High efficient solid-phase microextraction based on a covalent organic framework for determination of trifluralin and chlorpyrifos in water and food samples by GC-CD-IMS

Rapidly enrichment and detection of per-and polyfluoroalkyl substances in foods using a novel bifunctional covalent organic framework

Per- and polyfluoroalkyl substances (PFASs) are extensively found in foods, posing potential toxicity to humans. Therefore, rapid analysis and monitoring of PFASs in foods are crucial for public health and also a challenge. To detect trace PFASs in foods, construction of sorbents with multiple interactions could be an effective approach. Herein, a cationic-fluorinated covalent organic framework (CF-COF) was prepared by post-modification and used as a magnetic solid-phase extraction adsorbent for adsorption of PFASs. By combining magnetic solid-phase extraction based on CF-COF with liquid chromatography-tandem mass spectrometry (LC - MS/MS), a novel method was developed for determination of eight long-chain PFASs in foods. Under optimized conditions, the method exhibited low detection limits (0.003-0.019 ng/g) and satisfactory recovery rates (73.5-118%) for PFASs. This study introduces a novel idea for the development of adsorbents targeting PFASs, along with a new analytical method for monitoring of PFASs in foods.

Supramolecular Materials as Solid-Phase Microextraction Coatings in Environmental Analysis

Solid-phase microextraction (SPME) has been widely proposed for the extraction, clean-up, and preconcentration of analytes of environmental concern. Enrichment capabilities, preconcentration efficiency, sample throughput, and selectivity in extracting target compounds greatly depend on the materials used as SPME coatings. Supramolecular materials have emerged as promising porous coatings to be used for the extraction of target compounds due to their unique selectivity, three-dimensional framework, flexible design, and possibility to promote the interaction between the analytes and the coating by means of multiple oriented functional groups. The present review will cover the state of the art of the last 5 years related to SPME coatings based on metal organic frameworks (MOFs), covalent organic frameworks (COFs), and supramolecular macrocycles used for environmental applications.

A simple AIE probe to pesticide trifluralin residues in aqueous phase: Ultra-fast response, high sensitivity, and quantitative detection utilizing a portable platform

The threat from pesticide trifluralin residues to ecological environment and public health is becoming a growing problem. Thus, rapid and sensitive detection, particularly a simple and portable detected platform for trifluralin residues, are highly desired. Here, a small organic aggregation-induced emission (AIE) molecule (TPETPy) is facilely synthesized and applied to detect trifluralin both in lab and in actual water systems. Based on the photo-induced electron transfer (PET) mechanism, the emissive peak of TPETPy located at 475 nm in tetrahydrofuran (THF)/water mixture (ƒw = 90 %) under the excitation of 340 nm, decreases dramatically upon trace trifluralin addition and exhibits ultra-fast response (3 s), high sensitivity and selectivity, and good anti-interference ability. The fluorescence sensing correlation with the concentration of trifluralin shows good linearity in the range of 20-90 μg L-1 with the limit of detection of 6.28 μg L-1. Moreover, a portable smartphone-integrated detected platform based on fluorescent pattern Red/Green/Blue (RGB) values is first employed to realize the real-time and on-site quantitative fluorescent detection of trifluralin in actual water sources, featuring good accuracy and reproducibility. Hereby, this work provides not only a highly efficient trifluralin residues fluorescent probe but also a portable and straightforward operating platform to detect trifluralin pesticides quantitatively.

Polymeric ionic liquid sorbent coatings in thin film microextraction: Insight into sorbent selectivity for pesticides and cannabinoids

Polymeric ionic liquid (PIL) sorbent coatings consisting of polymerizable cations and anions were employed as sorbent coatings in thin film microextraction (TFME) for the extraction of pesticides and cannabinoids. The blades consisted of a thin film of PIL sorbents chemically bonded to vinyltrimethoxysilane-functionalized nitinol sheets. The imidazolium- or ammonium-based PIL sorbents contained aromatic benzyl moieties as well as polar hydroxyl groups or aliphatic functional groups within the chemical structure of the IL monomer. The chemical structure of the IL crosslinkers of the PILs were kept constant across each sorbent, except for the anion, which consisted of either bis[(trifluoromethyl)sulfonyl]imide ([NTf2-]), p-styrenesulfonate ([SS-]), or 3-sulfopropyl acrylate ([SPA-]). Temperature, salt content, and methanol content were optimized as extraction conditions to maximize pesticide-cannabinoid selectivity using Doehlert design of experiments (DOE). Effects of these three factors on selectivity and extraction efficiency are discussed. The optimal extraction conditions consisting of sample temperature (31°C), sodium chloride (30% w/v), and methanol content (0.25% v/v) are compared to initial sorbent screening conditions at a sample temperature of 40°C, 15% (w/v) sodium chloride, and 2.5% (v/v) methanol content. PIL sorbent swelling behavior at different salt and methanol content conditions and its effect on extraction efficiency are hypothesized. Selectivity factors for the sorbents indicated that aromatic moieties within the IL monomer may enhance pesticide-cannabinoid selectivity under optimized conditions, but the extraction efficiency of pesticides that are known to coelute with cannabinoids in the chromatographic separation may be enhanced by employing sorbent coatings with [SPA-] anions.

