Evaluation of Graphene Aerogel Monolith-Based Solid-Phase Extraction for the Separation of Pyrethroids from Water Samples

Graphene-based nanomaterials as potential candidates for environmental mitigation of pesticides

Over the years, bioaccumulation of hazardous chemicals in the food chain has become a critical issue, resulting in numerous health risks. Environmental mitigation aims to clean up contaminated sites and eliminate hazardous materials from the air, water, or soil to restore the site to its original and safe condition. Pesticides constitute one of the most dangerous environmental pollutants which are generally used to increase crop production. Addressing the removal or treatment of pesticides has become pivotal in mitigating environmental threats. Diverse remediation methods are employed to protect the environment and public health. Graphene-based materials have emerged as promising candidates with exceptional properties, including excellent adsorption capacity due to their high surface area, strong hydrophilicity, and tunable properties. Owing to these properties, they have been attracting major research attention in the field of design and fabrication of materials for the mitigation of pesticides from the environment such as from contaminated food, water and other samples. Various physical, chemical and biological extraction techniques are adopted to remove pesticides. This review article provides an insight into the potential role of graphene-based materials in the environmental remediation of pesticides. We have focused on the removal of Organophosphates, Organochlorines, Carbamates and Pyrethroids present in water, fruit, vegetable and other samples, highlighting the urgent need for environmental remediation. While graphene-based materials hold potential for pesticide remediation, addressing challenges in scalable production, assessing long-term sustainability, and mitigating potential environmental impacts are critical steps for successful large-scale applications.

[Recent advance of new sample preparation materials in the analysis and detection of environmental pollutants]

To successfully analyze complex samples and detect trace targets, sample pretreatment is essential. Efficient sample pretreatment techniques can remove or reduce interference from the sample matrix. It can also enrich analytes, thereby improving analytical accuracy and sensitivity. In recent years, various sample preparation techniques, including SPE, magnetic dispersion SPE, pipette tip SPE, stir bar extraction, fiber SPME, and in-tube SPME, have received increasing attention in environmental analysis and monitoring. The extraction efficiency mainly depends on the type of adsorbent material. Therefore, the development of efficient adsorbents is a crucial step toward sample preparation. This review summarizes and discusses the research advances in extraction materials over recent years. These extraction materials contain inorganic adsorbents, organic adsorbents, and inorganic-organic hybrid materials such as graphene, graphene oxide, carbon nanotubes, inorganic aerogels, organic aerogels, triazinyl-functionalized materials, triazine-based polymers, molecularly imprinted polymers, covalent organic frameworks, metal-organic frameworks, and their derivatives. These materials have been applied to extract different types of pollutants, including metal ions, polycyclic aromatic hydrocarbons, plasticizers, alkanes, phenols, chlorophenols, chlorobenzenes, polybrominated diphenyl ethers, perfluorosulfonic acids, perfluorocarboxylic acids, estrogens, drug residues, and pesticide residues, from environmental samples (such as water and soil samples). These sample preparation materials possess high surface areas, numerous adsorption sites, and allow extraction via various mechanisms, such as π-π, electrostatic, hydrophobic, and hydrophilic interactions, as well as hydrogen and halogen bond formation. Various sample pretreatment techniques based on these extraction materials have been combined with various detection methods, including chromatography, mass spectrometry, atomic absorption spectroscopy, fluorescence spectroscopy, and ion mobility spectroscopy, and have been extensively used for the determination of environmental pollutants. The existing challenges associated with the development of sample preparation techniques are proposed, and prospects for such extraction materials in environmental analysis and monitoring are discussed. Major trends in the field, including the development of efficient extraction materials with high enrichment ability, good selectivity, excellent thermal stability, and chemical stability, are discussed. Green sample pretreatment materials, environmentally friendly synthesis methods, and green sample pretreatment methods are also explored. Rapid sample pretreatment methods that can be conducted within minutes or seconds are of significant interest. Further, online sample pretreatment and automatic analysis methods have attracted increasing attention. Besides, real-time analysis and in situ detection have been important development directions, and are expected to be widely applicable in environmental analysis, biological detection, and other fields. Modern synthesis technology should be introduced to synthesize specific extraction materials. Controllable preparation methods for extraction materials, such as the in situ growth or in situ preparation of extraction coatings, will acquire importance in coming years. It will also be important to adopt high-performance materials from other fields for sample pretreatment. Organic-inorganic hybrid extraction materials can combine the advantages both organic materials and inorganic materials, and mutually compensate for any disadvantages. Extraction materials doped with nanomaterials are also promising. Although existing sample pretreatment techniques are relatively efficient, it is still imperative to develop novel sample preparation methods.

In-syringe extraction using compressible and self-recoverable, amphiphilic graphene aerogel as sorbent for determination of phenols

Graphene aerogels (GAs) have demonstrated great promise as sorbent materials. However, the intrinsically hydrophobic GAs are unsuitable for extraction of highly water-soluble analytes. Moreover, lack of compressibility limits the recyclability of GAs. In this work, an interesting type of water-induced self-recoverable amphiphilic GA was synthesized and employed as sorbent to extract nine priority phenols, listed as priority pollutants by the United States Environmental Protection Agency, from aqueous samples. The water-induced self-recoverability gives the GA the characteristic of a sponge, providing high recyclability and long-life. The aerogel was placed in a 2-mL microsyringe for in-syringe extraction of the phenols. The GA exhibits amphiphilicity due to the cross-linking by polyvinyl alcohol. At the same time, it exhibited selectivity to the water-soluble phenols. The extracted phenols were eluted with acetonitrile from the GA and the final extract was analyzed by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). The results showed that this method provided low limits of detection for the phenols (0.089-0.015 µg/L), good linearity (r² ≥ 0.9956) and low relative standard deviations (≤6.8%). The optimized method was applied successfully to river water samples. The simple in-syringe extraction procedure in combination with HPLC-UV analysis was demonstrated to be efficient, fast and convenient.