| In the current work, for the first time, a vitamin–based metal–organic framework constructed from cobalt
ions and vitamin B3 has been used as a sorbent in dispersive micro–solid–phase extraction. The proposed method was used to extract and enrich aflatoxins (B1, B2, G1, and G2) from soy milk samples
before their quantification by high performance liquid chromatography–tandem mass spectrometry. In
this work, first the metal–organic framework was synthesized and characterized using techniques such
as X–ray diffraction, Fourier transform infrared spectrophotometry, scanning electron microscopy, nitrogen adsorption/desorption, and energy–dispersive X–ray spectroscopy. Then it was used as an efficient
sorbent in the proposed dispersive micro–solid–phase extraction. For this purpose, after precipitating
the proteins of soy milk sample with the aid of trichloroacetic acid, the supernatant phase was taken,
mixed with the synthesized sorbent, and vortexed. After centrifuging, the analytes loaded on the adsorbent were eluted with methanol to transfer them into an organic phase which was compatible with the
subsequently employed separation system. The adsorption capacity of the synthesized MOF for aflatoxins
B1, B2, G1, and G2 were 0.77, 0.83, 0.70, and 0.54 mg g–1, respectively. Under the best experimental situations, satisfactory outcomes including acceptable extraction recoveries (64–75%), low limits of detection
(11.3–48.2 ng L–1) and quantification (42.8–161.6 ng L–1), and good repeatability (relative standard deviations equal or less than 4.0 and 4.7% for intra– and inter– day precisions, respectively) were obtained.
In addition, green synthesis of the metal–organic framework (using vitamin B3 as a linker, water as the
reaction solvent, and mild conditions) and usage low amount or volume of the adsorbent and organic
solvents during the extraction process were the other beneficial aspects of this work which caused the
suggested analytical method to be environmentally friendly |