Effect-directed Analysis (EDA)

A bioassay measures a particular effect of a substance, but does not identify the substance itself. In the case of an unexpected or increased bioassay response, the question remains: which substance is responsible for this? Effect Directed Analysis (EDA) is used to answer this. EDA is a combination of bioassays, liquid chromatography and screening. An (extract of) a water sample is separated via an LC column. The eluate is split in parts, and one part of it is sent to a mass spectrometer. The other part is collected in very small fractions and every fraction is then tested in a bioassay with a relevant effect as endpoint, such as genotoxicity or hormone disruption. The fractions which showed an effect contain a relevant chemical. The fractions correspond to a certain peak of the same chemical at the same retention time in the mass spectrometer. By using targeted or untargeted screening, the identity of the chemical is determined.

In collaboration with fellow researchers from the VU in Amsterdam, Het Waterlaboratorium has developed and implemented an EDA platform that performs fractionation at a very high resolution. A high correlation between bioassay activity and signal in the mass spectrometer can be achieved. As a result, the chance of successful identification of active substances is higher. The method is schematically depicted in the figure below.

Information and examples of applications of the EDA platform at HWL can be found here:

• Zwart N, Jonker W, Broek Rt, de Boer J, Somsen G, Kool J, et al. Identification of mutagenic and endocrine disrupting compounds in surface water and wastewater treatment plant effluents using high-resolution effect-directed analysis. Water Research. 2020;168:115204.
• Zwart N, Nio SL, Houtman CJ, de Boer J, Kool J, Hamers T, et al. High-Throughput Effect-Directed Analysis Using Downscaled in Vitro Reporter Gene Assays To Identify Endocrine Disruptors in Surface Water. Environmental Science & Technology. 2018;52:11.
• Houtman CJ, ten Broek R, van Oorschot Y, Kloes D, van der Oost R, Rosielle M, et al. High resolution effect-directed analysis of steroid hormone (ant)agonists in surface and wastewater quality monitoring. Environmental Toxicology and Pharmacology. 2020;80:103460.

In the project “RoutinEDA”, continuous research is done to improve the EDA platform. You can find information about this here

More information about Effect-Directed Analysis in general can be found here:

• Houtman CJ, Legler J, Thomas KV. Effect-Directed Analysis of Endocrine Disruptors in Aquatic Ecosystems. In: Brack W, editor. Effect-Directed Analysis of Complex Environmental Contamination. The Handbook of Environmental Chemistry. 15. Berlin-Heidelberg: Springer Verlag; 2011. p. 237-66.
• Jonker LW, Lamoree MH, Houtman CJ, Kool J. Methodologies for Effect-Directed Analysis: Environmental Applications, Food Analysis, and Drug Discovery. In: Kool J, Niessen WMA, editors. Analyzing Biomolecular Interactions by Mass Spectrometry. First Edition ed. Weinheim Germany: Wiley VCH Verlag GmbH & Co. KGaA; 2015. p. 111-63.