The solvent-assisted dispersive solid-phase extraction method revisited. Application for the determination of anionic surfactants

Abstract

A new approach in solvent-assisted dispersive solid-phase extraction (SA-DSPE) procedure using a supercooled liquid was developed. It demonstrates the first use of a supercooled liquid in this technique, in particular, and in chemical analysis in general. Moreover, to the best of our knowledge, this is the first work devoted to the determination of the total concentration of anionic surfactants (as LAS, Linear alkylbenzene sulfonate) using a micro-SPE technique. The method is based on the formation of an ion pair between astraphloxine (cationic dye) and an anionic surfactants, with subsequent extraction of the ion pair formed onto a benzophenone sorbent generated in situ after injection of its 5 % solution in an acetone:water 80:20 v/v mixture into an aqueous sample. The resulting turbidness was sedimented by centrifugation. The addition of a few crystals of benzophenone then leads to the solidification of a supercooled solution of the sorbent, which facilitates the separation. Afterwards, the bulk of the aqueous phase was easily decanted, and the resulting sediment was dissolved with 500 μL of acetone; absorbance measurements were carried out in a semi-microcuvette. The calibration plot was linear up to 0.5 µmol L⁻¹ of sodium dodecylbenzene sulfonate (SDBS). The LOD and LOQ, were 9.0 and 30 nmol L^-1 of SDBS, respectively. The developed procedure was applied for the determination of anionic surfactants in various real water samples.