Multifunctionalized Covalent Organic Frameworks for Broad-Spectrum Extraction and Ultrasensitive Analysis of Per- and Polyfluoroalkyl Substances.

The contamination of surface and ground water by per- and polyfluoroalkyl substances (PFASs) has become a growing concern, and the structural diversity of PFASs is the major challenge for their ubiquitous applications. Strategies for monitoring coexistent anionic, cationic, and zwitterionic PFASs even at trace levels in aquatic environments are urgently demanded for effective pollution control. Herein, novel amide group and perfluoroalkyl chain-functionalized covalent organic frameworks (COFs) named COF-NH-CO-F9 are successfully synthesized and used for highly efficient extraction of broad-spectrum PFASs, attributing to their unique structure and the multifunctional groups. Under the optimal conditions, a simple and high-sensitivity method is established to quantify 14 PFASs including anionic, cationic, and zwitterionic species by coupling solid-phase microextraction (SPME) with ultrahigh-performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS) for the first time. The established method displays high enrichment factors (EFs) of 66-160, ultrahigh sensitivity with low limits of detection (LODs) of 0.0035-0.18 ng L-1, a wide linearity of 0.1-2000 ng L-1 with correlation coefficient (R2) ≥0.9925, and satisfactory precision with relative standard deviations (RSDs) ≤11.2%. The excellent performance is validated in real water samples with recoveries of 77.1-108% and RSDs ≤11.4%. This work highlights the potential of rational design of COFs with the desired structure and functionality for the broad-spectrum enrichment and ultrasensitive determination of PFASs in real applications.

A Novel Strategy to Directly Quantify Polyethylene Microplastics in PM2.5 Based on Pyrolysis-Gas Chromatography-Tandem Mass Spectrometry.

The broad application of plastic products has resulted in a considerable release of microplastics (MPs) into the ecosystem. While MPs in other environmental matrices (e.g., soil and water) have been studied for a long time, the atmospheric fine particulate matter (PM2.5)-bound MPs are rarely investigated due to the lack of an appropriate analytical approach. The prevalently used visual and spectroscopic means (e.g., optical microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy) suffer from obvious drawbacks that cannot precisely detect MPs of tiny sizes and provide quantitative information. In the present study, a novel strategy that does not require sample pretreatment was developed to first effectuate accurate quantification of polyethylene MP (PE-MP) in PM2.5 based on pyrolysis-gas chromatography-tandem mass spectrometry (Pyr-GC-MS/MS). It featured acceptable recoveries (97%-110%), high sensitivity (LOD = 1 pg), and qualified precisions (RSD of 3%-13%). Employing this approach, for the first time, exact atmospheric concentrations of PE-MPs in PM2.5 from megacities in North (Zhengzhou and Taiyuan) and South (Guangzhou) China were obtained, and relatively serious pollution was found in Taiyuan. The 100% sample detection rates also suggested the widespread occurrence and possible human exposure risks of PM2.5-bound PE-MPs. In brief, the new strategy could conduct direct, sensitive, and accurate quantification of PE-MP in PM2.5, favoring further studies of environmental fates, distributions, and toxicities of atmospheric MPs.

A flexible electrochemical glucose sensing platform based on an electrospun PVA mat covered with in situ grown silver nanoparticles and a mixed self-assembled monolayer of glucose oxidase and ferrocene.

An electrochemical glucose sensor based on flexible materials is significant for wearable devices used for real-time health monitoring and diagnosis. However, applying flexible electrodes involves complex fabrication processes and might reduce detection sensitivity. To overcome these obstacles, we herein report a novel strategy for preparing a highly flexible enzyme electrode based on an electrospun poly(vinyl alcohol) (PVA) mat decorated with in situ grown silver nanoparticles (nano-Ag) for electrochemical glucose sensing. Ferrocene (Fc) was selected as an electron acceptor for glucose oxidase (GOD) in order to minimize the influence of oxygen. Electron transfer between GOD and Fc was facilitated by confining them within a mixed self-assembled monolayer (SAM) formed on a thin layer of gold deposited on top of the PVA/nano-Ag film. Nano-Ag was found to significantly increase the surface area of the electrode and improve the stability of electrode conductivity during tensile deformation. Electrochemical glucose detection was performed by chronoamperometry in the electroactivity domain of ferrocene, and good linearity (R2 = 0.993) was obtained in the range of 0.2-7 mM with a detection limit of 0.038 mM and a relative standard deviation (RSD) of 1.45% (n = 6). After being stuck to a bendable PDMS slice and bent, respectively, at 30° and 60° 50 times, the electrode showed slight changes in detection results (<4.78%), which remained within 8% when the bending angle increased to 90°. With its high flexibility, good detection performance, and convenient fabrication process, the proposed enzyme electrode showed good potential as a flexible platform for wearable glucose sensing systems.

