Solid-phase Extraction Adsorbent Research Articles

Emerald-based polyaniline-modified polyacrylonitrile nanofiber mats based solid-phase extraction for efficient and simple detection of Sudan dyes in poultry feed

Emerald-based polyaniline-modified polyacrylonitrile nanofiber mats (emerald-based PANI-PAN NFMs) were prepared and their performance as solid-phase extraction (SPE) adsorbent for extracting four Sudan dyes (Sudan I–IV) from poultry feed was evaluated. After solvent extraction, the poultry feed samples extraction solution was directly used for SPE by diluted with ultra-high purity water without any other treatment. No washing step was needed before elution, and the eluent was directly detected by the high-performance liquid chromatography-diode array detector (HPLC-DAD) without conventional concentration and filtration. The results showed that emerald-based PANI-PAN NFMs could effectively adsorb Sudan dyes through π-π conjugation and hydrogen bond. The amount of adsorbent and eluent required for the entire SPE process was only 10 mg and 600 µL, respectively. Furthermore, the emerald-based PANI-PAN NFMs were easy to regenerate, and no performance degradation was found after at least 6 times reuses. The detection limits of Sudan I–IV were 6–15 μg·kg−1 and the recoveries were 88.48 % –101.88 % with relative standard deviations (RSDs) less than 15 %, indicating the method has good sensitivity, accuracy, and precision. Compared with existing methods, the proposed method has simpler processes with practical application potential.

Covalent Organic Framework/Polyacrylonitrile Electrospun Nanofiber for Dispersive Solid-Phase Extraction of Trace Quinolones in Food Samples.

The extraction of quinolone antibiotics (QAs) is crucial for the environment and human health. In this work, polyacrylonitrile (PAN)/covalent organic framework TpPa–1 nanofiber was prepared by an electrospinning technique and used as an adsorbent for dispersive solid-phase extraction (dSPE) of five QAs in the honey and pork. The morphology and structure of the adsorbent were characterized, and the extraction and desorption conditions for the targeted analytes were optimized. Under the optimal conditions, a sensitive method was developed by using PAN/TpPa–1 nanofiber as an adsorbent coupled with high-performance liquid chromatography (HPLC) for five QAs detection. It offered good linearity in the ranges of 0.5–200 ng·mL−1 for pefloxacin, enrofloxacin, and orbifloxacin, and of 1–200 ng·mL−1 for norfloxacin and sarafloxacin with correlation coefficients above 0.9946. The limits of detection (S/N = 3) of five QAs ranged from 0.03 to 0.133 ng·mL−1. The intra-day and inter-day relative standard deviations of the five QAs with the spiked concentration of 50 ng·mL−1 were 2.8–4.0 and 3.0–8.8, respectively. The recoveries of five QAs in the honey and pork samples were 81.6–119.7%, which proved that the proposed method has great potential for the efficient extraction and determination of QAs in complex samples.

Exploration of an imine-based covalent organic framework for the solid phase extraction of nitroimidazoles in milk and meat samples

TAPT-AN-COF, an imine-based covalent organic framework, was synthesized by a solvothermal method of 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (TP) and 4,4′,4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (TAPT). The structure was characterized and tested by several techniques, revealing that the material had good stability and high specific surface area. The adsorption experiment demonstrates that the adsorption isotherm of TAPT-AN-COF followed the Freundlich isothermal equation, while its adsorption kinetics conformed to the pseudo second-order kinetic model. After characterization, the prepared TAPT-AN-COF was used to separate and enrich nitroimidazoles (NDZs) in milk and meat as the solid-phase extraction (SPE) adsorbent. The effects of adsorbent dosage, pH value, washing solvent, elution solvent type and volume on recoveries were studied. Under the optimal conditions, a method for the determination of NDZs in milk and meat samples was established based on high performance liquid chromatography-ultraviolet detection(HPLC-UVD).The result showed that NDZs had good linearity in the concentration range of 25-500 µg·kg−1, and the determination coefficients (r2) were all above 0.99. When spiked at 25, 50 and 125 µg·kg−1, the recoveries of three kinds of food samples ranged from 64.5% to 85.3%, the limits of detection (LODs) were between 2 and 10 µg·kg−1, and the relative standard deviations were all below 15.9%. In addition, the recoveries of NDZs didn't decrease significantly after being reused for 6 times, showing that TAPT-AN-COF has excellent reusability. Compared with HLB and MCX sorbents, TAPT-AN-COF had better extraction efficiency and qualified purification efficiency. The established method had a satisfying performance on the determination of NDZs in food samples.

