Ultrasound assisted-dispersive-modification solid-phase extraction using task-specific ionic liquid immobilized on multiwall carbon nanotubes for speciation and determination mercury in water samples

Abstract

An efficient method based on 1-(3-aminopropyl)-3-methylimidazolium hexafluorophosphate (TSIL) immobilized on multiwall carbon nanotubes (MWCNTs@ [Apmim][PF6]) was used for speciation of inorganic/organic mercury (Hg2+, R-Hg or O-Hg) by ultrasound assisted-dispersive modification solid-phase extraction (UAS-DM-SPE) which was combined with cold vapor atomic absorption spectrometry (CV-AAS). The mixture of MWCNTs @ [Apmim][PF6] in acetone was injected to water samples in polypropylene syringe filters (PSF) which was already adjusted pH up to 8.5. After shaking, the Hg(II) and O-Hg were simply extracted on amine group of [Apmim][PF6] as TSIL and then, separated from the liquid phase by pushing plunger of PSF. The Hg(II) and O-Hg loaded in MWCNTs @ [Apmim][PF6] were back-extracted based on the eluent solution (HNO3, 0.5 mL, 0.2 mol L−1) with/without microwave system (UV radiation at 165 °C). Finally, the concentration of mercury was determined by CV-AAS. By microwave, organic mercury species in remained solution were changed to Hg (II) and the total amount of mercury (T-Hg) was determined. Finally, O-Hg concentration was computed by subtracting the Hg (II) concentration from T-Hg. Under the optimized conditions, the linear range, LOD and enrichment factor for Hg (II) and O-Hg were achieved (0.02–3.6 μg L−1; 0.02–3.4 μg L−1), (5.2 ng L−1; 5.8 ng L−1) and (19.9; 19.7), respectively (Mean of RSD<1.91%). Also, the capacity absorption based on MWCNTs and MWCNTs@ [Apmim][PF6] for O-Hg and Hg(II) ions were achieved 23.6/27.3 mg g−1 and 174.3/186.2 mg g−1, respectively. The proposed method validated for speciation of mercury by ICP-MS and standard reference material (SRM).