Microwave-assisted preparation of magnetic nanoparticles modified with graphene oxide for the extraction and analysis of phenolic compounds

Recent Trends in Graphene-Based Sorbents for LC Analysis of Food and Environmental Water Samples

This review provides an overview of recent advancements in applying graphene-based materials as sorbents for liquid chromatography (LC) analysis. Graphene-based materials are promising for analytical chemistry, including applications as sorbents in liquid chromatography. These sorbents can be functionalized to produce unique extraction or stationary phases. Additionally, graphene-based sorbents can be supported in various materials and have consequently been applied to produce various devices for sample preparation. Graphene-based sorbents are employed in diverse applications, including food and environmental LC analysis. This review summarizes the application of graphene-based materials in food and environmental water analysis in the last five years (2019 to 2023). Offline and online sample preparation methods, such as dispersive solid phase microextraction, stir bar sorptive extraction, pipette tip solid phase extraction, in-tube solid-phase microextraction, and others, are reviewed. The review also summarizes the application of the columns produced with graphene-based materials in separating food and water components and contaminants. Graphene-based materials have been reported as stationary phases for LC columns. Graphene-based stationary phases have been reported in packed, monolithic, and open tubular columns and have been used in LC and capillary electrochromatography modes.

Synthesis of natural proanthocyanidin based novel magnetic nanoporous organic polymer as advanced sorbent for neonicotinoid insecticides

In this work, a natural proanthocyanidin (PA) based magnetic nanoporous organic polymer (named as PA-MOP) was successfully synthesized for the first time. The PA-MOP possessed high hydrophilic-surface, good magnetic responsiveness and high affinity for neonicotinoid insecticides. It was applied as an advanced magnetic sorbent for extraction of four neonicotinoids (thiamethoxam, imidacloprid, acetamiprid and thiacloprid) from environmental water, peach juice and honey samples prior to HPLC analysis. Under optimal conditions, the limits of detection for the analytes at S/N = 3 were 0.02-0.08 ng mL^-1 for water, 0.03-0.10 ng mL^-1 for peach juice and 0.05-0.16 ng g^-1 for honey sample. The method recoveries were 80.0%-114.8%, with the relative standard deviations below 6.8%. The values of matrix effect were from -1.5% to -9.3%. Based on theory calculation, the extraction mechanism can be attributed to multiple interactions between the PA-MOP and the neonicotinoids, in which hydrogen bonding, π-π stacking and electrostatic interactions are the major interactions.

Sensing Methods for Hazardous Phenolic Compounds Based on Graphene and Conducting Polymers-Based Materials

It has been known for years that the phenolic compounds are able to exert harmful effects toward living organisms including humans due to their high toxicity. Living organisms were exposed to these phenolic compounds as they were released into the environment as waste products from several fast-growing industries. In this regard, tremendous efforts have been made by researchers to develop sensing methods for the detection of these phenolic compounds. Graphene and conducting polymers-based materials have arisen as a high potential sensing layer to improve the performance of the developed sensors. Henceforth, this paper reviews the existing investigations on graphene and conducting polymer-based materials incorporated with various sensors that aimed to detect hazardous phenolic compounds, i.e., phenol, 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, and 2,4-dimethylphenol. The whole picture and up-to-date information on the graphene and conducting polymers-based sensors are arranged in systematic chronological order to provide a clearer insight in this research area. The future perspectives of this study are also included, and the development of sensing methods for hazardous phenolic compounds using graphene and conducting polymers-based materials is expected to grow more in the future.

The Current Role of Graphene-Based Nanomaterials in the Sample Preparation Arena

Since its discovery in 2004 by Novoselov et al., graphene has attracted increasing attention in the scientific community due to its excellent physical and chemical properties, such as thermal/mechanical resistance, electronic stability, high Young's modulus, and fast mobility of charged atoms. In addition, other remarkable characteristics support its use in analytical chemistry, especially as sorbent. For these reasons, graphene-based materials (GBMs) have been used as a promising material in sample preparation. Graphene and graphene oxide, owing to their excellent physical and chemical properties as a large surface area, good mechanical strength, thermal stability, and delocalized π-electrons, are ideal sorbents, especially for molecules containing aromatic rings. They have been used in several sample preparation techniques such as solid-phase extraction (SPE), stir bar sorptive extraction (SBSE), magnetic solid-phase extraction (MSPE), as well as in miniaturized modes as solid-phase microextraction (SPME) in their different configurations. However, the reduced size and weight of graphene sheets can limit their use since they commonly aggregate to each other, causing clogging in high-pressure extractive devices. One way to overcome it and other drawbacks consists of covalently attaching the graphene sheets to support materials (e.g., silica, polymers, and magnetically modified supports). Also, graphene-based materials can be further chemically modified to favor some interactions with specific analytes, resulting in more efficient hybrid sorbents with higher selectivity for specific chemical classes. As a result of this wide variety of graphene-based sorbents, several studies have shown the current potential of applying GBMs in different fields such as food, biological, pharmaceutical, and environmental applications. Within such a context, this review will focus on the last five years of achievements in graphene-based materials for sample preparation techniques highlighting their synthesis, chemical structure, and potential application for the extraction of target analytes in different complex matrices.

Extraction of phenolic compounds from water samples by dispersive micro-solid-phase extraction

In this article, the use of magnetically separable sorbent polyaniline/silica-coated nickel nanoparticles is evaluated under a dispersive micro-solid-phase extraction approach for the extraction of phenolic compounds from water samples. The sorbent was prepared by in situ chemical polymerization of aniline on the surface of silica-modified nickel nanoparticles and was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, and vibrating sample magnetometry. Effective variables such as amount of sorbent (milligrams), pH and ionic strength of sample solution, volume of eluent solvent (microliters), vortex, and ultrasonic times (minutes) were investigated by fractional factorial design. The significant variables optimized by a Box-Behnken design were combined by a desirability function. Under the optimized conditions, the calibration graphs of analytes were linear in a concentration range of 0.02-100 μg/mL, and with correlation coefficients more than 0.999. The limits of detection and quantification were in the ranges of 10-23 and 33-77 μg/L, respectively. This procedure was successfully employed in the determination of target analytes in spiked water samples; the relative mean recoveries ranged from 96 to 105%.

Ionic liquid-coated Fe3O4/APTES/graphene oxide nanocomposites: synthesis, characterization and evaluation in protein extraction processes

A magnetic solid-phase extraction (MSPE) procedure with ionic liquid (IL) coated 3-aminopropyltriethoxysilane (APTES)-Fe₃O₄ grafted graphene oxide (GO) nanocomposite (Fe₃O₄/APTES/GO/IL) as adsorbent has been developed for protein extraction.