Quinoline Bridging Hyperconjugated Covalent Organic Framework as Solid-Phase Microextraction Coating for Ultrasensitive Determination of Phthalate Esters in Water Samples

Covalent organic framework coating with abundant hydrogen bonding sites for efficient enrichment and sensitive detection of oxygenated polycyclic aromatic hydrocarbons in tea

Monitoring trace oxygenated polycyclic aromatic hydrocarbons (O-PAHs) in tea infusions is crucial, as long-term consumption of O-PAHs-contaminated tea can harm health. In this work, covalent organic framework (COF) TpBD-(OH)2 coating was fabricated for solid-phase microextraction (SPME) of O-PAHs. The coating contains abundant benzene rings and hydrogen bonding sites (oxygen and nitrogen groups). Density functional theory calculations, electrostatic potential distribution and X-ray photoelectron spectroscopy analysis indicated the COF efficiently adsorbs O-PAHs via van der Waals force, hydrogen bonding, electrostatic force, size matching, and π-π interaction. Under the best SPME conditions, a method for detecting O-PAHs in tea infusions was developed using gas chromatography-tandem mass spectrometry (GC-MS/MS). The method possessed low limit of detection (0.5-1.0 ng L-1), wide linearity (2.0-1000.0 ng L-1) and satisfactory recoveries (82.5 %-117.5 %). Furthermore, the method was used to study the impacts of different roasting methods on O-PAHs contamination, and results showed carbon roasting posed a higher risk.

One pot preparation of magnetic benzylated cyclodextrin-based hyper-cross-linked polymer for phthalate esters extraction from tea beverages

The increasing popularity of packaged beverages has raised concerns about the health risks associated with phthalate esters (PAEs), which are commonly found in plastics used for packaging. This study presents an eco-friendly approach for synthesizing a magnetic benzylated cyclodextrin-based hyper-cross-linked polymer (Fe3O4/BnCD-HCPP), in which FeCl3serves both as a catalyst for the Friedel-Crafts reaction and as an iron source for Fe3O4 nanoparticles. The Fe3O4/BnCD-HCPP composite was used as an adsorbent to extract of PAEs from tea beverages via magnetic solid-phase extraction, followed by gas chromatography-mass spectrometry analysis. The optimized method exhibited excellent sensitivity, with limits of detection ranging from 0.1 to 0.5 μg L-1. Additionally, the method achieved high recovery rates, ranging from 81.5 % to 118.5 %, and demonstrated precision (relative standard deviations <11.6 %) for PAEs spiked into tea beverages. Mechanistic studies indicated that the high extraction efficiency of Fe3O4/BnCD-HCPP for PAEs is due to its favorable pore size distribution, large specific surface area, and multiple interactions, including π-π stacking, hydrophobic force, and host-guest inclusion. This research not only provides an effective method for determining PAEs in complex aqueous matrices but also introduces a novel and sustainable approach for the fabrication of magnetic composites.

3D microporous metal-organic framework Ca-TCPB as a fiber coating for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) as a type of persistent organic pollutants in environment can pose serious threat to ecosystem and human health. Herein, a microporous metal-organic framework (MOF) material namely Ca-TCPB [H4TCPB: 1,2,4,5-tetrakis(4-carboxyphenyl)-benzene] with three-dimensional (3D) structure was synthesized via simple solvothermal method. The Ca-TCPB served as fiber coating of solid-phase microextraction (SPME) to extract and enrich PAHs prior to gas chromatography analysis. The results showed that the established method has a wide linear range (0.005-40 ng⋅mL-1), high coefficient of determination (R2>0.9961), low detection limit (0.0017-0.003 ng⋅mL-1), and high enrichment factor (7504-13,932), respectively. In addition, the analytical method was successful detected trace target PAHs in pond water with recoveries in the range of 83.3-114.1 %. The excellent extraction ability of this Ca-TCPB crystalline material for target PAHs can be attributed to strong interactions between Ca-TCPB and PAHs, including π-π stacking interactions and hydrogen bonding interactions. It was shown that Ca-TCPB material as fiber coating material possessed the merits of facile and eco-friendly synthesis process, high enrichment multiples, superior thermal stability (470 °C), and high number of reuse times (75 times). Furthermore, the biocompatible Ca-TCPB is alternative material that are green, safe and sustainable. Therefore, the innovative use of Ca-TCPB material as a fiber coating for HP-SPME in this work opens new horizons for sample preparation and environmental analysis.

Determination of tetracycline antibiotics in food using covalent organic frameworks composites-based on magnetic solid phase extraction coupled to HPLC

Tetracycline antibiotics (TCs) has been widely applied as animal and human medicine for the prevention and treatment of diseases. The unsafe residues of TCs pose serious risks to human health. Development of a rapid and sensitive method for determining TCs residues in environment and food samples is still challenging. Herein, we report the in-situ one-pot self-assembly preparation of core-shell magnetic covalent organic frameworks (Fe3O4@COFs) composites with crystalline structure for efficient magnetic solid-phase extraction (MSPE) of TCs from various samples. Fe3O4@COFs showed good enrichment performance for TCs and excellent recyclability. Under optimal MSPE conditions, the developed Fe3O4@COFs-MSPE-liquid chromatogram method possessed wide linear range (0.80-10000 µg L-1), low limits of detection (0.24-0.30 µg L-1), low adsorbent consumption (5 mg) and short extraction time (10 min). The extraction mechanism of hydrogen bonding, π-π and hydrophobic interactions was investigated by comparison experiment and adequate analysis and characterizations. This work reveals the potential of crystalline Fe3O4@COFs composites in sample pretreatment.

