Inorganic-Organic Nanoarchitectonics: MXene/Covalent Organic Framework Heterostructure for Superior Microextraction.

One of the difficulties limiting covalent organic frameworks (COFs) from becoming excellent adsorbents is their stacking/aggregation architectures owing to poor morphology/structure control during the synthesis process. Herein, an inorganic-organic nanoarchitectonics strategy to synthesize the MXene/COF heterostructure (Ti3 C2 Tx /TAPT-TFP) is developed by the assembly of ß-ketoenamine-linked COF on the Ti3 C2 Tx MXene nanosheets. The as-prepared Ti3 C2 Tx /TAPT-TFP retains the 2D architecture and high adsorption capacity of MXenes as well as large specific surface area and hierarchical porous structure of COFs. As a proof of concept, the potential of Ti3 C2 Tx /TAPT-TFP for solid-phase microextraction (SPME) of trace organochlorine pesticides (OCPs) is investigated. The Ti3 C2 Tx /TAPT-TFP based SPME method achieves low limits of detection (0.036-0.126 ng g-1 ), wide linearity ranges (0.12-20.0 ng g-1 ), and acceptable repeatabilities for preconcentrating trace OCPs from fruit and vegetable samples. This study offers insights into the potential of constructing COF or MXene-based heterostructures for the microextraction of environmental pollutants.

Determination of phthalate esters in bottled beverages by direct immersion solid-phase microextraction with a porous boron nitride coated fiber followed by gas chromatography-mass spectrometry.

A porous boron nitride with a large surface area was synthesized by a one-step grinding method with melamine, urea, and boric acid as the precursors. The prepared porous boron nitride was used as the fiber coating material for the solid-phase microextraction of seven phthalate esters (diethyl phthalate, diallyl phthalate, diisobutyl phthalate, dibutyl phthalate, butylbenzyl phthalate, dicyclohexyl phthalate, and di-2-ethylhexyl phthalate) prior to their gas chromatography-mass spectrometric detection. The important experimental parameters including the extraction time, extraction temperature, salt concentration, and stirring rate were optimized by both single factor and central composite design methods. Under the optimized experimental conditions, the linear response range for the analytes was from 0.030 to 30.0 µg/L, and the limits of detection were from 0.010 to 0.040 µg/L, respectively. The relative recoveries of the analytes for spiked samples at two concentration levels were 83.0-109% with the relative standard deviations less than 12%. The established method was successfully applied for the determination of the phthalate esters in bottled juice beverage samples.

Boron nitride modified reduced graphene oxide as solid-phase microextraction coating material for the extraction of seven polycyclic aromatic hydrocarbons from water and soil samples.

A novel hexagonal boron nitride modified reduced graphene oxide material was synthesized and used as the adsorbent for the solid-phase microextraction of seven polycyclic aromatic hydrocarbons from water and soil samples prior to their detection by gas chromatography-flame ionization detector. Under optimal conditions, the linear response range of the analytes for water sample is 0.25-50 ng/mL with the correlation coefficients (r) ranging between 0.9953 and 0.9996. The linear range for soil sample is 1.0-400 ng/g with r ranging from 0.9959 to 0.9999. On the basis of the signal-to-noise ratio of 3, the limits of detections for the analytes ranged from 0.05 to 0.15 ng/mL for water samples, and from 0.3 to 0.5 ng/g for soil samples. The relative recoveries of the seven polycyclic aromatic hydrocarbons for water and soil samples were in the range of 79.55-120.0 and 78.76-120.8%, respectively. The relative standard deviations for the determination of the analytes in water and soil samples were lower than 11 and 10%, respectively. The method is simple and suitable for the determination of polycyclic aromatic hydrocarbon residues in water and soil samples.

Triazine-based covalent organic polymer: A promising coating for solid-phase microextraction.

Advancement of novel coating materials for solid-phase microextraction is highly needed for sample pretreatment. Herein, a triazine-based covalent organic polymer was constructed from the monomers of cyanuric chloride and trans-stilbene via the Friedel-Crafts reaction and thereafter used as a solid-phase microextraction fiber coating for the extraction of polycyclic aromatic hydrocarbons and their nitrated and oxygenated derivatives. The newly-developed solid-phase microextraction method coupled with gas chromatography/flame ionization detection gives enhancement factors of 548-1236 and limits of detection of 0.40-2.81 ng/L for the determination of polycyclic aromatic hydrocarbons and their derivatives. The one fiber precision for five replicate determinations of the analytes and the fiber-to-fiber precision with three parallel prepared fibers, expressed as relative standard deviations, was in the range of 4.6-9.4% and 6.2-10.9%, respectively. The relative recoveries of the analytes for environmental water samples were in the range of 88.6-106.4% with the relative standard deviations ranging from 4.0 to 11.7% (n = 5).

