Metal-organic frameworks as advanced sorbents for the extraction and determination of pollutants from environmental, biological, and food media

Tertiary amine-functionalized metal-organic frameworks for high adsorption of perfluoroalkyl and polyfluoroalkyl substances in environmental water samples

Sensitive monitoring of per- and polyfluoroalkyl substances (PFASs) is critical for environmental and health risk assessment. In this work, metal-organic frameworks (MOFs) functionalized with positively charged tertiary amines (UiO-67-CH2-N(CH3)2) were synthesized by the one-pot route, which integrated solvothermal MOFs assembly and in-situ reductive amination of formyl groups. The fabricated UiO-67-CH2-N(CH3)2 exhibited exceptional performance as adsorbents for solid-phase extraction (SPE), and the efficient adsorption of PFASs was attribute to the electrostatic attraction and hydrogen bonding. The proposed SPE-HPLC-MS/MS method demonstrated low limit of detection (0.02-0.88 ng·L-1), good linearity (0.2-400 ng·L-1) and high precision (RSD < 8.18 %). The effectiveness of the established method was assessed through the analysis of PFASs in environmental waters, and recoveries in spiked samples were 84.0-117 % with RSD < 13 %. This study highlighted the efficacy of the functionalized UiO-67-CH2-N(CH3)2 in trace PFASs analysis, advancing their application in environmental monitoring.

Waste PET Plastic-Derived UIO-66(Zr)-MOF Adsorbent for Dispersive Solid Phase Extraction and Removal of Penicillin Antibiotics Water Systems

The extensive use or misuse of broad-spectrum antibiotics such as penicillins and their existence in various water bodies is still one of increasing global concern due to their persistent nature, which could potentially lead to human health and environmental risks. Recycling or upcycling plastic waste to value-added products such as metal-organic frameworks (MOF) to solve other environmental problems, such as water pollution, has received more attention. As a result, UiO-66(Zr)-MOF derived from recycled waste PET bottles (PET-derived UiO-66(Zr)-MOF) was investigated for enrichment and removal of amoxicillin (AMX) and penicillin G (PNG) in water bodies. The synthesised adsorbent was characterised using different analytical characterisation techniques. UiO-66(Zr)-MOF produced the maximum adsorption capacities of 139 and 147 mg/g for AMX and PNG, respectively. Freundlich and pseudo-second-order kinetics models best explained the adsorption process. The dispersive micro-solid phase extraction (D-μ-SPE) of the target analytes was performed using a high-performance liquid chromatography-diode array detector (HPLC-DAD). The effectiveness of the developed method was confirmed by its remarkable analytical performances, such as limits of detection (0.19-0.21 µg/L) while the linear range was 0.6-1000 µg/L. The feasibility and applicability of the validated UiO-66(Zr)-MOF-D-μ-SPE/HPLC-DAD method were confirmed by applying it in real water analysis. The AMX and PNG were detected in wastewater samples in the ranges of 1.51-4.71 µg/L and 0.195-1.19 µg/L for influent and effluent. The spike recoveries ranged from 89.9% to 101%, while the precision (intraday and interday) of the method was less than 5%.

Recent advances in nanomaterial-based adsorbents for removal of pharmaceutical pollutants from wastewater

To cope with the environmental risks posed by pharmaceutical waste, adsorption is considered a viable option due to its simplicity, cost-effectiveness, and reliability. This review explores the opportunities and challenges involved in applying nanomaterial-based adsorbents in their metallic, non-metallic, and hybrid forms for removal of common pharmaceuticals (e.g., antibiotics, beta-blockers, analgesics, non-steroidal anti-inflammatory drugs, endocrine disrupters, and anticancer drugs) from water. To improve the selectivity and scalability of diverse adsorbents against such targets, the adsorption capacity and partition coefficient (PC) of each adsorbent are evaluated. Among the reported materials, magnetic nitrogen-doped carbon displays the highest adsorption capacity (1563.7 mg g-1) for common targets such as ciprofloxacin, while carbon nanotube-SiO2-Al2O3 has the highest PC (1425 mg g-1 μM-1) for estradiol. Despite the advances in adsorption technologies, their commercial applications are yet limited by several defects such as low efficiency, high costs, and poor scalability. This review examines current strategies for addressing pharmaceutical contamination and outlines potential directions for future research.

