Cyclic volatile methyl siloxanes (cVMS), a subgroup of organosilicone, are organic compounds characterized by alternating [Si-O] atomic units [1] and a methyl group attached to each silicon atom [2]. Since 1940, cVMS have been extensively manufactured and utilized in various consumer goods and industrial products [3], including cosmetics and toiletries [4], resulting in their widespread distribution in the environment due to their volatility [5]. Furthermore, cVMS serve as common precursors and intermediates in the industrial production of various silicon oils and silicon rubbers, which are extensively used in textile, medical, food, transportation, aerospace and other fields [6]. Given the frequent usage of cVMS across diverse fields [7], they can easily accumulate in the environment through multiple pathways such as urban sewage systems [8] or deposition in landfills for solid waste disposal purposes [9], [10], [11]. Furthermore, cVMS has even been reported in plateau regions [12] and polar regions [13].

However, the predominant cVMS compounds, namely octamethylcyclotetrasiloxane (D4), decmethylcyclopentasiloxane (D5) and dodecmethylcyclohexosiloxane (D6), were reported to exhibit both direct and indirect toxicity. As evidenced by animal studies, a range of diseases resulted from prolonged exposure to these substances, including adverse immune reactions [14]. There are also reports indicating that these cVMS can significantly impair liver and lung function [15,16]. Additionally, studies have demonstrated that these substances can disrupt hormone distribution and induce reproductive toxicity in mice [17,18]. Recent scrutiny by various countries and organizations such as Canada, Denmark, and the United Kingdom has confirmed cVMS as a potential emerging pollutant due to its persistence, bioaccumulation potential, and long-range transport characteristics [19]. Thus, it is essential to develop a convenient method to determine cVMS in surrounding media.

Currently, GC/MS is the primary method for the determination of cVMS, due to its high sensitivity and excellent selectivity [20,21]. Meanwhile, several pretreatment methods, such as headspace solid-phase microextraction [22,23], purging and trapping [24], bulk injection [25], and headspace injector [26], have been developed to enrich these trace cVMS and to minimize interference in various samples before GC-MS analysis. Moreover, in the quantitative analysis of cVMS, various adsorbent materials [27], [28], [29] are typically utilized to enrich the target compounds during sample pre-treatment. However, these materials tend to be complex to prepare and unsuitable for routine detection purposes.

Regardless of the pretreatment method employed, accurate determination of trace cVMS remains a challenge for analysts, because they are ubiquitously present in the background due to their volatility. Moreover, silicon rubber is the essential material of GC/MS accessories, such as the coating of a capillary column, critical injection port seals, and injection septum, and the decomposition of these accessories will result in cVMS [30]. In addition, these transdermally absorbed cVMS can also be released into the air through respiration [31], leading to background interference. Given their extensive use in laboratory equipment and high volatility [32], current analytical methods often yield false positives and fail to effectively detect these substances at a trace level. Consequently, the quantitative analysis of trace cVMS remains a formidable task.

In this work, the main pollution sources of trace cVMS in GC-MS analysis were explored, and various measures were taken to eliminate background interference to establish a simple, effective and accurate analysis method for the determination of trace cVMS. The feasibility of the method was verified by testing the three main cVMS in actual water samples.