Carbon nanospheres as solid-phase microextraction coating for the extraction of polycyclic aromatic hydrocarbons from water and soil samples.

A solid-phase microextraction with carbon nanospheres coated fiber coupled with gas chromatographic detection was established for the determination of eight polycyclic aromatic hydrocarbons (naphthalene, biphenyl, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, and pyrene) in water and soil samples. The experimental parameters (extraction temperature, extraction time, stirring rate, headspace volume, salt content, and desorption temperature) which affect the extraction efficiency were studied. Under the optimized conditions, good linearity between the peak areas and the concentrations of the analytes was achieved in the concentration range of 0.5-300 ng/mL for water samples, and in the concentration range of 6.0-2700 ng/g for soil samples. The detection limits for the analytes were in the range of 0.12-0.45 ng/mL for water samples, and in the range of 1.53-2.70 ng/g for soil samples. The method recoveries of the polycyclic aromatic hydrocarbons for spiked water samples were 80.10-120.1% with relative standard deviations less than 13.9%. The method recoveries of the analytes for spiked soil samples were 80.40-119.6% with relative standard deviations less than 14.4%. The fiber was reused over 100 times without a significant loss of extraction efficiency.

Synthesis of nanoporous poly-melamine-formaldehyde (PMF) based on Schiff base chemistry as a highly efficient adsorbent.

This study proposes the construction of nanoporous poly-melamine-formaldehyde (PMF) through the Schiff base condensation reaction of paraformaldehyde and melamine. The PMF nanoparticles showed a good adsorption capability to some benzene-ring-containing dyes including acid fuchsine, nigrosine, and methyl orange. Moreover, the as-prepared PMF nanoparticles were employed as the coating adsorbent for the solid-phase microextraction (SPME) of seven volatile fatty acids (VFAs) with high enrichment factors. A PMF-assisted SPME method was established for the enrichment of VFAs from environmental water samples with satisfactory recoveries (88.5%-102.0%) and acceptable precisions (relative standard deviations <10.9%). This contribution might furnish an advanced benchmark for the exploitation of new porous organic polymers as the effective adsorbents for SPME or other fields of utilization.

Determination of pesticides residues in vegetable and fruit samples by solid-phase microextraction with a covalent organic framework as the fiber coating coupled with gas chromatography and electron capture detection.

In this study, a covalent organic framework designated as TpPaNO2 was synthesized by a mechanochemical grinding method and then coated on stainless steel wire by a sol-gel technique to prepare a solid-phase microextraction fiber. The TpPaNO2 fiber based solid-phase microextraction coupled with gas chromatography-electron capture detection was applied to determine the residues of 11 pesticides (trlfuralln, dicofol, α-endosulfan, 1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene, nitrofen, ß-endosulfan, 1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethyl]benzene, 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane, bifenthrin, permethrin and fenvalerate) in vegetable and fruit samples. The effects of extraction time, extraction temperature, sample pH, stirring rate and desorption temperature on the extraction efficiency were investigated. Under the optimized conditions, the limits of detection for the eleven pesticides were in the range of 0.04-0.25 µg/kg. The recoveries of the eleven pesticides in the vegetable and fruit samples were 81.5-111% with the relative standard deviations less than 11.2%.

Fibrous boron nitride nanocomposite for magnetic solid phase extraction of ten pesticides prior to the quantitation by gas chromatography.

A fibrous magnetic boron nitride nanocomposite was synthesized and is shown to be a viable adsorbent for the magnetic solid phase extraction of pesticides prior to their quantitation by gas chromatography with electron capture detection. The optimum conditions were obtained by both single factor optimization and response surface analysis (Box-Behnken design). Under the optimized conditions, the response to the ten pesticides (dicofol, α-endosulfan, p,p'-DDE, nitrofen, ß-endosulfan, p,p'-DDD, p,p'-DDT, bifenthrin, permethrin and fenvalerate) is linear in the 0.03-40 ng·mL-1 concentration range with the coefficients of determination ranging from 0.9970 to 0.9992. The relative standard deviations at concentration levels of 0.5 ng·mL-1, 20 ng·mL-1 and 40 ng·mL-1 were below 8.7%. The recoveries of the analytes from spiked tea water and tea beverage samples varied between 84.5% and 122%, with relative standard deviations ranging from 4.8 to 12%. The limits of detection are between 0.01 and 0.05 ng·mL-1. The adsorbent can be reused over 50 times without significant loss of extraction efficiency. Graphical abstract A novel fibrous-shape magnetic boron nitride nanocomposite (Fe3O4@f-BN) was used as the adsorbent for the magnetic solid phase extraction (MSPE) of ten pesticides from tea water and tea beverage samples prior to their determination by gas chromatography (GC).

