Fluorinated-Squaramide Covalent Organic Frameworks for High-Performance and Interference-Free Extraction of Synthetic Cannabinoids.

Synthetic cannabinoids (SCs), one of the largest groups of new psychoactive substances (NPSs), have emerged as a significant public health threat in different regions worldwide. Analyzing SCs in water samples is critical to estimate their consumption and control. However, due to their low background concentration and the coexistence of complex matrix, the selective and effective enrichment of SCs is still challenging. In this study, a series of fluorinated-squaramide-based covalent organic frameworks (COF: FSQ-2, FSQ-3, and FSQ-4) are synthesized, and the as-prepared FSQ-4 exhibits strong affinity to different SCs. The proper pore size (1.4 nm) and pre-located functional groups (hydrogen-bond donors, hydrogen-bond acceptors, and fluorophilic segments) work synergistically for efficient SCs capture. Remarkably, when coupled FSQ-4 with solid-phase microextraction (SPME), trace-level (part per trillion, 10-9 ) determination of 13 SCs can be easily achieved, representing one of the best results among NPS analyses, and the excellent extraction performance can be maintained under various interfering conditions.

Simultaneous separation and determination of several chiral antidepressants and their enantiomers in wastewater by online heart-cutting two-dimensional liquid chromatography.

A novel method for simultaneous separation and detection of the racemates and the enantiomers of common chiral antidepressants in wastewater matrix was developed by online heart-cutting two-dimensional liquid chromatography (2D-LC) coupled to solid-phase extraction (SPE). Screening of chiral stationary phases (CSPs) and chromatographic conditions was investigated for complete enantioseparation to be compatible with RP-HPLC in 1st D-LC. Using methanol-0.1 % (v/v) ammonia solution as mobile phase, a 2D-LC system was configured by reversed mode with a combination of C18 column and the serially CPS columns as 2D-LC stationary phases respectively. The target analytes could achieve satisfactory transformation between 2D-LCs with transfer rate of 90.57-98.58 %. By means of freeze-drying and SPE, three antidepressants in wastewater were greatly preconcentrated under the optimized conditions, improving the method performance. The racemates and the enantiomers of mirtazapine, bupropion and fluoxetine exhibited good linearity in the range of 0.10-30.00 ng/mL (R2≥0.9986), and LODs and LOQs ranged in 0.0183-0.0549 ng/mL and 0.0661-0.1831 ng/mL, respectively. By this way, the method was successfully applied to simultaneous determination of the racemates and the enantiomers of mirtazapine, bupropion and fluoxetine in wastewater samples. Among them, three samples contained bupropion at level of 0.401-0.822 ng/mL, and mirtazapine at level of 0.328 and fluoxetine at level of 0.381 ng/mL were detected respectively in the other two samples. The enantiomers were at level of 0.140-0.189 ng/mL for mirtazapine, 0.182-0.419 ng/mL for bupropion and 0.179-0.204 ng/mL for fluoxetine, respectively. The proposed method providing an efficient approach to monitoring chiral drugs and their enantiomers in wastewater, facilitating to pollution assessment of chiral drugs in the environment and regional survey of illicit abuse in drug control.

Sheathed in-situ room-temperature growth covalent organic framework solid-phase microextraction fiber for detecting ultratrace polybrominated diphenyl ethers from environmental samples.

The extraction performance of solid-phase microextraction (SPME) fiber is significantly influenced by coating materials and fabricating process. It is urgently needed for fabricating robust SPME fiber with facile preparation methods. Herein, a novel polyimide (PI) @ covalent organic framework (COF) synthesized by 1,3,5-Tris (4-aminophenyl) benzene (TPB) and 2,5-dimethoxyterephthalaldehyde (DMTP) fiber, named PI@TPB-DMTP fiber, was successfully fabricated with facile method at room temperature. Firstly, a COF crystals TPB-DMTP was in situ grown on stainless steel fiber, where the COF crystals was synthesized by the Schiff-base reaction between TPB and DMTP. Subsequently, the COF coating was covered with an ultrathin layer of PI through a simple dip-coating method to improve the fiber stability. By coupled PI@TPB-DMTP SPME fiber with gas chromatography-negative chemical ion-mass spectrometry (GC-NCI-MS), a sensitive analytical method was established for the determination of ultratrace polybrominated diphenyl ethers (PBDEs) in water sample. To achieve the best efficiency and sensitivity for the analysis of PBDEs, six potential influencing factors in extraction step and desorption step were optimized. Under optimized conditions, the established method showed high enhancement factors of 1470-3555, wide linear range of 0.05-100 ng L-1, low detection limits of 0.0083-0.0190 ng L-1, good repeatability for intra-day in the range of 3.71%-7.62% and inter-day in the range of 5.12%-8.81%, good reproducibility in the range of 6.83%-9.21%. The satisfactory recovery was ranged from 79.2% to 117.3% in determining real water samples. The excellent experimental performance was mainly attributed to the large specific surface area of TPB-DMTP, as well as the high permeability of porous PI film. The results demonstrated that the COF-based fiber showed great potential for analysis of PBDEs in complex environmental samples.

