A magnetic knitting aromatic polymer as a new sorbent for use in solid-phase extraction of organics

Construction of magnetic recoverable porous electron-rich organic frameworks for efficiently enrichment of phenylurea herbicides from water and milk samples prior to HPLC detection

Porous electron-rich organic frameworks have attracted an increased attention in the adsorption and removal of pollutants due to their abundant electron-rich nitrogen atoms, which can effectively interact with positively charged substance. In this study, a porous electron-rich organic framework (Car-POF) and positively charged amino-functionalized magnetic nanoparticles (Fe3O4-NH2) were used to construct a magnetic electron-rich Fe3O4-NH2@Car-POF for the enrichment of some phenylurea herbicides from water and milk samples prior to high performance liquid chromatographic detection. The adsorption capacity of Fe3O4-NH2@Car-POF for the phenylureas ranged from 14.93 to 28.83 mg g-1. The LODs were observed in the range of 0.05-0.20 ng mL-1 and 0.5-1.5 ng mL-1, and LOQs in the range of 0.17-0.66 ng mL-1 and 1.7-5.0 ng mL-1 for water and milk samples with RSD less than 9.0. The adsorption studies with cationic and anionic dyes revealed that Fe3O4-NH2@Car-POF is favorable for the adsorption of positively charged compounds.

N-rich hypercrosslinked porous polymers for highly efficient preconcentration and sensitive detection of chlorophenols

Three novel N-rich hypercrosslinked porous polymers (NHCP1, NHCP2, and NHCP3) were facilely developed using Friedel-Crafts alkylation. NHCP1 with a remarkably large surface area (2066 m² g^-1) showed the best adsorption performance for chlorophenol pollutants. A sensitive and simple method was developed by using NHCP1 as a sorbent for solid-phase extraction to preconcentrate several chlorophenols in honey, water, and peach beverage samples followed by determination using a high-performance liquid chromatography-ultraviolet detector. The detection wavelength was 280 nm. Under the optimized conditions, the linear ranges were 1.67-1000 ng g^-1 for honey, 0.170-100 ng mL^-1 for water, and 0.330-100 ng mL^-1 for peach beverage samples. The detection limits (S/N = 3) were 0.500-2.00 ng g^-1, 0.0500-0.100 ng mL^-1, and 0.100-0.200 ng mL^-1, respectively. Recovery values were 89.3-111% with relative standard deviations <9.4%. The proposed extraction/preconcentration and quantitative analysis method provides an affordable and effective alternative for the preconcentration and determination of low levels of chlorophenols in real samples.

Synthesis of natural proanthocyanidin based novel magnetic nanoporous organic polymer as advanced sorbent for neonicotinoid insecticides

In this work, a natural proanthocyanidin (PA) based magnetic nanoporous organic polymer (named as PA-MOP) was successfully synthesized for the first time. The PA-MOP possessed high hydrophilic-surface, good magnetic responsiveness and high affinity for neonicotinoid insecticides. It was applied as an advanced magnetic sorbent for extraction of four neonicotinoids (thiamethoxam, imidacloprid, acetamiprid and thiacloprid) from environmental water, peach juice and honey samples prior to HPLC analysis. Under optimal conditions, the limits of detection for the analytes at S/N = 3 were 0.02-0.08 ng mL^-1 for water, 0.03-0.10 ng mL^-1 for peach juice and 0.05-0.16 ng g^-1 for honey sample. The method recoveries were 80.0%-114.8%, with the relative standard deviations below 6.8%. The values of matrix effect were from -1.5% to -9.3%. Based on theory calculation, the extraction mechanism can be attributed to multiple interactions between the PA-MOP and the neonicotinoids, in which hydrogen bonding, π-π stacking and electrostatic interactions are the major interactions.

Construction of hydroxyl functionalized magnetic porous organic framework for the effective detection of organic micropollutants in water, drink and cucumber samples

Organic micropollutants have been extensively detected in environmental waters, posing severe hazards to organisms and humans. Effective detection of micropollutants in environmental water and food samples is of significant importance. Herein, a novel magnetic porous organic framework (labeled as M-Qu-POF) was synthesized using natural quercetin as building units via a facile azo-coupling reaction for the first time. Featuring with good magnetism, intrinsic porosity, high surface area and hydrophilic-lipophilic (amphiphilic) structure, the M-Qu-POF displayed high adsorption capacity for phenylurea herbicides (PUHs) pollutants. The adsorption mechanism was investigated by theory calculation, confirming that the hydrogen bonds interaction, π-π interactions and electrostatic interactions play an important role in the adsorption. With the M-Qu-POF as adsorbent, a magnetic solid phase extraction-high performance liquid chromatography method was first established for simultaneous enrichment and detection of six PUHs in environmental water, tea drink and cucumber samples. Under the optimized experimental conditions, good linear range, low detection limits and high enrichment factors were obtained. The method was successfully applied for determination of PUHs in environmental water, tea drink and cucumber samples with satisfactory recoveries (80.0-118%). The result demonstrates that the M-Qu-POF material has a good application prospect in the detection of other organic micropollutants.

