Monitoring of patulin and ochratoxin A in apple juices using covalent organic framework-reinforced hollow fiber-solid phase microextraction method and HPLC

In the current work, a covalent organic framework-reinforced hollow fiber-solid phase microextraction method has been introduced for the extraction of patulin and ochratoxin A from commercial apple juices before their determination with high-performance liquid chromatography-tandem mass spectrometry. This method benefited from the advantages of traditional hollow fiber-liquid phase microextraction and solid phase microextraction methods. Briefly, in this method, after preparation of the covalent organic framework-reinforced hollow fiber through a simple method, it was placed into the sample solution and the mixture was stirred to increase the contact surface. After stopping the stirring process, the hollow fiber was taken and placed into a vial containing choline chloride: dichloroacetic acid deep eutectic solvent as an elution solvent. In the following, the mixture was sonicated to accelerate the desorption process. Finally, the eluate containing the extracted analytes was taken and injected into separation system. Under optimized conditions, validation of the developed method was done and the outcomes indicated great precision (relative standard deviations ≤ 5.2%), good linearity (coefficient of determination ≥ 0.9974) in a wide range (77.3–1 × 10⁶ ng L⁻¹), and low limits of detection (23.2 and 15.6 ng L⁻¹ for patulin and ochratoxin A, respectively) and quantification (77.3 and 52.1 ng L⁻¹ for patulin and ochratoxin A, respectively). At the end, the suggested approach was employed for the analysis of patulin and ochratoxin A in thirty commercial apple juice samples. Based on the results, patulin and ochratoxin A were detected in 17% and 23% of the investigated apple juice samples, respectively.