Contamination profiles and potential health risks of environmentally persistent free radicals in PM2.5 over typical central Chinese megacity.

As one of the most important transportation hubs and industrial bases in China, Zhengzhou has suffered from serious PM2.5 pollution for a long time. However, the investigation of contamination status and possible exposure risks of environmentally persistent free radicals (EPFRs) in PM2.5 from Zhengzhou is rare. In this work, a comprehensive study of pollution levels, seasonal variations, sources, and potential health risks of PM2.5-bound EPFRs in Zhengzhou was conducted for the first time. The atmospheric concentrations of EPFRs in PM2.5 from Zhengzhou ranged from 1.732 × 1012 spin m-3 to 7.182 × 1014 spin m-3 between 2019 and 2020. Relatively serious contamination was noticed in winter and spring. Primary fossil fuel combustion and Fe-mediated secondary formation were apportioned as possible sources of PM2.5-bound EPFRs in Zhengzhou. Moreover, to avert the bias of the toxicity assessment induced by utilization of incompletely extracted EPFRs from sample filter, simulatively generated EPFRs were applied to toxicological evaluations (cell viability and reactive oxygen species assays). Corresponding experimental dosages were based on the estimated adults' annual exposure amounts of EPFRs in real PM2.5 samples. The results elucidated that EPFRs might cause growth inhibition and oxidative stress of human lung cells, suggesting the possible exposure-induced health concerns for local people in Zhengzhou. This study provides practical information of real contamination status of PM2.5-bound EPFRs in Zhengzhou, which is favorable to local air pollution control and reduction of exposure risks on public health in central China.

Silica microparticles modified with ionic liquid bonded chitosan as hydrophilic moieties for preparation of high-performance liquid chromatographic stationary phases.

Two novel stationary phases, 1-(4-bromobutyl)-3-methylimidazolium bromide bonded chitosan modified silica and 1-(4-bromobutyl)-3-methylimidazolium bromide bonded chitosan derivatized calix[4]arene modified silica stationary phase, were synthesized using 1-(4-bromobutyl)-3-methylimidazolium bromide bonding chitosan as a polarity regulator solving the limitation of the strong hydrophobicity of calixarene in the application of hydrophilic field. The resulting materials were characterized by solid-state nuclear magnetic resonance, Fourier-transform infrared spectra, scanning electron microscopy, elemental analysis, and thermogravimetric analysis. Based on the hydrophilicity endowed by 1-(4-bromobutyl)-3-methylimidazolium bromide bonded chitosan, the retention mode of ILC-Sil and ILCC4-Sil could be effectively switched from the hydrophilic mode to a hydrophilic/hydrophobic mixed mode and could simultaneously provide various interactions with solutes, including hydrophilic, π-π, ion-exchange, inclusion, hydrophobic, and electrostatic interactions. On the basis of these interactions, successful separation and higher shape selectivity were achieved among compounds that vary in polarity under both reverse-phase and hydrophilic interactive liquid chromatography conditions. Moreover, the ILCC4-Sil was successfully applied to the determination of morphine in actual samples using solid-phase extraction and mass spectrometry. The LOD and LOQ were 15 pg/mL and 54 pg/mL, respectively. This work presents an exceptionally flexible adjustment strategy for the retention and selectivity of a silica stationary phase by tuning the modification group.

Sulfonic acid functionalized monolithic column for high selectivity capillary electrochromatography separation.