Highly efficient amino-functionalized aluminum-based metal organic frameworks mesoporous nanorods for selective extraction of hydrocortisone in pharmaceutical wastewater

Hydrocortisone (HC), as a common steroid hormone drug, is also one of the key intermediates involved in the synthesis of multiple steroid hormone drugs. Residual HC in pharmaceutical wastewater frequently pollutes environmental water as steroid hormone contaminant and possesses great threat to human health as well as sustainable development of the ecosystem. Herein, in order to develop a highly efficient adsorbent system for selective enrichment and detection of HC in pharmaceutical wastewater, a novel amino-functionalized aluminum-based metal organic frameworks (Al-MOFs@NH2) mesoporous nanorod is fabricated, in which 2-aminoterephthalic acid plays a dual role as organic linker and functional modification unit. The resultant Al-MOFs@NH2 not only exhibits stable mesoporous structure but also has large specific surface area (849.76 m2 g−1) and plentiful binding sites, which significantly increases the adsorption capacity for HC. Under the promotion of hydrogen bonding and hydrophobic interaction together, Al-MOFs@NH2 possesses high adsorption capacity (218.53 mg g−1) for HC, as well as shows satisfactory selectivity for HC and other steroid hormones. Moreover, a method using Al-MOFs@NH2 as solid phase extraction adsorbents combined with high performance liquid chromatography (HPLC) has been developed to specifically enrich and detect trace amount of HC in pharmaceutical wastewater. The developed method has a low limit of detection (LOD) (0.5×10−3 μg mL−1) and shows satisfactory recoveries for HC (75.9%−102.5%) with an acceptable relative standard deviation (RSD). These results demonstrate that the facile one-step preparation and excellent adsorption capacity makes Al-MOFs@NH2 attractive to capture and remove environmental steroid hormone pollutants. More importantly, the method proposed in this work is expected to provide a prospective solution for analysis of strong bioactive contaminants in pharmaceutical wastewater.

Magnetic solid-phase extraction of bisphenol A from water samples using nanostructured material based on graphene with few layers and cobalt ferrite

In this study, magnetic hybrid materials composed of cobalt ferrite, natural organic matter, and graphene (CoFe2O4/NOM/graphene) were synthesized and applied as adsorbents in the magnetic solid-phase extraction (MSPE) of bisphenol A (BPA) from aqueous matrices. To our knowledge, no studies have been previously conducted using this material for MSPE. Techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and transmission electron microscopy (TEM) were used to investigate the composition and morphology of the adsorbent. The MSPE method was optimized considering the main parameters influencing the process, with the best results obtained using 50.0 mg of adsorbent, agitation at 150 rpm, total extraction time of 7.5 min, 10 mL of methanol as extractant, and pH between 4 and 10. BPA analysis was performed using HPLC-DAD and HPLC-FL, with the latter showing better sensitivity. The developed method provided a wide linear range from 0.1 to 5000 μg L−1, with limits of detection (LOD) and quantification (LOQ) of 0.022 and 0.072 μg L−1, respectively. The extraction procedure presented reproducibility (RSD) of 2.13–2.21% and excellent recoveries in the range 99.3–104%. The developed MSPE method using CoFe2O4/NOM/graphene proved to be simple, fast, and efficient for the analysis of BPA in a variety of aqueous matrices.

A cleanup method of serum extracts with molecular sieves as SPE sorbents for the analysis of polybrominated diphenyl ethers.

