Effects of aerosol size and coating thickness on the molecular detection using extractive electrospray ionization

Abstract. Extractive electrospray ionization (EESI) has been a well-known technique for high-throughput online molecular characterization of chemical reaction products and intermediates, detection native biomolecules, in vivo metabolomics, environmental monitoring with negligible thermal ionization-induced fragmentation over two decades. However, the EESI extraction mechanism remains uncertain. Prior studies disagree on whether particles between 20 400 nm diameter are fully extracted or if is limited to surface layer. Here, we examined analyte by assessing influence particle size coating thickness molecules therein. We find that fully: organics-coated NH4NO3 fixed core volume (156 226 without coating) showed constant signals independent shell thickness, while secondary organic comprising varied proportionally volume. also found sensitivity exhibited strong dependence, an increase 1–3 orders magnitude as decreased from 300 30 nm. This dependence (ES) droplet size, residence time coagulation inlet, suggesting was influenced coefficient ES droplets. Overall, our results indicate that, EESI, droplets regardless composition, when they collected their coalescence not complete depends strongly size. especially relevant used probe size-varying case aerosol formation growth ranges below 100