A new nano-scale spherical vinyl-functionalized covalent organic polymer (TAPT-DVA-COP) with uniform sizes around 300 nm was initially constructed using 2,5-divinyl-1,4-benzaldehyde (DVA) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) as monomers. Then, a sulfonic acid (-SO3H) modified COP termed COP-SO3H was developed based on post-sythesis method employing TAPT-DVA-COP as precursor. Capillary electrochromatography (CEC) monolithic columns were fabricated using the physical doping technique to exhibit the application potential of TAPT-DVA-COP and COP-SO3H. Compared to the TAPT-DVA-COP monolithic column, the COP-SO3H monolithic column achieved a highly selective separation between analytes with different properties, including monosubstituted benzenes, alkylbenzenes, hydroxybenzoates, nucleoside bases, and biogenic amines. Non-covalent interaction (NCI) analysis and experimental data show that the synergism of the sulfonic acid group and aromatic moieties on COP-SO3H endows the new stationary phase with diverse interactions, including ion exchange, hydrophobic, π-π and hydrogen bonding. In addition, the COP-SO3H monolithic column exhibited good reproducibility and excellent potential for the determination of hydroxybenzoates in compact powders and alkylbenzenes in effluent samples.

Developing a Noncontact Heating Matrix Spraying Apparatus with Controllable Matrix Film Formation for MALDI Mass Spectrometry Imaging.

Matrix deposition plays an important role in obtaining high-quality and reliable molecular spatial location information for matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). To control the matrix film formation, an automatic matrix spraying apparatus was developed with the introduction of a noncontact heating lamp. Compared with the unheated condition, the noncontact heating lamp suppressed the coffee-ring effect and the diffusion phenomenon of the analyte effectively by controllable matrix film formation. Meanwhile, the signal intensity was increased by 2-5 fold. To prove the ability of the matrix deposition apparatus, the apparatus combined with metabolomics analysis was used to show the spatial distribution of the substance in sprouted potato tubers. The potential biomarkers at m/z 868.5049 and m/z 852.5101 were identified as α-solanine and α-chaconine, and the synthesis pathways were further searched. To further demonstrate the quality of MALDI images including localization and spatial resolution, lipid distribution in rat brain tissue was investigated by the developed noncontact heating matrix spraying apparatus. An excellent match with distinguishable compartments of lipids in the rat brain was obtained between the H&E-stained sections and MALDI-MSI images. These results indicate that the developed noncontact heating matrix spraying apparatus is reliable and provides a low-cost, high-quality, rapid approach for MALDI-MSI.

p-Phenylenediamine Antioxidants in PM2.5: The Underestimated Urban Air Pollutants.

The wide use and continuous abrasion of rubber-related products appears to be leading to an incredible release of p-phenylenediamine (PPD) antioxidants in the environment. However, no related research has been conducted on the pollution characteristics and potential health risks of PM2.5-bound PPDs. We report for the first time the ubiquitous distributions of six emerging PPDs and a quinone derivative, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPDQ), in PM2.5 from urban areas of China. Atmospheric contamination levels of PM2.5-bound PPDs were found to be mostly in pg m-3 amounts between 2018 and 2019. Urban vehicle rubber tire abrasion was found to probably contribute to the PPDs in PM2.5 and accounted for their significant spatiotemporal-dependent concentration variations. Furthermore, 6PPDQ, an emerging oxidation product of 6PPD in the environment, was first quantified (pg m-3) with a total detection rate of 81% in the urban PM2.5, demonstrating its broad existence. On the basis of the determined ambient concentrations, the annual intakes of PPDs and 6PPDQ for adults were not low, indicating their possible human health risks induced by long-term exposure. This study confirms the widespread occurrence of PPDs and 6PPDQ in PM2.5, showing that the pollution of such compounds in urban air should not be underestimated.

Magnetic porous aromatic framework with a core-shell structure as a sorbent for rapid extraction of phenols and their quantitation in urine by HPLC-UV.

