Application of 3D covalent organic framework in dispersive micro solid phase extraction of mycotoxins in black tea...

In the present study, a method for covalent organic framework (COF)-based dispersive micro solid phase extraction (DµSPE) of aflatoxins (AFs) and ochratoxin A from black tea samples was presented. The extracted toxins were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In this approach, a three dimensional (3D)-COF was used as an effective adsorbent from the sample solution. The analytes were eluted using a vitamin-based ionic liquid (IL) eliminating the need for toxic eluents. The extraction procedure involved extracting the analytes from tea particles into a mixture of ethanol (1.5 mL) and deionized water (13.5 mL) in a 15 mL solution. This was achieved by passing the mixture through the dried black tea filled into a syringe at a flow rate of 2 mL/min. The extraction of the analytes was also involved the removal of tea polyphenols and acidic compounds with the aid of ethylenediamine- n-propyl (PSA) particles. The analytes were then adsorbed onto the synthesized 3D-COF (7 mg) from the pretreated sample solution while undergoing sonication for 2 min. The adsorbed analytes on the sorbent were eluted using cholinium nicotinate ionic liquid and subsequently analyzed. The method showed low limits of detection (LODs) (0.011-0.031 ng/g), a wide linear range (LRs) (0.103-250 ng/g), good relative standard deviations (RSDs) (≤8.9 %), and high extraction recoveries (ERs) (72-80 %). Twenty tea samples were analyzed and aflatoxin B₁ and ochratoxin A were found in several samples.