Magnetic and electric field assisted electrospun polyamide nanofibers for on-line μ-solid phase extraction and HPLC

Abstract

The effects of applied magnetic and electric fields on electrospinning were investigated to produce more efficient nanofibers. Considering the previous extensive studies, polyamide nanofibers were prepared by a conventional approach and under auxiliary electric and magnetic fields. The first sorbent was synthesized by electrospinning of a solution of 18% polyamide in formic acid. The second and third types of polyamide were prepared similarly while the electrospinning processes were assisted by an electric and a magnetic field. The third type of polyamide contained a magnetic ionic liquid (MIL) to induce sufficient magnetic susceptibility in the polymeric solution. The SEM images revealed that the application of auxiliary electric and magnetic fields led to the aligned nanofibers with mean diameters of 200 and 90 nm, respectively while for the conventional electrospun non-woven nanofibers the mean diameter was 500 nm. To evaluate the extraction efficiency of the prepared nanofibers, they were removed from the collector electrode and packed into the μ-solid phase extraction (μ-SPE) cartridge, coupled on-line with high performance liquid chromatography (HPLC). Apart from the influence of the assisted fields on electrospinning, the effects of size of the nanofibers and the ionic liquid content on the μ-SPE of imidacloprid, metribuzin, ametryn and chlorpyrifos were investigated. The highest extraction efficiency was achieved for the third sorbent due to its higher aspect ratio. After preparation of five sets of nanofibers, it was revealed that the presence of MIL dopant up to 10% in a solution of 18% polyamide exhibited the most satisfactory results. The linearity for the analytes was in the range of 1–500 μg L⁻¹. The limit of detection (LOD) was in the range of 0.4–4 μg L⁻¹ and the RSD% values (n = 5) were all satisfactory at the 20 and 200 μg L⁻¹ levels. The applicability of the developed on-line μ-SPE-HPLC method was examined by analyzing real water samples obtained from spiked Zayandeh rood river and Caspian Sea and the relative recovery percentages were from 84 to 108% at 20 and 200 μg L⁻¹ levels.