Novel magnetic coordination polymer gel facilitates high efficiency dual-mode trace Cd(II) detection and cleanup from real samples

Cadmium (Cd(II)) is highly toxic to humans and the environment. Therefore, efficient monitoring and control of Cd(II) is required for environmental protection and human security. Over the years, impressive advances have been made, however, majority of the research focuses on either detection or removal. Herein, a novel magnetic coordination polymer gel, CoFe2O4@Zrtdpa, is explored for the twin objectives of dual mode trace Cd(II) determination and removal from real samples. Box-Behnken design combined genetic algorithm and Taguchi L32 (46 21) design optimized the removal and extraction process variables, respectively. The experimental adsorption capacity at saturation was 179.07 mg g-1 at 298 K. The uptake of Cd(II) was multimolecular (n > 1), endothermic and spontaneous. XPS revealed that two active sites were oxygen and sulphur. The adsorption energies (E1 = 41.79-46.00 kJ mol-1, E2 = 29.85-32.19 kJ mol-1) indicated that complexation at the first and electrostatic interaction through ion exchange at the second active site are at play. Density functional theory (DFT) calculations verified the same asserting that the uptake was more favorable onto the first active site (sulphur). The best fit fractal like pseudo second order model and site energy distribution analysis established energetic heterogeneity. The limits of detection (LODs) and limits of quantifications (LOQs) for the enrichment-spectrophotometric and ICP-AES methods were 1.36 μg L-1, 4.11 μg L-1, and 0.019 μg L-1, 0.062 μg L-1 respectively. The developed adsorption, enrichment-spectrophotometric and ICP-AES methods were successfully employed for the removal and trace Cd(II) determination in real samples with good reusability.

Bioinspired metal-organic frameworks for aqueous environment decontamination: from laboratory scale to real-world technologies

Concerns regarding water contamination are escalating due to the increasing presence of all types of pollutants in water sources, which pose serious health risks to humans and wildlife, disrupt ecosystems, and compromise the safety of drinking water. Addressing water contamination requires stringent regulations and increased public awareness, but especially, it requires the development of highly effective new technologies to decontaminate those aquatic environments that have been already polluted over the past few decades. Since the emergence of metal-organic frameworks (MOFs), their use has been proposed in a multitude of fields, given their unique physicochemical properties, and one of the fields where a realistic application can be expected in the near future is water remediation. In particular, oxamidato-based biological MOFs (bioMOFs) have demonstrated, in recent years, unique properties such as extraordinary robustness, crystallinity and water- and pH-stability as well as very easy functionalisation, which situates them among the best adsorbents for this environmental purpose. In this review, we have summarised the most remarkable results of oxamidato-based bioMOFs in the field of water remediation. Moreover, on the basis of the reported results, we dare to suggest the real possibilities of application, in relevant real-world environments, for these and other MOFs, as well as the main obstacles that will need to be overcome, aiming to widening the range of applicability of MOFs and making solid headway towards sustainable development.

Recent Progress and Applications of Advanced Nanomaterials in Solid-Phase Extraction

Sample preparation maintains a key bottleneck in the whole analytical procedure. Solid-phase sorbents (SPSs) have garnered increasing attention in sample preparation research due to their crucial roles in achieving high clean-up and enrichment efficiency in the analysis of trace targets present in complex matrices. Novel nanoscale materials with improved characteristics have garnered considerable interest across different scientific disciplines due to the limited capabilities of traditional bulk-scale materials. The purpose of this review is to offer a thorough summary of the latest developments and uses of SPSs in preparing samples for chromatographic analysis, focusing on the years 2020-2024. The techniques for preparing SPSs are examined, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), carbon nanoparticles (CNPs), molecularly imprinted polymers (MIPs), and metallic nanomaterials (MNs). Examining the pros and cons of different extraction methods, including solid-phase extraction (SPE), magnetic SPE (MSPE), flow-based SPE (FBA-SPE), solid-phase microextraction (SPME), stir-bar sorptive extraction (SBSE), and dispersive SPE (DSPE), is the main focus. Furthermore, this article presents the utilization of SPE technology for isolating common contaminants in various environmental, biological, and food specimens. We highlight the persistent challenges in SPSs and anticipate future advancements and applications of novel SPSs.

Facile preparation of hollow covalent organic frameworks as superior and universal matrix clean-up micro-structures for high throughout determination of food hazards

The complicated food matrix seriously limits the one-time test for the potential food hazards in non-targeted analysis. Accordingly, developing advanced sample pretreatment strategy to reduce matrix effects is of great significance. Herein, newly-integrated hollow-structured covalent organic frameworks (HCOFs) with large internal adsorption capacity and target-matched pore size were synthesized via etching the core-shell structured COFs. The as-prepared HCOFs could be directly applied for matrix clean-up of vegetable samples, while further modification of polydopamine (PDA) network facilitated application for animal samples. Both HCOFs and HCOFs@PDA with the comparable sizes to the matrix interference gave excellent adsorption performance to targets, achieving satisfied recoveries (70%-120%) toward 90 pesticides and 44 veterinary drugs in one-test, respectively. This work showed the great potential of the facile-integrated HCOFs with high stability and customized size to remove interference matrix and offered a universal strategy to achieve simultaneous screening of hazards with considerable quantity in high-throughput non-targeted analysis.

