Concise, Rapid, and Comprehensive Approach for Microplastic Detection Based on Ambient Microwave Plasma Torch Desorption/Ionization Mass Spectrometry

Abstract

Microplastics (MPs) have been universally recognized as a pervasive and enduring environmental hazard, promoting research on relevant analytical techniques. Despite the unique advantages of mass spectrometry (MS) for polymer identification, lengthy procedures and complex data processing are always ineluctable. In this study, an ambient microwave plasma torch (MPT) ion source coupled with an LTQ Orbitrap MS was developed, presenting a rapid and concise analytical approach for MPs with simplified pretreatment and intuitive mass spectra. One testing process took approximately 30 s, enabling a higher efficiency of analysis. Furthermore, the method was not constrained by the MP size limitation; even macroscale polymer blocks could be detected. Under the optimized conditions, the method was proven to be efficient for the desorption and ionization of a wide range of MPs (polyamide, poly(ethylene terephthalate), polymethacrylate, polylactic acid, poly(3-hydroxybutyrate), polypropylene, and polythene), while the distinctly decipherable spectra intuitively reflected the mass intervals conforming to the corresponding monomer of MPs. Linear relationships were established between sample mass and the intensity of characteristic ion, with R² exceeding 0.98. Additionally, a simplified pretreatment process in conjunction with MPT-MS was explored, verifying the method’s resilience to matrix interferences and its applicability to environmental sample analysis. Furthermore, the compatibility of the established method with scanning electron microscopy was taken into consideration, thereby complementing traditional MS analysis by providing additional insights into the size and morphology of MPs. This study employed MPT as the ion source for MS detection of MPs, establishing a concise, rapid, and comprehensive method specifically targeting the analysis of MPs, which provided inspiration for the extraction and characterization of MPs in environmental samples.