A porous aromatic framework (PAF) is shown to be a viable sorbent for the adsorption of phenols. To overcome the difficulty of quick adsorption and enrichment by phenols from the matrix, a sorbent material consisting of porous aromatic framework magnetic nanoparticles (PAF MNPs) with a core-shell structure was fabricated by an in situ growth method. The PAF MNP sorbent was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy and other techniques. The factors affecting enrichment performance including the amount of PAF-6 MNPs, sample pH, extraction time and elution conditions were optimized. Under the optimal conditions, a method utilizing high-performance liquid chromatography with an ultraviolet detector (HPLC-UV) was developed to quantify phenols in urine. The method showed good linearity (r ≥ 0.998), good precision (RSD ≤ 9.9%, n = 6) and a low limit of detection (1.0-2.0 ng/mL, S/N = 3), with recoveries performed in urine matrix ranging from 76.7% to 113.2%. The method is simple, time-saving and sensitive. Moreover, compared with traditional mass spectrometry detection methods, this method has advantages in terms of low cost and repeatability. Graphical abstract.

Facile preparation of a cationic COF functionalized magnetic nanoparticle and its use for the determination of nine hydroxylated polycyclic aromatic hydrocarbons in smokers' urine.

A novel dual-shell magnetic nanoparticle coated with a cationic covalent organic framework, containing ethidium bromide, is easily prepared, characterized and applied as an adsorbent for fast, simple and highly selective capture of nine hydroxylated polycyclic aromatic hydrocarbons in urine samples of non-smokers and smokers who smoked cigarettes with different tar yields. This is the first time that a cationic crystalline framework with high thermal and chemical stability was used for magnetic solid phase extraction. Multiple probes and quantum chemistry theory calculations were conducted to describe the versatile adsorption property directly and quantifiably. A method using high-performance liquid chromatography with a fluorescence detector based on the prepared magnetic adsorbent was established and used to investigate differences in the exposure levels of OH-PAHs in non-smokers and smokers smoking cigarettes with different tar yields. All the OH-PAH analyses present good linearities in the range of 0.1-100 ng mL-1, with R2 > 0.9965. The LOD for the 9 OH-PAHs ranged from 0.0030 to 0.0096 ng mL-1 and the LOQ ranged from 0.096 to 0.030 ng mL-1. The recoveries of the 9 OH-PAHs ranged from 93.3 to 121.3% with the RSD ranging from 0.47 to 3.53%. These results imply that the versatile EB-DS MNPs as adsorbents have great potential in the analysis of trace targets in samples with complex matrices.

Tetra-proline-modified calix[4]arene-bonded silica stationary phase for simultaneous reversed-phase/hydrophilic interaction mixed-mode chromatography.

A new water-soluble tetra-proline-modified calix[4]arene-bonded silica stationary phase was prepared straightforwardly by an indirect method and characterized by elemental analysis, energy dispersive Spectrometry, solid-state 13 C NMR spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Due to the simultaneous introduction of polar tetra-proline and nonpolar calix[4]arene, the developed column possessing a double retention mode of reverse-phase liquid chromatography and hydrophilic interaction liquid chromatography. A series of hydrophobic and hydrophilic test samples, including nucleosides and nucleotides, amines, monosubstituted benzenes, chiral compounds, and phenols, were used to evaluate the developed stationary phase. A rapid separation capability, high separation efficiency, and selectivity were achieved based on the multiple interactions between solutes and tetra-proline-modified calix[4]arene-bonded silica stationary phase. Moreover, the developed stationary phase was further used to detect and separate hexamethylenetetramine in rice flour. All the results indicated the potential merits of the developed stationary phase for simultaneous separation of complex hydrophobic and hydrophilic samples with high selectivity.

Determination of oxalate and citrate in urine by capillary electrophoresis using solid-phase extraction and capacitively coupled contactless conductivity based on an improved mini-cell.

A new method for the rapid determination of the metabolites oxalate and citrate in urine samples was based on capillary electrophoresis and capacitively coupled contactless conductivity detection coupled with solid-phase extraction. The detection cell for capacitively coupled contactless conductivity detection was improved with a smaller inner volume (1.5 nL), reduced noise (0.2∼0.5 mV) and better reproducibility and durability. Under optimal conditions, oxalate and citrate can achieve baseline separation within 4 min and the detection limits (S/N = 3) for oxalate and citrate are about 44 and 244 ng/mL, respectively. The overall recovery is between 80.0 and 89.2%. This method offers a better choice for quantitative analysis of strong anions such as oxalate and citrate in diagnostic testing associated with human diseases.

