Sensitive detection of phthalates in Chinese Baijiu by online in-tube SPME-HPLC-DAD based on carbonized COF-coated carbon fibers.

The monitoring of phthalates (PAEs) is essential for ensuring the quality and safety of Chinese Baijiu. However, the complex matrices and low level pose significant technical challenges. Herein, an online in-tube solid-phase microextraction coupled with high-performance liquid chromatography-diode array detector (IT-SPME-HPLC-DAD) was proposed for detecting PAEs in Baijiu. A covalent organic framework was grown onto carbon fibers, then the material was carbonized to get another fibers (CFs@C-COF). The CFs@C-COF as a sorbent of IT-SPME demonstrated enhanced physicochemical properties, including highly a graphitized structure with mild defects, a high surface area, abundant mesopores and excellent durability. The superior extraction efficiency of CFs@C-COF for PAEs can be ascribed to multiple interactions, such as hydrophobic, π-stacking, and pore-filling effects. The developed online IT-SPME-HPLC-DAD method exhibited the linear ranges (1.0-10.0, 1.5-10.0 μg L), the limits of detection (0.3-0.5 μg L), acceptable relative recoveries (72.7 %-125.8 %), and satisfactory repeatability. In addition, the total duration of this online extraction procedure was only 23 min and no any pretreatment of the samples was required except for diluting Baijiu samples. This research not only offered a simple and effective strategy for the analysis of Baijiu but also expanded the application of carbonized COFs in food safety.