Sample bottle coated with sorbent as a novel solid-phase extraction device for rapid on-site detection of BTEX in water.

Solid-phase extraction (SPE) is a popular technique for environmental sample pretreatment. However, SPE usually requires complex sample pretreatment processes, which is time-consuming and inconvenient for real-time and on-site monitoring. Herein, a solvent-free, rapid, and user-friendly SPE device was developed by coating the polydimethylsiloxane (PDMS)/divinylbenzene (DVB) sorbent on the inner wall of a sample bottle. The extraction process and desorption process were both carried out in the bottle. The analytes trapped in the sorbent were thermally desorbed and simultaneously sucked out from the bottle by an air sampling tube equipped on field-portable GC-MS. Different to previous work, the sample pretreatment process didn't require any complicated and time-consuming steps, such as centrifugation or filtration. The total analysis time for each sample was less than 25 min, which was feasible for rapid on-site detection, and thus avoided the losses and contamination of samples in conventional sample storage and transportation processes. Under optimal conditions, the proposed SPE method exhibited wide linear ranges, low detection limits (0.010-0.036 µg L-1, which were much lower than the maximum levels restricted by the US Environmental Protection Agency and the Chinese GB3838-2002 standard), good intra-bottle repeatability (6.13-7.17%, n = 3) and satisfactory inter-bottle reproducibility (4.73-6.47%, n = 3). Finally, the method was successfully applied to the rapid detection of BTEX in the field. The recoveries of BTEX in spiked water samples ranged from 89.1% to 116.2%. This work presents a novel SPE approach for rapid on-site monitoring in water samples.

The effect of different binders on the comprehensive performance of solid phase microextraction fiber.

Binders are significant components for the preparation of solid-phase microextraction (SPME) fibers. However, little attention has been paid to the effect of different binders. Considering their diverse properties, in this work, we select three kinds of commonly used binders including polydimethylsiloxane (PDMS), polyacrylonitrile (PAN) and Nafion, as well as introduce a new binder of poly (vinylidene fluoride) (PVDF) to synthetically study the influence of binders. By using the commercial active carbons (ACs) with different binders, four SPME fibers with uniform morphologies and comparative thicknesses (i.e., ACs-PDMS-coated, ACs-PAN-coated, ACs-Nafion-coated and ACs-PVDF-coated fibers) have been prepared successfully. The effect of binders on the pore structure of ACs is firstly investigated. It is found that PDMS and PAN would cause pore blocking, and the specific surface area of ACs coatings decreases from 1362 m2 g-1 to 280 and 196 m2 g-1, respectively. While the specific surface area of ACs-PVDF composite remains 940 m2 g-1. Based on SPME, the influences of acid/alkali, high temperature and matrix towards different fibers are further systematically surveyed. Finally, the enrichment performance of prepared fibers towards various organic pollutants is preliminarily discussed. The comparison results show that PVDF demonstrates outstanding stability in all aspects. Therefore, PVDF might be an excellent candidate for the preparation of SPME fiber. Moreover, all obtained results are expected to provide the reference value for the further development of novel SPME fibers.

A polymeric solid-phase microextraction fiber for the detection of pharmaceuticals in water samples.

A novel disposable styrene based solid-phase microextraction (SPME) fiber was synthesized for the detection of lipid-lowering and antihypertensive drugs in real aquatic environment. Styrene and poly(ethylene glycol) diacrylate were co-polymerized on quartz fibers by thermal polymerization in capillary molds. The polymeric fiber possessed a homogeneous, dense as well as porous surface, showing excellent chemical and mechanical stability. The performance of the fiber was evaluated through the extraction of seven pharmaceuticals by coupling SPME with high performance liquid chromatography-tandem mass spectrometry under the optimized extraction conditions. The extraction efficiency of the fiber was up to 278 times of PDMS fiber and the enrichment factors ranged from 55 to 1183. The limits of detection were in the range from 1.7 ng L-1 to 11.7 ng L-1, with good reproducibility. Moreover, the fiber was used in the real water samples of the Pearl River Delta. The recoveries of the target analytes from river water and sea water samples at different spiked concentrations were in the range from 84.1% to 133.4% and from 81.5% to 105.5%, respectively.

Determination of the mass transfer coefficients in direct immersion solid-phase microextraction.