Microextraction techniques for occupational biological monitoring: Basic principles, current applications and future perspectives

The application of green microextraction techniques (METs) is constantly being developed in different areas including pharmaceutical, forensic, food and environmental analysis. However, they are less used in biological monitoring of workers in occupational settings. Developing valid extraction methods and analytical techniques for the determination of occupational indicators plays a critical role in the management of workers' exposure to chemicals in workplaces. Microextraction techniques have become increasingly important because they are inexpensive, robust and environmentally friendly. This study aimed to provide a comprehensive review and interpret the applications of METs and novel sorbents and liquids in biological monitoring. Future perspectives and occupational indicators that METs have not yet been developed for are also discussed.

Synthesis and characterization of Fe3O4@SiO2 -supported metal-organic framework PAEDTC@MIL-101 (Fe) for degradation of chlorpyrifos and diazinon pesticides

In this study, a new core-shell Fe3O4@SiO2/PAEDTC@MIL-101 (Fe) photocatalyst was prepared by sol-gel method and used to degrade diazinon (DZN) and chlorpyrifos (CPS) from aqueous solutions. The characteristics analyzed by various techniques indicate that the core-shell photocatalyst with a specific surface area of 992 m2/g, pore size of 1.35 nm and saturation magnetization of nanocomposite was 12 emu/g has been successfully synthesized and can be separated from the reaction solution by a magnetic field. The maximum efficiencies of DZN (98.8%) and CPS (99.9%) were provided at pH of 5, photocatalyst dosage of 0.6 g/L, pollutant concentration of 25 mg/L, radiation intensity of 15 W, and time of 60 min. The presence of anions such as sulfate, nitrate, bicarbonate, phosphate, and chloride had a negative effect on the performance of the photocatalysis system. Compared to the adsorption and photolysis systems alone, the photocatalytic process based on Fe3O4@SiO2/PAEDTC@MIL-101 (Fe) under two UV and visible light sources showed a high efficiency of 90% in the reaction time of 60 min. The BOD5/COD ratio improved after 50 min to above 0.4 with TOC and COD removal rates >80%. Scavenging tests showed that •OH radical, hole (h+), electron (e-), and O2•- anion were produced in the reaction reactor, and the •OH radical was the dominant species in the degradation of DZN and CPS. The stability tests confirmed the recyclability of the photocatalyst in 360 min of reactions, with a minimum reduction of 7%. Energy consumption for the present system during different reactions was between 15.61 and 25.06 kWh/m3 for DZN degradation and 10-22.87 kWh/m3 for CPS degradation.

Coordination polymer gel mediated spectrophotometric, ICP-AES and spectrofluorimetric methods for trace As(III) determination in water and food samples

Herein, a coordination polymer gel is proposed for the determination of As(III) in real samples through multispectroscopic techniques viz. spectrophotometry, spectrofluorimetry, and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Taguchi L32 (46 21) design and adaptive neuro fuzzy inference system (ANFIS) optimized the controllable factors affecting the extraction yielding an experimental S/N ratio of 39.94 dB. The fluorescence quenching (KSV = 2.63 × 106 L mol-1) was static with photoelectron transfer being the main mechanism confirmed by the density functional theory calculations. The limits of detection (LODs), limits of quantification (LOQs) and linear ranges were 0.038 μg L-1, 0.13 μg L-1 and 1.67-116.67 μg L-1, 0.40 μg L-1, 1.21 μg L-1 and 1.67-33.33 μg L-1, 1.07 μg L-1, 3.24 μg L-1 and 3.32-35.37 μg L-1 for the developed enrichment coupled ICP-AES, spectrophotometry and fluorescence sensing methods. Among these methods, the enrichment - ICP-AES method has the lowest LOD, LOQ and the widest linear range followed by the enrichment - spectrophotometry and fluorescene sensing methods. Spectrofluorimetry offers high sensitivity, selectivity, and possible real time monitoring, spectrophotometry provides a cost-effective and versatile option, while ICP-AES manifests multi-element analysis with high sensitivity and low interference. The developed methods were validated and employed for the successful determination of trace As(III) in real samples. The employment of these methods enhances the overall analytical capability for a wide range of sample types and concentrations.

