A 3D nanoscale polyhedral oligomeric silsesquioxanes network for microextraction of polycyclic aromatic hydrocarbons.

Polyhedral oligomeric silsesquioxanes are 3D nanoscaled materials with large potential in solid phase microextraction (SPME). Here, as a case study, an octaglycidyldimethylsilyl modified polyhedral oligomeric silsesquioxane network is described. It was deposited on a stainless steel wire via a sol-gel method and used as a fiber coating for SPME of aromatic compounds. The uniform pore structure, high surface area, and hydrophobicity of the network make it susceptible toward isolation of non-polar and semi-polar chemical compounds. The performance of the fiber coating was tested with three classes of environmental pollutants, viz. chlorobenzenes (CBs), benzenes (benzene, toluene, ethylbenzene, xylene; known as BTEX), and polycyclic aromatic hydrocarbons. The effects of various types of sol-gel precursors on the fabrication and performance of fiber coatings were investigated. The extraction capability of the fiber coating was compared with the polydimethyl siloxane/divinylbenzene based commercial fiber. Parameters affecting headspace analysis and gas chromatographic quantitation were optimized. The method was applied to the quantification of PAHs, as model analytes, in tea, coffee and some environmental waters. Linear responses typically cover the 1-200 ng·L-1 concentration range, limits of detection are between 0.1 and 0.3 ng·L-1, intra-day relative standard deviation are <10%, and inter-day RSDs are <12%. The fiber has a long lifespan and can be used >200 times. Graphical abstract Schematic presentation of a headspace solid phase microextraction process which is implemented to the analysis of PAHs in tea and coffee samples. The SEM image of the SPME fiber coating, the 3D nanoscale polyhedral oligomeric silsesquioxane (POSS) network, and the POSS-epoxy molecular structure are shown.

Nanostructured molybdenum oxide in a 3D metal organic framework and in a 2D polyoxometalate network for extraction of chlorinated benzenes prior to their quantification by GC-MS.

A three-dimensional metal organic framework (3D-MOF) and a two-dimensional polyoxometalate (2D-POM), both incorporating nanostructured molybdenum (VI) oxide, were synthesized and implemented for headspace needle trap extraction of traces of chlorobenzenes (CBs). The 3D-MOF of type {(Mo2O6)(4,4'-bpy)}n and the 2D-POM of type [4,4'-bpy][Mo7O22] were synthesized by a solvothermal process and characterized by FT-IR, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetry, energy dispersive X-ray, elemental mapping and Brunner-Emmet-Teller adsorption analyses. The 3D-MOF proved to be superior. Following thermal desorption, the CBs (monochlorobenzene, 1,4-dichlorobenzene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene and 1,2,3,4-tetrachlorobenzene) were quantified by GC-MS. Under optimized conditions, the calibration plots are linear in the 1-1000 ng.L-1 concentration range, and the limits of detection range from 0.2 to 2 ng.L-1. The intra- and inter-day relative standard deviations for three replicates at levels of 10 and 200 ng.L-1 are in the range of 5-12% and 10-15%, respectively. The needle-to-needle reproducibility was also found to be in the range of 6-13%. The application of the method to the analysis of various spiked real water samples resulted in recoveries between 84 and 114%. Graphical abstract A comparison of extraction efficiency between 3D-MOF and 2D-POM, in which 3D-MOF is superior to isolate organic pollutants, due to possession of more 4,4'-bpy ligands and interaction sites.

Sequential thin film microextraction and overcoated thin film microextraction devices for characterization of sparkling wine aroma profiles and partitioning equilibria.

Solid Phase Microextraction (SPME) is a commonly used, robust method for characterization of aroma profiles in food matrices. However, challenges such as saturation, swelling, and competition can occur when sampling such complex matrices, resulting in decreased accuracy in the quantitation of polar compounds. In this study, sequential thin film micro-extraction (TFME) was employed to study the aroma profile of sparkling wine, with a focus to evaluate the displacement of polar analytes at extraction times longer than their corresponding equilibrium time. This investigation also describes advancements in the production of TFME devices, specifically the overcoating of hydrophilic-lipophilic balance/polydimethylsiloxane (HLB/PDMS) thin films to increase their matrix compatibility. Sequential thin film micro-extraction and overcoated HLB/PDMS thin films were evaluated for characterization of sparkling wine samples. The results were encouraging, showing that these advancements can decrease competition phenomena and increase the calibration linearity range compared to traditional micro-extraction approaches more commonly used for the characterization of such samples. In addition, multiphase equilibria investigation involving micellar systems enabled by the microextraction technology provides better understanding between wine aroma and its composition.

