Solvent-saving approaches for the extraction of siloxanes from pine needles, soils and passive air samplers

Abstract

In this study, a solvent-saving analytical strategy was validated to quantify the levels of 8 volatile methyl siloxanes (VMSs) in pine needles, soils and air (measured by sorbent-impregnated polyurethane foam passive samplers, SIPs). Different extraction solvents and sample handling procedures were tested and the protocol that reached the highest recoveries employed QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) and was adapted to pine needles and soils. For SIPs, another method was developed in parallel, as QuEChERS could not be applied to this matrix due to logistic and operative constraints. Thus, extraction was performed using classic Soxhlet extractors and a short clean-up step, limited to the removal of water by a solid-phase extraction (SPE) column containing sodium sulphate. The quantification of the target compounds was performed by gas chromatography/mass spectroscopy (GC/MS), with identical set-ups for the three matrices. Similar validation protocols were applied and yielded limits of detection (LODs) from 1.8 to 10.8 ng kg⁻¹ (dry weight) for pine needles, from 3.4 to 19.8 ng kg⁻¹ (dw) for soils and from 4.7 to 10.2 ng_SIP⁻¹ (dw) for SIPs. The overall mean recoveries were 75 ± 11%, 69 ± 17% and 87 ± 8%, respectively. The application of the methodologies to naturally contaminated samples collected in an urban and a remote site revealed siloxane levels comparable to other studies in the literature and a predominance of the cyclic siloxanes over the linear ones, which were frequently not detected.