Química verde aplicada para determinação de arsênio em tecido animal e vegetal por ICP-MS
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Data
2021-07-23
Autores
Pedrosa, Fabiana Lopes
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Universidade Estadual Paulista (Unesp)
Resumo
O desenvolvimento e a otimização de novas metodologias que diminuam o impacto ao meio ambiente e contribuam para uma química mais sustentável se faz necessário, assim a busca por métodos analíticos que minimizem o uso de reagente e de energia e que reduzam a quantidade de resíduos gerados é recomendável pelos conceitos da Química Verde. Este trabalho teve como objetivo o desenvolvimento e otimização de dois procedimentos de preparo de amostras para tecidos vegetal e animal: um baseado na digestão ácida assistida por radiação micro-ondas (MW-AD) e um segundo empregando radiação ultravioleta (UV), utilizando HNO₃ diluído e peróxido de hidrogênio (H₂O₂) como oxidante auxiliar, para amostra vegetal (Marandu, EMBRAPA E1001a) e tecido animal (Peixe – Tissue the Fish-Ipen) e determinação de arsênio empregando espectrometria de massa com plasma acoplado indutivamente (ICP-MS). Para a otimização dos procedimentos foram aplicados planejamentos fatoriais do tipo Doehlert, onde, a triagem e o ajuste fino das variáveis envolvidas nos processos foram realizadas e os modelos matemáticos gerados foram avaliados pela ANOVA (p < 0,05), onde não apresentaram falta de ajuste significativa. A melhor condição experimental para a decomposição de aproximadamente 200 mg de ambas as amostras por MW-AD foi uma mistura de 6 mL de HNO₃ (5 mol L-1 ) associada a 2,0 mL de H₂O₂ (30% v v-1 ), tempo de 15 minutos e temperatura de 190 °C, com um teor de 5 e 3 % de carbono residual para a forrageira marandu e o tecido de peixe, respectivamente. Para a metodologia de UV, a melhor condição para ambos tecidos foi de 150 mg de amostra, 6 mL de HNO₃ (0,65 mol L-1 ), 2,0 mL de H₂O₂ (30% v v-1 ) em um tempo de 24 minutos, com recuperação de arsênio de 93% para o marandu e 85% para o tecido de peixe. Os resultados mostraram que esses dois métodos estão de acordo com a Química Verde, evidenciando vantagens como o emprego de menores quantidade de solventes, de tempo de reação e de geração de resíduos, sendo considerados pela a Eco-Escala analítica métodos ambientalmente amigáveis e uma alternativa válida aos métodos convencionais de preparo de amostra.
The development and optimization of new methodologies that reduce the impact on the environment and contribute to more sustainable chemistry is necessary, as well as a search for analytical methods that minimize the use of reagent and energy and that reduce the amount of waste generated is recommended by the concepts of Green Chemistry. This work aimed to develop and optimize two sample preparation procedures: one based on Microwave-assisted Acid Digestion (MW-AD) and a second using ultraviolet (UV) radiation, using dilute nitric acid and hydrogen peroxide as auxiliary oxidant, for vegetable (Marandu, EMBRAPA E1001a) and animal tissue (Fish tissue, IPEN) and arsenic determination using inductively coupled plasma mass spectrometry (ICP-MS). For the optimization of the procedures, Doehlert design was used, in which the screening and fine-tuning of the variables involved in the processes performed and the generated mathematical models were assessed by ANOVA (p < 0.05), where non-synchronized lack of adjustment. The best experimental condition for decomposition of approximately 200 mg of both samples by MW-AD was a mixture of 6 mL of HNO₃ (5 mol L-1 ) and 2.0 mL of H₂O₂ (30% v v-1 ), time of 15 min and temperature of 190 °C, with a content of 5 and 3% of residual carbon for marandu and fish, respectively. For the UV methodology, the best condition for both tissues was 150 mg of sample, 6 mL of HNO₃ (0.65 mol L-1 ), 2.0 mL of H₂O₂ (30% v v-1 ) in one time 24 minutes, with 95% of recovery for arsenic in marandu and 93% for fish tissue. The results confirm that these two are in accordance with Green Chemistry, showing advantages such as the use of lower amounts of solvents, reaction time and waste generation, considered by the Eco-scale analytical environmentally friendly methods, and a valid alternative to conventional methods of sample preparation.
The development and optimization of new methodologies that reduce the impact on the environment and contribute to more sustainable chemistry is necessary, as well as a search for analytical methods that minimize the use of reagent and energy and that reduce the amount of waste generated is recommended by the concepts of Green Chemistry. This work aimed to develop and optimize two sample preparation procedures: one based on Microwave-assisted Acid Digestion (MW-AD) and a second using ultraviolet (UV) radiation, using dilute nitric acid and hydrogen peroxide as auxiliary oxidant, for vegetable (Marandu, EMBRAPA E1001a) and animal tissue (Fish tissue, IPEN) and arsenic determination using inductively coupled plasma mass spectrometry (ICP-MS). For the optimization of the procedures, Doehlert design was used, in which the screening and fine-tuning of the variables involved in the processes performed and the generated mathematical models were assessed by ANOVA (p < 0.05), where non-synchronized lack of adjustment. The best experimental condition for decomposition of approximately 200 mg of both samples by MW-AD was a mixture of 6 mL of HNO₃ (5 mol L-1 ) and 2.0 mL of H₂O₂ (30% v v-1 ), time of 15 min and temperature of 190 °C, with a content of 5 and 3% of residual carbon for marandu and fish, respectively. For the UV methodology, the best condition for both tissues was 150 mg of sample, 6 mL of HNO₃ (0.65 mol L-1 ), 2.0 mL of H₂O₂ (30% v v-1 ) in one time 24 minutes, with 95% of recovery for arsenic in marandu and 93% for fish tissue. The results confirm that these two are in accordance with Green Chemistry, showing advantages such as the use of lower amounts of solvents, reaction time and waste generation, considered by the Eco-scale analytical environmentally friendly methods, and a valid alternative to conventional methods of sample preparation.
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Palavras-chave
Análise elementar, Preparo de amostra, UV, Radiação micro-ondas, ICP-MS, Elemental analysis, Sample preparation, Microwave radiation