Micro-solid phase extraction of chlorophenols using reduced graphene oxide functionalized with magnetic nanoparticles and graphitic carbon nitride as the adsorbent.

A magnetic micro-solid phase extraction method was applied for the extraction of trace levels of various chlorophenols prior to their determination by high performance liquid chromatography. The reduced graphene oxide functionalized with magnetic iron oxide nanoparticles and graphitic carbon nitride was prepared and used as adsorbent. It was characterized by scanning electron microscope, X-ray diffraction and vibrating sample magnetometer. Placed in a polypropylene hollow tube, the material was applied to the extraction of 3-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol in cosmetic samples. Several experimental parameters that affect extraction efficiency were optimized. Following desorption with alkaline methanol, the chlorophenols were quantified by high performance liquid chromatography. A linear response was observed in the 1.0-200 µg·kg-1 CP concentration ranges. The detection limits (at a signal-to-noise ratio of 3) are between 0.20 and 0.30 µg·kg-1. The relative recoveries of the CPs from spiked cosmetics samples were in the range from 80.5 to 104%, with relative standard deviations lower than 12%. The filled extraction tube is high durable and stable. It can be used for 120 extraction cycles without a significant loss of extraction efficiency. The good adsorption ability of the sorbent was attributed to the strong π stacking interaction between the graphitic carbon nitride functionalized reduced graphene oxide and the aromatic rings in the CPs. Graphical abstract A magnetic micro-solid phase extraction (M-µSPE) method was applied to the extraction of various trace chlorophenols prior to their determination by high performance liquid chromatography. The M-µSPE method combines the advantages of both MSPE and µSPE.

A porous carbon derived from amino-functionalized material of Institut Lavoisier as a solid-phase microextraction fiber coating for the extraction of phthalate esters from tea.

In this work, a porous carbon derived from amino-functionalized material of Institut Lavoisier (C-NH2 -MIL-125) was prepared and coated onto a stainless-steel wire through sol-gel technique. The coated fiber was used for the solid-phase microextraction of trace levels of phthalate esters (diallyl phthalate, di-iso-butyl ortho-phthalate, di-n-butyl ortho-phthalate, benzyl-n-butyl ortho-phthalate, and bis(2-ethylhexy) ortho-phthalate) from tea beverage samples before gas chromatography with mass spectrometric analysis. Several experimental parameters that could influence the extraction efficiency such as extraction time, extraction temperature, sample pH, sample salinity, stirring rate, desorption temperature and desorption time, were investigated. Under the optimal conditions, the linearity existed in the range of 0.05-30.00 µg/L for green jasmine tea beverage samples, and 0.10-30.00 µg/L for honey jasmine tea beverage samples, with the correlation coefficients (r) ranging from 0.9939 to 0.9981. The limits of detection of the analytes for the method were 2.0-3.0 ng/L for green jasmine tea beverage sample, and 4.0-5.0 ng/L for honey jasmine tea beverage sample, depending on the compounds. The recoveries of the analytes for the spiked samples were in the range of 82.0-106.0%, and the precision, expressed as the relative standard deviations, was less than 11.1%.

Metal-organic framework UiO-67-coated fiber for the solid-phase microextraction of nitrobenzene compounds from water.

A sol-gel coating technique was applied for the preparation of a solid-phase microextraction fiber by coating the metal-organic framework UiO-67 onto a stainless-steel wire. The prepared fiber was explored for the headspace solid-phase microextraction of five nitrobenzene compounds from water samples before gas chromatography with mass spectrometric detection. The effects of the extraction temperature, extraction time, sample solution volume, salt addition, and desorption conditions on the extraction efficiency were optimized. Under the optimal conditions, the linearity was observed in the range of 0.015-12.0 µg/L for the compounds in water samples, with the correlation coefficients (r) of 0.9945-0.9987. The limits of detection of the method were 5.0-10.0 ng/L, and the recoveries of the analytes from spiked water samples for the method were in the range of 74.0-102.0%. The precision for the measurements, expressed as the relative standard deviation, was less than 11.9%.

Application of mesoporous carbon as a solid-phase microextraction fiber coating for the extraction of volatile aromatic compounds.

