Characterization of a novel particle into liquid sampler for analysis of single fluorescent aerosol particles through capillary electrophoresis

Evaluating important analytical figures of merit for PILSNER: particle-into-liquid sampling for nanoliter electrochemical reactions

Recently introduced as a method for aerosol electroanalysis, particle-into-liquid sampling for nanoliter electrochemical reactions (PILSNER) has shown promise as a versatile, highly sensitive analytical technique. To further validate the analytical figures of merit, we present correlated fluorescence microscopy and electrochemical data. The results show excellent agreement as to the detected concentration of a common redox mediator, ferrocyanide. Experimental data also suggest that PILSNER's unconventional two-electrode system is not a contributing source of error when appropriate controls are established. Finally, we address the concern that arises from two electrodes operating within such close proximity. COMSOL Multiphysics simulations confirm that with the present parameters, positive feedback is not a contributing source of error in voltammetric experiments. The simulations also show at what distances feedback could become a source of concern, which will be a factor in future investigations. Thus, this paper provides validation of PILSNER's analytical figures of merit, as well as voltammetric controls and COMSOL Multiphysics simulations to address possible confounding factors that could arise from PILSNER's experimental setup.

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.