Based on the size- and shape-selective sorption, 13X molecular sieves were developed as solid-phase extraction adsorbents to cleanup serum extract for the determination of polybrominated diphenyl ethers. The important parameters affecting the cleanup efficiency were investigated including the amount of sorbents, the type, and volume of solvents. Under the optimized conditions, the capacity for removing impurities was evaluated via gel permeation chromatography and gas chromatography with mass spectrometry. The results demonstrated that up to 99% of lipids in corn oil (13 mg) can be removed after cleanup, and endogenous compounds in serum can also be effectively eliminated. The cleanup efficiency is not only superior to hydrophile-lipophile balance column, but also close to acid silica gel and multifunction impurity sorbents. Generally, the developed cleanup method exhibited higher recovery for polybrominated diphenyl ethers with more than four bromines, especially for nona- and deca-brominated diphenyl ethers (99.1-117.8%). The cleanup method can be coupled with gas chromatography and tandem mass spectrometry for polybrominated diphenyl ethers analysis in human serum. The method detection limits were 0.01-0.27 ng/mL and average recovery was 50.9-113.3%, except 2,3',4',6-tetrabrominated, 2,3',4,4',6-pentabrominated, and 2,3,3',4,4',5',6-heptabrominated diphenyl ethers. 2,2',4,5'-Tetrabrominated diphenyl ethers had the highest detection frequency (95%) in human serum, whereas decabrominated diphenyl ethers had the maximum mean concentration (0.50 ng/mL).

Optimized synthesis of molecularly imprinted polymers coated magnetic UIO-66 MOFs for simultaneous specific removal and determination of multi types of macrolide antibiotics in water

Macrolide antibiotics (MALs) are widely used in various fields and are resistant to degrade in the water environment, thus constituting potential hazards to human health. In this work, a new composite, molecularly imprinted polymers coated magnetic metal-organic frameworks with carboxyl modification (M-UIO-66@MIPs) was selected and characterized, for the simultaneous specific adsorption and determination of five MALs from aqueous solution. It was found that UIO-66-COOH with ligand defects showed better pre-polymerization effect than other matrix materials. The synthesis conditions for the imprinting polymer were optimized via response surface methodology. The characteristics of related materials were studied, and a series of adsorption experiments were carried out. The results showed that the adsorption equilibriums of M-UIO-66@MIPs were reached within 1 h, with the total adsorption capacity for the five MALs was 99.05 mg g−1. The pseudo-second-order kinetic model and Freundlich isotherm model could best fit the adsorption process, and the adsorption thermodynamics was controlled by the change of entropy. Adsorption mechanisms were deduced as hydrogen bonding interaction and electrostatic interaction. In addition, M-UIO-66@MIPs has good selectivity and reusability. Furthermore, a new detection method for the five MALs was developed, using the prepared material as the adsorbent for magnetic solid-phase extraction, coupled with high-performance liquid chromatography. Under the optimal extraction condition, the limits of detection for five MALs were 3.1–44.6 μg L−1, and the recoveries were 92.9–108.7 % in the determination of real water samples. Therefore, the M-UIO-66@MIPs could be the efficient adsorbent for simultaneous selective removal and sensitive determination of multi-residual MALs.

Effective extraction of fluoroquinolones from water using facile modified plant fibers

In this study, ecofriendly and economic carboxy-terminated plant fibers (PFs) were used as adsorbents for the effective in-syringe solid phase extraction (IS-SPE) of fluoroquinolone (FQ) residues from water. Based on the thermal esterification and etherification reaction of cellulose hydroxy with citric acid (CA) and sodium chloroacetate in aqueous solutions, carboxy groups grafted onto cotton, cattail, and corncob fibers were fabricated. Compared with carboxy-terminated corncob and cotton, CA-modified cattail with more carboxy groups showed excellent adsorption capacity for FQs. The modified cattail fibers were reproducible and reusable with relative standard deviations of 3.2%–4.2% within 10 cycles of adsorption-desorption. A good extraction efficiency of 71.3%–80.9% was achieved after optimizing the extraction condition. Based on carboxylated cattail, IS-SPE coupled with ultra-performance liquid chromatography with a photodiode array detector was conducted to analyze FQs in environmental water samples. High sensitivity with limit of detections of 0.08–0.25 μg/L and good accuracy with recoveries of 83.8%–111.7% were obtained. Overall, the simple and environment-friendly modified waste PFs have potential applications in the effective extraction and detection of FQs in natural waters.