A mesoporous carbon was fabricated using MCM-41 as a template and sucrose as a carbon source. The carbon material was coated on stainless-steel wires by using the sol-gel technique. The prepared solid-phase microextraction fiber was used for the extraction of five volatile aromatic compounds (chlorobenzene, ethylbenzene, o-xylene, bromobenzene, and 4-chlorotoluene) from tea beverage samples (red tea and green tea) prior to gas chromatography with mass spectrometric detection. The main experimental parameters affecting the extraction of the volatile aromatic compounds by the fiber, including the extraction time, sample volume, extraction temperature, salt addition, and desorption conditions, were investigated. The linearity was observed in the range from 0.1 to 10.0 µg/L with the correlation coefficients (r) ranging from 0.9923 to 0.9982 and the limits of detection were less than 10.0 ng/L. The recoveries of the volatile aromatic compounds by the method from tea beverage samples at spiking levels of 1.0 and 10.0 µg/L ranged from 73.1 to 99.1%.

Metal-organic framework derived magnetic nanoporous carbon: novel adsorbent for magnetic solid-phase extraction.

The fabrication of a magnetic nanoporous carbon (MNPC) via one-step direct carbonization of Co-based metal-organic framework has been achieved without using any additional carbon precursors. The morphology, structure, and magnetic behavior of the as-prepared Co-MNPC were characterized by using the techniques of scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Raman spectroscopy, N2 adsorption, and vibrating sample magnetometer. The Co-MNPC has a high specific surface area, large pore volume, and super paramagnetism. Its performance was evaluated by the magnetic solid-phase extraction of some neonicotinoid insecticides from water and fatmelon samples followed by high-performance liquid chromatographic analysis. The effects of the main experimental parameters that could affect the extraction efficiencies were investigated. The results demonstrated that the Co-MNPC had an excellent adsorption capability for the compounds.

Graphene oxide as a micro-solid-phase extraction sorbent for the enrichment of parabens from water and vinegar samples.

A simple hydrophilic polyamide organic membrane protected micro-solid-phase extraction method with graphene oxide as the sorbent was developed for the enrichment of some parabens from water and vinegar samples prior to gas chromatography with mass spectrometry detection. The main experimental parameters affecting the extraction efficiencies, such as the type and amount of the sorbent, extraction time, stirring rate, salt addition, sample solution pH and desorption conditions, were investigated. Under the optimized experimental conditions, the method showed a good linearity in the range of 0.1-100.0 ng/mL for water samples and 0.5-100.0 ng/mL for vinegar samples, with the correlation coefficients varying from 0.9978 to 0.9997. The limits of detection (S/N = 3) of the method were in the range of 0.005-0.010 ng/mL for water samples and 0.01-0.05 ng/mL for vinegar samples, respectively. The recoveries of the method for the analytes at spiking levels of 5.0 and 70.0 ng/mL were between 84.6 and 106.4% with the relative standard deviations varying from 4.2 to 9.5%. The results indicated that the developed method could be a practical approach for the determination of paraben residues in water and vinegar samples.

Solid-phase microextraction with a graphene-composite-coated fiber coupled with GC for the determination of some halogenated aromatic hydrocarbons in water samples.

In this work, a graphene composite was coated onto etched stainless-steel wire through a sol-gel technique and it was used as a solid-phase microextraction (SPME) fiber. The prepared fiber was characterized by SEM, which revealed that the fiber had a highly porous structure. The application of the fiber was evaluated through the headspace SPME of five halogenated aromatic hydrocarbons (chlorobenzene, bromobenzene, 1,3-dichlorobenzene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene) in water samples followed by GC with flame ionization detection. The main factors influencing the extraction efficiency, including headspace volume, extraction time, extraction temperature, stirring rate, ionic strength of sample solution, and desorption conditions, were studied and optimized. Under the optimum conditions, the linearity of the method ranged from 2.5 to 800.0 µg/L for 1,2,4-trichlorobenzene and from 2.5 to 500.0 µg/L for chlorobenzene, bromobenzene, 1,3-dichlorobenzene, and 1,2-dichlorobenzene, with the correlation coefficients (r) ranging from 0.9962 to 0.9980, respectively. The LODs (S/N = 3) of the method for the analytes were in the range between 0.5 and 1.0 µg/L. The recoveries of the method for the analytes obtained for the spiked water samples at 50.0 and 250.0 µg/L were from 76.0 to 104.0%.

The use of silica-coated magnetic graphene microspheres as the adsorbent for the extraction of pyrethroid pesticides from orange and lettuce samples followed by GC-MS analysis.

