Aerosol Electroanalysis by PILSNER: Particle-into-Liquid Sampling for Nanoliter Electrochemical Reactions

Particle-into-liquid sampling (PILS) has enabled robust quantification of analytes of interest in aerosol particles. In PILS, the limit of detection is limited by the factor of particle dilution into the liquid sampling volume. Thus, much lower limits of detection can be achieved by decreasing the sampling volume and increasing the surface area-to-volume ratio of the collection substrate. Unfortunately, few analytical techniques can realize this miniaturization. Here, we use an ultramicroelectrode in a microliter or smaller sampling volume to detect redox active species in aerosols to develop the technique of Particle-into-Liquid Sampling for Nanoliter Electrochemical Reactions (PILSNER). As a proof-of-concept to validate this technique, we demonstrate the detection of K₄Fe(CN)₆ in aerosol particles (diameter ∼0.1-2 μm) and quantify the electrochemical response. To further explore the utility of the method to detect environmentally relevant redox molecules, we show PILSNER can detect 1 ng/m³ airborne Pb in aerosols. We also demonstrate the feasibility of detecting perfluorooctanesulfonate (PFOS), a persistent environmental contaminant, using this technique. PILSNER is shown to represent a significant advancement toward simple and effective detection of a variety of emerging contaminants with an easily miniaturizable and tunable electroanalytical platform.