Oxygenated carbon nanotubes cages coated solid-phase microextraction fiber for selective extraction of migrated aromatic amines from food contact materials

Synthesis of stable and efficient amide-based covalent organic frameworks fiber coatings for the improved solid-phase microextraction of polar aromatic amines

BACKGROUND

Developing facile and general functionalization strategies to improve the durability of covalent organic framework (COF) coatings and their affinity for polar targets is of great significance for solid-phase microextraction (SPME) technology.

RESULTS

In this work, a facile and general amidation strategy was developed for conversion from reversible (imine) to irreversible (amide) linkages in COF coatings. After the amidation, the durability of the obtained amide-linked covalent organic framework (Am-P-COF) coating was greatly improved, and the adsorption efficiency for polar aromatic amines (AAs) was also significantly increased. Moreover, this strategy is also applicable to the amidation of other two COF coatings, showing good general applicability. The obtained Am-P-COF coated fiber was used for SPME, and then coupled with gas chromatography tandem mass spectrometry (GC-MS/MS) to detect AAs. Under the optimal SPME conditions (extraction temperature: 50 °C, extraction time: 30 min, stirring rate: 600 rpm, pH: 8, NaCl concentration: 5.0 mg mL-1, desorption temperature: 290 °C and desorption time: 10 min), a detection method for trace AAs was established. The established method possess wide linear ranges (0.5-500.0 ng L-1), good correlation coefficients (0.9986-0.9993) and low detection limits (0.1-0.5 ng L-1). Moreover, the established method had also been successfully applied to detection of trace AAs in bottled tea beverage and plastic bags packed tea with satisfactory recoveries (83.5 %-116.8 %).

SIGNIFICANCE AND NOVELTY

This research provides a facile and general pathway for increasing the durability of COF coatings and affinity to the polar AAs. The detection method based on the obtained fibers possesses high sensitivity, satisfactory reproducibility and good precision.

Recent Advances in Non-Targeted Screening of Compounds in Plastic-Based/Paper-Based Food Contact Materials

Ensuring the safety of food contact materials has become a pressing concern in recent times. However, detecting hazardous compounds in such materials can be a complex task, and traditional screening methods may not be sufficient. Non-targeted screening technologies can provide comprehensive information on all detectable compounds, thereby supporting the identification, detection, and risk assessment of food contact materials. Nonetheless, the non-targeted screening of food contact materials remains a challenging issue. This paper presents a detailed review of non-targeted screening technologies relying on high-resolution mass spectrometry for plastic-based and paper-based food contact materials over the past five years. Methods of extracting, separating, concentrating, and enriching compounds, as well as migration experiments related to non-targeted screening, are examined in detail. Furthermore, instruments and devices of high-resolution mass spectrometry used in non-targeted screening technologies for food contact materials are discussed and summarized. The research findings aim to provide a theoretical basis and practical reference for the risk management of food contact materials and the development of relevant regulations and standards.

Carboxylated mesoporous carbon hollow spheres for the efficient solid-phase microextraction of aromatic amines

An efficient and stable fiber coating is of great importance for solid-phase microextraction (SPME). In this study, carboxylated mesoporous carbon hollow spheres (MCHS-COOH) were developed as an efficient SPME coating of polar aromatic amines (AAs) for the first time. The MCHS-COOH coating material with high specific surface area (1182.32 m² g^-1), large pore size (10.14 nm), and rich oxygen-containing groups was fabricated via a facile H₂O₂ post-treatment. The as-prepared MCHS-COOH-coated fiber exhibited fast adsorption rate and excellent extraction properties, mainly due to its π-π interactions, hollow structure, and abundant affinity sites (carboxyl groups). Subsequently, coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS), a sensitive method with low limits of detection (0.08-2.0 ng L^-1), a wide linear range (0.3-500.0 ng L^-1), and good repeatability (2.0-8.8%, n = 6) was developed for the analysis of AAs. The developed method was validated against three river water samples, with satisfactory relative recoveries being obtained. The above results demonstrated that the prepared MCHS-COOH-coated fiber exhibited good adsorption capacity, suggesting a promising application to monitor trace polar compounds in real environment.

In Situ Rapid Electrochemical Fabrication of Porphyrin-Based Covalent Organic Frameworks: Novel Fibers for Electro-Enhanced Solid-Phase Microextraction

Electro-enhanced solid-phase microextraction (EE-SPME) is a bright separation and enrichment technique that integrates solid-phase microextraction with the electric field. It retains the excellent extraction performance of SPME technology while having the advantages of efficient driving of electric field and special interaction between the electric field and electrons in the molecules of material structure. Replacing conventional SPME fibers with highly efficient and highly conductive original EE-SPME fibers is critical for the practical applications of these technologies. Here, a novel fiber preparation strategy was proposed to obtain a highly conductive porphyrin-based covalent organic framework (POR-COF) by one-step electropolymerization. Benefiting from the excellent semiconducting properties of porphyrin groups, the POR-COF can be spontaneously polymerized on the fiber surface under an appropriate voltage within a few hours. Its performance was evaluated by the EE-SPME of phthalate esters (PAEs) from food and environmental samples, followed by gas chromatography-tandem triple quadrupole mass spectrometry (GC-MS/MS) technology. The results showed that the POR-COF fiber has been successfully used for the detection of trace PAEs in beverages, industrial wastewater, lake water, and oyster samples with high adsorption selectivity and satisfactory sensitivity. The remarkable extraction properties are mainly attributed to the synergistic effect from material characteristics and electrical parameters' control in the extraction process. The presented strategy for the controlled design and synthesis of highly conductive porphyrin-based covalent organic framework fibers offers prospects in developing EE-SPME technologies.

A multi-site recognition molecularly imprinted solid-phase microextraction fiber for selective enrichment of three cross-class environmental endocrine disruptors

Molecularly imprinted solid-phase microextraction fibers with multi-site recognition were prepared for the simultaneous enrichment of three cross-class environmental endocrine disruptors (EEDs) in environmental water. The surface morphology of the multi-site recognition molecularly imprinted fibers was characterized using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and surface area and pore size analyzer. Under optimal extraction conditions, the molecularly imprinted fibers showed higher extraction capacity to bisphenol F, diethyl phthalate, and methyl paraben than non-imprinted polymer fibers and commercial fibers. Compared with commercial solid-phase microextraction fibers, the multi-site recognition molecularly imprinted fibers showed superior extraction performance at different concentrations of analytes. The selectivity study confirmed that the multi-site recognition molecularly imprinted solid-phase microextraction fibers were highly selective not only for specific template molecules but also for bisphenols, parabens, and phthalates. Furthermore, the method achieved a limit of detection of 0.003-0.02 μg L^-1 for the three cross-class EEDs in environmental water samples with recoveries ranging from 75.76% to 112.69% and relative standard deviations below 11.46%. Thus, the novel MIP fibers with multi-site recognition prepared in this work have provided a promising approach in the field of specific adsorption and a strategy for the simultaneous and sensitive monitoring of multiple cross-class trace EEDs.