Development of a magnetic sorbent based on synthesis of MOF-on-MOF composite for dispersive solid-phase microextraction of five phthalate esters in bottled water and fruit juice samples

Abstract

A straightforward sample preparation method based on dispersive micro solid-phase extraction was developed to simultaneous extract phthalate esters in bottled water and fruit juice samples. The novel and efficient sorbent for the extraction of phthalate esters was prepared by combining three components, including ZIF-8 @ ZIF-67 as a MOF-on-MOF and Fe3O4 nanoparticles as a magnet component, and SiO2 using the sol–gel technique. A simplex centroid mixture design was generated to optimize the value of sorbent components. The optimum sorbent was characterized by investigating the FTIR spectra, FE-SEM images, EDX pattern, VSM image, and XRD pattern. Besides, practical factors in the microextraction procedure were optimized using one factor at a time and experimental design (definitive screening design and central composite design). The method was linear for determining dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, benzyl butyl phthalate, and di-isobutyl phthalate were 0.03–25, 0.03–25, 0.05–30, 0.07–30, and 0.05–30 ng mL−1 with determination coefficients (R2) higher than 0.9907, respectively. Intra-day and inter-day RSDs were in the ranges of 3.18–4.97 % and 5.16–6.35 %, respectively. Also, the limit of detections and limit of quantitation for the analyte determination were lower than 0.02 and 0.07 ng mL−1, respectively. Analysis of two mineral water samples, drinking water, and two fruit juice samples (apple and grape) packed in bottles as real samples using the procedure indicated that the method is satisfactory for measuring phthalate esters due to proper recoveries and relative standard deviations in the range of 84.0–106.0 % and 3.57–8.33 %, respectively.