Single-Particle Microplastics Analysis via Laser-Assisted MicroPyrolysis Flowing Atmospheric-Pressure Afterglow Mass Spectrometry Imaging

Microplastics (MPs) have emerged as ubiquitous contaminants in the environment. Thus, novel MP characterization techniques are in urgent demand to achieve the necessary environmental monitoring, as well as studying the impact of MPs on human health. Herein, laser-assisted micropyrolysis flowing atmospheric pressure afterglow high-resolution mass spectrometry (LAMP FAPA MS) is developed toward direct imaging of single-particle MPs collected on filters. The use of a CO2 laser (10.6 μm) is shown to yield up to >100× higher signal intensity for polyethylene terephthalate fragment ions compared to a diode laser (405 nm) at the same power. Also, a mass spectral analysis algorithm was developed and implemented for fast polymer identification in MPs based on the corresponding fragment ion series separated by the repeating base unit. Furthermore, additive identification is shown for single-particle MPs. Finally, LAMP FAPA MS is demonstrated for quantitative analysis of polymer mass with a detection limit of 0.083 ng for polyethylene microspheres, which corresponds to a spherical particle with a 5.4 μm diameter.