Authors
Abstract(s)
O objetivo desta tese é a implementação e validação dos métodos para determinação de sulfato, alcalinidade e cloreto em águas para consumo humano, águas naturais doces e águas residuais usando um autoanalisador multiparamétrico Aquakem no Laboratório dos Serviços Municipalizados de Água e Saneamento de Sintra (SMAS de Sintra).
A análise de sulfatos no Aquakem baseia-se na precipitação do sulfato, em meio ácido, como sulfato de bário. O precipitado obtido é estabilizado com uma solução de gelatina ou Tween 20 e a suspensão homogénea é então medida no Aquakem, a um comprimento de onda de 420 nm, contra uma reta de calibração.
A alcalinidade no Aquakem é determinada pela medição da absorvância de um complexo formado pela amostra com o azul de bromofenol (pigmento aniónico), numa solução tampão com pH 3,5. O aumento de cor é proporcional ao aumento de alcalinidade na amostra e é medido a 600 nm.
O princípio do método de análise de cloreto no Aquakem baseia-se na reação do cloreto com o tiocianato de mercúrio (II) que forma um composto não iónico. Os iões de tiocianato libertados reagem em solução ácida com o nitrato de ferro (II) formado um complexo corado castanho avermelhado cuja coloração é posteriormente medida a 480nm. Esta concentração é relacionada com a concentração de cloreto por uma curva de calibração.
Amostras das diferentes matrizes foram analisadas no Aquakem e os resultados obtidos nos diferentes métodos implementados foram comparados com os resultados obtidos em métodos já acreditados, e foram considerados equivalentes. Amostras provenientes de ensaios interlaboratoriais revelaram resultados satisfatórios em todos os métodos.
Com base nestes resultados obtidos e pelo cumprimento dos critérios estabelecidos nos procedimentos de validação de métodos analíticos foi possível a validação destes métodos implementados no laboratório do SMAS de Sintra.
The objective of this work is the implementation and validation of methods for sulphate, alkalinity and chloride determination in drinking water, fresh water and wastewater using an auto analyser Aquakem in the SMAS de Sintra laboratory. The sulphate analysis on Aquakem is based on precipitating the sulphate, in acid solution, as barium sulphate. The obtained precipitate is stabilized with a gelatine solution or Tween 20, and the suspension is then measured at a wavelength of 420 nm, against a calibration curve. Alkalinity on Aquakem is determined by measuring the absorbance of a complex formed by the sample with bromophenol blue (anionic pigment), using a buffer solution of pH 3.5. The colour increase is proportional to the increase of alkalinity in the sample and is measured at 600 nm. The principle of chloride analysis on Aquakem is based on the reaction of the chloride with thiocyanate mercury (II) forming a non-ionic compound. The released thiocyanate ions react in acid solution with the iron (II) nitrate forming a reddish brown complex whose colour is subsequently measured at 480 nm. This concentration is proportional to the chloride concentration using a calibration curve. Different matrices samples were analysed in Aquakem and the results obtained in the Aquakem methods were compared with the results obtained from methods previously accredited, and were considered equivalents. Samples from interlaboratory tests showed satisfactory results in all methods. Based on these results and on the fulfilment of the criteria set out in the analytical methods validation procedures was possible to validate these methods implemented in the laboratory of SMAS Sintra.
The objective of this work is the implementation and validation of methods for sulphate, alkalinity and chloride determination in drinking water, fresh water and wastewater using an auto analyser Aquakem in the SMAS de Sintra laboratory. The sulphate analysis on Aquakem is based on precipitating the sulphate, in acid solution, as barium sulphate. The obtained precipitate is stabilized with a gelatine solution or Tween 20, and the suspension is then measured at a wavelength of 420 nm, against a calibration curve. Alkalinity on Aquakem is determined by measuring the absorbance of a complex formed by the sample with bromophenol blue (anionic pigment), using a buffer solution of pH 3.5. The colour increase is proportional to the increase of alkalinity in the sample and is measured at 600 nm. The principle of chloride analysis on Aquakem is based on the reaction of the chloride with thiocyanate mercury (II) forming a non-ionic compound. The released thiocyanate ions react in acid solution with the iron (II) nitrate forming a reddish brown complex whose colour is subsequently measured at 480 nm. This concentration is proportional to the chloride concentration using a calibration curve. Different matrices samples were analysed in Aquakem and the results obtained in the Aquakem methods were compared with the results obtained from methods previously accredited, and were considered equivalents. Samples from interlaboratory tests showed satisfactory results in all methods. Based on these results and on the fulfilment of the criteria set out in the analytical methods validation procedures was possible to validate these methods implemented in the laboratory of SMAS Sintra.
Description
Trabalho Final de mestrado para obtenção do grau de Mestre em Engenharia Química e Biológica
Keywords
Sulfato Sulphate Alcalinidade Alkalinity Cloreto Chloride Aquakem SMAS de Sintra
Pedagogical Context
Citation
LUZ, Célia Maria Mendes da - Desenvolvimento de métodos de análise físico-química em águas usando um analisador multiparamétrico AQUAKEM. Lisboa: Instituto Superior de Engenharia de Lisboa, 2015. Dissertação de mestrado.
Publisher
Instituto Superior de Engenharia de Lisboa