MOF-801 based solid phase microextraction fiber for the monitoring of indoor BTEX pollution

Benzene, toluene, ethylbenzene and xylenes (BTEX) are some of the better-known indoor air pollutants, for which effective monitoring is important. The analysis of BTEX can be performed by different type of solid phase microextraction (SPME) fibers. This study presents a proposal for a low cost, convenient and environmentally friendly analytical method for the determination of BTEX in air samples using custom made SPME fibers. In this context, custom made metal organic frameworks (MOF-801) were coated on a stainless-steel wire for SPME fiber preparation. The analysis of BTEX was performed by introducing SPME fiber into an analyte-containing Tedlar bag in steady-state conditions. After the sampling step, the analytes were analyzed using gas chromatography mass spectrometry in selected ion monitoring mode. Parameters that affect the analysis results were optimized; these include desorption temperature and time, preconditioning time, extraction temperature and time, and sample volume. Under optimized conditions, analytical figure of merits of developed method were obtained, including limits of detection (LOD) (0.012 - 0.048 mg/m3), linear ranges (0.041-18 mg/m3), intraday and interday repeatability (2.08 - 4.04% and 3.94 - 6.35%), and fiber to fiber reproducibility (7.51 - 11.17%). The proposed method was successfully applied to real air samples with an acceptable recovery values between 84.5% and 110.9%. The developed method can be applied for the effective monitoring of BTEX.

Schiff base MOFs and their derivatives for sequestration and degradation of pollutants: present and future

Removal of contaminants via adsorption and catalysis have received a significant interest as energy and money-saving solutions for treating the world's wastewater. Metal-organic frameworks (MOFs), a newly discovered class of porous crystalline materials, have demonstrated tremendous promise in the removal and destruction of contaminants for water purification. In order to improve the interactions of MOFs with the target pollutants for their selective removal and degradation, the Schiff base functionalities emerged as promising active sites. Through pre- and post-synthetic alterations, Schiff base functionalities are integrated into the pore cages of MOF adsorbent materials. To understand the adsorptive/catalytic mechanism, potential interactions between the Schiff base sites and the target pollutants are discussed. Based on cutting-edge techniques for their synthesis, this paper examines current developments in the creation of Schiff base-functionalized MOFs as innovative materials for adsorptive removal and catalytic degradation of contaminants for water remediation.

Schiff base-functionalized metal-organic frameworks as an efficient adsorbent for the decontamination of heavy metal ions in water

Adsorptive removal of heavy metal ions from water is an energy- and cost-effective water decontamination technology. Schiff base functionalities can be incorporated into the pore cages of metal-organic frameworks (MOFs) via direct synthesis, post-synthetic modification, and composite formation. Such incorporation can efficiently enhance the interactions between the MOF adsorbent and target heavy metal ions to promote the selective adsorption of the latter. Accordingly, Schiff base-functionalized MOFs have great potential to selectively remove a particular metal ion from the aqueous solutions in the presence of coexisting (interfering) metal ions through the binding sites within their pore cages. Schiff base-functionalized MOFs can bind divalent metal ions (e.g., Pb(II), Co(II), Cu(II), Cd (II), and Hg (II)) more strongly than trivalent metal ions (e.g., Cr(III)). The adsorption capacity range of Schiff base-functionalized MOFs for divalent ions is thus much more broad (22.4-713 mg g-1) than that of trivalent metal ions (118-127 mg g-1). To evaluate the adsorption performance between different adsorbents, the two parameters (i.e., adsorption capacity and partition coefficient (PC)) are derived and used for comparison. Further, the possible interactions between the Schiff base sites and the target heavy metal ions are discussed to help understand the associated removal mechanisms. This review delivers actionable knowledge for developing Schiff-base functionalized MOFs toward the adsorptive removal of heavy metal ions in water in line with their performance evaluation and associated removal mechanisms. Finally, this review highlights the challenges and forthcoming research and development needs of Schiff base-functionalized MOFs for diverse fields of operations.

