Development of a dynamic headspace solid-phase microextraction procedure coupled to GC–qMSD for evaluation the chemical profile in alcoholic beverages

In the present study, a simple and sensitive methodology based on dynamic headspace solid-phase microextraction (HS-SPME) followed by thermal desorption gas chromatography with quadrupole mass detection (GC–qMSD), was developed and optimized for the determination of volatile (VOCs) and semi-volatile (SVOCs) compounds from different alcoholic beverages: wine, beer and whisky. Key experimental factors influencing the equilibrium of the VOCs and SVOCs between the sample and the SPME fibre, as the type of fibre coating, extraction time and temperature, sample stirring and ionic strength, were optimized. The performance of five commercially available SPME fibres was evaluated and compared, namely polydimethylsiloxane (PDMS, 100 μm); polyacrylate (PA, 85 μm); polydimethylsiloxane/divinylbenzene (PDMS/DVB, 65 μm); carboxen™/polydimethylsiloxane (CAR/PDMS, 75 μm) and the divinylbenzene/carboxen on polydimethylsiloxane (DVB/CAR/PDMS, 50/30 μm) (StableFlex). An objective comparison among different alcoholic beverages has been established in terms of qualitative and semi-quantitative differences on volatile and semi-volatile compounds. These compounds belong to several chemical families, including higher alcohols, ethyl esters, fatty acids, higher alcohol acetates, isoamyl esters, carbonyl compounds, furanic compounds, terpenoids, C13-norisoprenoids and volatile phenols. The optimized extraction conditions and GC–qMSD, lead to the successful identification of 44 compounds in white wines, 64 in beers and 104 in whiskys. Some of these compounds were found in all of the examined beverage samples. The main components of the HS-SPME found in white wines were ethyl octanoate (46.9%), ethyl decanoate (30.3%), ethyl 9-decenoate (10.7%), ethyl hexanoate (3.1%), and isoamyl octanoate (2.7%). As for beers, the major compounds were isoamyl alcohol (11.5%), ethyl octanoate (9.1%), isoamyl acetate (8.2%), 2-ethyl-1-hexanol (5.9%), and octanoic acid (5.5%). Ethyl decanoate (58.0%), ethyl octanoate (15.1%), ethyl dodecanoate (13.9%) followed by 3-methyl-1-butanol (1.8%) and isoamyl acetate (1.4%) were found to be the major VOCs in whisky samples.

De aluna a professora e vice-versa

O presente relatório de estágio “De aluna a professora e vice-versa” foi elaborado no âmbito do Mestrado em Ensino da Matemática, no 3º ciclo do Ensino Básico e Secundário da Universidade da Madeira, no decurso do ano letivo de 2012/2013. Este trabalho tem por objetivo apresentar, estudar e compreender o tema proposto. Assim sendo, neste estudo serão analisadas as atividades matemáticas dos alunos, desenvolvidas nas turmas 1, 2 e 4 do 9.º ano, mais especificamente quando postos em contato com estratégias e recursos educativos diversificados. O tema tem em vista uma reflexão sobre a prática letiva e o imperativo da formação contínua, que são, incontornavelmente, o ponto-chave da vida profissional de um professor. No decorrer do estágio, tive a experiência direta de contato com os alunos, o que me permitiu uma aprendizagem real do dia-a-dia concreto de um professor. Concluímos que todo o ensino deverá estar centrado no aluno, na sua progressão, permitindo-lhe ter resultados satisfatórios, devendo o professor ter um papel mediador, embora assumindo o seu papel de liderança, nunca perdendo de vista, enquanto princípios orientadores deontológicos e éticos da sua ação, o sentido de responsabilidade, de justiça, de sensibilidade humana, de consciência do dever de coerência nas palavras e nos atos e sempre animado de um cooperativo espírito de equipa.