ESR9 Carina Schönsee – University of Copenhagen

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ESR9 Carina Schönsee

Project: Physico-chemical property determination of natural toxins

Principal supervisor: Dr. Thomas Bucheli

Intro to project:

Aquatic fate and mobility of any organic compound in the environment can be systematically and quantitatively described by distribution coefficients such as those defining octanol-water partitioning (Kow) and sorption processes (Kd). The Kow as a merely lab-based model phase partitioning constant is known to be related to water solubility (sw), organic carbon partitioning coefficients (Koc) and bioconcentration factors. From this value a tendency on a compound’s hydrophobicity or lipophilicity can be derived making it an important estimate for toxicity evaluation. In contrast, the solid-water distribution coefficient Kd directly describes sorption processes in the aqueous environment. The Kd is not only influenced by the compound’s properties but also by aqueous phase composition (e.g., pH, ionic strength) and solid matter characteristics, such as surface charge, types of functional groups or pore volumes. Transport, phase transfer, bioavailability as well as accessibility of molecules for transformation reactions are notably controlled by sorption or surface complexation to surface-functional groups of geosorbents. Leaching of chemicals into water bodies can be prevented and the risk for drinking water contamination reduced due to retardation and accumulation of contaminants in soils or sediments as a result of sorption processes. However, sorption to suspended particulate or dissolved matter can also strongly increase a compound’s mobility by particle-facilitated transport and can trigger widespread contamination.

Up to now, hardly any data defining those key parameters for plant-produced natural toxins, so called phytotoxins, is available and in silico prediction tools show limited applicability for multifunctional organics as they are found within this group of chemicals. The wide variety of compound classes together with the frequent unavailability of pure standards pose a challenge. In addition, time-consuming and material-intensive standard methods are a major drawback when it comes to determining relevant properties for as many toxins as possible. Altogether, the lack in experimental data and poor quality of estimated values stress the urgent need for reliable, robust methods for high-throughput determination of physico-chemical properties as basis for profound environmental risk assessment.

Therefore, this project aims to establish HPLC-based high-throughput methods for property determination for a wide range of phytotoxins. For the determination of Kow, different approaches will be followed to evaluate which is the best applicable method for phytotoxins. Column chromatography will be applied in systematic studies of sorption behavior of phytotoxins to solid surfaces, focusing on both method optimization and mechanistic aspects of sorption processes under different environmental conditions. Subsequently, generated data for Kow and Kd will help to validate and calibrate prediction models for parameter estimation. Ultimately, the outcome of this project will also provide first indications on those phytotoxins that should be further considered and investigated as part of the complex mixture of micropollutants affecting water quality.