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Validação e implementação de um método de determinação de hidrocarbonetos aromáticos policíclicos (PAHs) em sedimentos marinhos
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Resumo(s)
A poluição é algo que afeta não só habitats como os seres vivos que neles vivem. O meio marinho acaba inevitavelmente, de forma direta e indireta, por ser afetado pela poluição que nos rodeia, sendo cada vez mais importante desenvolver formas de monitorizar e minimizar as fontes de poluição. Os hidrocarbonetos aromáticos policíclicos (PAH) são compostos orgânicos considerados poluentes face às propriedades carcinogénicas e mutagénicas que possuem. Estes compostos possuem ainda a capacidade para se depositarem e acumularem em sedimentos marinhos, pelo que a determinação da concentração dos PAH neles presentes é fundamental, para que seja possível agir em conformidade com os resultados obtidos. Face às características destes compostos orgânicos uma técnica usada para a sua análise é a cromatografia em fase gasosa acoplada à espetrometria de massa (GC-MS). Esta técnica permite identificar e quantificar compostos voláteis e semi-voláteis utilizando métodos desenvolvidos para a análise destes hidrocarbonetos, devendo esses métodos serem validados antes de serem implementados. Na primeira parte deste trabalho foi realizada a otimização das condições de aquisição de dados cromatográficos, sendo realizados estudos alterando condições de um GC-MS, nomeadamente a temperatura de injeção e da fonte iónica, os modos de injeção, o fluxo do gás de arraste e outros parâmetros inerentes ao tipo de injetor usado. A alteração destes parâmetros pressupôs a otimização da resolução, eficiência e sensibilidade dos picos cromatográficos, para ser possível identificar os analitos presentes nas amostras. Numa segunda parte, foi realizada a validação de um método para determinação de PAH em sedimentos marinhos, sendo avaliados os parâmetros: sensibilidade, gama de trabalho, linearidade, limiares analíticos, veracidade, precisão, incerteza e validação do software. Os dados para esta avaliação foram obtidos através da análise de amostras de sedimentos marinhos, que possuíam não só os PAH de interesse como também possíveis interferentes, tornando assim os dados obtidos o mais próximo possível da realidade. Inerente à validação do método, foram estabelecidos critérios para controlo interno da qualidade, nomeadamente para controlo de brancos, amostras duplicadas, amostras fortificadas, veracidade e linearidade. Estes critérios foram estabelecidos para que fosse possível garantir a qualidade dos ensaios e resultados reportados aquando da aplicação em rotina do método validado. Numa última etapa foram analisadas amostras reais para ser possível implementar o método. Verificou-se a presença de alguns PAH em níveis quantificáveis em duas das quatro amostras analisadas, mas que não excediam o limite máximo considerado de referência.
Pollution is something that affects not only habitats but also the living beings that live in them. The marine environment is inevitably, directly and indirectly, affected by the pollution that surrounds us, and it is becoming increasingly important to develop ways to monitor and minimise the sources of pollution. Polycyclic aromatic hydrocarbons (PAH) are organic compounds considered to be pollutants due to their carcinogenic and mutagenic properties. These compounds also have the ability to deposit and accumulate in marine sediments, therefore the determination of the concentration of PAH present in them is fundamental, so that it is possible to act in accordance with the results obtained. Given the characteristics of these organic compounds, one technique used for their analysis is gas chromatography coupled with mass spectrometry (GC-MS). This technique allows the identification and quantification of volatile and semi-volatile compounds using methods developed for the analysis of these hydrocarbons, and these methods must be validated before being implemented. In the first part of this work, optimization of the chromatographic data acquisition conditions was carried out. Studies were performed by changing the conditions of a GC-MS, namely the injection and ion source temperatures, the injection modes, the flow rate of the carrier gas and other parameters inherent to the type of injector used. The alteration of these parameters presupposed the optimization of the resolution, efficiency and sensitivity of the chromatographic peaks, in order to be able to identify the analytes present in the samples. In a second part, the validation of a method for the determination of PAH in marine sediments was performed, evaluating the parameters: sensitivity, working range, linearity, analytical thresholds, trueness, precision, uncertainty and software validation. The data for this evaluation were obtained through the analysis of marine sediment samples, which had not only the PAH of interest but also possible interferents, thus making the data obtained as close as possible to reality. Inherent to the method validation, criteria for internal quality control were established, namely for blank control, duplicate samples, fortified samples, trueness and linearity. These criteria were established to guarantee the quality of the assays and results reported when routinely applying the validated method. In a last step, real samples were analysed to be able to implement the method. Some PAH were found to be present at quantifiable levels in two of the four samples analysed, but not exceeding the maximum limit considered as reference.
Pollution is something that affects not only habitats but also the living beings that live in them. The marine environment is inevitably, directly and indirectly, affected by the pollution that surrounds us, and it is becoming increasingly important to develop ways to monitor and minimise the sources of pollution. Polycyclic aromatic hydrocarbons (PAH) are organic compounds considered to be pollutants due to their carcinogenic and mutagenic properties. These compounds also have the ability to deposit and accumulate in marine sediments, therefore the determination of the concentration of PAH present in them is fundamental, so that it is possible to act in accordance with the results obtained. Given the characteristics of these organic compounds, one technique used for their analysis is gas chromatography coupled with mass spectrometry (GC-MS). This technique allows the identification and quantification of volatile and semi-volatile compounds using methods developed for the analysis of these hydrocarbons, and these methods must be validated before being implemented. In the first part of this work, optimization of the chromatographic data acquisition conditions was carried out. Studies were performed by changing the conditions of a GC-MS, namely the injection and ion source temperatures, the injection modes, the flow rate of the carrier gas and other parameters inherent to the type of injector used. The alteration of these parameters presupposed the optimization of the resolution, efficiency and sensitivity of the chromatographic peaks, in order to be able to identify the analytes present in the samples. In a second part, the validation of a method for the determination of PAH in marine sediments was performed, evaluating the parameters: sensitivity, working range, linearity, analytical thresholds, trueness, precision, uncertainty and software validation. The data for this evaluation were obtained through the analysis of marine sediment samples, which had not only the PAH of interest but also possible interferents, thus making the data obtained as close as possible to reality. Inherent to the method validation, criteria for internal quality control were established, namely for blank control, duplicate samples, fortified samples, trueness and linearity. These criteria were established to guarantee the quality of the assays and results reported when routinely applying the validated method. In a last step, real samples were analysed to be able to implement the method. Some PAH were found to be present at quantifiable levels in two of the four samples analysed, but not exceeding the maximum limit considered as reference.
Descrição
Tese de Mestrado, Química, 2021, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Hidrocarbonetos aromáticos policíclicos Sedimentos marinhos Cromatografia em fase gasosa Espetrometria de massa Validação Teses de mestrado - 2021