Incorporation of Cu-TATAB metal-organic framework within polyurethane nanocomposite for enhanced thin film microextraction of some chlorinated pesticides.

In this research, electrospun nanofibers based on copper-based metal organic framework (MOF)/polyurethane (PU) were prepared in order to achieve an applicable and superior extractive phase. The incorporation of MOF, in the synthesized nanocomposite contributed to the enhanced sorption efficiency. The prepared sorbent was implemented for the thin film microextraction (TFME) of target compounds with subsequent quantification using gas chromatography-mass spectrometry (GC-MS). To obtain the maximum efficiency of the synthesized sorbent, the influential parameters on extraction and desorption steps, including the MOF percentage in nanocomposite, desorption solvent type and its volume, desorption time, solution ionic strength and extraction time were optimized. After method development, the linear dynamic range (0.02-700 µg L-1), limits of detection (LODs) (0.005-0.1 µg L-1) and limits of quantification (LOQs))0.02-0.33 µg L-1(were calculated. The relative standard deviations values for intra-day and inter-day analysis were found to be in the range of 4.3-5.3 % and 6.2-8.1 %, respectively. The developed method was validated for the TFME of model organochlorine (OC) pesticide residues in fish, soil and water samples. the recovery values for the spiked samples at two concentration levels of 5 and 100 µg l-1 were found in the range of 72-110 %.

From waste to health: Application of MOF modified walnut biochars for the determination of twenty pesticides in wheat flour by ultra-high performance liquid chromatography-tandem mass spectrometry.

In this research, walnut shell along with a Ni-metal organic framework (Ni-MOF) was thermally treated to obtain a highly efficient biochar. A µ-solid phase extraction (µ-SPE) setup containing the optimized walnut modified biochar was implemented for the extraction of 20 wheat specified pesticides with a wide range of polarities. The modified biochars were characterized and the role of Ni-MOF on the porosity of the obtained biochars was investigated. After optimizing the extraction parameters, the 50 %-Ni-MOF-walnut shell biochar was selected. Accordingly, the precision for intra-day (2.4-25 %), inter-day (7-28.3 %) and synthesis procedure (4.1-26.7 %) was calculated. The limits of detection and quantification were in the range of 0.01-12.1 µg/L and 0.03-40.5 µg/L, respectively. This method was applied for the analysis of 29 wheat samples. The risk assessment study demonstrates that the contaminated wheat samples cannot cause non-carcinogenic harm to adults but might have an impact on children.

Roles of metal, ligand and post synthetic modification on metal organic frameworks to extend their hydrophobicity and applicability toward ultra-trace determination of priority organic pollutants.

Implementation of metal organic frameworks (MOFs) in the separation science has attracted many researchers attention. In this study, the role of metal, ligand, the reaction condition and modification on the extraction efficiency of some MOFs was investigated. Among the prevalent reported MOFs, some members of the MIL and MOF-5 families were chosen, and eleven MOF-based sorbents were prepared by changing the metal and ligand type, reaction condition, and/or functionality through post synthetic modification (PSM). MIL-101 and MIL-101-NH2 based structures were initially synthesized based on the chromium and iron salts. Also, three zinc-based structures including MOF-5, [NH2(CH3)2]2 [Zn3(C6H4(CO2)2)4].DMF.H2O and [NH2(CH3)2]2 [Zn3((C6H4)2(CO2)2)4].5DMF were synthesized. The PSM hydrophobic-oriented products of MILs were obtained by their reactions with benzyl alcohol. The resulted MOFs were characterized by FT-IR, PXRD, SEM, BET, BJH, water contact angle and TG analyses. The extraction trends of these nanostructures were studied toward some priority environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs), chlorobenzenes (CBs), and benzene homologs. The extraction procedures were performed via adapting a home-made headspace needle trap extraction (HS-NTE) setup, and determinations were followed by gas chromatography-mass spectrometry (GC-MS). Among all the synthesized nanostructures, the chromium-based PSM product of MIL-101-NH-CH2C6H5 proves its improved extraction capability for most of the model compounds. Eventually, the superior MOF was applied as the extractive phase in a HS-NTE-GC-MS method for isolation and trace determination of PAHs, in tea, coffee, and some other environmental water samples. Under the optimized conditions, the linear dynamic range (LDR) was in the range of 1-1000 ng L-1 (R2 > 0.992) while the limits of detection (LOD) and limits of quantification (LOQ) values were 0.1-0.2 and 0.3-0.7 ng L-1, respectively. Also, the extraction capability of the Cr-based MIL-101-NH-CH2C6H5 was compared with commercial polydimethyl siloxane-divinyl benzene (PDMS-DVB) fiber coating. The intra-and inter-day relative standard deviations for three replicates at the concentration levels of 20 and 500 ng L-1 were in the range of 4-7% and 5-10%, respectively. The needle-to-needle reproducibility was also found to be in the range of 6-10%. Acceptable relative recovery values at the concentration levels of 20 and 500 ng L-1 ranged from 89 to 98%, showing no significant matrix effect.

