Thermally stable ionic liquid-based sol–gel coating for ultrasonic extraction–solid-phase microextraction–gas chromatography determination of phthalate esters in agricultural plastic films

A novel sol–gel-coated ionic liquid-based ([AMIM][N(SO2CF3)2]–OH-TSO) fiber was successfully applied for the determination of phthalate esters (PAEs) in agricultural plastic films by ultrasonic extraction (UE) combined with solid phase microextraction–gas chromatography (SPME–GC) due to its high thermal stability, specific selectivity and extraction efficiency. The extractant for UE and the adsorption time for SPME were optimized to achieve higher extraction efficiency. The desorption temperature and time were also optimized to avoid the carryover effect of previous extraction, and ultimately improve the precision and accuracy of the method. The [AMIM][N(SO2CF3)2]–OH-TSO fiber showed comparable, or even higher response to most of the investigated PAEs than the commercial PDMS, PDMS–DVB and PA fibers. The carryover problem, often encountered when using commercial fibers, had been eliminated when desorption was performed at 360 °C for 8 min. The proposed SPME–GC method showed good linearity over three to four orders of magnitude, and low limits of detection ranged from 0.003 to 0.063 μg L−1. The relative standard deviation values obtained were below 10%, and the recoveries were in the ranges of 90.2–111.4%. Some of the PAEs studied were detected at very high concentration in these agricultural plastic film samples, resulting in a potential risk of crop damage, environmental contamination and human health exposure.