Graphene-grafted ferroferric oxide microspheres were used as the adsorbent to extract some pyrethroid pesticides (bifenthrin, λ-cyhalothrin, cyfluthrin, cypermethrin, fenvalerate, and deltamethrin) from orange and lettuce samples prior to their determination by GC-MS. The main variables that could affect the extraction, including the amount of the adsorbent, pH of the sample solution, extraction time, concentration of salt, and desorption conditions, were investigated and optimized. Under the optimized conditions, a linear response was obtained in the concentration range of 0.3-100.0 ng/g for the analytes with the coefficients of determination ranging from 0.9877 to 0.9925. The LODs for the pyrethroids ranged from 0.01 to 0.02 ng/g. The method provided a good repeatability with RSDs < 10.6%. The recoveries for the six pyrethroid pesticides were in the range from 90.0 to 103.7%. The method was applied to the determination of the pesticides in orange and lettuce samples with a satisfactory result.

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.

The use of graphene-based magnetic nanoparticles as adsorbent for the extraction of triazole fungicides from environmental water.

A graphene-based magnetic nanocomposite (graphene-ferriferrous oxide; G-Fe(3)O(4)) was synthesized and used as an effective adsorbent for the preconcentration of some triazole fungicides (myclobutanil, tebuconazole, and hexaconazole) in environmental water samples prior to high-performance liquid chromatography-ultraviolet detection. The method, which takes the advantages of both nanoparticle adsorption and magnetic phase separation from the sample solution, could avoid the time-consuming experimental procedures commonly involved in the traditional solid phase extraction such as centrifugation and filtrations. Various experimental parameters affecting the extraction efficiencies such as the amount of the magnetic nanocomposite, extraction time, the pH values of the sample solution, salt concentration, and desorption conditions were investigated. Under the optimum conditions, the enrichment factors of the method for the three analytes were 5824, 3600, and 4761, respectively. A good linearity was observed in the range of 0.1-50 ng/mL for tebuconazole and 0.05-50 ng/mL for myclobutanil and hexaconazole, respectively, with the correlation coefficients ranging from 0.9992 to 0.9996. The limits of detection (S/N = 3) of the method were between 0.005 and 0.01 ng/mL. The results indicated that as a magnetic solid-phase extraction adsorbent, the graphene-ferriferrous oxide (G-Fe(3)O(4)) has a great potential for the preconcentration of some compounds from liquid samples.

A novel porphyrin-based conjugated microporous nanomaterial for solid-phase microextraction of phthalate esters residues in children's food.

A novel porphyrin-based conjugated microporous polymer (PCMP) with microporous structure and nitrogen-rich pyrrole building blocks was synthesized. The PCMP was used as a coating material to prepare solid-phase microextraction (SPME) fibers by sol-gel technique. Due to the toxicity of the phthalate esters (PAEs) and the necessity for their sensitive determinations in some food samples, the SPME fiber was investigated for the extraction of eleven PAEs from six different children's milk beverages prior to their detection by gas chromatography-mass spectrometry. Under the optimal conditions, the linear response range for the PAEs was in the range from 0.03 to 200 µg L-1 and the limits of detection (S/N = 3) for the analytes were 0.01-3.00 µg L-1. The method recoveries for the PAEs were between 80% and 120%, with the relative standard deviations varying from 1.3% to 9.8%. The method was successfully applied for the determination of PAEs in children's milk beverages.

Efficient solid-phase microextraction of twelve halogens-containing environmental hormones from fruits and vegetables by triazine-based conjugated microporous polymer coating.

A triazine-based conjugated microporous polymer (TCMP) was generated by introduced 1, 3, 5-triazine into conjugated microporous polymer network via Friedel-Crafts reaction. Under the optimum synthesis conditions, the obtained TCMP has a loose and porous structure. It was then used as a fiber coating material for solid-phase microextraction (SPME) of halogens-containing environmental hormones. It showed a strong adsorption capability due to the halogen bond, electrostatic, π-π stacking and hydrophobicity interactions. An analytical method combining the TCMP coated fiber-based SPME with gas chromatography-electron capture detection was developed to determine twelve halogens-containing environmental hormones in vegetable and fruit samples. A wide linear range (0.07-100.0 ng g-1) with the determination coefficients in the range of 0.9907-0.9996 and low limits of detection (0.02-0.04 ng g-1, S/N = 3) were achieved under optimized experimental conditions. The applicability of the established method was evaluated by the determination of the environmental hormones from three different fruit samples (apple, nectarine and pear) and five vegetable samples (Chinese cabbage, pakchoi, baby cabbage, rape and round lettuce). The resulting relative recoveries ranged from 76.6% to 123% with the relative standard deviations less than 10%. This research demonstrates the application potential of the TCMP coated fiber in the analysis of the halogens-containing environmental hormones in real vegetable and fruit samples.