Tetraazacalix[2]arence[2]triazine Coated Fe3O4/SiO2 Magnetic Nanoparticles for Simultaneous Dispersive Solid Phase Extraction and Determination of Trace Multitarget Analytes.

To satisfy the requirement of simultaneous extraction and characterization of diverse kinds of multitarget analytes, the preparation, characterization, and application of a novel tetraazacalix[2]arene[2]triazine (TCT) coated magnetic nanoparticle (TCT MNP) adsorbent are presented in this paper. TCT assembles two benzene rings and two triazines with nitrogen cross-bridging links, which exhibits a unique structural framework and versatile recognition features based on the multiple recognition sites. These include π electron stacking, charge transfer, hydrogen bonding, and ion-exchange. TCT MNPs acted as a dispersive SPE adsorbent showing strong interaction with and adsorption of polycyclic aromatic hydrocarbons (PAHs), nitroaromatics, and heavy metal ions. The dispersive magnetic nanoparticle solid phase extraction (d-MNSPE) strategy with the simultaneous extraction and stepwise elution (SESE) procedure was designed and optimized for the five PAHs (phenanthrene, anthracene, pyrene, chrysene, and benzo(a)pyrene), six nitroaromatics (4-nitrotoluene, 2,4-dinitrotoluene, 2,4,6-trinitrotoluene, 4-nitrophenol, 2,4-dinitrophenol, and 2,4,6-trinitrophenol), and four metal ions (Cu, Zn, Mn, Cd) in aqueous samples. Due to the high stability, desirable durability, larger saturation magnetization, reuse and distinct enrichment capacity of TCT MNPs, the d-MNSPE method with the SESE strategy provided high recovery (>90%) and good precision (relative standard deviations, RSD < 10%). Coupled with the commonly used HPLC-fluorescence detection, HPLC-UV detection, and atomic absorption spectrometry, these trace probes in tap water, river water, and lake water were determined with very low detection limits, in the range of 0.09-0.15 pg mL-1 for PAHs, 6-11 pg mL-1 for nitroaromatics, and 17-53 pg mL-1 for metal ions after being enriched by the d-MNSPE. The determination of trace PAHs in urine samples from smokers and nonsmokers was successfully carried out with this method, which implied that the versatile TCT MNPs and the robust method together represent a significant potential application in the analysis of body fluids and disease markers. Such methods for accurate quantification of trace components in water are very valuable as they fulfill an unmet need in environmental and medicinal chemistry.

Determination of trace morphine and its metabolites in mouse urine using a TpBD functionalized bivalve magnetic nano-adsorbent.

In this study, a new type of covalent organic framework (TpBD) functionalized bivalved magnetic microsphere (TpBD-DS MNS) adsorbent was applied for the enrichment and detection of trace morphine and its metabolites in mouse urine. The main factors affecting the efficiency of magnetic solid phase extraction were optimized, and the optimal MSPE conditions were obtained. Combined with the UPLC-MS/MS technique, a new method for determining trace morphine and its metabolites in urine was established. The detection (LOD) and quantification (LOQ) limits for morphine and its metabolites ranged from 0.16 pg mL-1 to 0.53 pg mL-1 and 0.26 pg mL-1 to 1.25 pg mL-1, respectively. The recovery of the methods ranged from 87.4-97.3%, and the RSD was less than 5%. By employing this methodology, we successfully obtained the temporal change curve of morphine and its metabolites in mouse urine through collection and measurement post intravenous administration of morphine. This approach not only presents a novel means for investigating pharmacokinetics and drug monitoring but also demonstrates significant potential in the fields of forensic toxicology and drug abuse surveillance.

[Synthesis of fluorinated nitrogen-rich porous organic polymers and removal of perfluorooctanoic acid from water].

