Desenvolvimento de métodos eletroanalíticos para determinação de compostos nitrogenados em combustíveis derivados do petróleo
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Data
2008-02-29
Autores
Okumura, Leonardo Luiz [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A presença de traços de compostos organonitrogenados (básicos e neutros), tais como, quinolina, piridina, carbazol e indol em combustíveis derivados do petróleo desempenham um importante papel no tempo de vida dos motores dos veículos. No entanto, essas substâncias podem contaminar o meio ambiente e por isso devem ser controladas, pois a maioria delas são potencialmente carcinogênicas e mutagênicas. Por estas razões, um método confiável e sensível foi desenvolvido para a determinação de compostos nitrogenados básicos e neutros em amostras de combustíveis, como a gasolina e o diesel. Este método utiliza pré–concentração com resina de troca iônica (Amberlyte® IR–120 H) e sílica gel modificada, seguido pelo uso de voltametria de pulso diferencial (DPV) em um eletrodo de carbono vítreo. O comportamento eletroquímico da quinolina, piridina, carbazol e indol estudado por voltametria cíclica (VC) sugere que a redução ocorre por meio de uma transferência eletrônica reversível seguido por uma reação química acoplada. Picos voltamétricos controlados por difusão bem resolvidos foram obtidos em N`,N`–dimetilformamida (DMF) com tetrafluoroborato de tetrabutilamônio (TBABF4 0,1 M) para quinolina (−1,95 V), piridina (−2,52 V), carbazol (−2,67 V) e indol (− 2,27 V) vs. eletrodo de referência Ag|AgCl|KClsat. O método voltamétrico proposto (DPV) apresentou uma boa resposta linear a partir 0,10 até 300 mg L−1 e um limite de detecção (L.D.) de 5,05 e 0,25 μg L−1 para quinolina e piridina, e 2,66 e 7,48 μg L−1 para carbazol e indol, respectivamente. Utilizando o método da adição de padrão, a determinação simultânea de quinolina e piridina na amostra de gasolina resultou em 25,0 ± 0,3 e 33,0 ± 0,7 mg L−1 e na amostra de diesel 80,3 ± 0,2 e 131 ± 0,4 mg L−1, respectivamente.
The presence of trace organonitrogen compounds (basic and neutral) such as quinoline, pyridine, carbazole and indole in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic and neutral nitrogen compounds in fuel samples such as gasoline and diesel. This method describes the use of preconcentration on an ion−exchange resin (Amberlyte® IR−120 H) and modified silica gel followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline, pyridine, carbazol and indole as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by a coupled chemical reaction. Very well resolved diffusion–controlled voltammetric peaks were obtained in N`,N`–dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBABF4 0.1 M) for quinoline (–1.95 V), pyridine (–2.52 V), carbazole (−2.67 V) and indole (−2.27 V) vs. Ag|AgCl|KClsat reference electrode. The proposed voltammetric method (DPV) displayed a good linear response from 0.10 to 300 mg L−1 and a limit of detection (L.O.D) of 5.05 and 0.25 μg L−1 for quinoline and pyridine and 2.66 e 7.48 μg L−1 for carbazole and indole, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline sample yielded 25.0 ± 0.3 and 33.0 ± 0.7 mg L–1 and in diesel sample yielded 80.3 ± 0.2 and 131 ± 0.4 mg L–1, respectively. On the other hand, simultaneous determination of carbazole and indole in gasoline sample was 64.6 ± 0.9 and 15.8 ± 0.3 mg L–1 and in the diesel sample 142 ± 1 and 9.28 ± 1 mg L–1, respectively.
The presence of trace organonitrogen compounds (basic and neutral) such as quinoline, pyridine, carbazole and indole in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic and neutral nitrogen compounds in fuel samples such as gasoline and diesel. This method describes the use of preconcentration on an ion−exchange resin (Amberlyte® IR−120 H) and modified silica gel followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline, pyridine, carbazol and indole as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by a coupled chemical reaction. Very well resolved diffusion–controlled voltammetric peaks were obtained in N`,N`–dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBABF4 0.1 M) for quinoline (–1.95 V), pyridine (–2.52 V), carbazole (−2.67 V) and indole (−2.27 V) vs. Ag|AgCl|KClsat reference electrode. The proposed voltammetric method (DPV) displayed a good linear response from 0.10 to 300 mg L−1 and a limit of detection (L.O.D) of 5.05 and 0.25 μg L−1 for quinoline and pyridine and 2.66 e 7.48 μg L−1 for carbazole and indole, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline sample yielded 25.0 ± 0.3 and 33.0 ± 0.7 mg L–1 and in diesel sample yielded 80.3 ± 0.2 and 131 ± 0.4 mg L–1, respectively. On the other hand, simultaneous determination of carbazole and indole in gasoline sample was 64.6 ± 0.9 and 15.8 ± 0.3 mg L–1 and in the diesel sample 142 ± 1 and 9.28 ± 1 mg L–1, respectively.
Descrição
Palavras-chave
Quimica analitica, Voltametria, Resina de troca iônica, Gasolina, Diesel
Como citar
OKUMURA, Leonardo Luiz. Desenvolvimento de métodos eletroanalíticos para determinação de compostos nitrogenados em combustíveis derivados do petróleo. 2008. 227 f. Tese (Doutorado) - Universidade Estadual Paulista, Instituto de Química., 2008.