Characterization of organic compounds and oxidative potential of aqueous PM2.5 suspensions collected via an aerosol-into-liquid collector for use in toxicology studies

In this study, we investigated the organic constituents and toxicological characteristics of PM2.5 liquid suspensions collected by the means of a modified versatile aerosol concentration enrichment system (VACES)/aerosol-into-liquid collector tandem technology. Filter and slurry PM2.5 samples were collected during warm (spanning from mid-August 2019 to early-September 2019) and cold (from mid-December 2019 to early-January 2020) seasons at an urban site in central Los Angeles. The collected samples were chemically analyzed for their total organic carbon (TOC) as well as individual organic species, including polycyclic aromatic hydrocarbons (PAHs), hopanes and steranes, n-alkanes, and organic acids. In addition, the oxidative potential of PM2.5 samples was quantified by means of the 2′,7′-dichlorodihydrofluorescein (DCFH) in vitro assay. Overall, our findings revealed a very good agreement between the mass fractions of organic compounds in the collected PM2.5 slurries and filters, judging by the average slurry-to -filter ratios of 1.17 ± 0.15, 1.13 ± 0.14, 1.13 ± 0.15, and 1.16 ± 0.22 for PAHs, hopanes and steranes, n-alkanes, and organic acids, respectively. Moreover, comparable (Pvalue = 0.2) oxidative potential levels were observed between the collected filters and PM2.5 liquid suspensions. The aqueous PM suspensions collected by the VACES/aerosol-into-liquid collector exhibited slightly higher (although not statistically significant) capture of some semi-volatile organic compounds (SVOCs), probably due to less sampling artifacts and better preservation of these SVOCs collected directly into aqueous suspensions compared to the filter samplers. The outcomes of this study confirm the efficient collection of PM-bound organic species in aqueous slurries by the aerosol-into-liquid collector, further corroborating the ability of this sampler to be used as an attractive alternative to filter samplers for collection of PM2.5 for toxicological studies. •PM2.5 liquid suspensions and filters were analyzed for their organic constituents in central Los Angeles.•TOC, PAHs, hopanes and steranes, n-alkanes, and organic acids fractions were comparable between filter and slurry samples.•Slightly higher contribution of organics to slurries were due to the sampling artifacts for slurry/filter collection.•Results underscored the efficiency of VACES/aerosol-into-liquid collector for PM2.5 slurry collection.