Novel Graphene oxide-Polyethylene Glycol mono-4-nonylphenyl Ether adsorbent for solid phase extraction of Pb2+ in blood and water samples.

A novel and efficient Graphene Oxide-Polyethylene Glycol mono-4-nonylphenyl Ether (GO-PEGPE) nanocomposite was synthesized and used for solid phase extraction of trace levels of Pb2+ in different water and blood samples. The synthesized adsorbent was then characterized by the Fourier Transform-Infrared spectrophotometry (FT-IR), Field Emission-Scanning Electron Microscopy (FE-SEM), Energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD). To optimize the critical parameters including pH of samples solution, amounts of adsorbent and extraction time, the response surface methodology based on the central composite design (RSM-CCD) was used and based on the results, pH = 6.0, extraction time = 22min and amounts of adsorbent = 15mg were selected as the optimum conditions. The relative standard deviation based on seven replicate analysis of 2µg L-1 Pb2+ was 5.2% and the limit of detection was 0.023µg L-1 (n = 8). The results of adsorption isotherm investigation show that the adsorption of Pb2+ onto the GO-PEGPE nanocomposite obeyed by the Langmuir isotherm with the maximum adsorption capacity of 69.44mgg-1. Also, based on the Temkin and Dubinin-Radushkevich (DR) isotherms, the adsorption of Pb2+ onto the GO-PEGPE nanocomposite is a physisorption phenomenon and the consequences of the kinetic models illustrated that the adsorption of Pb2+ followed by the pseudo second order adsorption kinetic model. Finally, the proposed method was successfully applied for preconcentration of Pb2+ in different water and blood samples of turning industry workers.

Facile synthesis of a novel magnetic covalent organic frameworks for extraction and determination of five fungicides in Chinese herbal medicines.

A novel magnetic covalent organic framework was synthesized via a one-step coating approach with solvothermal reaction employing 2,4,6-tris(4-aminophen-yl)-1,3,5-triazine and 2,4,6-triformylphloroglucinol as two building blocks by covalent bonding. The prepared magnetic covalent organic frameworks were properly characterized by different techniques and employed as adsorbents of magnetic solid-phase extraction. An analytical method was developed for the simultaneous determination of five fungicides in two Chinese herbal medicine samples via magnetic solid-phase extraction coupled to ultra high performance liquid chromatography with tandem mass spectrometry analysis. Under optimized magnetic solid-phase extraction conditions, the method exhibited satisfactory recoveries (74.0-109.6%) with relative standard deviations of 0.4-4.6%, low limits of detection (0.003-0.015 μg/kg), and good linearity (R2 > 0.9960). Compared with the traditional extraction method, the proposed method required a lower amount of adsorbent (3mg) and extraction time (5min). The adsorbent also had favorable reusability (not less than eight times). Therefore, the magnetic covalent organic frameworks could be a promising adsorbent for the extraction and quantitation of fungicides in Chinese herbal medicines.

Amino-functionalized hypercrosslinked polymer as sorbent for effective extraction of nitroimidazoles from water, drink and honey samples

The three hypercrosslinked polymers (HCP) materials, designated as OPD-HCP, MPD-HCP and PPD-HCP, were synthesized by using o-phenylenediamine (OPD), m-phenylenediamine (MPD) and p-phenylenediamine (PPD) as monomers. They were characterized by infrared spectroscopy, powder X-ray diffraction, nitrogen sorption isotherms, and scanning electron microscopy. Then, the HCPs were explored as solid-phase extraction (SPE) adsorbent for the extraction of five nitroimidazoles (NDZs) (metronidazole, ronidazole, secnidazole, dimetridazole and ornidazole). Among the three HCPs, the MPD-HCP has the best adsorption performance for the NDZs. With the help of high-performance liquid chromatography with ultraviolet detection (HPLC-UV), good linear response range (0.07-40.0 ng mL-1), high method recovery (86.8%-113.3%), low limits of detection (0.02-0.15 ng mL-1) and good precision with the relative standard deviations of less than 8.1% were achieved for the determination of the NDZs in water samples. The effective determination of the NDZs in peach juice, honey tea, and honey samples were also realized by the developed method with satisfactory results. Based on both the experimental results and density functional theory calculation, the adsorption mechanism can be attributed to multiple interactions between the MPD-HCP and the NDZs, including hydrogen bonding, hydrophilic, and electrostatic interactions. The method provides a new alternative of choice for the determination of some NDZs in real samples.