Extraction of short-chain fatty acid ethyl Ester in Baijiu using covalent organic framework-based magnetic nanoparticles: Theoretical screening and experimental validation

Short-chain fatty acid ethyl esters (SFAEEs) are critical aroma compounds in Baijiu, and their wider concentration range can lead to differences in the quality grade of Baijiu. Efficiently designing an SFAEEs adsorbent before instrument analysis remains challenging. In this work, nine functionalized covalent organic frameworks (COFs) with different postmodification groups were designed for targeting SFAEEs. Based on interaction energy as the evaluation criterion, COFs modified with 5-Mercapto-1-methyltetrazole (MMTZ) had been identified through density functional theory screening. Using imine COFs and MMTZ, novel magnetic nanoparticles (Fe3O4@COFs@MMTZ) were prepared and used to develop the magnetic solid-phase extraction of SFAEEs from Baijiu. The adsorption mechanism of Fe3O4@COFs@MMTZ was analyzed using wave function analysis, revealing that adsorption occurred via vdW interaction, CH···π interaction, and hydrogen bonding. This study provides a new concept for the rapid detection of SFAEEs and theoretical support for the scientific construction of quality control during Baijiu production.

Boronic acid functionalized of covalent organic framework for high performance capture of trace phthalates

In order to improve the enrichment performance of parent covalent organic frameworks (COFs), boronic acid functionalized of COF (COF-B(OH)2) was obtained by a simple standing method for the first time. The obtained COF-B(OH)2 exhibited the new characteristics that were not possessed by pure COF and was employed as the solid phase microextraction (SPME) coating material for highly efficient enrichment of trace endocrine disruptors phthalates (PAEs). Compared to pure COF, the synergistic effect of the newly emerged unique pore structure and boric acid interaction sites, and the large specific surface area and the abundant benzene ring structure inherited by original COF framework endowed COF-B(OH)2 with enhanced enrichment performance for PAEs. Combined with gas chromatography-mass spectrometry (GC-MS), COF-B(OH)2 exhibited the good linearity over a wide concentration of 0.1-3000 ng l-1 with good coefficients (R2, 0.9916-0.9998) for PAEs. The developed method was successfully employed for detection of trace PAEs in milk and water samples, demonstrating high recoveries (90.6-111.3 %). This work provides a sustainable approach to developing high-performance materials for enriching environmental pollutants.

Development of a Novel SPME Coating for Efficient Extraction of Organochlorine Pesticides in Liquid Dairy Products

A sensitive and accurate analysis of organochlorine pesticide (OCP) residues in dairy products poses a significant challenge. Herein, a novel covalent organic polymer, Azo-COP-1, was synthesized for the enhanced extraction of OCPs in dairy products. The solid phase microextraction fiber coated with Azo-COP-1 demonstrated excellent extraction performance for the OCPs via hydrogen bonding, halogen bonding, π-π stacking, and electrostatic interactions. Coupled with gas chromatography-electron capture detection, we developed a facile and reliable method for detecting OCPs in six types of dairy products with low limits of detection (2.0-400 pg g-1) and high method recoveries (82.6-113%). Azo-COP-1 coatings exhibited good stability and durability. The results verified the feasibility of using Azo-COP-1-based SPME to extract OCP residues in dairy product samples, highlighting its potential for routine monitoring of pesticide residues and food safety assessments.

Simultaneous determination of 28 illegal drugs in sewage by high throughput online SPE-ISTD-UHPLC-MS/MS

This study developed an online solid-phase extraction ultra-high performance liquid chromatography-tandem mass spectrometry (Online-SPE-UHPLC-MS/MS) method for the analysis of 28 illegal drugs in sewage. To achieve this, 28 isotope internal standards (ISTDs) were added to 3 mL sewage samples, the pH was adjusted to 7-8 using hydrochloric acid or 20% ammonia water, followed by centrifugation, filtration, and analysis using UHPLC-MS/MS. The results indicated an excellent linearity of 1-300 ng L-1, and cotinine in the concentration range of 20-6000 ng L-1, linear correlation coefficient R2 > 0.995, with the limit of detection (LOD) of 0.01-6 ng L-1, and a limit of quantification (LOQ) of 0.1-20 ng L-1. The addition of three concentrates of low (2 ng L-1/40 ng L-1), medium (20 ng L-1/400 ng L-1), and high concentration (200 ng L-1/4000 ng L-1) demonstrated the matrix effect of the target compound between ± 22.0%. The extraction recovery was 70.0-119.4%, and a percent accuracy of 75.7-118.1%. Similarly, the intra- and inter-day precisions were 1.8-20.0% and 1.5-18.9%, respectively. The results cemented the sensitivity, accuracy, reliability, strong specificity, and reproducibility, which can be used to screen 28 illegal drugs in sewage for trace analysis.