Development of a solid-phase microextraction fiber by chemical binding of polymeric ionic liquid on a silica coated stainless steel wire

Abstract

A novel approach was developed for the fabrication of solid-phase microextraction (SPME) fiber by coating stainless steel fiber with a polymeric ionic liquid (PIL) through covalent bond. The stainless steel fiber was sequentially coated with a gold film by replacement reaction between Fe and Au when immerged in chloroauric acid, assembled with a monolayer of 3-(mercaptopropyl) triethoxysilane on the gold layer through the Au–S bond, and coated with a silica layer by the hydrolysis and polycondensation reaction of the surface-bonded siloxane moieties and the active silicate solution. Then, 1-vinyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium chloride ionic liquid was anchored on the silica layer by covalent bond, and the PIL film was further formed by free radical copolymerization between 1-vinyl-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazdium and vinyl-substituted imidazolium with azobisisobutyronitrile (AIBN) as initiator. Parameters influencing the preparation of PIL fiber were optimized, and the developed SPME fiber has a coating thickness of ∼20 μm with good thermal stability and long lifetime. The performance of the PIL fiber was evaluated by analysis of polycyclic aromatic hydrocarbons (PAHs) in water samples. The developed PIL fiber showed good linearity between 0.5 and 20 μg l⁻¹ with regression coefficient in the range of 0.963–0.999, detection limit ranging from 0.05 to 0.25 μg l⁻¹, and relative standard deviation of 9.2–29% (n = 7). This developed PIL fiber exhibited comparable analytical performance to commercial 7 μm thickness PDMS fiber in the extraction of PAHs. The spiked recoveries for three real water samples at 0.5–5 μg l⁻¹ levels were 49.6–111% for the PIL fiber and 40.8–103% for the commercial PDMS fiber.