Fabrication of montmorillonite/ionic liquid composite coated solid-phase microextraction fibers for determination of phenolic compounds in fruit juices by gas chromatography and liquid chromatography

A Zn-based metal coordination cluster Zn5 used for solid phase microextraction of ten phenolic compounds from water and soil

Exploring coating materials with superior extraction efficiency has always been the pursuit in the field of solid phase microextraction (SPME). Metal coordination clusters with high thermal and chemical stability, abundant functional groups as active adsorption site are the promising coatings. In the study, a Zn₅(H₂Lⁿ)₆(NO₃)₄ (Zn₅, H₃Lⁿ =(1,2-bis-(benzo[d]imidazol-2-yl)-ethenol) cluster coating was prepared and applied for SPME of ten phenols. Zn₅ based SPME fiber exhibited high extraction efficiencies for phenols in headspace (HS) mode, which circumvented the pollution of SPME fiber. The adsorption isotherm and theoretical calculation indicated the adsorption mechanism of phenols on Zn₅ was hydrophobic interaction, H-bond interaction and π-π stacking. Under the optimized extraction conditions, an HS-SPME-GC-MS/MS method was developed for the determination of ten phenols in water and soil samples. For ten phenolic compounds in water and soil samples, the linear ranges were 0.5-5000 ng/L and 0.5-250 ng/g, respectively. The limits of detection (LODs, S/N = 3) were 0.010-1.20 ng/L and 0.0048-0.16 ng/g, respectively. The precisions of single fiber and fiber-to-fiber were lower than 9.0% and 14.1%, respectively. The proposed method was applied for the detection of ten phenolic compounds in various water and soil samples, showing satisfactory recovery (72.1-118.8%). This study delivered a novel and efficient SPME coating material for the extraction of phenols.

Ionic Liquid-Assisted DLLME and SPME for the Determination of Contaminants in Food Samples

Developing effective and green methods for food analysis and separation has become an urgent issue regarding the ever-increasing concern of food quality and safety. Ionic liquids (ILs) are a new chemical medium and soft functional material developed under the framework of green chemistry and possess many unique properties, such as low melting points, low-to-negligible vapor pressures, excellent solubility, structural designability and high thermal stability. Combining ILs with extraction techniques not only takes advantage of ILs but also overcomes the disadvantages of traditional extraction methods. This subject has attracted intensive research efforts recently. Here, we present a brief review of the current research status and latest developments regarding the application of IL-assisted microextraction, including dispersive liquid–liquid microextraction (DLLME) and solid-phase microextraction (SPME), in food analysis and separation. The practical applications of ILs in determining toxic and harmful substances in food specimens with quite different natures are summarized and discussed. The critical function of ILs and the advantages of IL-based microextraction techniques over conventional extraction techniques are discussed in detail. Additionally, the recovery of ILs using different approaches is also presented to comply with green analytical chemistry requirements.

Chitosan and dicationic ionic liquid intercalated clay-coated solid-phase microextraction fiber for determination of sixteen polycyclic aromatic hydrocarbons in coffee and tea samples

In the present study, solid-phase microextraction (SPME) fiber was prepared by coating clay (MMT)-chitosan (CH) and dicationic ionic liquid (DIL) onto the stainless-steel wire step by step. The characterization of fibers was performed by Fourier transform infrared spectroscopy, thermal analysis, x-ray diffraction analysis, and scanning electron microscopy. The prepared fibers were evaluated for separation and determination of 16 polycyclic aromatic hydrocarbons (PAHs) in coffee and tea samples in headspace- and direct immersion-SPME by coupling with gas chromatography/mass spectrometry. The analytical performance of MMT/CH/DIL fibers was carried out for the extraction of PAHs and compared with the performance of carboxen/polydimethylsiloxane (CAR/PDMS) and divinylbenzene/CAR/PDMS (DVB/CAR/PDMS) fibers under optimized conditions. The wider linear ranges between 0.001 and 25 μg L^-1 with a coefficient of determination above 0.9962, low limits of detection between 0.0001 and 0.05 μg L^-1 and good intra-day repeatability from 2.45 to 6.48 % and fiber-to-fiber reproducibility from 3.19 % to 8.82 % were obtained for all PAHs in both methods with MMT/CH/octyl (O)-DIL fiber. The extraction recoveries of coffee and tea samples ranged from 87.5 to 112 % using the MMT/CH/O-DIL fiber in both SPME methods.

