata calcolata utilizzando l'equazione IAC = Hip / (height x √height) – 18. RISULTATI: Hanno partecipato allo studio un totale di 205 donne anziane, con un'età media di 67,3 ± 5,8 anni. C'è una maggiore prevalenza di donne con un partner (61,5%), pensionate (90,2%) e con tra i 4 e gli 8 anni di scolarizzazione (47,3%). Per quanto riguarda l'adiposità, la %BF media dimostrata dall'IAC era del 34% e valutata dalla DXA era del 40,59%. La correlazione di Pearson era significativa e alta (r=0,714; p<0,001) e il coefficiente di correlazione intraclasse era 0,649 (IC 95%, -0,106 e 0,852, p<0,001) essendo considerato forte. Conclusione: nel campione di donne anziane del sud del Brasile, l'IAC ha avuto un'elevata correlazione con la % di GC misurata da DXA e può essere utilizzato come indice complementare per valutare l'adiposità di questa popolazione.
Objetivo: Verificar a correlação entre o percentual de gordura corporal (%GC) avaliado pelo Índice de Adiposidade Corporal (IAC) com o %GC avaliado por absorciometria por dupla emissão de raios X (DXA) em mulheres idosas. Materiais e Métodos: Estudo transversal, com idosas submetidas à densitometria óssea em uma clínica de imagem no noroeste do Rio Grande do Sul. Os dados sociodemográficos foram avaliados por meio de questionário estruturado pelos pesquisadores. O %GC foi avaliado por DXA e pelo IAC. Para o cálculo do IAC foi aferida a estatura utilizando um estadiômetro de balança antropométrica. A circunferência do quadril (CQ) foi medida com uma fita métrica na parte mais protuberante do quadril. O IAC foi calculado por meio da equação IAC = Quadril / (altura x √altura) – 18. Resultados: Participaram do estudo 205 idosas, com idade média de 67,3 ± 5,8 anos. Houve maior prevalência de mulheres com companheiro (61,5%), aposentadas (90,2%) e com escolaridade entre 4 e 8 anos de estudo (47,3%). Em relação à adiposidade, a média do %GC demonstrado pelo IAC foi de 34%, e avaliado por DXA foi de 40,59%. A correlação de Pearson foi significativa e alta (r=0,714; p<0,001) e o Coeficiente de Correlação Intraclasse foi de 0,649 (IC95%, -0,106 e 0,852, p<0,001) sendo considerado forte. Conclusão: Na amostra de idosas do sul do Brasil, o IAC obteve uma alta correlação com o % de GC mensurado pela DXA, podendo ser utilizado como um índice complementar para avaliar a adiposidade desta população.
Objetivo: Verificar la correlación entre el porcentaje de grasa corporal (%GC) evaluado por el Índice de Adiposidad Corporal (BAI) con el %GC evaluado por absorciometría de rayos X de doble emisión (DXA) en mujeres ancianas. Materiales y Métodos: Estudio transversal con ancianas sometidas a densitometría ósea en una clínica de imagen del noroeste de Rio Grande do Sul. Los datos sociodemográficos se evaluaron mediante un cuestionario estructurado por los investigadores. El %BC se evaluó mediante DXA e IAC. Para el cálculo del IAC se midió la talla con un estadiómetro de escala antropométrica. La circunferencia de la cadera (CC) se midió con una cinta métrica en la parte más sobresaliente de la cadera. El IAC se calculó mediante la ecuación IAC = Cadera / (altura x √altura) – 18. Resultados: Participaron del estudio 205 ancianas, con una edad media de 67,3 ± 5,8 años. Hubo mayor prevalencia de mujeres con pareja (61,5%), jubiladas (90,2%) y con entre 4 y 8 años de escolaridad (47,3%). En cuanto a la adiposidad, el %GC medio demostrado por el IAC fue del 34% y evaluado por DXA fue del 40,59%. La correlación de Pearson fue significativa y alta (r=0,714; p<0,001) y el Coeficiente de Correlación Intraclase fue de 0,649 (IC 95%, -0,106 y 0,852, p<0,001) considerándose fuerte. Conclusión: En la muestra de ancianas del sur de Brasil, el IAC tuvo una alta correlación con el % de GC medido por DXA, y puede ser utilizado como índice complementario para evaluar la adiposidad de esta población.
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