Nanocomposites of functionalized Metal−Organic frameworks and magnetic graphene oxide for selective adsorption and efficient determination of Lead(II)

A novel nanocomposite of functionalized Metal−Organic frameworks and magnetic graphene oxide (Fe3O4@C-GO-MOF) was successfully synthesized as a new magnetic solid-phase extraction (MSPE) adsorbent for selective adsorption and efficient determination of lead ions at trace level. The prepared Fe3O4@C-GO-MOF nanocomposite possessed high surface area and sufficient porosity. The nanocomposite was magnetic and could be facilely separated from the solution by an external magnetic field. The hybrid nanocomposite showed remarkable maximum adsorption capacity and was estimated as 344.83 ​mg/g. The adsorption parameters including the solution pH, the adsorbent amount and the adsorption time were optimized by batch adsorption experiments. The adsorption kinetics, isotherm and adsorption mechanism were also discussed in detail. The prepared composite selectively adsorbed Pb(II) from the mixed solution of multiple coexisting ions and had good recovery performance after five adsorption-desorption cycles. Under the optimized experimental conditions, a new MSPE method was established with good linearity, low detection limit and great reproducibility for the determination of Pb(II). The selectivity extraction of Pb(II) in different environmental samples showed satisfactory recoveries. The results show that the Fe3O4@C-GO-MOF nanocomposite is a promising candidate for sample pretreatment and preconcentration in the detection of lead ions.

Progress in preparation of plant biomass-derived biochar and application in pesticide residues field

随着农药的广泛使用,其已普遍存在于环境中,对人们的身体健康产生巨大影响。因此,环境中农药残留的去除和分析检测对保护人体安全健康至关重要。同时,农药在环境中残留浓度低,需要一种对目标物有较强选择性和富集作用,并对环境影响小的前处理吸附剂。植物源生物炭是由植物源生物质作为碳源衍生得到的材料,其比表面积大、孔容量高、表面官能团可调节,且环境相容性好,其原料植物源生物质的价格低廉、来源广泛并可再生,是一种廉价高效的吸附剂。该文主要综述了近10年来植物源生物炭用于环境中农药残留去除和分析检测前处理的应用进展。其中在农药残留去除方面的应用主要包括降低农药在土壤中的移动性,修复手性农药造成的污染,负载降解农药的细菌及作为化肥的缓释载体。在农药残留分析检测前处理方面,植物源生物炭可用作分散固相萃取、固相微萃取和磁性固相萃取的吸附剂来选择性吸附水果和蔬菜中的有机磷类和三唑类农药,以及水环境中的有机氯类农药。另外,还介绍了植物源生物炭的吸附机理,详细阐述了基于计算模拟如密度泛函理论、分子动力学模拟和巨正则蒙特卡洛模拟的吸附机理研究并讨论了其优势。最后,总结了植物源生物炭在农药去除和农药残留分析检测前处理方面应用的优势,指出了其在农药残留领域应用待解决的问题。

APTMS-BCAD modified magnetic iron oxide for magnetic solid-phase extraction of Cu(II) from aqueous solutions

Fe3O4@SiO2-3-aminopropyltrimethoxysilane-1,8-bis (3-chloropropoxy) anthracene-9,10-dione was synthesized as a new, sustainable, and environmentally friendly adsorbent for magnetic solid-phase extraction of Cu(II) from aqueous solutions. The structure of the adsorbent was characterized by FTIR, XRD, SEM, EDX, and TEM analysis. Optimum conditions for Cu(II) adsorption were determined as adsorbent dose 0.04 g, pH 5.0, contact time 120 min, and beginning concentration of 30 mg/L in the adsorption process. The adsorption capacity for Cu(II) ions was 43.67 mg/g and the removal efficiency was 84.72 percent. The Langmuir isotherm and the pseudo-second-order model fit the experimental data better. Adsorption was a spontaneous and endothermic process based on the obtained thermodynamic properties such as ΔG°, ΔH°, and ΔS°. The results showed that the sorbent has good selectivity in the presence of competing ions. The method was determined to be accurate and effective using real water samples and CRM.