Determination of tetrabromobisphenol A and its brominated derivatives in water, sediment and soil by high performance liquid chromatography-tandem mass spectrometry

Tetrabromobisphenol A (TBBPA) was typical brominated flame retardant and potential environmental endocrine disruptor, and it had persistence, bioaccumulation and chronic toxicity. Simultaneous determination of ultra-trace TBBPA, tribromobiphenol A (tri-BBPA), dibromobiphenol A (di-BBPA), monobromobisphenol A (mono-BBPA) and bisphenol A (BPA) was developed by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS), the parent ion charge ratios (m/z) had been optimized. The linear range was wider and the limit of detection was (LOD) 0.09 ~ 0.21 ng mL-1, which could detect trace pollutants. The extraction efficiency was improved by optimizing the parameters, HLB cartridge was used in the water sample by solid phase extraction (SPE), the recovery rates in water samples were over 80.28% with three concentration levels, the relative standard deviations (RSD) were less than 7.12%, and the minimum detection limit of the method was 0.90 ~ 2.10 × 10-3 ng mL-1. Soil and sediment samples were extracted by accelerated solvent extraction (ASE), the recovery rates in soil and sediment were over 79.40% and 75.65%, the minimum detection limit was 0.0225 ~ 0.0525 ng g-1, RSD was less than 7.19%. The proffered method was successfully utilized to detect actual samples, the residue of di-BBPA and mono-BBPA are detected in Naihe River and Shuxi River in Tai'an City, residue of di-BBPA and mono-BBPA was detected in the soil, and there was low residual amount of di-BBPA, mono-BBPA and BPA in the sediment of Shuxi River.

Small nanofibrous disks for preconcentration of environmental contaminants followed by direct in-vial elution and chromatographic determination

A novel method for the extraction of river water contaminants as model analytes of ranging polarities, including bisphenols A, C, S, Z, fenoxycarb, kadethrin, and deltamethrin, using small compact fibrous disks has been developed and validated. Polymer nanofibers and microfibers prepared from poly(3-hydroxybutyrate), polypropylene, polyurethane, polyacrylonitrile, poly(lactic acid), and polycaprolactone doped with graphene were evaluated in terms of extraction efficiency, selectivity, and stability in organic solutions. Our novel extraction procedure comprised preconcentration of analytes from 150 mL river water to 1 mL of eluent using a compact nanofibrous disk freely vortexed in the sample. Small nanofibrous disks with a diameter of 10 mm were cut from a compact and mechanically stable 1-2 mm thick micro/nanofibrous sheet. After 60 min extraction in a magnetically stirred sample located in a beaker, the disk was removed from the liquid and washed with water. Then, the disk was inserted into a 1.5 mL HPLC vial and extracted with 1.0 ml methanol upon short intensive shaking. Our approach avoided the undesired problems related to the manual handling typical of "classical" SPE procedure since the extraction was carried out directly in the HPLC vial. No sample evaporation, reconstitution, or pipetting was required. The nanofibrous disk is affordable, needs no support or holder, and its use avoids creation of plastic waste originating from disposable materials. Recovery of compounds from the disks was 47.2-141.4% depending on the type of polymer used and the relative standard deviations calculated from 5 extractions ranged from 6.1 to 11.8% for poly(3-hydroxybutyrate), 6.3-14.8% for polyurethane, and 1.7-16.2% for polycaprolactone doped with graphene. A small enrichment factor was obtained for polar bisphenol S using all sorbents. A higher preconcentration reaching up to 40-fold was achieved for lipophilic compounds such as deltamethrin when using poly(3-hydroxybutyrate) and graphene-doped polycaprolactone.

Metal-organic frameworks for food contaminant adsorption and detection

Metal-organic framework materials (MOFs) have been widely used in food contamination adsorption and detection due to their large specific surface area, specific pore structure and flexible post-modification. MOFs with specific pore size can be targeted for selective adsorption of some contaminants and can be used as pretreatment and pre-concentration steps to purify samples and enrich target analytes for food contamination detection to improve the detection efficiency. In addition, MOFs, as a new functional material, play an important role in developing new rapid detection methods that are simple, portable, inexpensive and with high sensitivity and accuracy. The aim of this paper is to summarize the latest and insightful research results on MOFs for the adsorption and detection of food contaminants. By summarizing Zn-based, Cu-based and Zr-based MOFs with low cost, easily available raw materials and convenient synthesis conditions, we describe their principles and discuss their applications in chemical and biological contaminant adsorption and sensing detection in terms of stability, adsorption capacity and sensitivity. Finally, we present the limitations and challenges of MOFs in food detection, hoping to provide some ideas for future development.

