A novel method for measuring polymer-water partition coefficients

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Polymer Science

Background:

• Low density polyethylene (LDPE) is widely used in passive sampling devices to estimate chemical concentrations in aquatic environments.
• Accurate calculation of water phase concentrations from LDPE requires reliable LDPE-water partition coefficients (KPE-w).
• Direct experimental measurement of KPE-w for hydrophobic chemicals is challenging due to large partition values.

Purpose of the Study:

• To evaluate a simple and accurate three-phase system for determining LDPE-water partition coefficients (KPE-w).
• To validate the method by measuring KPE-w for various hydrophobic organic contaminants.
• To compare the determined KPE-w values with existing literature data.

Main Methods:

• A three-phase system was developed involving LDPE, surfactant micelles (Brij 30), and water.
• Chemical equilibrium was established between LDPE and micelle pseudo-phases to determine the LDPE-micelle partition coefficient (KPE-mic).
• The micelle-water partition coefficient (Kmic-w) was measured experimentally, and KPE-w was calculated as the product of KPE-mic and Kmic-w.

Main Results:

• The method successfully determined KPE-w values for 17 polycyclic aromatic hydrocarbons, 37 polychlorinated biphenyls, and 9 polybrominated diphenylethers.
• Calculated KPE-w values showed good agreement with literature data.
• Chemical activity coefficients indicated nearly identical affinities of micelles and LDPE for the tested chemicals.

Conclusions:

• The proposed three-phase system provides an accurate and accessible method for measuring LDPE-water partition coefficients.
• This method facilitates reliable environmental monitoring and risk assessment of hydrophobic contaminants using LDPE-based passive samplers.
• The findings contribute to improved understanding of chemical partitioning in environmental matrices.