A core-shell structured magnetic covalent organic framework as a magnetic solid-phase extraction adsorbent for phenylurea herbicides

In this work, a core-shell structured magnetic covalent organic framework named as M-TpDAB was constructed with 3,3'-diaminobenzidine (DAB) and 1,3,5-triformylphloroglucinol (Tp) as building units. M-TpDAB was characterized by infrared spectroscopy, nitrogen adsorption-desorption isotherms, powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Using the M-TpDAB as adsorbent, a simple and highly effective method was proposed for preconcentrating phenylurea herbicides before high performance liquid-phase chromatography analysis. In the optimized conditions, a good linearity was achieved within the range of 0.15-100 ng mL^-1 for water sample, 1.0-100.0 ng mL^-1 for tea drink samples. The limits of detection for the analytes were 0.05-0.15 ng mL^-1 for water sample and 0.30-0.50 ng mL^-1 for drink samples. Satisfactory recoveries of spiked target compounds were in the range of 84.6%-105% for water sample and 80.3%-102% for tea drink samples. Finally, the M-TpDAB based method was successfully used to determine phenylurea herbicides in tea drinks and water samples, demonstrating a good alternative for analyzing trace level of phenylurea herbicides in water samples.

Extraction of phenylurea herbicides from rice and environmental water utilizing MIL-100(Fe)-functionalized magnetic adsorbents

In this paper, a novel method is reported for the extraction and enrichment of phenylurea herbicides (PUHs) from rice and environmental water samples using MIL-100(Fe)-functionalized magnetic nanoparticles as adsorbents.

Preparation of a Magnetic Nanoporous Polymer for the Fast and Efficient Extraction of 5-Nitroimidazoles in Milk

A magnetic nanoporous organic polymer (M-NOP) was prepared as a new adsorbent with excellent extraction capacity and rapid adsorption kinetics for 5-nitroimidazoles (5-NDZs). Hence, a rapid and effective method was proposed for determination of 5-NDZs in milk by combining M-NOP-based magnetic solid-phase extraction with high-performance liquid chromatography. Main extraction conditions were investigated. Under optimal conditions, good linear response was achieved in a range of 2.4-100 ng mL^-1 with a lower detection limit of 0.8-1.0 ng mL^-1. High accuracy with a recovery of 80.0-116.0% for the fortified samples, good repeatability with relative standard deviation below 10%, and a high enrichment factor of 97-111 were obtained. The rapid adsorption of 5-NDZs on M-NOP is mainly driven by H-bonding, π-stacking, and polar interactions. Finally, the M-NOP-based method was successfully used to determine 5-NDZs in milk samples. The M-NOP is expected to present promising application in the extraction and quantitative analysis of other compounds.

A magnetic covalent aromatic polymer as an efficient and recyclable adsorbent for phenylurea herbicides

A magnetic covalent aromatic polymer (Fe₃O₄-NH₂-CAP) was synthesized by grinding a covalent aromatic polymer (CAP) and amino-functionalized magnetic nanoparticles (Fe₃O₄-NH₂ NPs). The CAP was prepared by a Friedel-Crafts reaction between biphenyl and 1,3,5-benzenetricarbonyl trichloride. The interaction in the Fe₃O₄-NH₂-CAP is based on hydrogen bond formation between the carbonyl groups in the CAP and the amino groups in the Fe₃O₄-NH₂ NPs. The adsorbent inherits the advantages of the CAP and also has the superior magnetic property of the Fe₃O₄ NPs. The adsorbent was applied to magnetic solid-phase extraction of six phenylurea herbicides (metoxuron, monuron, chlortoluron, isoproturon, monolinuron, buturon) from soil and water samples. Following elution with 600 μL methanol, the herbicides were quantified by HPLC. The calibration plots are linear in the 1.00-100 ng g^-1 herbicide concentration ranges in case of spiked soil samples, and in the 0.10-40 ng mL^-1 concentration range for spiked water samples. The limits of detection range from 0.3 to 0.5 ng g^-1 (soil) and from 0.01 to 0.03 ng mL^-1 (water), with relative standard deviations of <8.0% and < 6.9%, respectively. Graphical abstract Schematic presentation for the preparation of the magnetic covalent aromatic polymer (Fe₃O₄-NH₂-CAP) and of magnetic solid-phase extraction.