A new analytical method for quantifying cVMS in indoor and outdoor air

Introduction: Cyclic volatile methylsiloxanes (cVMS) are widely used in industrial applications, notably in the production of silicone polymers and personal care products (PCPs) [1,2]. The environmental detection of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) has raised growing concern, leading to recent regulatory restrictions on their use [3].However, key environmental processes, including the deposition of cVMS in remote regions, remain poorly understood. In this context, the atmosphere represents a critical matrix for elucidating their environmental fate. The determination of cVMS in air is analytically challenging due to the high risk of contamination during sample preparation, arising both from operator handling— particularly the use of siloxane-containing PCPs—and from their widespread presence in laboratory materials and instrumentation [4]. Method: One of the aims of this work is to develop a new method for monitoring cVMS in air with minimal sample handling and external contamination. Analytical steps were carefully evaluated to select optimal sampling support, adsorber, and elution conditions, with strict blank control. The final method was applied to indoor air sampling in various Ca’ Foscari University laboratories—including general- purpose and clean- room facilities for organic contaminants—as well as in a private residence, to assess different potential contamination levels during routine activities. These indoor measurements were compared with cVMS levels in outdoor urban and alpine atmospheres. The improved method provides a robust tool to study cVMS atmospheric behavior and lays the groundwork for future environmental research. Results: A final method configuration was established, providing recoveries of 77–87% and trueness of 95– 99%. The method was then applied to indoor and outdoor air sampling. The highest cVMS concentrations were observed in indoor environments, particularly in the private residence (D4: 122– 1,420 ng/m³; D5: 632– 62,400 ng/m³; D6: 38–469 ng/m³). No significant differences were found among the different types of clean rooms (D4: 1.8–29.7 ng/m³; D5: 0.38–53.6 ng/m³; D6: 0.47–11.7 ng/m³), with concentrations comparable to those measured in outdoor urban air in Mestre (D4: 4.7–68.8 ng/m³; D5: 6.6–59.4 ng/m³; D6: 1.0–24.5 ng/m³). Blank elutions performed in remote areas showed lower absolute cVMS amounts (D4: 0.72 ± 0.10 ng abs; D5: 1.43 ± 0.23 ng abs; D6: 0.84 ± 0.47 ng abs) compared to those obtained in laboratory fume hoods (D4: 1.32 ± 0.68 ng abs; D5: 2.07 ± 1.00 ng abs; D6: 1.52 ± 0.78 ng abs); however, most remote outdoor samples had concentrations below the limit of detection (LOD) and were comparable to the elution blanks. Conclusions: The results indicate that indoor environments are a potential source of cVMS contamination, likely due to the ubiquity of silicone-containing materials and the presence of operators. The study also highlights the importance of low-contamination sampling strategies for the accurate determination of cVMS in air, particularly in outdoor settings and remote areas, where concentrations are generally near detection limits. Bibliography: [1] Hobson J.F. et al. 1997. https://doi.org/10.1007/978-3-540-68331-5_6 [2] Montemayor B.P. et al. 2013. https://doi.org/10.1016/j.chemosphere.2012.10.043 [3] European Commission. 2024. https://eurlex.europa.eu/legalcontent/EN/TXT/?uri=CELEX:32024R1328 [4] Gerhards R. et al. 2022. https://doi.org/10.1016/j.scitotenv.2022.158275