A highly porous fiber coating based on a Zn-MOF/COF hybrid material for solid-phase microextraction of PAHs in soil

This study involved the development of a novel adsorbent by combining a Zn-based MOF with a melamine-based COF, resulting in the formation of a hybrid material known as Zn-MOF/COF. The adsorbent was characterized using FT-IR, SEM, XRD, EDX, and BET analysis techniques. The resulting Zn-MOF/COF sorbent was employed to prepare solid-phase microextraction (SPME) fibers for the extraction and enrichment of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil samples, after coupling with GC-FID. A Box-Behnken design (BBD) was used to optimize key variables of SPME conditions. Under optimal conditions of 85 °C for 30 min extraction with 23 μL g-1 sample's moisture level, linear responses of six PAHs were ranging from 1 to 20000 ng g⁻1 with determination coefficients greater than 0.99. Limits of detection (LODs) were over the ranges of 0.1-1 ng g-1. The RSDs for intra-fiber and inter-fiber analyses were obtained 2.2-6.6% and 5.2-11.6%, respectively. Relative recoveries values for real soil samples were found to be 91.1-110.2%. The results showed lower cost and higher extraction efficiency for the Zn-MOF/COF fiber, compared with commercial and homemade adsorbents.

Evaluation of Fourier deconvolution ion mobility spectrometer as high-performance gas chromatography detector for the analysis of plant extract flavors

The Fourier deconvolution ion mobility spectrometer (FDIMS) offers multiplexing and improves the resolving power and signal-to-noise ratio. To evaluate the FDIMS as a detector for gas chromatography for the analysis of complex samples, we connected a drift tube ion mobility spectrometer to a commercial gas chromatograph and compared the performance including resolving power, sensitivity, and linear range using 2,6-di‑tert-butylpyridine. Mixed standards were also injected into the tandem system to evaluate the performance under optimized conditions. A complex plant extract sample used as natural flavoring was investigated using the resulting system. The results show that the instrument implemented with the Fourier deconvolution multiplexing method demonstrated higher performance over the traditional signal averaging method including higher resolving power, better limit of detection, and wider linear range for a variety of compounds and natural plant extract flavorings.

Preparation of a magnetic molecularly imprinted polymer on fibrous silica nanosphere via self-polycondensation for micro solid-phase extraction of chlorpyrifos

Throughout this research, a new magnetic molecularly imprinted polymer on fibrous silica nanosphere was prepared through self-polycondensation. The selective extraction of chlorpyrifos was performed by the synthesized sorbent and as a determination system, a gas chromatography-electron capture was applied. The formation of sorbent was confirmed through the use of Fourier transform infrared spectroscopy and field emission scanning electron microscopy techniques. The parameters affecting the extraction efficacy of the proposed method were scrutinized in an optimized way. The linear range and the detection limit of the studied method were 0.003-0.3 and 0.001 ng mL-1, respectively. The relative standard deviations were 4.1-5.2 and 5.6-7.6 % for intra- and inter-day (n = 3), respectively. To assess the performance of the proposed method, some water and fruit samples were analyzed and the extraction recoveries of 83-109 % were obtained. These results revealed the method's performance in the analysis of chlorpyrifos in real samples.

Preparation of black phosphorus nanosheets/ zeolitic imidazolate framework nanocomposite for high-performance solid-phase microextraction of organophosphorus pesticides

Design and preparation of new fiber coatings for solid-phase microextraction (SPME) is of significance to the sample preparation techniques. Herein, a facile strategy has been developed for the integration of the black phosphorus (BP) nanosheets with metal-organic framework (ZIF-8) to generate a BP/ZIF-8 nanocomposite. For the first time, the newly-synthesized BP/ZIF-8 nanocomposite was adopted as the SPME fiber coating for the extraction of organophosphorus pesticides (OPPs). Under the optimized conditions, the BP/ZIF-8 based SPME method gained acceptable linearity (0.04-20 µg L-1), low limits of detection (0.012-0.051 µg L-1) and good repeatability (3.2-8.1%). Coupled with gas chromatography-mass spectrometric detection, the developed SPME method was successfully used for the preconcentration of OPPs from environmental waters with the method recoveries from 92.0%-103.8%. This method offers a good alternative for the analysis of trace OPPs in environmental water samples.

