Development of solid-phase microextraction to study dissolved organic matter--polycyclic aromatic hydrocarbon...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are persistent organic pollutants.
• Dissolved Organic Matter (DOM) significantly influences the fate and transport of PAHs in aquatic environments.
• Understanding PAH-DOM interactions is crucial for environmental risk assessment.

Purpose of the Study:

• To develop and validate a Solid-Phase Microextraction coupled with Gas Chromatography and Mass Spectrometry (SPME-GC-MS) method for studying PAH-DOM interactions.
• To determine the dissolved organic carbon water distribution coefficient (K(DOC)) for various PAHs in the presence of DOM.
• To investigate the competitive binding dynamics between different PAHs and DOM.

Main Methods:

• Optimization of SPME extraction conditions for PAHs.
• Quantification of freely dissolved PAHs using deuterated naphthalene as an internal standard.
• Calculation of K(DOC) values using SPME-GC-MS and fluorescence quenching data.
• Analysis of PAH-DOM interactions with varying PAH mixtures and Aldrich humic acid.

Main Results:

• The developed SPME-GC-MS method accurately quantified PAHs and their interactions with DOM.
• Deuterated naphthalene internal standardization improved the accuracy of freely dissolved PAH quantification compared to external calibration.
• K(DOC) values for 18 PAHs were determined for the first time using this combined approach, showing agreement with previous studies.
• Evidence of competition between PAHs, deuterated PAHs, and DOM was observed, indicating non-linear PAH-DOM interactions.

Conclusions:

• The study successfully established a robust SPME-GC-MS method for PAH-DOM interaction studies.
• PAH-DOM interactions are non-linear and influenced by the molecular weight of PAHs.
• Lighter molecular weight PAHs exhibit stronger interactions (higher K(DOC)) with DOM, especially when heavier PAHs are absent.