Recent applications of organic molecule-based framework porous materials in solid-phase microextraction for pharmaceutical analysis

Sample preparation is an indispensable part of detection of complex samples in pharmaceutical analysis. Solid-phase microextraction (SPME) has obtained a lot of attention due to its advantages of time saving, less solvent and easily automation. A variety of functional materials are used as sorbents in SPME to carry out selective and high extraction. This review centers around the recent applications of organic molecule-based framework porous materials, such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), as SPME coating materials mainly focus on pharmaceutical analysis in food, environment, and biological samples. Four representative extraction devices are introduced, including on-fiber SPME, in-tube SPME, thin film SPME, stir bar SPME. The application prospect of other organic porous materials as sorbents for pharmaceutical analysis are also discussed, such as hyper crosslinked polymers (HCPs) and conjugated microporous polymers (CMPs). The progresses and discusses are provided to offer references for further research focusing on application and development of organic molecule-based framework porous materials in the field of SPME.

[Metal-organic framework UiO-67-based enrichment and purification of progesterone residues in milk]

Progesterone functions as an endocrine-disrupting compound. Imitating endogenous hormones disrupt the animals' hormone levels. The potential hazard of progesterone in milk cannot be neglected. Thus, research has focused on establishing an efficient and convenient pretreatment and analytical approach. In this study, a metal-organic framework (MOF) material UiO-67 was prepared, which possessed a large specific surface area and excellent stability. It was employed to enrich and purify trace progesterones in a complex milk matrix as a filler to integrate the solid phase extraction column. An approach based on MOF was developed using ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS). This approach could simultaneously determine seven kinds of progesterone residues in milk. The element spectra of UiO-67 were first measured and analyzed using X-ray photoelectron spectroscopy. The chemical interaction between UiO-67 and progesterone was proved by comparing the changes in binding energy and relative contents of functional groups, and the adsorption efficiency of 1 mg/L and 5 mg/L progesterones by UiO-67 was studied. The adsorption efficiencies of UiO-67 for 1 mg/L and 5 mg/L progesterones were 99.73%-99.95% and 88.87%-99.23%, respectively, according to the results. It proved the efficient adsorption of UiO-67 to progesterones and ensured that subsequent studies went smoothly. Furthermore, key parameters, such as the amount of sorbent, elution solvent type, and pH value, were examined and optimized to obtain optimal extraction recovery of the progesterones. Spiked concentrations of 50 μg/L were employed for extraction optimization. All experiments were performed three times. It also evaluated the matrix effect on mass spectrum signal of the progesterones. The optimized results showed that the seven progesterones could be satisfactorily recovered when the amount of adsorbent was 40 mg, pH value of the sample solution was 5, and elution solution was 5-mL acetone. Additionally, the matrix effect of progesterone in the milk sample was <20%. The matrix effect could be neglected using the aforementioned approach to extract and purify progesterones in milk. Finally, the seven progesterones showed good linearity between 1 and 100 μg/L under the optimized conditions, with linear correlation coefficients values >0.99. The limits of detection (LODs) ranged from 0.06 to 0.30 μg/L, and limits of quantification (LOQs) ranged from 0.19 to 1.0 μg/L, respectively. At various concentration levels of progesterones in milk, the recoveries were 87.10%-105.58%, with relative standard deviations of 2.66%-9.64%. Most importantly, the approach was successfully employed to determine progesterone levels in milk samples, with results in good agreement with the standard SN/T 1980-2007. The proposed approach had the advantages of high sensitivity and satisfactory accuracy compared with the reported pretreatment and detection approaches of progesterone in milk. Satisfactory experimental results can be obtained without the calibration by isotope inner standard. Meanwhile, considering the excellent performance of MOF materials in reducing matrix interference in complex samples, such the application of materials offers a new approach. It can be employed to enrich and detect hazards in a complex matrix in the future.

Review of recently used adsorbents for antimony removal from contaminated water

As prior pollutants, antimony (Sb) and its compounds are carcinogenic to threaten human health. With the development of the industry, various Sb-contained pollutants have been released into nature, thus heavily damaging the ecological environment. Effectively treating Sb-polluted waterbodies is very important and have obtained ever-growing attention. In this review, we have summarized and classified the adsorbents used for removing Sb from water in recent two decades as natural and synthetic biological adsorbents, mineral adsorbents, natural and synthetic carbon materials, metal-based adsorbents, and metal-organic frameworks. We focus on the adsorption behavior of various adsorbents for Sb, including adsorption capacity, isotherms, kinetics, thermodynamics, and effects of environmental factors (e.g., pH, coexisting anions, and natural organic matter). Meanwhile, the involved adsorption mechanisms of Sb by different adsorbents are discussed. Finally, we have outlined the development of adsorbents over the last two decades and summarized the performance characteristics of effective adsorbents, such as the rich functional groups on the surface of the adsorbents (i.e., hydroxyl, carboxyl and amino groups), and the presence of metal elements to coordinate with Sb in (i.e., iron and manganese). We hope this review give enlightenment to design adsorbents for effective removal of Sb.

