In-Situ Elemental Composition Analysis of Large Inhalable Aerosol Using Laser Induced Breakdown Spectroscopy

The ability to obtain information on the composition of airborne particles is a necessary part of identifying and controlling risksfrom exposure to potentially toxic materials, especially in the workplace. However, very few aerosol sampling instruments cancharacterize elemental composition in real time or measure large inhalable particles with aerodynamic diameter exceeding20 mu m. Here, we present the development and validation of a method for real time elemental composition analysis of largeinhalable particles using laser-induced breakdown spectroscopy (LIBS). The prototype sensor uses a passive inlet and an opticaltriggering system to ablate falling particles with an LIBS plasma. Particle composition is quantified based on collected emissionspectra using a real-time material classification algorithm. The approach was validated with a set of 1480 experimental spectrafrom four different aerosol test materials. We have studied effects of varying detection thresholds andfind operating conditionswith good agreement to truth values (F-1 score >= 0.9). Details of the analysis method, including subtracting the spectralcontribution from the air plasma and reasons for the infrequent misclassifications, are discussed. The LIBS elemental analysis canbe combined with our previously demonstrated direct-reading particle sizer (DRPS) to provide a system capable of bothcounting, sizing, and elemental analysis of large inhalable particles