Development of multi-residue and selective methods for the ultra-sensitive determination of endocrine disrupting chemicals in aqueous samples
Since World War II, the world has witnessed a large increase in the production of chemicals. Some of these chemicals, like pesticides, were designed for wide spread use. Others, like polychlorinated biphenyls (PCBs), were rather accidentally released into the environment by leakages or waste dumping. At that time, little or no attention was paid to the possible consequences that could result from the use, misuse and distribution of these chemicals. This ignorance changed with the publication of Rachel Carson’s Silent Spring in 1962. This book documented for the first time the detrimental effects of pesticides on wildlife. More specifically, the link was proven between egg shell thinning of birds and the pollution of the surrounding environment with dichlorodiphenyltrichloroethane (DDT) [1]. From that time, public awareness was born and grew ever since. Only three decades later, a new disturbing event was signalled in an article by Theo Colborn [2]. He described the deleterious influence that certain chemicals can have on the development of endocrine systems. These endocrine disrupting chemicals (EDCs) were linked to reproductive problems like the decrease in fertility of bird. Since then, there is a growing scientific concern, public debate and media attention over the possible effects on wildlife and humans that may result from exposure to chemicals that have the potential of interfering with the endocrine system [3]. Establishing a causal relationship between the presence of EDCs in the environment and their possible effects on human health is a challenging quest. Not only are the EDCs chemically very heterogeneous, but they cause adverse effects at concentration levels as low as 1 ng/L. In addition, the environmental matrix is very complex. Therefore, sample clean-up en pre-concentration of the sample is necessary before analysis. In this framework, the current work focuses on the optimization of the sample preparation in order to develop selective and multi-residue methods for the determination of EDCs in aqueous samples. In the first part of the work, a multi-residue method is developed using sorptive extraction in combination with in-situ derivatization. Since the extraction of polar analytes is limited when using sorptive extraction with polydimethylsiloxane (PDMS), a novel type of sample preparation namely sorptive membrane solvent extraction, was developed and evaluated for the determination of atrazine and its polar metabolites in aqueous samples. Another attempt for the determination of polar analytes was done by preparing monoliths as extraction medium. Finally, a new selective artificial receptor for endocrine disrupting chemicals, based on the human estrogen receptor, was synthesized and evaluated using affinity chromatography and solid phase extraction (SPE). Although this work merely tips the iceberg with regard to providing total insight in the analysis of EDCs in aqueous samples, it aims to present the reader a broad overview of the different analytical techniques that can be used, their corresponding shortcomings and possible solutions. Furthermore, this work aims at inciting other investigators and the governmental bodies to continue the research in this area; as large deficits remain especially with regard to environmental and public safety.
Chemistry, aqueous sample, sample preparation, EDC, chromatography
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