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Implementação e validação de métodos de quantificação de cloro e PCBs em óleos usados, pelas normas EPA Method 9075 e EN 12766, na Carmona S.A.
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Este trabalho foi executado na Carmona S.A, empresa da região de Setúbal, com a missão de
recolha e tratamento de resíduos perigosos e tinha por objetivo a validação de dois métodos de
quantificação cloro em óleos usados por forma a definir o destino destes resíduos.
O trabalho iniciou-se estudando e avaliando o método de quantificação de PCBs por cromatografia
gasosa com ECD, tendo-se concluído que a forma como o método tinha sido implementado tinha de ser
modificada. Alterou-se o método de processamento anterior e traçaram-se seis curvas de calibração,
uma para cada congénere, por forma que a determinação da quantidade total de PCBs, refletisse a
variabilidade da resposta instrumental dos diversos compostos. Os coeficientes de correlação obtidos
foram todos superiores a 0,999 e os limites de deteção e quantificação do método calculados foram de
1,12 e 3,58 mg/kg, respetivamente. A avaliação da precisão implicou estudos de repetibilidade, precisão
intermédia e de duplicados que foram bem conseguidos, tendo-se obtido coeficientes de variação
inferiores aos definidos na norma do método, EN 12766. Para avaliar a justeza avaliou-se um material
de referência certificado, efetuaram-se ensaios de fortificação e realizou-se um ensaio interlaboratorial
de aptidão onde se obtiveram bons Z-scores. Finalmente determinou-se a incerteza do método (0,352
mg/kg), concluindo-se as etapas de validação.
O estudo do método de quantificação de cloro por espectroscopia de fluorescência de raios X, foi
iniciado e verificou-se que a metodologia implementada não correspondia às diretrizes da norma EPA
Method 9075, pois a interferência do enxofre não era contabilizada. Efectuaram-se ensaios com este
interferente e foi possível obter um bom ajuste com a função não linear [𝐶𝑙 = (0,77249 × 𝐼 −
50,24905) × (1 + 0,16691 × 𝑆)]. Foram ainda avaliadas várias condições de trabalho por forma a
melhorar a razão sinal / ruído, no entanto, por falta de tempo, não foi possível otimizar por completo as
condições de trabalho.
This work was carried out at Carmona S.A., a company in the Setúbal region dedicated to the collection and treatment of hazardous waste. The aim was to validate two methods for quantifying chlorinated compounds in used oil to assess the destination of these oil wastes. This work began with the PCBs quantifying method by ECD gas chromatography, and a preliminary analysis revealed the overall methodology previously implemented had to thoroughly reviewed. In short, the existing processing method was changed, and six calibration curves were drawn, one for each PCB congener, so that the determination of the total quantity of PCBs would mimic the real instrumental response of these compounds. All the curves showed a correlation coefficient larger than 0.999 and the calculated detection and quantification limits of the method were 1.12 and 3.58 mg/kg, respectively. The precision evaluation was based on a repeatability, intermediate precision, and duplicates study, which proved successful with variation coefficients lower than those mentioned in the method standard, EN 12766. To assess the fairness of the methods, a certified reference material was evaluated and fortification tests, as well as an interlaboratory suitability test were carried out. In the latter ones the Z-score values were mostly classified as good. The uncertainty of the method (0.352 mg/kg) was determined. In the total chlorine quantification method by X-ray fluorescence spectroscopy, it was found that the previously implemented method did not follow EPA Method 9075 guidelines of. A non-linear fit was implemented [𝐶𝑙 = (0.77249 × 𝐼 − 50.24905) × (1 + 0.16691 × 𝑆)] showing a correlation coefficient of over 0.999. In addition, the working conditions allowing the highest possible peak and the lowest background were evaluated, however, it the full optimization of integration interval and analysis time was not concluded due to lack of time.
This work was carried out at Carmona S.A., a company in the Setúbal region dedicated to the collection and treatment of hazardous waste. The aim was to validate two methods for quantifying chlorinated compounds in used oil to assess the destination of these oil wastes. This work began with the PCBs quantifying method by ECD gas chromatography, and a preliminary analysis revealed the overall methodology previously implemented had to thoroughly reviewed. In short, the existing processing method was changed, and six calibration curves were drawn, one for each PCB congener, so that the determination of the total quantity of PCBs would mimic the real instrumental response of these compounds. All the curves showed a correlation coefficient larger than 0.999 and the calculated detection and quantification limits of the method were 1.12 and 3.58 mg/kg, respectively. The precision evaluation was based on a repeatability, intermediate precision, and duplicates study, which proved successful with variation coefficients lower than those mentioned in the method standard, EN 12766. To assess the fairness of the methods, a certified reference material was evaluated and fortification tests, as well as an interlaboratory suitability test were carried out. In the latter ones the Z-score values were mostly classified as good. The uncertainty of the method (0.352 mg/kg) was determined. In the total chlorine quantification method by X-ray fluorescence spectroscopy, it was found that the previously implemented method did not follow EPA Method 9075 guidelines of. A non-linear fit was implemented [𝐶𝑙 = (0.77249 × 𝐼 − 50.24905) × (1 + 0.16691 × 𝑆)] showing a correlation coefficient of over 0.999. In addition, the working conditions allowing the highest possible peak and the lowest background were evaluated, however, it the full optimization of integration interval and analysis time was not concluded due to lack of time.
Descrição
Tese de Mestrado, Química Tecnológica, 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Quantificação de compostos clorados em óleos usados Implementação Validação Cromatografia gasosa com ECD Espectroscopia de fluorescência de raios X Teses de mestrado - 2024