A new magnetic metal–organic framework composite synthesized via a post-synthetic functionalization approach for ultra-trace extraction/determination of mercury in real matrixes

Abstract

Herein, a novel magnetic metal–organic framework (MMOF) composite was prepared via a post-synthetic modification method was employed to the ultra-trace determination of mercury in food samples. At first, magnetite nanoparticles were fabricated and afterward functionalized with a SiO2 layer (MNPs@silica). After that, MIL-101(Fe) as a MOF was synthesized in the presence of MNPs@silica to obtain magnetic MIL-101 (MMIL-101). Finally, MMIL-101(Fe) was functionalized with dithizone as a chelator via diazonation reaction. The nanomaterial fabrication was approved by diverse techniques including, SEM, EDX-mapping, TEM, XRD, FT-IR, VSM, BET, and CHNS. Optimizing of affecting experimental factors on the extraction process was conducted via a Box-Behnken design approach. Determination of the mercury ions was conducted by a cold vapor atomic absorption spectrometer. The LOD and LOQ values were 0.015 µg kg−1 and 0.045 µg kg−1, respectively, and the method's repeatability as RSD% was evaluated for 1.0, 20, and 50 ng mL−1 standard solutions (n = 5), which were 10.1, 7.6, and 4.8 %, respectively. The new method was validated by analyzing a CRM. The maximum adsorption capacity of 213 mg g−1 was obtained, and the preconcentration factor was 316. Finally, the fabricated nanomaterials was successfully utilized to the separation/quantification of mercury in diverse food samples, and satisfactory results were obtained (RSD, 5.9–10.2 %; recovery, 82–112 %).