Diffusion of the analytes across the diffusion boundary layers and subsequently through the fiber coatings determines the extraction kinetics of solid-phase microextraction in aqueous matrices. Besides, the matrix effects can distort the behaviors of the analytes transferring across the diffusion boundary layers. However, these processes were always studied via certain simplification, which often left the mass transfer through the fiber coatings unconsidered and the matrix effects partially investigated. Herein, a comprehensive study on the mass transfer processes in direct immersion solid-phase microextraction was presented. Under different agitation speeds, it was determined that the mass transfer coefficients across the diffusion boundary layers were three to six orders larger than those through the fiber coatings. However, the mass transfer across the diffusion boundary layers was generally the major rate-limiting step. In addition, the shuttle effect and the barrier effect, which were responsible for accelerating and retarding the extraction kinetics, respectively, were found to be the dominant matrix effect alternately under different agitation speeds. This study comprehensively illustrated the major rate-limiting step and the dominant matrix effects through recording the mass transfer coefficients.

Dual-fiber solid-phase microextraction coupled with gas chromatography-mass spectrometry for the analysis of volatile compounds in traditional Chinese dry-cured ham.

For the purpose of obtaining a more comprehensive flavor profile, volatile compounds in traditional Chinese dry-cured hams were studied by dual-fiber solid-phase microextraction (SPME) using two fibers simultaneously. By using the selected pair of fibers and under the optimal extraction time, there were total seventy-two volatile compounds identified, which was higher than the mono-fiber SPME method using a single fiber. Out of the seventy-two compounds, twenty-six compounds were not detected by using mono-fiber SPME and five among them are classified as the major aromatic compounds in the literatures. Due to the higher coverage and less tendency for the occurrence of competition among the volatiles, the total amount of volatiles extracted by dual-fiber SPME (510.02 ng/kg) was higher than mono-fiber SPME. Three grades of dry-cured hams were successfully distinguished based on dual-fiber SPME. The volatile compounds belonged to nine chemical families and differed in different grades of dry-cured hams. These results show that dual-fiber SPME is capable of analyzing flavor profiles more comprehensively and distinguishing traditional Chinese dry-cured hams.

Peanut shell-derived biochar materials for effective solid-phase microextraction of polycyclic aromatic hydrocarbons in environmental waters.

In this contribution, low-cost and robust biochar material fabricated from waste peanut shells manifest highly-efficient adsorption capability and was prepared into a solid-phase microextraction fiber coating on the external surface of a stainless-steel wire. It was observed from scanning electron microscopy that, a homogeneity of cavities makes up the external surface of the coating, and Raman signals revealed that it contained graphite structures. Coupled with gas chromatography-mass spectrometry (GC-MS), headspace SPME (HS-SPME) based on the novel fiber was applied for the analysis of six polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. Under the selected optimum conditions in both extraction and desorption processes, satisfactory analytical performances were achieved, which included good intra-fiber repeatability (relative standard deviations, RSDs in the range from 6.93% to 10.86%, n = 6) and inter-fiber reproducibility (RSDs from 5.61% to 13.59%, n = 4), together with low limits of detection (LODs, 1.09-2.46 ng L-1) and limits of quantification (LOQs, 3.62-8.20 ng L-1), as well as a satisfactory linear range for the analysis of the target PAHs (10-2000 ng L-1). This established method also showed good reliability in the analysis of target PAHs in river water as well as pond water in the downtown area of Guangzhou, China, as the spiked recoveries were in the range from 81% to 116%.

Development of an on-site detection approach for rapid and highly sensitive determination of persistent organic pollutants in real aquatic environment.

Analysis of organic pollutants is usually accomplished in centralized laboratories. However, the time-delayed and time-consuming process is insufficient and risky for precisely detection due to the contamination of vials, the losses of analytes during transportation and storage. Herein, a rapid and highly sensitive on-site detection approach was developed without using any vials by coupling an on-site pre-equilibrium solid phase microextraction (SPME) sampling method with a portable gas chromatography mass spectrometer (portable GC-MS), for the determination of three families of persistent organic pollutants (polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons). Based on sampling-rate (SR) calibration method, the concentrations of target analytes in aquatic systems could be easily determined. Limits of detection (LODs) in the low parts-per-tillion levels (≤5.25 ng·L-1) were obtained for most of the investigated analytes with a total analysis time only ∼30 min. The proposed on-site detection approach was then successfully applied in the determination of persistent organic pollutants in real aquatic environment. A comparable result obtained by liquid extraction (LE) equipped with laboratorial GC-MS demonstrated the accuracy of the on-site detection method. In general, this study demonstrated a rapid and highly sensitive on-site approach, avoiding any risks of contamination during sampling and analysis, for determination of POPs as well as the potential applications for other organic pollutants in aquatic phase.

Enhancing enrichment ability of a nanoporous carbon based solid-phase microextraction device by a morphological modulation strategy.

