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 ngSIP -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. IntroductionThe analysis of siloxanes in environmental matrices is quite a challenging task, mainly due to their ubiquitous use since they were first produced in the 1940s. 1 The recent attention given by the scientific community to these chemicals (in particular to organosiloxanes) derives from reports mentioning persistence and possible harmful effects to the environment and ecosystems. 2 Siloxanes are organosilicon compounds consisting of alternating Si-O bonds as a backbone with organic side chains which can be classified as either linear or cyclic according to their structure. 3 These anthropogenic compounds have a wide range of use and are incorporated into a variety of household and industrial applications, such as in cosmetics and other 2 personal care products, textiles, pharmaceuticals, electronics, furniture, food and construction, among others. 4-6A special focus has been given to volatile methyl siloxanes (VMSs), which are organosilicons with low molecular weights and high vapour pressures that can be derived from PDMS hydrolysis. 7,8 Their presence was shown in several environmental matrices such as outdoor and indoor air, 9-11 soil 12,13 aquatic media, 14,15 sediments, 16 wastewater and sludge, 17-19 biota 20,21 or vegetation. 22 Regarding the extraction and quantification of VMSs in these complex matrices, also the analytical approaches reflect an increasing development in the last years. Three recent reviews reported a thorough list of options that include extraction by Soxhlet, ...

Characterizing the regional concentrations and seasonality of the emerging pollutant decamethylcyclopentasiloxane (D5) using a WRF+CHIMERE modeling approach

“…As the intention was to study the common climatic extremes in southern Europe latitudes (winter and summer), two campaigns were performed: one in winter, from the last week of November 2013 to the last week of February 2014; the other in summer, from the first week of June to the first week of September 2014. The analytical protocol for the analysis and quantification of D5 in SIP disks is detailed elsewhere (Ramos et al, 2016). In brief, SIPs were extracted overnight with a mixture of hexane and dichloromethane (1:1) in a 200-mL Soxhlet extractor.…”

US EPA to evaluate cyclic siloxane

“…Soil samples (0-10 cm) an urban area and a remote area of Portugal as part of a method validation study for the determination of D4 in air (Ramos et al, 2016). Samples from the urban area and the remote area had soil concentrations of D4 of 4.4 ng/g dw and 0.10 ng/g dw, respectively.…”

“…Remarks: This publication will be consulted during preparation of the ecological risk assessment for D4. Passive air samplers were deployed in an urban area and a remote area of Portugal as part of a method validation study for the determination of D4 in air (Ramos et al, 2016). XAD-4 impregnated SIPs were deployed for 3 months.…”

Marine vegetation analysis for the determination of volatile methylsiloxanes in coastal areas

“…The development of the extraction procedure was initially based on the protocol validated by Ramos et al (2016) for the extraction and quantification of VMSs in pine needles and soils, and recently optimized and validated for the analysis of 7 VMSs in marine vegetation samples (work submitted for publication).…”