A solid-phase microextraction coating of sol–gel-derived perhydroxy cucurbit[6]uril and its application on to the determination of polycyclic aromatic hydrocarbon

Multipurpose new gas chromatography column based on pillararenes functionalized with imidazolium ionic liquids

BACKGROUND

Gas chromatography is worldwide recognized as one of the most important analytical techniques, due to its high versatility and reliability. The heart of a gas chromatograph is the column, that allows analyte peak separations and, consequently, accurate qualitative and qualitative analyses. New and more efficient columns are always requested to satisfy new and challenging analytical needs.

RESULTS

In this work, imidazolium ionic liquids functionalized pillar [5] arenes have been used for the first time as gas chromatographic stationary phases, considering their highly symmetric pillar-shaped architecture with cavities rich in π-electrons. Four imidazolium ionic liquids functionalized pillar [5] arenes have been tested as stationary phases with numerous analytes and isomers. In particular, one of these showed superior performances if compared to commercial columns, enabling challenging isomeric separations of halogenated benzenes, aromatic aldehydes, and aromatic anilines.

SIGNIFICANCE AND NOVELTY

To our knowledge, this is the first report on the use of the ionic liquid P[n]A as a stationary phase in chromatography, either in GC or liquid chromatography (LC) separations. This work demonstrates the promising potential of ionic liquid P[n]A stationary phases for chromatographic separations.

Sponge-like porous manganese(II, III) oxide as a coating for solvent-assisted solid-phase microextraction of polycyclic aromatic hydrocarbons followed by gas chromatography-mass spectrometry

A nanostructure sponge-like porous manganese(II, III) oxide was synthesized and applied as a new fiber coating for solvent-assisted solid-phase microextraction. The synthesized material was characterized via Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and N₂ adsorption/desorption techniques. To investigate the extraction performance of the prepared material, direct immersion solid-phase microextraction followed by gas chromatography-mass spectrometry was used for the determination of the selected polycyclic aromatic hydrocarbons in wastewater samples. Three polycyclic aromatic hydrocarbons including 1-methylnaphthalene, anthracene, and pyrene were selected as model analytes. To maximize the sensitivity of the method, key experimental factors affecting the extraction efficiency of the analytes such as ionic strength, extraction solvent, stirring rate, extraction temperature and time, and desorption temperature and time were optimized. The applicability of the new coating material for the extraction of the selected analytes from wastewater samples was evaluated. Under the optimum conditions, detection limits between 0.7 and 1.5 ng L^-1 were obtained for the model analytes. The linear dynamic range was 5.0-3.0 × 10³ ng L^-1 for all the analytes. Relative standard deviations were between 2 and 11%. In the case of real sample analysis, the extraction recoveries of the analytes were obtained in the range of 77-111%.

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).

Microextraction by packed sorbent of selected pesticides in coffee samples employing ionic liquids supported on graphene nanosheets as extraction phase

This paper describes the synthesis, characterization, and use of ionic liquids supported on silica, functionalized with graphene oxide through covalent bonding (ILz/Si@GO), as sorbents for microextraction by packed sorbent (MEPS). Seven selected pesticides (diazinon, heptachlor, aldrin, endrin, dieldrin, endosulfan, and methoxychlor), used for the prevention of pests in coffee crops, and endosulfan sulfate-an endosulfan metabolite-were selected for this study as model compounds for evaluating the sorbent performance of the synthesized materials in the MEPS device. The cycles of each of the stages were previously optimized through univariate experiments to carry out the extraction. The ILz/Si@GO phase was compared to other sorbents used in MEPS (GO, DVB-MMA, C₄/SiO₂, C₈/SiO₂, ILz/SiO₂, and bare silica) and also with graphene functionalized through other methodologies, where ILz/Si@GO showed the best results. The material was characterized using a range of techniques. The selectivity of the sorbent material and its adsorption capacity were evaluated by gas chromatography coupled with tandem mass spectrometry. The precision and accuracy of the method showed a relative standard deviation lower than 10% and recoveries from 35 to 97%. Finally, the proposed method was employed for the determination of pesticide residues in coffee samples.

Specific recognition of cationic paraquat in environmental water and vegetable samples by molecularly imprinted stir-bar sorptive extraction based on monohydroxylcucurbit[7]uril-paraquat inclusion complex

Molecularly imprinted stir-bar coatings were created based on a hydroxylcucurbit[7]uril-paraquat inclusion complex. The inclusion complex that contained paraquat (PQ) as a template and monohydroxylcucurbit[7]uril ((OH)Q[7]) as a monomer was preassembled mainly through cavity inclusion interaction of (OH)Q[7] to form a one-dimensional self-assembly structure. The inclusion complex was anchored chemically on the surface of a glass stir bar with hydroxy-terminated poly(dimethylsiloxane) by the sol-gel technique to obtain a molecularly imprinted polymer-coated stir bar (MIP-SB). The molecularly imprinted coating showed specific adsorption for cationic PQ in aqueous media. Other quaternary amine compounds with a similar structure that coexisted in the solution, such as ethyl-viologen, diquat, and difenzoquat, were almost not extracted by the prepared MIP-SB. The sorptive capacity of the MIP-SB for PQ was nearly four times that of the non-imprinted stir bar (NIP-SB). The recognition mechanism indicated that the selectivity and extraction capacity resulted mainly from the imprinted cavity in the polymer that was formed by a one-dimensional assembly structure consisting of the (OH)Q[7]-PQ inclusion complex. The imprinted cavity was complementary to the PQ in shape, size, and functionality. A method to determine PQ in environmental water and vegetable samples was developed by combining MIP-SB sorptive extraction with HPLC-UV. The linear range was from 100 to 10,000 ng L^-1 with a 8.2 ng L^-1 detection limit for water samples and 0.02-0.85 mg kg^-1 with a 0.005 mg kg^-1 detection limit for vegetable samples. The limit of detection for both samples was lower than the EU-established maximum residual levels and that of other previously reported methods. The average recoveries were 70.0-96.1% with a relative standard deviation ≤ 7.6%, which showed the successful application in real sample analysis. Molecularly imprinted stir-bar coatings were created based on a hydroxylcucurbit[7]uril-paraquat (PQ) inclusion complex, which showed a specific recognition toward cationic PQ. A method to determine PQ in environmental water and vegetable samples was established by combining MIP-SB sorptive extraction with HPLC-UV.

Helianthus-like cucurbit[4]uril and cucurbit[5]uril analogues

Two cucurbituril-like macrocycles were synthesized by condensing cyclopentano-substituted propanediurea with formaldehyde in the presence and absence of Ca²⁺.