Analysis of linear and cyclic methylsiloxanes in sewage sludges and urban soils by concurrent solvent recondensation – large volume injection – gas chromatography–mass spectrometry

Concurrent solvent recondensation–large volume injection (CSR–LVI) is a gas chromatography injection technique that is particularly suitable for determining volatile compounds. In the present work, we evaluated the applicability of this technique for the analysis of linear and cyclic methylsiloxanes in sewage sludges and soils after solvent extraction to prevent losses of low-molecular-weight compounds. The CSR–LVI injection method was optimised to achieve maximum sensitivity and good chromatographic peak shapes. A liner packed with deactivated glass wool and a 5 m × 0.32 mm I.D. uncoated fused-silica precolumn was used. This made it possible to inject extract volumes of up to 30 μl. Good linearity (r > 0.9993) and precision (RSD <15%), with recoveries ranging from 80 to 100% and method limits of quantification from 0.03 to 0.4 ng g−1 wet weight (0.04–1.5 ng g−1 dry weight for sewage sludges and 0.01–0.5 ng g−1 dry weight for soils) were obtained. The developed method was applied to the analysis of linear and cyclic methylsiloxanes in sewage sludges collected from several wastewater treatment plants in Catalonia (NE Spain) and urban soils from the city of Barcelona.

► A new method for methylsiloxane determination in sewage sludge and soils was proposed.
► The CSR–LVI technique provides high sensitivity injecting extract volumes up to 30 μL.
► The method provided good precision (RSD < 15%) and low LOQs (0.01–1.5 ng g−1 dw).
► Methylsiloxane concentrations in sludge samples ranged from 4.8 to 82,112 ng g−1 dw.
► Levels of cyclic methylsiloxanes in urban soils was found from 7.2 to 47 ng g−1 dw.