A contamination-controlled analytical method for the determination of cVMS in indoor and outdoor air

Cyclic volatile methylsiloxanes (cVMS) are compounds widely used in industrial applications, including silicone polymers and personal care products (PCPs). The detection in the environment of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) has raised increasing concerns and recent restrictions to use (Regulation EU, 2024/1328). However, some key environmental processes, including the deposition of cVMS in remote areas, are still not clear. In this context, the atmosphere represents the key matrix to understand their environmental fate. The determination of cVMS in air represents an analytical challenge due to the high risk of contamination during sample preparation, linked both to the handling by the operators, potentially using PCPs containing siloxanes, as well as to their widespread presence in materials and instrumentation normally used inside the laboratories. The aim of this work was to develop a method to monitor cVMS in air, minimizing sample handling and external contamination: a thorough evaluation of the analytical steps was conducted selecting the most appropriate sampling supports, adsorbers and elution conditions, with a strict control of blanks. The final method (recoveries: 77-87%, trueness: 95-99%) was applied to the sampling of cVMS in the indoor air of different laboratories at Ca’ Foscari University of Venice, including general-purpose areas, combined hood and stainless- steel clean-room laboratories for organic contaminants, to characterize their different potential contamination levels during working activities. These samples were compared to the levels of cVMS detected in outdoor atmosphere from urban and background alpine areas. The analytical improvements introduced by this method will provide a useful tool for studying the atmospheric behavior of cVMS, constituting a basic starting point for future environmental research.