In-situ sorbent formation for the extraction of pesticides from honey.

An organic polymer was re-precipitated in solution to use as an adsorbent in dispersive solid-phase extraction of some pesticides from honey samples prior to their determination by high-performance liquid chromatography-tandem mass spectrometry. In this approach, different deep eutectic solvents were prepared using lysine and their ability in elution of the analytes from the adsorbent surface was tested. A diluted honey solution was transferred into a glass test tube and then a solution of polystyrene dissolved in dimethylformamide was injected into the solution. By doing this, polystyrene is re-precipitated in the solution and dispersed in whole parts of it as many tiny particles. Then the mixture was centrifuged and the adsorbed analytes on the particles were eluted using a proper hydrophilic deep eutectic solvent. The central composite design approach was used for the optimization of effective parameters. The limits of detection and quantification were in the ranges of 0.06-0.20 and 0.22-0.69ng/g, respectively. The calibration curves obtained by matrix-matched standard solutions were linear in the range of 0.69-500ng/g with a coefficient of determinations ≥0.9962. The method provided high extraction recoveries (70-99%) and enrichment factors (140-198), and an acceptable precision (relative standard deviations ≤7.1%).

Dual-Template Magnetic Molecularly Imprinted Polymer for Simultaneous Determination of Spot Urine Metanephrines and 3-Methoxytyramine for the Diagnosis of Pheochromocytomas and Paragangliomas.

A novel dual-template magnetic molecularly imprinted polymer (MMIP) was synthesized to extract normetanephrine (NMN), metanephrine (MN) and 3-methoxytyramine (3-MT) from spot urine samples. As the adsorbent of dispersive solid-phase extraction (d-SPE), the MMIP was prepared using dopamine and MN as dual templates, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the crosslinking reagent and magnetic nanoparticles as the magnetic core. NMN, MN, 3-MT and creatinine (Cr) in spot urine samples were selectively enriched by d-SPE and detected by HPLC-fluorescence detection/ultraviolet detection. The peak area (A) ratios of NMN, MN and 3-MT to Cr were used for the diagnosis of pheochromocytomas and paragangliomas (PPGLs). The results showed that the adsorption efficiencies of MMIP for target analytes were all higher than 89.0%, and the coefficient variation precisions of intra-assay and inter-assay for the analytes were within 4.9% and 6.3%, respectively. The recoveries of the analytes were from 93.2% to 112.8%. The MMIP was still functional within 14 days and could be reused at least seven times. The d-SPE and recommended solid-phase extraction (SPE) were both used to pretreat spot urine samples from 18 PPGLs patients and 22 healthy controls. The correlation coefficients of ANMN/ACr and AMN/ACr between d-SPE and SPE were both higher than 0.95. In addition, the areas under the receiver operator curves for spot urine ANMN/ACr, AMN/ACr and plasma free NMN and MN were 0.975, 0.773 and 0.990, 0.821, respectively, indicating the two methods had the similar performances. The d-SPE method took only 20 min, which was effective in clinical application.

Solid Phase Extraction for the Determination of Methylene Blue Using Lignocellulosic Biosorbent in Aqueous Solutions.

The recent introduction of a large number of synthetic dyes, which are toxic, mutagenic, and carcinogenic, has made the situation worse by disrupting normal aquatic life. For this reason, the detection and removal of dyestuffs in wastewater become important. In this study, for the extraction of methylene blue, used as solid phase extraction adsorbent, lignocellulosic biosorbent of tea waste activated with ZnCl2 was prepared. The factors affecting its extraction were studied in detail. To determine the sensitivity and certainty of the solid phase extraction process; optimized to have an adsorbent amount (75mg), wash solvent (3mL water), loading volume (20mL), elution solvent methanol/acetic acid (80:20, v/v), and eluent volume (8mL). As a result of the optimization processes, rates ranging from 94.4% to 98.9% recovery were obtained in methylene blue extraction in aqueous solutions. According to the results obtained, this method can be extensively applied in the efficient removal of colored contaminants.

