Novel N-riched covalent organic framework for solid-phase microextraction of organochlorine pesticides in vegetable and fruit samples

A covalent organic framework named N-COF was successfully constructed by the aldehyde-amine condensation reaction between 2,4,6-tris (4-formyl phenoxy)-1,3,5-triazine and 1,3-bis(4-aminophenyl) urea for the first time. The prepared N-COF exhibited good stability and high affinity to organochlorine pesticides (OCPs). Thus, the N-COF was served as solid phase microextraction fiber coating for extraction of six OCPs from vegetables and fruits including romaine lettuce, cabbage, Chinese cabbage, apple, pear and peach, followed by quantitation with gas chromatography-electron capture detector (GC-ECD). Under the optimal conditions, good linearities for the OCPs existed in the ranges from 0.1 to 1.0 ng g-1 to 100.0 ng g-1 for the samples. The low limits of detection for analytes were obtained in the range of 0.03-0.3 ng g-1. The present work can offer new alternative for sensitive analysis of trace level of OCPs in vegetables and fruits.