Metal organic framework/chitosan/polyethylene oxide composite columnar foam as a sorbent for the enrichment and determination of estrogens in environmental aqueous solutions

A MIL-53(Al)/CS/PEO columnar foam was fabricated for the determination of estrogens in larger-volume environmental water samples by VA-SPE and HPLC-FLD.

A review on recent advances in the enrichment of glycopeptides and glycoproteins by liquid chromatographic methods: 2016-Present

Among various protein post-translational modifications (PTMs), glycosylation has received special attention due to its immense role in molecular interactions, cellular signal transduction, immune response, etc. Aberration in glycan moieties of a glycoprotein is associated with cancer, diabetes, and bacterial and viral infections. In biofluids (plasma, saliva, urine, milk, etc.), glycoproteins are low in abundance and are masked by the presence of high abundant proteins. Hence, prior to their identification using mass spectrometry methods, liquid chromatography (LC)-based approaches were widely used. A general enrichment strategy involves a protein digestion step, followed by LC-based enrichment and desorption of glycopeptides, and enzymatic excision of the glycans. The focus of this review article is to highlight the articles published since 2016 that dealt with different LC-based approaches for glycopeptide and glycoprotein enrichment. The preparation of stationary phases, their surface activation, and ligand immobilization strategies have been discussed in detail. Finally, the major developments and future trends in the field have been summarized.

Critical review of solid phase extraction for multiresidue clean-up and pre-concentration of antibiotics from livestock and poultry manure

The release of antibiotics into the environment from agricultural industries has received tremendous attention in recent years. Nonpoint source contamination of the terrestrial environment by these compounds can result from fertilisation of agricultural soils with manure. The presence of antibiotics and their metabolites in manure may pose a threat to agro-ecosystems. This may result in the emergence of antibiotic resistance bacteria in humans through the food chain and this is a major concern globally at the moment. Therefore, monitoring of manure for antibiotic residues is of vital importance in order to assess the risks of environmental pollution to human health by these drugs. Several sample pre-treatment techniques have been developed for the extraction of antibiotic residues from complex matrices including manure over the years. Despite new developments in recent years in separation science where the common trend is miniaturisation and green approaches, solid-phase extraction is still the most widely used technique in the extraction of antibiotics from agricultural wastes such as manure. In view of this, the aim of this review was to give a critical overview of studies that have been conducted in the past 6 years on the extraction of antibiotic residues from manure employing solid-phase extraction based on Oasis HLB and Strata-X. Adsorption mechanisms of these sorbents were also briefly discussed.

On the use of metal-organic frameworks for the extraction of organic compounds from environmental samples

The determination of trace metals and organic contaminants in environmental samples, such as water, air, soil, and sediment, is until today a challenging process for the analytical chemistry. Metal-organic frameworks (MOFs) are novel porous nanomaterials that are composed of metal ions and an organic connector. These materials are gaining more and more attention due to their superior characteristics, such as high surface area, tunable pore size, mechanical and thermal stability, luminosity, and charge transfer ability between metals and ligands. Among the various applications of MOFs are gas storage, separation, catalysis, and drug delivery. Recently, MOFs have been successfully introduced in the field of sample preparation for analytical chemistry and they have been used for sample pretreatment of various matrices. This review focuses on the applications of MOFs as novel adsorbents for the extraction of organic compounds from environmental samples.

A dumbbell-shaped stir bar made from poly(3,4-ethylenedioxythiophene)-coated porous cryogel incorporating metal organic frameworks for the extraction of synthetic phenolic antioxidants in foodstuffs

A dumbbell-shaped stir bar adsorbent of MIL-101 entrapped in PVA cryogel coated with poly(3,4-ethylenedioxythiophene) was fabricated to extract synthetic phenolic antioxidants in foodstuffs. The interconnected porous of cryogel allowed the entrapment of MIL-101 and enhanced the surface areas of poly(3,4-ethylenedioxythiophene) coating which facilitated multiple adsorptions. The fabricated adsorbent was characterized and measured the adsorption capacities for synthetic phenolic antioxidants. Extraction efficiency was optimized by evaluating the effect of adsorbent compositions, extraction time, stirring speed, sample pH, desorption conditions, sample volume and ionic strength. The analysis of extracted synthetic phenolic antioxidants was carried out using high performance liquid chromatography. The developed analysis method provided a wide linear range of 0.20 - 200 µg kg^-1 for butylated hydroxyanisole and 0.50 - 200 µg kg^-1 for tert‑butylhydroquinone and butylated hydroxytoluene. The limits of detection were between 0.05 and 0.15 µg kg^-1. The developed stir bar adsorbent was utilized to extract these three synthetic phenolic antioxidants from juice, milk, infant formula and coffee creamer. Recoveries ranged from 87 to 101% with RSDs below 7%. The developed composite stir bar adsorbent was convenient to use, and good physical and chemical stability allowed efficient extraction for 12 extraction cycles.

