Determination of siloxanes in water samples employing graphene oxide/Fe3O4 nanocomposite as sorbent for magnetic solid-phase extraction prior to GC-MS

A new, fast, simple, and environmentally friendly analytical method has been developed to determine six siloxanes in water samples: octamethyltrisiloxane, octamethylcyclotetrasiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, dodecamethylpentasiloxane and dodecamethylcyclohexasiloxane. The analytical method consists of magnetic solid-phase extraction employing graphene oxide/Fe3O4 as sorbent for the separation and preconcentration of siloxanes prior to GC-MS determination. The extraction procedure was optimized by means of a Plackett-Burman design. Under the optimized extraction conditions (graphene oxide/Fe3O4, 20 mg; extraction time, 10 min; eluent volume, 0.5 mL ACN; elution time, 2.5 min; sample volume, 20 mL), the method rendered repeatability levels with a relative standard deviation between 9 and 20% (n = 6, 10 mu g/L). Methodological limits of detection ranged from 0.003 to 0.1 mu g/L. The linearity of the method was studied between the methodological limit of quantification and 100 mu g/L, obtaining correlation coefficient values between 0.990 and 0.999. The applicability of the method was assessed by analyzing drinking, river and wastewater samples. Relative recovery values ranged between 70 and 120% (1 and 60 mu g/L spiking level) showing that the matrix had a negligible effect on extraction. Finally, the greenness of this method was confirmed by the semiquantitative Eco-Scale metrics.