Perfluorooctanoic acid (PFOA) is a persistent contaminant with detrimental effects on the natural environment. This persistence leads to potential enrichment and osmotic transfer, which can affect normal circulation in the environment. PFOA poses significant threats to both the natural environment and human health. Therefore, the development of cost-effective, highly efficient, and environment-friendly PFOA adsorbents is a crucial endeavor. This paper presents the catalyst-free one-pot synthesis of fluorinated nitrogen-rich porous organic polymers (POP-3F) via a Schiff-base condensation reaction. The reaction between the nitrogen-rich compound 1,4-bis(2,4-diamino-1,3,5-triazine)benzene and p-trifluoromethylbenzaldehyde yielded POP-3F. The introduction of fluorine atoms into the nitrogen-rich porous organic polymer enhanced its hydrophobicity, thereby facilitating favorable fluoro-fluorine interactions with PFOA and, thus, improving the efficacy of the adsorbent. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), solid-state nuclear magnetic resonance (ssNMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption analysis, and thermogravimetric analysis (TGA) were used to confirm the successful synthesis and characterization of POP-3F. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted in negative electrospray ionization (ESI) mode coupled with multi-reaction monitoring mode (MRM). The instrument was equipped with an Atlantis T3 column (100 mm×2.1 mm, 3 µm), and analysis was conducted using an external standard method. The influences of various factors on PFOA adsorption by POP-3F, including pH, salt concentration, and humic acid presence, were investigated. The highest PFOA removal rate (98.6%) was achieved at a pH of 2, indicating the applicability of POP-3F for the effective removal of PFOA from acidic industrial wastewater. The removal rate of PFOA was unaffected by increases in NaCl concentration. This phenomenon can be attributed to electrostatic interactions between the protonated secondary amines in POP-3F and deprotonated PFOA. Upon the addition of NaCl, a double electric layer is formed on the POP-3F surface, with Cl- ions in the outer layer and Na+ ions in the inner layer, which weakened these interactions. Humic acid is competitively adsorbed with PFOA. However, POP-3F demonstrated good removal rates even in the presence of high humic acid concentrations in water. Adsorption isotherm and kinetics experiments were conducted at the optimal pH to explore the relevant adsorption mechanism. The results showed a rapid initial adsorption rate, with 95.4% PFOA removal within 5 min. Optimal adsorption equilibrium was achieved within 6 h, and the removal rate decreased by only 0.3% after 24 h. This finding indicates that POP-3F exhibits sustained efficacy for PFOA removal. Langmuir fitting analysis revealed a theoretical maximum adsorption capacity of 191 mg/g for POP-3F; this value surpasses those of activated carbon materials and most other adsorbents, highlighting the superior PFOA-adsorption performance of POP-3F. Additionally, matrix effects minimally affected the removal of PFOA by POP-3F, with only a slight reduction (0.1%) observed in simulated natural water. The recyclability of POP-3F was assessed over five adsorption-desorption cycles. The removal efficenecy exhibited a minor decrease of only 0.67% after five cycles. These results demonstrate the recyclability of the proposed adsorbent, which translates into cost reduction through reusability. This characteristic renders POP-3F a promising candidate for the economical and efficient removal of PFOA from wastewater in practical applications.

Industrializable and pH-tolerant electropositive imidazolium chloride polymer for high-efficiency removal of perfluoroalkyl carboxylic acids from aqueous solution.

In recent years, various materials have been used to adsorb and remove perfluoroalkyl compounds from water. However, most of these materials have limited applications due to their high cost, complex synthesis, inadequate selectivity and sensitivity, and, even worse, the possibility of introducing secondary pollution. Here, under mild conditions, we prepared an inexpensive imidazolium chloride and nitrogen-rich polymer (TAGX-Cl) with a high cationic loading rate and a high yield (>82%). The adsorbent exhibits excellent pH tolerance (pH=1-9) and achieves nearly 99.9% removal of nine perfluoroalkyl carboxylic acids (PFCAs) within 120 min. Experimental data and theoretical simulations confirmed that synergistic electrostatic interactions, hydrogen bonds, and P-π interactions control the adsorptive ability of TAGX-Cl. This work provides a practical strategy for PFCAs removal.

