Desenvolvimento de métodos analíticos ambientalmente amigáveis utilizando plataforma de papel com detecção por imagens digitais
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Data
2019-05-16
Autores
Rocha, Thiago Luís Canozza
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Este trabalho aborda o desenvolvimento de spot tests em plataforma de papel, utilizando barreiras hidrofóbicas feitas com impressora de cera para o confinamento de soluções para fins de análise quantitativa de ferro, níquel e cromo. Foram construídas também barreiras hidrofóbicas utilizando lápis de cor, que contém cera em sua composição. Como método de detecção da coloração dos spots, utilizou-se um scanner para digitalizar as áreas dos spots e, a partir da imagem digitalizada, foi possível determinar as intensidades de coloração dos spots contendo soluções padrão e compará-las com a coloração das amostras, sendo possível, dessa maneira, a quantificação dos elementos químicos estudados. As amostras foram escolhidas de acordo com a facilidade de obtenção e utilização no dia a dia, além da necessidade de desenvolvimento de novos métodos que reduzem tempo de análise e custo. Para o ferro foi escolhido um medicamento contendo sulfato ferroso em sua composição. A equação da curva de calibração obtida é Ir = 284,8xC + 0,003; R2 = 0,992, onde Ir é a Intensidade relativa, e o resultado obtido foi 42,2 ± 0,4 mg de ferro por comprimido. Os limites de detecção e quantificação foram determinados experimentalmente e os resultados são, respectivamente, em mol L-1: 1,17x10-4 e 3,52x10-4. Um método espectrofotométrico foi utilizado como comparativo e apresentou curva de calibração cuja equação é A = 11,158xC e R2 = 0,999. O resultado apresentado por esse método é 40,0 ± 0,1 mg de Fe por comprimido. Já os outros metais, cromo e níquel, foram analisados em uma amostra padrão certificada de aço inoxidável AISI 316. Para o cromo e o níquel, não foram necessárias análises comparativas, uma vez que o material era certificado por órgão competente. O spot test para determinação de cromo apresentou curva analítica de equação Ir = 46,83xC + 0,004, limites de detecção e quantificação de 1,91x10-6 e 6,38x10-6, respectivamente, em mol L-1 e resultado de 16,6 ± 1,2%. O resultado que consta no certificado de análise do padrão é 17,37%. Já no caso do níquel, o spot test para determinação desse metal apresentou curva analítica de equação Ir = 23,51xC – 0,011, limites de detecção e quantificação de 1,00x10-5 e 3,34x10-5, respectivamente, em mol L-1 e resultado de 10,7 ± 0,4%. O resultado que consta no certificado de análise do padrão é 11,12%. Em todos os casos, foram feitos testes de comparação entre médias utilizando o teste t de Student, concluindo que todos os spot tests se mostraram tão confiáveis quanto métodos referenciados.
This work tells about the development of paper based spot tests, using hydrophobic bareers built with waxjet printer for the confinement of solutions for purposes of quantitative analisys of Iron, nickel and chrome. Hydrophobic barriers were also built using color pencil, which contains wax in its composition. As a color detection method, a scanner was used to scan the spot areas and, using the digital images, it was possible to determine the color intensities of the spots containing pattern solutions and compare them with those ones containing the sample solutions, so that it was possible to quantify the target elements. The samples were chosen according to the facility to obtain and their day by day use, besides the necessity of developing new methods that reduce time and costs. For the iron it was chosen a medicine containing ferrous sulfate in its composition. The equation of the calibration curve was Ir = 284,8xC + 0,003, R2 = 0,992 and the result obtained was 42,2 ± 0,4 mg of iron in each tablet. The detection and quantification limits were determined and the results are, respectively, 1,17x10-4 e 3,52x10-4 mol L-1. A spectrophotometric method was used as comparative method and provided calibration curve with equation A = 11,158xC e R2 = 0,999. The result provided by this method was 40,0 ± 0,1 mg of Fe in each tablet. The other metals, chrome and nickel, were analised in a pattern sample of stainless steel AISI 316. For these analites, there were no need of comparative methods, once the sample had already been certified. The spot test for chrome provided analitycal curve which equation was Ir = 46,83xC + 0,004, limits of detection and quantification 1,91x10-6 e 6,38x10-6, respectively, in mol L-1 and result 16,6 ± 1,2%. The value in the certificate of analisys of the pattern is 17,37%. For the nickel, the spot test provided analitycal curve with equation Ir = 23,51xC – 0,011, limits of detection and quantification 1,00x10-5 e 3,34x10-5, respectively, in mol L-1 and result 10,7 ± 0,4%. The value in the certificate of analisys of the pattern is 11,12%. In all these cases, were made comparative tests using Student t test, concluding that all the spot tests are as trustable as the reference methods.
This work tells about the development of paper based spot tests, using hydrophobic bareers built with waxjet printer for the confinement of solutions for purposes of quantitative analisys of Iron, nickel and chrome. Hydrophobic barriers were also built using color pencil, which contains wax in its composition. As a color detection method, a scanner was used to scan the spot areas and, using the digital images, it was possible to determine the color intensities of the spots containing pattern solutions and compare them with those ones containing the sample solutions, so that it was possible to quantify the target elements. The samples were chosen according to the facility to obtain and their day by day use, besides the necessity of developing new methods that reduce time and costs. For the iron it was chosen a medicine containing ferrous sulfate in its composition. The equation of the calibration curve was Ir = 284,8xC + 0,003, R2 = 0,992 and the result obtained was 42,2 ± 0,4 mg of iron in each tablet. The detection and quantification limits were determined and the results are, respectively, 1,17x10-4 e 3,52x10-4 mol L-1. A spectrophotometric method was used as comparative method and provided calibration curve with equation A = 11,158xC e R2 = 0,999. The result provided by this method was 40,0 ± 0,1 mg of Fe in each tablet. The other metals, chrome and nickel, were analised in a pattern sample of stainless steel AISI 316. For these analites, there were no need of comparative methods, once the sample had already been certified. The spot test for chrome provided analitycal curve which equation was Ir = 46,83xC + 0,004, limits of detection and quantification 1,91x10-6 e 6,38x10-6, respectively, in mol L-1 and result 16,6 ± 1,2%. The value in the certificate of analisys of the pattern is 17,37%. For the nickel, the spot test provided analitycal curve with equation Ir = 23,51xC – 0,011, limits of detection and quantification 1,00x10-5 e 3,34x10-5, respectively, in mol L-1 and result 10,7 ± 0,4%. The value in the certificate of analisys of the pattern is 11,12%. In all these cases, were made comparative tests using Student t test, concluding that all the spot tests are as trustable as the reference methods.
Descrição
Palavras-chave
Escanometria, Spot test, Química verde