Modulating covalent organic frameworks with accessible carboxyl to boost superior extraction of polar nitrobenzene compounds from matrix-complicated beverages

The wide use and high polarity of nitrobenzene compounds (NBCs) have caused a concern for their residues in daily beverages. Herein, the covalent organic frameworks (COFs) with abundant carboxyl were ingeniously designed by introducing a novel modulator, and further developed as solid phase microextraction (SPME) coatings. Due to the enhanced polar interaction, the extraction efficiencies of modified COF for NBCs were sharply increased. After coupling the high-performance SPME fiber with gas chromatograph-mass spectrometry (GC-MS), an ultrasensitive analytical method was developed, with a wide linear range (0.50-5000 ng/L), and low limits of detection (0.15-3.0 ng/L). More importantly, the method was highly feasible and practical, leading to the precise determinations of trace NBCs from variously matrix-complicated samples. This work provides a viable and efficacious approach for the extraction and analysis of polar pollutants form complicated matrices, and is of great significance for mild COF modification and its extended applications in analytical chemistry.

κ-Carrageenan/triazin-based covalent organic framework bionanocomposite: Preparation, characterization, and its application in fast removing of BB41 dye from aqueous solution

A novel and high efficient adsorbent was prepared based on an environmentally friendly substrate, κ-carrageenan, and a triazine-based covalent organic framework as a co-adsorbent component. Combining these two precursors leads to an effective nanocomposite for removing Basic blue 41 dye from aqueous media. After confirm the structural of prepared composite by various analysis, the adsorption properties were investigated. The optimum conditions were obtained in: pH: 7, temperature: 25 °C and contact time: 210 min; and adsorbent dosage of 10 mg. According to the isotherms study, the basic blue 41 dye adsorption was matched to the Longmuir model with single-layer mechanism. The kinetic of adsorption was studied and fitted with pseudo-second order model with R² = 0.971. From the results the maximum adsorption capacity of 833 mg/g was obtained in 15 min and the reusability tests showed 24% decrease in yield after three cycles.

Improving the Reaction-to-Fire Properties of Thermoplastic Polyurethane by New Phosphazene-Triazinyl-Based Covalent Organic Framework

In this study, an approach to simultaneously improve fire resistance and mechanical performance of thermoplastic polyurethane (TPU) was introduced through the penetration of a conjugated network containing nitrogen and phosphorus elements. For this purpose, a Bg-HCCP COF was synthesized through a solvothermal method from benzoguanamine (Bg) and hexachlorophosphazene (HCCP) monomers. Then, it was combined with TPU using the wet mixing method. The TPU/Bg-HCCP composites showed better mechanical strength than the untreated sample. The fire safety of TPU/Bg-HCCP composites was greatly improved by increasing the Bg-HCCP contents. The reduction of the peak heat release rate and the total heat release for the TPU/Bg-HCCP composite with 3 wt % Bg-HCCP were about 44.8 and 60.4%, respectively. Besides, the results showed that adding Bg-HCCP to TPU significantly improved the suppression of smoke generation so that 3% by weight of the fire retardant reduced the total smoke released by 53.1%. It also decreased the peak of the carbon monoxide production rate by 26.5%. Generally, our research provides a promising strategy for constructing flame-retardant composites with high performance.

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.

Volatile Variation of Theobroma cacao Malvaceae L. Beans Cultivated in Taiwan Affected by Processing via Fermentation and Roasting

After being harvested, cacao beans are usually subjected to very complex processes in order to improve their chemical and physical characteristics, like tastefulness with chocolate characteristic flavors. The traditional process consists of three major processing stages: fermentation, drying, and roasting, while most of the fermentation is carried out by an on-farm in-box process. In Taiwan, we have two major cocoa beans, the red and the yellow. We proposed that the major factor affecting the variation in tastes and colors in the finished cocoa might be the difference between cultivars. To uncover this, we examined the effect of the three major processes including fermentation, drying and roasting on these two cocoa beans. Results indicated that the two cultivars really behaved differently (despite before or after processing with fermentation, drying, and roasting) with respect to the patterns of fatty acids (palmitic, stearic, oleic, and arachidonic); triacylglycerols:1,2,3-trioleoyl-glycerol (OOO); 1-stearoyl-2,3-oleoyl-glycerol (SOO); 1-stearoyl-sn-2-oleoyl-3-arachidoyl- glycerol (SOA); 1,3-distearyol-sn-2-oleoyl-glycerol (SOS); organic acids (citric, tartaric, acetic, and malic); soluble sugars (glucose and fructose); amino acids; total phenolics; total flavonoids; and volatiles. Our findings suggest that to choose specific processing conditions for each specific cocoa genotype is the crucial point of processing cocoa with consistent taste and color.