A novel approach for the preparation of core-shell MOF/polymer composites as mixed-mode stationary phase

The nickel organic framework capped with polyvinylpyrrolidone was prepared and synergistically immobilized onto porous silica surface as the mixed-mode stationary phase for high-performance liquid chromatography. Here, polyvinylpyrrolidone firstly was chosen as functional molecules to change morphology and size of the metal organic framework. The silica microspheres were then modified by them via a simple bonding method rather than in-situ growth method with the aid of electrostatic interaction commonly used before. The stationary phase showed flexible selectivity for separation of both hydrophilic and hydrophobic compounds, especially for hydrophilic compounds such as carbohydrates, alkaloids and sulfonamides etc. The chromatographic behaviors were evaluated by investigating various factors, and a typical mixed-mode retention feature of the column was observed. The composites could be prepared repetitively, and relative standard deviations of retention time of objective compounds among different batches were less than 1.75%. It also showed excellent chromatographic reproducibility, stability and potentiality for application in real samples. In short, the composites can be used for a feasible option for analysis of multiple compounds as the mixed-mode stationary phase and it provides a general approach for preparing MOFs-based composites by changing morphology and size of MOFs.

Novel solid-phase extraction filter based on a zirconium meta-organic framework for determination of non-steroidal anti-inflammatory drugs residues

In this study, a zirconium-based metal-organic framework UiO-66-NH₂ modified cotton fiber (CF@UiO-66-NH₂) was fabricated for the extraction of five common NSAIDs, namely ketoprofen, naproxen, flurbiprofen, diclofenac sodium, and ibuprofen. UiO-66-NH₂ was synthesized and immobilized on the surface of cotton fiber using an environmentally friendly aqueous synthesis method. The prepared CF@UiO-66-NH₂ composite of 50 mg was loaded into a 13 mm recessed filter for use as a solid-phase extraction (SPE) adsorbent material. The filter was then used to enrich NSAIDs in fish and shrimp muscle tissues followed by ultra-high performance liquid chromatography (UPLC) detection. Several key parameters were evaluated and optimized, including adsorption flow rate, pH value of sample, desorption flow rate, and the formic acid content of the eluent. Under optimized conditions, linear ranges of ketoprofen, naproxen, flurbiprofen, diclofenac sodium, and ibuprofen were 2.0-300.0 ng/mL, 1.4-280.0 ng/mL, 3.0-400.0 ng/mL, 1.0-500.0 ng/mL, and 14.0-560.0 ng/mL, respectively. The detection limits ranged from 0.12 ng/mL to 3.50 ng/mL with recoveries in the range of 72.95-116.99%, RSDs < 9.90%. The results demonstrated that the homemade filters based on CF@UiO-66-NH₂ exhibited good reproducibility, stability and adsorption property for the determination of trace-level NSAIDs in complex matrix.

Determination of quinolones in environmental water and fish by magnetic metal organic frameworks based magnetic solid-phase extraction followed by high-performance liquid chromatography-tandem mass spectrometry

The widespread use of quinolones has become an increasing global public health threat. In this study, IRMOF-3 coated SiO₂/Fe₃O₄ were prepared via a facile room-temperature method. The prepared IRMOF-3 coated SiO₂/Fe₃O₄ was used as a sorbent for magnetic solid phase extraction, and then combined with high-performance liquid chromatography-tandem mass spectrometry for the determination of 10 quinolines. The extraction conditions of magnetic solid phase extraction were studied in detail, and the optimal conditions were established. Under the optimal experimental conditions, the limits of quantification of 10 quinolones were in the range of 0.005-0.01 μg L^-1, the relative standard deviations were 6.58-10.6% (n=7), the enrichment factors were 21.0-23.8 for water samples. The limits of quantification of 10 quinolones were in the range of 0.10-0.20 μg kg^-1, the relative standard deviations were 5.95-14.5% (n=7), the enrichment factors were 1.08-1.24 for fish samples. The proposed method was applied for the determination of 10 quinolones in river water, aquacultural water and a fish sample, and enrofloxacin and ciprofloxacin were found in the fish sample.