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Abstract(s)
O trimetoprim (TMP) é um fármaco antibacteriano sintético cujo consumo crescente tem levado à sua presença em ambientes aquáticos sendo, assim, detetado frequentemente em massas de água e em espécies aquáticas. A sua presença no meio ambiente pode causar consequências nos ecossistemas podendo provocar efeitos negativos nos mesmos. O objetivo deste trabalho consistiu no desenvolvimento de um sensor eletroquímico de papel fibra de carbono (CP) não modificado para a deteção do TMP. Inicialmente foram realizados ensaios com diferentes técnicas eletroquímicas de forma a avaliar qual delas apresenta uma melhor resposta à presença do fármaco. As técnicas eletroquímicas utilizadas foram a voltametria cíclica (CV), voltametria de pulso diferencial (DPV) e voltametria de onda quadrada (SWV). Avaliou-se, também, numa fase inicial, vários pré-tratamentos a conferir ao elétrodo sem modificação de forma a garantir o máximo sinal analítico, nomeadamente pré-tratamentos eletroquímicos baseados em CV e amperometria a diferentes potenciais fixos num eletrólito básico ou ácido. Verificou-se, contudo, que o CP sem qualquer pré-tratamento obteve uma boa resposta eletroquímica ao TMP comparado com o CP pré-tratado sendo assim usado para o desenvolvimento do sensor. A técnica selecionada foi a SWV (de acordo com o melhor sinal obtido) tendo-se em seguida otimizado as condições analíticas, nomeadamente o pH da solução, os parâmetros da técnica (amplitude, frequência e degrau de potencial) e a deposição de analito (potencial de deposição e tempo de deposição). Obteve-se um valor de pH ótimo igual 7 e, para os parâmetros de SWV, uma amplitude ótima de 0,02 V, uma frequência de 50 Hz e um degrau de potencial de 0,015 V. O tempo e potencial de deposição que maximizam o sinal foram de 60 s e 0,7 V, respetivamente. Aplicando os parâmetros ótimos, foram feitos ensaios de linearidade numa gama de concentrações entre 0,1 µM e 80 µM de TMP, tendo-se atingido a saturação após os 40 µM. A curva de calibração foi dividida em duas zonas lineares. Com base na primeira zona de linearidade (concentrações entre 0,1 µM e 1 µM) obteve-se um limite de deteção igual a 0,16 ± 0,03 µM (n=3) e um limite de quantificação igual a 0,47 ± 0,09 µM, sendo bastante competitivo em relação a elétrodos mais tradicionais nanoestruturados como o de carbono vítreo e o de pasta de carbono. Por fim, o sensor CP demonstrou capacidade para ser aplicado na determinação de TMP em amostras ambientais (água de rio), obtendo-se uma recuperação de 89% através do método de adição padrão, contudo sendo ainda necessário mais ensaios para obtenção de percentagens de recuperação próximas de 100%. Conclui-se que este tipo de sensor apresenta um grande potencial para ser aplicado na deteção de contaminantes em amostras ambientais.
Trimethoprim (TMP) is a synthetic antibacterial drug, whose increasing consumption has led to its presence in aquatic environments, thus being detected very frequently both in bodies of water and in aquatic species. Its presence in the environment can have consequences on ecosystems and may have negative effects on them. The main goal of this work consisted in the development of an electrochemical sensor of unmodified carbon fiber paper (CP) for the detection of TMP. Initially, tests were performed with different electrochemical techniques to determine which one was the most sensitive. The electrochemical techniques used were cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). In an initial phase, several pre-treatments were applied to the electrode without modification to guarantee the maximum analytical signal, namely electrochemical pre-treatments based on CV and amperometry at different fixed potentials in a basic or acid electrolyte. However, it was found that the CP without any pre-treatment obtained the best electrochemical response to TMP, thus being used for the development of the sensor. The selected technique was SWV according to the best signal obtained, with the analytical conditions being then optimized, namely the pH of the solution, the parameters of the SWV technique (amplitude, frequency and step potential) and finally the analyte deposition (deposition potential and deposition time). An optimal pH value equal to 7 was obtained; regarding the SWV parameters, the optimal amplitude was 0.02 V, the frequency 50 Hz and the step potential 0.015 V. The optimal deposition time and potential were equal to 60 s and 0.7 V, respectively. Applying the optimized parameters, the linearity was assessed in the concentration range between 0.1 µM and 80 µM, reaching saturation after 40 µM. The calibration curve was divided into two linear zones. Based on the first linearity zone (concentrations between 0.1 µM and 1 µM), a detection limit equal to 0.155 ± 0.03 µM (n=3) was obtained and a quantification limit equal to 0.466 ± 0.09 µM, being quite competitive in relation to more traditional nanostructured electrodes such as glassy carbon and carbon paste. Finally, the CP sensor demonstrated the ability to be applied in the determination of TMP in environmental samples (river water), with recuperation of 89%, however, more tests are still needed to obtain recovery percentages close to 100%. This type of sensor has great potential to be applied in the detection of contaminants in environmental samples.
Trimethoprim (TMP) is a synthetic antibacterial drug, whose increasing consumption has led to its presence in aquatic environments, thus being detected very frequently both in bodies of water and in aquatic species. Its presence in the environment can have consequences on ecosystems and may have negative effects on them. The main goal of this work consisted in the development of an electrochemical sensor of unmodified carbon fiber paper (CP) for the detection of TMP. Initially, tests were performed with different electrochemical techniques to determine which one was the most sensitive. The electrochemical techniques used were cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). In an initial phase, several pre-treatments were applied to the electrode without modification to guarantee the maximum analytical signal, namely electrochemical pre-treatments based on CV and amperometry at different fixed potentials in a basic or acid electrolyte. However, it was found that the CP without any pre-treatment obtained the best electrochemical response to TMP, thus being used for the development of the sensor. The selected technique was SWV according to the best signal obtained, with the analytical conditions being then optimized, namely the pH of the solution, the parameters of the SWV technique (amplitude, frequency and step potential) and finally the analyte deposition (deposition potential and deposition time). An optimal pH value equal to 7 was obtained; regarding the SWV parameters, the optimal amplitude was 0.02 V, the frequency 50 Hz and the step potential 0.015 V. The optimal deposition time and potential were equal to 60 s and 0.7 V, respectively. Applying the optimized parameters, the linearity was assessed in the concentration range between 0.1 µM and 80 µM, reaching saturation after 40 µM. The calibration curve was divided into two linear zones. Based on the first linearity zone (concentrations between 0.1 µM and 1 µM), a detection limit equal to 0.155 ± 0.03 µM (n=3) was obtained and a quantification limit equal to 0.466 ± 0.09 µM, being quite competitive in relation to more traditional nanostructured electrodes such as glassy carbon and carbon paste. Finally, the CP sensor demonstrated the ability to be applied in the determination of TMP in environmental samples (river water), with recuperation of 89%, however, more tests are still needed to obtain recovery percentages close to 100%. This type of sensor has great potential to be applied in the detection of contaminants in environmental samples.
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Keywords
Sensor eletroquímico Trimetroprim Voltametria de onda quadrada Contaminantes emergentes Electrochemical sensor Trimethoprim Square wave voltammetry Emerging contaminants