Synthesis of polydopamine coated magnetic halloysite nanotubes for fast enrichment and extraction of anthraquinones in brewed slimming tea

In this work, a magnetic halloysite nanotubes composite material modified with polydopamine (MHNTs@PDA) was synthesized through a facile and green synthesis strategy, and employed as an efficient adsorbent for magnetic solid-phase extraction (MSPE) of three anthraquinones. The material showed very fast adsorption ability (adsorption time of 3 min), good reusability and strong magnetic response. The main parameters affecting the extraction efficiency of MSPE, including adsorption time, amounts of adsorbent, sample pH, salt concentration and desorption conditions, were investigated and optimized. By coupling MHNTs@PDA-based MSPE with HPLC-UV, the method exhibited good linearity (R2 ≥ 0.9944) in the concentration range of 5–1000 μg L-1 and low limits of detection (1.0–1.5 μg L-1) for anthraquinones. Finally, the developed method was successfully applied to determine anthraquinones in brewed slimming tea, and the obtained recoveries were in the range of 73.5–119.1%, with RSD less than 9.7%.

Preparation of polyethylenimine modified molecular imprinting adsorbent with immobilized metal oxides for highly efficient ovalbumin adsorption

In this study, ZIF-based metal oxide molecularly imprinted polymers (ZIF@PEI@TiO2-MIPs) were prepared for efficient and selective separation and enrichment of ovalbumin (OVA) in egg white samples. The effects of pH, OVA concentration, ionic strength, and elution type on the adsorption process were investigated. ZIF@PEI@TiO2-MIPs have rich imprinted sites and large specific surface area. PEI provides a large amount of amino to bind TiO2. As a new type of solid phase extraction adsorbent, ZIF@PEI@TiO2-MIPs can rapidly adsorb OVA and have a large adsorption capacity. The adsorption time is 35 min, and the maximum adsorption capacity is 417.6 mg g−1. The imprinted sites of adsorbent can distinguish the template protein (OVA) from interference proteins, indicating that ZIF@PEI@TiO2-MIPs have good selectivity and adsorption specificity, and the adsorption model conforms to Langmuir adsorption model and pseudo-second-order kinetics. The adsorbent still has good adsorption performance after six adsorption and elution cycles with 0.5% cetyltrimethylammonium bromide (CTAB) as the eluent, indicating its good stability. In conclusion, ZIF@PEI@TiO2-MIPs can specifically identify OVA in complex samples, providing a large possibility for the application of glycoprotein in activities such as biology and clinical practice.

Functionally modified cross-linked molecularly imprinted resins: separation and purification of camptothecin and its theoretical study

This work has prepared a hyper-crosslinked molecularly imprinted resins (MIRs) with chloromethylated polystyrene resin as a carrier through post-crosslinked Friedel-Crafts and surface imprinting. The prepared MIRs were used for the selective separation and purification of camptothecin (CPT). The prepared MIRs are grafted with a large amount of active group phenol, which have good hydrophilicity and are favorable for application in aqueous environments. The results of Scatchard analysis and contact angle test have proved that MIRs have good adsorption capacity and excellent hydrophilicity. In addition, the results of density functional theory (DFT) analysis show that the possible interaction forces between the template molecule CPT and the functional monomer phenol are the hydrogen bonds and electrostatic attraction. Moreover, MIRs are successfully used as a solid phase extraction (SPE) adsorbent to separate and purify CPT from Camptotheca acuminata fruit. The eluent obtained by SPE is analyzed through HPLC. The detection limit for CPT is 0.23 μg mL−1. The established method preforms high the recovery of CPT (91.2–103.4%) with relative standard deviation less than 4.5%. The reusability of MIRs adsorbent is also investigated, and the adsorption efficiency is still above 95% after being recycled five times. The study provides a feasible and efficient method for selective separate and purify CPT from complicated system.