Utilization of montmorillonite nanocomposite incorporated with natural biopolymers and benzyl functionalized dicationic imidazolium based ionic liquid coated fiber for solid-phase microextraction of organochlorine pesticides prior to GC/MS and GC/ECD

A novel montmorillonite clay (MMT) bionanocomposite modified with chitosan (CH), carboxymethyl cellulose (CMC), and benzylimidazolium based dicationic ionic liquid with tetraethylene glycol linker (DIL) was fabricated on stainless steel wire by in situ process. The MMT-CH-CMC-DIL coated solid-phase microextraction (SPME) fiber was examined for the determination of organochlorine pesticides (OCPs) in real samples by HS-SPME-GC method using mass spectrometry (MS) and electron capture detector (ECD). Under optimized conditions, the proposed method exhibited low limits of detection (0.5 ng L^-1 with MS and 0.1 ng L^-1 with ECD detection), good linearities (R² = 0.9972-0.9993 with MS and 0.9987-0.9998 with ECD detection), favorable single-fiber repeatability, and fiber-to-fiber reproducibility (less than 8.2% and 9.9% for both types of detection) and high reusability around 125 cycles. Recovery studies were carried out for OCPs in tap water, green tea, and milk samples to verify the applicability of the developed SPME-GC method.

Development of magnetism-assisted in-tube solid phase microextraction of phenolic acids in fruit juices prior to high-performance liquid chromatography quantification

Magnetism-assisted in-tube solid phase microextraction based on porous monolith mingled with Fe₃ O₄ nanoparticles was developed for capture of phenolic acids in fruit juices. First, poly (1-allyl-3-methylimidazolium bis [(trifluoro methyl) sulfonyl] imide-co-ethylene dimethacrylate) monolith embedded with Fe₃ O₄ nanoparticles was facile fabrication in a capillary and employed as microextraction column. Subsequently, a magnetic coil adopted to produce variable magnetic fields during extraction stage was twined on the microextraction column. The analytes contents in eluant were quantified by high performance liquid chromatogram with diode array detector. Various parameters affecting the extraction performance were inspected and optimized in detail. Results revealed that the exertion of magnetic fields in adsorption and desorption steps enhanced the extraction efficiencies of analytes from 44.9-64.0% to 78.6-87.1%. Under the optimal extraction factors, the limits of detection were between 0.012 and 0.061 μg/L, relative standard deviations for precision in terms of intra- and inter-day assay variability ranged from 1.9 to 9.8%. The introduced approach was successfully applied to simultaneously quantify the contents of five analytes in real fruit juices with satisfying fortified recoveries (80.1-116%). The obtained results well demonstrate the promising potential of the developed method in the highly sensitive quantification of trace phenolic acids in complex samples.

Wine Polyphenol Content and Its Influence on Wine Quality and Properties: A Review

Wine is one of the most consumed beverages around the world. It is composed of alcohols, sugars, acids, minerals, proteins and other compounds, such as organic acids and volatile and phenolic compounds (also called polyphenols). Polyphenols have been shown to be highly related to both (i) wine quality (color, flavor, and taste) and (ii) health-promoting properties (antioxidant and cardioprotective among others). Polyphenols can be grouped into two big families: (i) Flavonoids, including anthocyanidins, flavonols, flavanols, hydrolysable and condensed tannins, flavanones, flavones and chalcones; and (ii) Non-flavonoids, including hydroxycinnamic acids, hydroxybenzoic acids, stilbenes, tyrosol and hydroxytyrosol. Each group affects in some way the different properties of wine to a greater or a lesser extent. For that reason, the phenolic composition can be managed to obtain singular wines with specific, desirable characteristics. The current review presents a summary of the ways in which the phenolic composition of wine can be modulated, including (a) invariable factors such as variety, field management or climatic conditions; (b) pre-fermentative strategies such as maceration, thermovinification and pulsed electric field; (c) fermentative strategies such as the use of different yeasts and bacteria; and (d) post-fermentative strategies such as maceration, fining agents and aging. Finally, the different extraction methods and analytical techniques used for polyphenol detection and quantification have been also reviewed.