Advances in the Separation and Detection of Secondary Organic Aerosol Produced by Decamethylcyclopentasiloxane (D) in Laboratory-Generated and Ambient Aerosol.

Decamethylcyclopentasiloxane (D), a common ingredient in many personal care products (PCPs), undergoes oxidation in the atmosphere, leading to the formation of secondary organic aerosol (SOA). Yet, the specific contributions of D-derived SOA on ambient fine particulate matter (PM) have not been characterized. This study addresses this knowledge gap by introducing a new analytical method to advance the molecular characterization of oxidized D and its detection in ambient aerosol. The newly developed reversed phase liquid chromatography method, in conjunction with high-resolution mass spectrometry, separates and detects D oxidation products, enabling new insights into their molecular and isomeric composition. Application of this method to laboratory-generated SOA and urban PM in New York City expands the number of D oxidation products observed in ambient aerosol and informs a list of molecular candidates to track D-derived SOA in the atmosphere. An oxidation series was observed in which one or more methyl groups in D (CHOSi) is replaced by a hydroxyl group, which indicates the presence of multistep oxidation products in ambient PM. Because of their specificity to PCPs and demonstrated detectability in ambient PM, several oxidation products are proposed as molecular tracers for D-derived SOA and may prove useful in assessing the impact of PCPs-derived SOA in the atmosphere.