Magnetic porous organic polymers for magnetic solid-phase extraction of triazole fungicides in vegetables prior to their determination by gas chromatography-flame ionization detection.

Magnetic porous organic polymers (MOPs) were synthesized by a simple azo reaction, with 1,3,5-tris (4-aminophenoxy) benzene and 1,3,5-trihydroxybenzene as the monomers, and Fe3O4@SiO2 as the core. The preparation process was mild, green and environmental-friendly, avoiding the use of high temperature, metal catalysis and harmful organic reagent. The obtained MOPs were characterized in terms of morphology, pore structure, and magnetism; they exhibited high surface area, good stability/dispersibility, and excellent extraction performance for interest triazole fungicides (TFs). With the prepared MOPs as adsorbent, a method of magnetic solid phase extraction-gas chromatography-flame ionization detection (MSPE-GC-FID) was proposed for the analysis of target TFs in vegetables. After the vegetable samples were chopped and homogenized, acetonitrile was added for ultrasonic extraction, and the extract was diluted for subsequent MSPE process. Different operating conditions affecting the extraction efficiency of TFs, such as extraction time, pH, ionic strength, adsorbent dosage, and volume of sample as well as eluent were carefully optimized. Under the optimized experimental conditions, quantitative extraction could be achieved for target TFs (extraction efficiency of 84.5-90.3%), and the limits of detection were in the rage of 0.12-0.19 μg/L, which is the lowest among the reported GC-FID methods for target TFs presently. The linear range of the method for five TFs was 0.5-200 μg/L with the reproducibility of 2.6-6.8% (n = 7, c = 2 μg/L). The method was assessed by the analysis of target TFs in vegetables, and the recoveries for the spiked cucumber and cabbage were 86.9-117% and 84.7-114% (spiking levels of 80, 400 and 800 μg/kg), respectively, indicating that the matrix effect was negligible in the proposed MSPE procedure. The results show that the developed method of MSPE-GC-FID with MOPs as adsorbent is efficient for the analysis of trace TFs in vegetables.