Expanding the PAH Profile of Partially Combusted Microplastics Collected from the Marine Environment

Analyzing Microplastics in the Environment
Oral Presentation

Prepared by D. Stevens1, F. Dorman1, B. James2, C. Reddy3, R. Nelson3
1 - Waters Corporation, 34 Maple Street, Milford, MA, 01757, United States
2 - Department of Chemical Engineering, Northeastern University, , Boston, MA, 02115, United States
3 - Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, , Woods Hole, MA, 02543, United States


Contact Information: [email protected]; 508-369-8311

ABSTRACT

The sinking of the M/V X-Press Pearl in 2021 resulted in the largest recorded release of microplastics (MP) into the marine environment. A significant portion of the spilled plastic was in the form of pyroplastic. The transformation of virgin plastic to pyroplastic has a range of effects including changes to transport and deposition and an increased ability to camouflage among natural organic matter. These factors contribute to an increased need for chemical characterization of pyroplastics to ensure their presence is recognized; they are quantified accurately; and their source is determined with confidence. Because PAHs are known products of partial combustion, in this work the search for markers of pyroplastics was extended to high molecular weight (HMW) PAHs in the 314 to >600Da range. Previous GC-APCI MS/MS analyses provided evidence that temperature limitations imposed by the GC hardware and column stationary phase were hindering investigation of PAHs of 400 – 600 Da where potential new markers exist. Direct probe analysis using atmospheric pressure ionization was performed using a Xevo TQ Absolute (Waters Corporation) tandem quadrupole system. Temperature was ramped to 650C to fully volatilize HMW PAHs. In addition to the MP extracts, NIST coal tar SRMs 1597 and 1991 were analyzed. The HMW PAHs studied have the potential to be persistent source markers for pyroplastics found in the environment due to their low volatility and water solubility. Positive ion neutral loss data demonstrated the ability to provide comprehensive PAH profiles for major and minor series for analytes of up to 600Da. Negative ion product ion data provides the ability to better characterize individual components of the PAH profile due to richer fragmentation than positive ion product ion data. This work demonstrates the utility of multiple MS/MS acquisition modes combined with direct probe analysis for the characterization of pyroplastics.