Ubiquitous occurrence of p-Phenylenediamine (PPD) antioxidants and PPD-quinones in fresh atmospheric snow and their amplification effects on associated aqueous contamination.

p-Phenylenediamine (PPD) antioxidants are heavily used for protection of commercial rubber products (e.g., vehicle tire), resulting in their widespread contamination in ecosystem. PPD-quinones (PPDQs), the toxic quinone derivatives of PPDs, are also discovered as novel environmental pollutants. However, the contamination characteristics of PPDs/PPDQs in fresh atmospheric snow (without deposition on the Earth surface) have seldom been studied. This work first reports the broad distributions of PPDs and PPDQs in fresh atmospheric snow collected from seven Chinese urban areas. Individual median values of detected concentrations were in the ranges of 0.4 to 260 pg g-1 (PPDs) and 0.7 to 104 pg g-1 (PPDQs). The concentration deviation by long-term deposition on the ground was eliminated. In most sampling regions, wearing of vehicle rubber tires was possibly responsible for spatial-dependent PPDs' pollution level variations, and high concentrations of PPDs promoted PPDQs' formation in snow from atmosphere. Yet, excessive O3 may further oxidize and reduce PPDQs in atmospheric fresh snow from Zhengzhou, which is different from previous research. Furthermore, snowfall was noticed might amplify concentrations of three PPDs and PPDQs in an inland lake, which possibly worsen corresponding pollution in water system. Current study elucidates the potential impacts of snow-bound PPDs/PPDQs on ecosystems should not be underestimated.

Photocatalytic degradation of perfluorooctanoic acid (PFOA) from water: A mini review.

Perfluorooctanoic acid (PFOA) has drawn increasing attention as a highly persistent organic pollutant. The inherent stability, rigidity and potential toxicities characteristics make it a challenge to develop efficient technologies to eliminate it from water. Photocatalytic technology, as one advanced method, has been widely used in the degradation of PFOA in water. In this review, recent progress in the design of photocatalysts including doping, defects engineering, heterojunction and surface modification to boost the photocatalytic performance toward PFOA is summarized. The relevant degradation mechanisms were also discussed in detail. Finally, future prospect and challenges are proposed. This review may provide new guidelines for researchers to design much more efficient photocatalysts applied in the elimination of PFOA.

Recent advances in analysis of capsaicin and its effects on metabolic pathways by mass spectrometry.

Capsaicin is the main food active component in Capsicum that has gained considerable attention due to its broad biological activities, including antioxidation, anti-inflammation, anti-tumor, weight regulation, cardiac protection, anti-calculi, and diurnal-circadian regulation. The potent biological effects of capsaicin are intimately related to metabolic pathways such as lipid metabolism, energy metabolism, and antioxidant stress. Mass spectrometry (MS) has emerged as an effective tool for deciphering the mechanisms underlying capsaicin metabolism and its biological impacts. However, it remains challenging to accurately identify and quantify capsaicin and its self-metabolites in complex food and biological samples, and to integrate multi-omics data generated from MS. In this work, we summarized recent advances in the detection of capsaicin and its self-metabolites using MS and discussed the relevant MS-based studies of metabolic pathways. Furthermore, we discussed current issues and future directions in this field. In-depth studies of capsaicin metabolism and its physiological functions based on MS is anticipated to yield new insights and methods for preventing and treating a wide range of diseases.

An ultrastable 2D covalent organic framework coating for headspace solid-phase microextraction of organochlorine pesticides in environmental water.

Herein, a quinoline-linked ultrastable 2D covalent organic framework (COF-CN) coated fiber was successfully prepared and used for highly-sensitive headspace solid-phase microextraction (HS-SPME) of organochlorine pesticides (OCPs) in environmental water. The extraction efficiency of the COF-CN coating for all 14 OCPs was higher than that of four commercial SPME fiber coatings and most of the published works, with enrichment factors ranging from 540 to 5065. In combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), a wide linear range (0.05-200 ng/L), low detection limits (LODs, 0.0010-13.54 ng/L) and satisfactory reproducibility and repeatability were obtained under optimal conditions. Compared with the published works, the LODs of the developed technique were improved 2-5.9 times, and the enrichment factors (EFs) of the developed method were enhanced at least 2 times. The COF-CN coated fiber can be easily recycled and reused at least 70 times without any washing step. The adsorption mechanism was first characterized by density functional theory calculations and X-ray photoelectron spectroscopy analysis. Besides, the established method was successfully applied to the analysis of the distribution of trace OCPs in real water samples from Henan Province. All these results proved the promising application of the developed HS-SPME-GC-MS/MS method for organic pollutants analysis in water samples.