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Contributions of COSMO-RS to Environmental-Chemistry Problems - Kai-Uwe Goss

Contributions of COSMO-RS to Environmental-Chemistry Problems - Kai-Uwe Goss. The problem. Transport. with water, DOM, air,aerosols,. salts, soot, organic matter, minerals, water. Bioaccumulation. Retention. adipose, proteins, membranes. soils, sediments. Toxicity. minerals,

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Contributions of COSMO-RS to Environmental-Chemistry Problems - Kai-Uwe Goss

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  1. Contributions of COSMO-RS to Environmental-Chemistry Problems -Kai-Uwe Goss

  2. The problem ... Transport with water, DOM, air,aerosols, ... salts, soot, organic matter, minerals, water Bioaccumulation Retention adipose, proteins, membranes soils, sediments Toxicity minerals, organic matter

  3. The players ... non-polar polar no functional groups multifunctional

  4. The challenge ... • ... we need a method that predicts partition constants for the whole variety of chemical structures between • various environmental phases: • air • water • humic substances • aerosols • biological tissues relevant for transport relevant for toxicology

  5. Sorption Paradigmsfrom the early days Octanol typically serves as model phase for all typesof natural organic phases (humic substances, organic fraction of aerosols, biological tissues). log Khumin/water = log Koctanol/water + const. log Kfat/water = log Koctanol/water + const. log Kaerosol OM/air = log Koctanol/air + const.

  6. KOW single parameter correlation Is octanol a suitable model for soil organic matter? non-polar chemicals yes

  7. KOW single parametercorrelation Is octanol a suitable model for natural organic matter? non-polar chemicals polar chemicals including 50 pesticides yes NO!!!!

  8. Linear Solvation Energy Relationship´s LSER equations describe partitioning of any chemical i between phases 1 and 2. log Ki 12=Cohesion∆12•Vi+vdW∆12•vdWi + ... energy of cavity formation van-der-Waals interactions s∆12•Si+c ... + HD∆12•HAi+HA∆12•HDi+ other electrostatic interactions H-bond interactions

  9. LSER for soil organic matter sorption of polar and apolar compounds to SOM predicted with a rmse of ca. 0.4 log units Disadvantage: chemical descriptors have to be determined experimentally!

  10. Predictions from molecular structure - current practice 70 000 chemical structures among them many multifunctional ones empiricalmodels (e.g. EPI suite) Kair/water Koctanol/water Bioaccumulation Sorption in Soil Organic Matter Sorption to Aerosols

  11. Shortcomings of increment methods • correction factors needed for non-additive behavior of multiple functional groups • => not feasible for the multitude of existing chemicals • application domain limited by the calibration • data set, e.g. perfluorinated compounds • no method provided to estimate the application • domain • the specific partition behavior of diastereomers and isomers such as , , -HCH is not reflected

  12. Predictions from molecular structure – COSMO-RS • allows to account for the 3-D conformation of a chemical Isomers of Dichlorophenol • not limited to specific • (simple) molecular structures • no need to define an application domain 1:1 line

  13. Predictions from molecular structure – COSMO-RS • Two modes of using COSMO-RS for complex • natural phases are conceivable : • Using COSMO-moments or predicting LSER descriptors=> information on the interaction properties of a chemical are reduced to 5 parameters • => complementary information on the natural phase is provided by a calibration with experimental data • 2. Representing natural organic phases by a molecular structure

  14. n Predicting Sorption to Leonardite Humic Acid Proposed Leonardite humic acid monomer (based on 13C-NMR and elemental analysis) : no fitting !

  15. Predicting Sorption to Aerosols generic model for organic aerosol components (Kalberer et al. 2004) no fitting !

  16. Summary of performance of COSMO-RS • generally good performance if suitable model structure was identified (rmse 0.6-0.8 log units) • performance is worse for - adsorption to water surface - partitioning of highly halogenated chemicals into the gas phase • COSMO-RS appears to be superior to existing QSARs for complex molecules in phases other than octanol • high-throughput screening is possible with COSMOfrag

  17. Outlook Polar and non-polar organic chemicals ? Aerosols various surfaces Biota DOM & SOM minerals, water (Humic Substances) aqueous and organic fraction storage lipids phospholipids proteins Ion Exchange Partitioning of Free Ions Formation and Partitioning of Ion Pairs Ionic organic compoundspesticides, surfactants, pharmaceuticals,...

  18. Thank you for your attention !

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