Photothermal-Enhanced Desorption and Internally Heated Photochemical Ionization TOF-MS for Rapid and Quantitative Analysis of Particulate PAH Composition

Fine particulate matter (such as PM_2.5) is one of the most critical areas of atmospheric pollution, posing significant risks to the health of the respiratory, circulatory, and nervous systems. An immediate concern is the inadequate characterization of highly toxic particulate compounds with boiling points exceeding 200 °C, such as polycyclic aromatic hydrocarbons (PAHs). To tackle these challenges, a photothermal-enhanced desorption device integrated with internally heated photochemical ionization time-of-flight mass spectrometry (PDD-IHPI-TOFMS) has been developed, enabling quantitative analysis of PAHs (fluorene, acenaphthene, acenaphthylene, and phenanthrene) within 2 min. Particulate PAHs are instantaneously desorbed via the halogen lamp-induced photothermal effect, achieving a 244 ± 2.95% signal enhancement compared to conventional heating methods. The desorbed PAHs are then efficiently purged by a downward-directed airflow generated through an internal flow-inducing convex design, contributing an additional 20.41 ± 1.06% signal improvement. Meanwhile, the internally heated ionization source effectively mitigates PAH wall adsorption, resulting in a 6.7-fold sensitivity enhancement, a linear response range of 2-300 ng, and a detection limit as low as 0.13 ± 0.0032 ng. The developed system has been validated for compositional analysis of particulate matters collected from an indoor sports environment. Specifically, in comparison with the results obtained from using the commercial filter inlet for gases and aerosols (FIGAERO), the new system achieved a 70-fold enhancement in PAH molecular ion peak intensity. Consequently, the PDD-IHPI-TOFMS demonstrates significant potential for particulate matter compositional analysis, holding broad prospects for practical applications.