Effect of dissolved organic matter on pre-equilibrium passive sampling: A predictive QSAR modeling study

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Computational Chemistry

Background:

• Pre-equilibrium passive sampling is vital for understanding hydrophobic organic compound (HOC) behavior in aquatic environments.
• Complex environmental water matrices challenge traditional calibration methods for accurate sampling rate constants.
• Dissolved organic matter (DOM) significantly influences the sampling kinetics of HOCs.

Purpose of the Study:

• To develop a quantitative structure-activity relationship (QSAR) model for predicting HOC sampling rate constants in complex aqueous systems.
• To investigate and quantify the effect of dissolved organic matter (DOM) on HOC sampling kinetics.
• To establish a reliable method for determining HOC distribution, transfer, and fate in environmental waters.

Main Methods:

• A flow-through system was used to simulate environmental aqueous conditions with humic acid (HA) and (2-Hydroxypropyl)-β-cyclodextrin (β-HPCD).
• Experimental sampling rate constants were determined for various HOCs (PAHs, PCBs, pesticides).
• A Genetic Algorithm-Multiple Linear Regression (GA-MLR) approach was employed to build the QSAR model using DFT and Chem 3D calculated descriptors.

Main Results:

• Experimental rate constants increased significantly with increasing DOM concentration.
• DOM, specifically HA and β-HPCD, enhanced HOC sampling rates by 70-fold and 34-fold, respectively.
• The developed QSAR model demonstrated high credibility (Adj. R²=0.862) and predictability (Q²=0.835) for complex aqueous sampling.

Conclusions:

• The QSAR model effectively predicts HOC sampling rate constants in complex matrices, overcoming traditional calibration limitations.
• DOM plays a crucial role in enhancing passive sampling kinetics for HOCs in aquatic environments.
• This study provides a validated tool for assessing the environmental fate and transport of HOCs.