Quantitative Chemical Assay of Nanogram-Level PM Using Aerosol Mass Spectrometry Coupled with an Isotopically Labeled Internal Standard: Application to Samples Collected from Uncrewed Arial Systems

CHRISTOPHER NIEDEK, Fan Mei, Maria Zawadowicz, Zihua Zhu, Beat Schmid, Qi Zhang, University of California, Davis

     Abstract Number: 512
     Working Group: Instrumentation and Methods

Abstract
Aerosol generation techniques have expanded the utility of aerosol mass spectrometry (AMS) for offline chemical analysis of airborne particles and droplets. However, standard aerosolization techniques require relatively large liquid volumes (e.g. several milliliters) and high sample masses that limit their utility. Here we report the development and characterization of a micronebulization-AMS technique that requires only microliter volumes of sample and can provide quantification of nanogram levels of organic and inorganic substances via the usage of an isotopically labeled internal standard (³⁴SO₄^2-). Using standard solutions, the detection limits for this technique were determined as 2.6 and 0.086 ng for organics and sulfate, respectively. This technique was applied successfully to analyzing filter and impactor samples collected using miniature particulate matter (PM) samplers deployable on uncrewed aerial systems (UASs). Chemical composition of ambient PM samples collected from a UAS field campaign conducted at the DOE Southern Great Plains (SGP) observatory was characterized and the results were compared to real-time aerosol chemistry measurements made by an Aerosol Chemical Speciation Monitor (ACSM). This study demonstrated that the micronebulization system in combination with offline AMS analysis provides a robust platform for quantitative chemical analysis of PM samples with solute concentrations in the μg/L range and sample volumes in the sub-mL range.