Development of SPME fiber coatings with tunable porosity for physical confinement of ionic liquids as an extraction media

Abstract

Extending the use of ionic liquids in sample preparation techniques remains a challenge. This paper presents procedures enabling the easy application of ionic liquids to the SPME technique. For this purpose, two approaches for producing a porous silica coating on a metal rod were investigated. Two silica precursor and porogen systems were used in the research: K2SiO3 + Formamide and Tetramethyl-orthosilicate + Polyethylene oxide. The procedure was optimized concerning its operational parameters: the possibility of immobilization of a possibly large volume of ionic liquid and mechanical strength and thermal resistance. In the course of the research, it was shown that the optimal parameters are ensured by using K2SiO3 with Formamide. The obtained material had an average pore diameter equal to 0.326 μm with a surface area of the pores similar to 6.33 m2/g. The size of the pores allows for the quantitative introduction of the ionic liquid and its immobilization to the extent of enabling the extraction of VOC and their subsequent thermal desorption. Finally, the conducted experiments showed that the dominant mechanism of retaining analytes in the IL-silica hybrid material is their dissolution in the ionic liquid, while adsorption on the silica surface plays a lesser role.