Recent works of designing excellent adsorbents emphasized on the specific surface areas and porosities of the materials. This study presents the influence of morphological modulation on extraction efficiencies of materials for the first time. Sea urchin-like nanoporous carbon (NPC), derived from metal organic framework (MOF), was synthesized and fabricated as solid phase microextraction (SPME) device. The morphological modulated structure of the NPC, with enhanced effective adsorption sites produced by the pointed and sharp edges, could improve the extraction efficiencies of the NPC. Comparing with the unmodulated one, NPC with morphological modulation possessed higher extraction efficiencies (2 flod) as well as accelerated sampling rates (5 flod) on benzene series compounds (BTEX), improving the sensitivity of the sampling method (limits of detection ranged from 0.08 ng L-1 to 0.36 ng L-1). Moreover, it was also the first time that the moisture sensitive MOF-derived NPC was exploited as the SPME adsorbent. In general, this study was expected to be an important advance in broadening the approaches on designing a superior SPME adsorbents not only emphasizing on the specific surface area as well as porosity but also the morphology.

A tri-metal centered metal-organic framework for solid-phase microextraction of environmental contaminants with enhanced extraction efficiency.

This study presents the preparation and the characterizations of six tri-metal centered metal-organic frameworks (tM-MOFs) as solid-phase microextraction (SPME) adsorbents. Possessing different proportions of Al, Ga and In atoms in their frameworks, the tM-MOF-based SPME coatings exhibited different extraction performance towards the organic pollutants. Extraction results showed that the M4 (Al0.593Ga0.167In0.240(O2C2H4)(h2fipbb)) coating exhibited the best enrichment ability among six tM-MOFs. In addition, it showed better extraction efficiency towards the analytes than three single-metal centered MOFs coatings and a commercial polydimethylsiloxane (PDMS) coating. The adsorption process of the M4 coating was physical adsorption and it was mainly affected by the diffusion process of the compound from the sample to the material, which is the same with the adsorption processes of the single-metal centered MOFs coatings. Under optimal conditions (extraction time, 3 min; NaCl concentration, 25% (w/v); desorption temperature, 270 °C; extraction temperature, 30 °C), the M4 coating achieved low detection limits (0.13-0.88 ng L-1) and good linearity (5-2000 and 5-5000 ng L-1) for benzene series compounds. The repeatabilities (n = 5) for single fiber were between 4.3 and 8.1%, while the reproducibilities (n = 3) of fiber-to-fiber were in the range of 7.9-12.7%. Finally, a M4 coated SPME fiber was successfully applied to the analysis of environmental water samples with satisfactory recoveries (80.8%-119.5%).

Enhanced Photocatalytic Degradation of Environmental Pollutants under Visible Irradiation by a Composite Coating.

Although nanotechnology has offered effective and efficient solutions for environmental remediation, the full utilization of sustainable energy and the avoidance of secondary pollution are still challenges. Herein, we report a two-step modification strategy for TiO2 nanoparticles by first forming a thin, surface-adherent polydopamine (PDA) shell onto the nanoparticles and then assembling core-shell nanoparticles as a photodegradation coating. The composite coating modified from TiO2 could not only realize the highly efficient utilization of photons from the visible region but also avoid the secondary pollution of nanoparticles during application. Additionally, improvements in the adsorption ability after modification greatly facilitated the photocatalytic process of the modified materials. A preliminary in vivo study on Daphnia magna and a wastewater treatment experiment suggest that treatment with the composite coating can effectively eliminate fluorene and significantly reduce its lethality. We believe the two-step modification scheme can open new avenues for the facile modification of nanomaterials for designed purposes, especially in the field of environmental remediation.

Knitting aromatic polymers for efficient solid-phase microextraction of trace organic pollutants.

A series of knitting aromatic polymers (KAPs) were successfully synthesized using a simple one-step Friedel-Crafts alkylation of aromatic monomers and were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Then, as-synthesized KAPs with large surface areas, unique pore structures and high thermal stability were prepared as solid-phase microextraction (SPME) coatings that exhibited good extraction abilities for a series of benzene compounds (i.e., benzene, toluene, ethylbenzene and m-xylene, which are referred to as BTEX) and polycyclic aromatic hydrocarbons (PAHs). Under the optimized conditions, the methodologies established for the determination of BTEX and PAHs using the KAPs-triPB and KAPs-B coatings, respectively, possessed wide linear ranges, low limits of detection (LODs, 0.10-1.13ngL(-1) for BTEX and 0.05-0.49ngL(-1) for PAHs) and good reproducibility. Finally, the proposed methods were successfully applied to the determination of BTEX and PAHs in environmental water samples, and satisfactory recoveries (93.6-124.2% for BTEX and 77.2-113.3% for PAHs) were achieved. This study provides a benchmark for exploiting novel microporous organic polymers (MOPs) for SPME applications.