Estratégias de preparo de amostras empregando solventes eutéticos profundos naturais para determinação de contaminantes inorgânicos em amostras vegetais e alimentícias.
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2022-10-04
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Universidade Estadual Paulista (Unesp)
Resumo
O desenvolvimento de métodos baseados na química analítica verde (QAV) tem atraído atenção nos últimos anos, priorizando a miniaturização de métodos, a diminuição do consumo de reagentes, a eficiência energética e a redução do uso de compostos tóxicos. O emprego de solventes é crucial para o preparo de amostras, havendo uma necessidade do desenvolvimento de novos compostos que sejam ambientalmente amigáveis, e que atendam às necessidades analíticas de cada método. Os solventes eutéticos profundos naturais (NADES) surgiram com enorme potencial de aplicação devido as suas vantagens como baixa toxicidade, propriedades físico-químicas possivelmente moduláveis, baixo custo e simples preparação. Neste trabalho, sintetizou-se NADES a partir de misturas de ácido málico, ácido cítrico, xilitol e água por agitação e aquecimento nas proporções definida por um planejamento de misturas previamente realizado, avaliando as propriedades de densidade e viscosidade. Os valores de densidade (1,25 ± 0,01 e 1,26 ± 0,01 g mL-1) e viscosidade (7,54 ± 0,03 e 5,20 ± 0,01 mPa s) para os solventes AC-Xil e AC-AM, foram obtidos, respectivamente. Estes solventes foram empregados em métodos assistidos por radiação micro-ondas e ultrassom (MAE e UAE, respectivamente) para determinações de As, Cd, Cr e Pb por espectrometria de massas com plasma indutivamente acoplado (ICP-MS) em amostra vegetal. A partir do planejamento Doehlert a condição ótima para MAE utilizando NADES AC-Xil e NADES AC-AM para extração de As, Cd e Pb no modo padrão e As no modo KED (vazão de 2,0 mL min-1 de He), sendo temperatura (100 ºC), tempo de extração (40 min) e razão m v-1 (40:1) com os valores otimizados. Para o método UAE escolheu-se a condição de 40 minutos, 40 ºC e razão m v-1 de 30:1. A aplicação da condição otimizada para cada método resultou em recuperações na faixa de 66,8 - 84,3 % para MAE (As, Cd e Pb) e 95,7 - 109,5 % para UAE (As) em amostra de capim forrageira, enquanto que para as amostras alimentícias os valores foram menores que o LOD. Os valores determinados para LODs e LOQs empregando NADES, em geral, foram superiores aos valores para MW-AD por conta do aumento do sinal analítico ocasionado por reações de transferência de carga entre o analito e espécies de carbono no plasma. Os métodos avaliados mostraram-se em consonância com os princípios da química analítica verde uma vez que foram considerados ambientalmente amigáveis devido a avaliação pelas métricas Eco escala analítica e GAPI.
The development of methods based on green analytical chemistry (QAV) had attracted attention in recent years prioritizing method miniaturization, reducing reagent consumption, energy efficiency, and reducing the use of toxic compounds. The use of solvents is crucial for sample preparation, and there is a need to develop new compounds that are environmentally friendly that meet the analytical needs of each method. Natural deep eutectic solvents (NADES) have emerged with enormous potential for application due to their advantages such as low toxicity, possibly modifiable physicochemical properties, low cost and simple preparation. In this work, NADES were synthesized from mixtures of malic acid, citric acid, xylitol and water by stirring and heating in the proportions defined by a previously mixture planning evaluating the properties of density and viscosity. The values of density (1.25 ± 0.01 and 1.26 ± 0.01 g mL-1) and viscosity (7.54 ± 0.03 and 5.20 ± 0.01 mPa s) for the solvents AC-Xil and AC-AM were obtained, respectively. These solvents were used in microwave and ultrasound-assisted methods (MAE and UAE, respectively) for determination of As, Cd, Cr and Pb by inductively coupled plasma mass spectrometry (ICP-MS) in plant and food samples. From the Doehlert design, the optimal condition for MAE was reached using NADES AC-Xil and NADES AC-AM for extraction of As, Cd and Pb in standard mode and As in KED mode (flow rate of 2.0 mL min-1 of He), being temperature (100 ºC), extraction time (40 min) and m v-1 ratio (40:1) the optimized values. For the UAE method, the condition of 40min, 40 ºC and 30:1 was chosen. The application of the optimized condition for each method resulted in recoveries in the range of 66.8 - 84.3 % for MAE (As, Cd and Pb) and 95.7 - 109.5 % for UAE (As) in a forage grass sample while whereas for the food samples the values were lower than the LOD. The values determined for LODs and LOQs using NADES, in general, were higher than the values for MW-AD due to the increase in the analytical signal caused by charge transfer reactions between the analyte and carbon species in the plasma. The methods evaluated were in line with the principles of green analytical chemistry since they were considered environmentally friendly due to evaluation by the Analytical Eco scale and GAPI metrics.
The development of methods based on green analytical chemistry (QAV) had attracted attention in recent years prioritizing method miniaturization, reducing reagent consumption, energy efficiency, and reducing the use of toxic compounds. The use of solvents is crucial for sample preparation, and there is a need to develop new compounds that are environmentally friendly that meet the analytical needs of each method. Natural deep eutectic solvents (NADES) have emerged with enormous potential for application due to their advantages such as low toxicity, possibly modifiable physicochemical properties, low cost and simple preparation. In this work, NADES were synthesized from mixtures of malic acid, citric acid, xylitol and water by stirring and heating in the proportions defined by a previously mixture planning evaluating the properties of density and viscosity. The values of density (1.25 ± 0.01 and 1.26 ± 0.01 g mL-1) and viscosity (7.54 ± 0.03 and 5.20 ± 0.01 mPa s) for the solvents AC-Xil and AC-AM were obtained, respectively. These solvents were used in microwave and ultrasound-assisted methods (MAE and UAE, respectively) for determination of As, Cd, Cr and Pb by inductively coupled plasma mass spectrometry (ICP-MS) in plant and food samples. From the Doehlert design, the optimal condition for MAE was reached using NADES AC-Xil and NADES AC-AM for extraction of As, Cd and Pb in standard mode and As in KED mode (flow rate of 2.0 mL min-1 of He), being temperature (100 ºC), extraction time (40 min) and m v-1 ratio (40:1) the optimized values. For the UAE method, the condition of 40min, 40 ºC and 30:1 was chosen. The application of the optimized condition for each method resulted in recoveries in the range of 66.8 - 84.3 % for MAE (As, Cd and Pb) and 95.7 - 109.5 % for UAE (As) in a forage grass sample while whereas for the food samples the values were lower than the LOD. The values determined for LODs and LOQs using NADES, in general, were higher than the values for MW-AD due to the increase in the analytical signal caused by charge transfer reactions between the analyte and carbon species in the plasma. The methods evaluated were in line with the principles of green analytical chemistry since they were considered environmentally friendly due to evaluation by the Analytical Eco scale and GAPI metrics.
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Palavras-chave
Química analítica verde, NADES, Composição inorgânica, ICP-MS, Green analytical chemistry, Natural deep eutectic solvents (NADES), Inorganic elements