Task specific ionic liquid-coated PTFE tube for solid-phase microextraction prior to chemical and photo-induced mercury cold vapour generation

New, simple and cost effective procedure using task specific ionic liquid coated PTFE tube for solid phase microextraction (TSIL PTFE SPME) combined with cold vapour atomic absorption spectrometry (CV AAS) for determination of mercury in soil samples was developed. Before IL coating, the surface of the PTFE tube was mechanically developed to make it rougher that facilitates the deposition of the ionic liquid on the surface. The TSIL-coated PTFE tube was employed for the direct immersed microextraction of mercury. The element was reduced with Sn2 + in HCl (chemical CVG) or in the presence of formic acid and UV (photo-induced CVG). Extraction of mercury was achieved without centrifugation step and without the back-extraction of mercury prior to determination by CV AAS. Some essential parameters of the microextraction and preparation of the SPME fibre surface as well as a volume of the deposited ionic liquid and extraction (stirring) time have been studied. Under optimal conditions, high extraction efficiency was achieved for the extraction of 2 ng mL− 1 mercury in 10.0 mL of solution employing PTFE tube coated with 32 μL of methyltrioctylammonium thiosalicylate ([N1888][TS]) as the extraction phase. The enrichment factors and detection limits for the chemical CVG were 21 and 0.04 ng mL− 1, respectively and for photo-induced CVG 21 and 0.09 ng mL− 1, respectively. The accuracy of the proposed method was evaluated by analysis of the Certified Reference Materials (SRM 2709 San Joaquin Soil, SRM 2711 Montana Soil and SRM 2704 Buffalo River Sediment). The recoveries for reference materials were in the range of 97-100%. The method was applied to analysis of soil samples.