The geometrical characteristics of nickel-based metal organic framework on its entrapment capability.

Here, a three dimensional nickel-based metal organic framework (MOF) was synthesized via solvothermal and room temperature protocols. In order to study the effects of the synthesis conditions on the physical properties such as pore sizes and shapes of the prepared MOFs, their extraction capabilities were examined. Both MOFs were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller and thermogravimetric analyses. Brilliant properties such as porous structure, high surface area and considerable thermal stability make them reasonable candidates to be employed as efficient extractive phases. The efficiency of the superior nickel-based MOF was evaluated for headspace needle trap extraction of chlorobenzenes as model compounds in conjunction with gas chromatography-mass spectrometry (GC-MS). The MOF-based extractive phase was conveniently packed in a needle trap device and after extraction, the desorption process was performed via direct insertion of needle into the GC inlet. After optimizing the extraction/desorption conditions, the figures of merit such as linear dynamic range was in the range of 5-1000 ng L-1 (R2 > 0.987) while the limits of detection and quantification values were 2-10 and 6-30 ng L-1, respectively. The intra- and inter-day relative standard deviations for three replicates at the concentration level of 50 ng L-1 were in the range of 7-9% and 9-12%, respectively. The needle-to-needle reproducibility was also found to be in the range of 5-11%. Acceptable relative recovery values at the concentration level of 50 ng L-1 ranged from 85 to 96%, showing no significant matrix effect.

A metal organic framework-polyaniline nanocomposite as a fiber coating for solid phase microextraction.

A metal organic framework-polyaniline (MOF/PANI) nanocomposite was electrodeposited on a stainless steel wire and used as a solid phase microextraction (SPME) fiber coating. The electropolymerization process was carried out under a constant deposition potential and applied to the corresponding aqueous electrolyte containing aniline and MOF particles. The employment of MOFs with their large and small cages and 3-D structures in synthesizing a nanocomposite was assumed to be efficient constitutes to induce more non-smooth and porous structures, approved by scanning electron microscopy (SEM) images. Three different MOFs were incorporated to synthesize the desired nanocomposites and the preliminary experiments showed that all of them, particularly the one containing MOF2, have higher extraction performances in compared with PANI. The applicability of the new fiber coating was examined by headspace-solid phase microextraction (HS-SPME) of some chlorobenzenes (CBs) from aqueous samples. Influencing parameters on the synthesize and extraction processes including the electrodeposition voltage and its duration time, the weight ratio of PANI and MOF, the ionic strength, desorption temperature and time, and extraction time and temperature were optimized. The developed method was validated by analyzing the spiked distilled water and gas chromatography-mass spectrometry (GC-MS). Under optimum condition, the relative standard deviation (RSD%) values for a double distilled water spiked with the selected CBs at 20ngL(-1) were 5-8% (n=3) and the detection limits were below 0.2ngL(-1). The linear dynamic range (LDR) of the method was in the concentration range of 0.5-1000ngL(-1) (R(2)>0.9994). The fiber-to-fiber reproducibility was found to be in the range of 4-7%. Eventually, various real-water samples were analyzed by the MOF/PANI-based HS-SPME and GC-MS and the relative recovery values were found to be in the range of 92-98%.