Analysis of organic contaminants in water intended for human consumption – analysis by GC-MS with different sample preparation techniques (LLE and SPE)

Dissertação de mestrado, Qualidade em Análises, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2016Water is a fundamental resource for human life, as well as for other organisms. Pesticides are one of the most critical group of components that can contaminate rivers and lakes, affecting the quality of water. EPAL, as the public water company of Lisbon, is responsible for monitoring the water quality, analyzing microbiological, inorganic and organic parameters in water, according to the established water legislation. However, new compounds are always being added to the legislation whenever it is revised. It is necessary to develop new analytical methods to cover the monitoring of these new added compounds. That is the case of some of the compounds of this study. Therefore, an analytical method was developed, optimized and validated for the analysis of organic components (pesticides) in different water matrices by gas chromatography coupled with mass spectrometry (GC-MS). The list of pesticides studied is composed by: biphenyl, dicofol, chlorpyrifos, aclonifen, quinoxyfen, cybutryne and the isomers of cypermethrine (alpha-cypermethrine, beta-cypermethrine, theta-cypermethrine and zeta-cypermethrine). In order to concentrate and extract the pesticides from the water sample, two different extractions techniques - liquid-liquid extraction (LLE) and solid phase extraction (SPE) - were tested. The results showed that LLE gave successful recovery values, while the extraction using SPE showed many problems. Different tests were carried out in order to solve the problems and to optimize the extraction procedure, such as matrix effect, salting-out or sodium thiosulfate tests. The method was validated, studying the working range, linearity, selectivity, precision, trueness and, LOD and LOQ. Uncertainty of the method was estimated following two different models, bottom-up and top down approach. Then, these results were compared with the limits set by the legislation for drinking and surface water, concluding that the method is effective for the analysis of these pesticides in drinking water and for some of them is also effective for their analysis in surface water, within the limits established by the legislation