Hollow Fiber Stir Bar Sorptive Extraction Combined with GC–MS for the Determination of Phthalate Esters from Children’s Food

Abstract

In this work, a zeolitic imidazolate framework-based graphene oxide composite (ZIF-8@GO) was prepared and used as the adsorbent in hollow fiber stir bar sorptive extraction. The stir bar was constructed of a small section of hollow fiber filled with 5 mg ZIF-8@GO and a thin stainless wire of 1.5 cm long in its lumen, and used to extract the trace levels of phthalate esters from children’s food samples prior to gas chromatography–mass spectrometric detection. The ZIF-8@GO showed a high adsorption efficiency for the compounds containing aromatic rings. The main experimental parameters that can impact the extraction efficiency including extraction temperature, extraction time, stirring rate, sample salinity, and desorption conditions were investigated. Under the optimized conditions, the limits of detection (LODs) for the five phthalate esters (diethyl phthalate, dipropyl phthalate, diisobutyl phthalate, butylbenzyl phthalate, and di(2-ethylhexyl) phthalate) were 0.15–0.6 µg L−1 for CiCi beverage and pear juice samples, and 0.75–2.2 µg kg−1 for jam samples. The limits of quantitation (LOQs) were 0.5–2.0 µg L−1 for CiCi beverage and pear juice samples, and 2.5–7.5 µg kg−1 for jam samples. Wide linear ranges of 0.5–500.0 µg L−1 and 2.5–2000 µg kg−1 were obtained for CiCi beverage, pear juice samples and jam samples, respectively, with good repeatability (RSD < 11%) and high method recoveries (72%–100%). The lifetime test results showed that the ZIF-8@GO-based hollow fiber stir bar can be reused for 120 extraction cycles without a significant loss of extraction efficiency, indicating its high durability and stability. The established method was applied successfully for the determination of the phthalate esters (PAEs) in children’s food samples.