Adsorption efficiency enhancing of electrospun polycaprolactone nanofibers towards acidic polar drugs through the incorporation of a composite of graphene oxide nanosheets and Al30 polyoxocations: a comparative study

Extraction improvement of ionic liquid-functionalized silica by in situ anion-exchange for online solid-phase extraction of estrogens in honey

The accurate detection of analytes in honey is affected by the complex substrates, making it crucial to employ an effective sample preparation technique. In this work, an imidazolium ionic liquid was functionalized to the silica surface by a click reaction for solid-phase extraction (SPE) column, and in situ anion-exchange process was performed with different organic anions (dodecyl sulfonate, dodecyl benzene sulfonate, and naphthalene sulfonate). These SPE columns were evaluated through extracting the estrogens. The naphthalene sulfonate-based SPE column displayed the best extraction ability among these, and it was combined with high-performance liquid chromatography-diode array detection to establish an online enrichment and analysis system. Under the optimal test conditions, an online analytical method was developed, with high enrichment factors (1872-4744), wide linear ranges (0.0033-1.50, 0.0165-1.50, and 0.0330-1.50 μg g-1), and low detection limits (0.001-0.010 μg g-1). The method successfully determined several estrogens in some honey samples, and achieved satisfactory recovery results.

Development of a new strategy for the synthesis of graphene oxide-alumina nanocomposite as an efficient adsorbent for dispersive solid-phase extraction of parabens

The present study investigates the synthesis and application of the graphene oxide-alumina nanocomposite as a new adsorbent for the dispersive solid-phase extraction of three parabens and their determination using high-performance liquid chromatography-ultraviolet detection. The characterization of the synthesized material was accomplished and its size, morphology, chemical composition, porosity, and thermal stability were studied. Application of the proposed strategy for the synthesis of the nanocomposite resulted in the incorporation of Al₂ O₃ nanoparticles into graphene oxide nanosheets, further resulting in the exfoliation of graphene oxide nanosheets increasing their surface area. An orthogonal rotatable central composite design was used to optimize the extraction. Under the optimum conditions, the analytical performance of the method showed a suitable linear dynamic range (0.2-100.0 μg/L), reasonable limits of detection (0.03-0.05 μg/L), and preconcentration factors ranging from 128 to 173. Finally, the new validated method was applied for the determination of parabens in some real samples including wastewater, cream, toothpaste, and juice samples with satisfactory recoveries (88%-109%), and relative standard deviations less than 8.7% (n = 3). Results demonstrated that inserting alumina nanoparticles into graphene oxide nanosheets improved the extraction efficiency of parabens, as polar acidic compounds, by providing additional efficient interactions including hydrogen bonding, dipole-dipole, and Brønsted and Lewis acid-base interactions.

Formation of Al30 aggregates and its correlation to the coagulation effect

Al₃₀ is the polycation with the highest degree of polymerization and surface charge in the currently known structural aluminum species. It shows excellent coagulation performance in water treatment process, and has the characteristics of wide application range of pH and dosage. pH value is one of the most important factors affecting the aggregation and coagulation process of Al₃₀, but the influence of Al₃₀ aggregation reaction on its coagulation effect is still unclear. Therefore, this article reports the deprotonation and aggregation reaction of Al₃₀ by adjusting the basicity (B) of the solution, particularly to further understand the coagulation mechanism of Al₃₀ under different conditions. The results showed that in the base titration process, when B < 2.86 in 0.01 M Al₃₀ solution as Al_T (the concentration of total Al), deprotonation and preliminary aggregation mainly occurred; when B > 2.86, the size of Al₃₀ aggregates (Al₃₀agg) increased rapidly, forming gels and gradually transforming into Al(OH)₃. In this process, in addition to the reduction of electrostatic repulsion induced by Al₃₀ deprotonation, the oligomers generated by the partial dissociation of Al₃₀ also play the role of bridging-connection. Under the experimental titration conditions, the Al₃₀agg always maintained a positive zeta potential. In addition, Al₃₀ can deprotonate and aggregate at lower pH, which is an important reason for its unique coagulation characteristics. The larger structure size of Al₃₀ also made it easy to form branched aggregates, so that it can play an effective role in a wider dosage range without destabilization of colloids. This study gives an insight in the advancement of coagulants and promotes the industrial application and commercialization of functional coagulants based on polyaluminum.

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.

Electrospun polyamide/graphene oxide/polypyrrole composite nanofibers: an efficient sorbent for headspace solid phase microextraction of methamphetamine in urine samples followed by GC-MS analysis

A novel polyamide/graphene oxide/polypyrrole nanofiber was fabricated with the aid of the electrospinning technique and applied in headspace solid phase microextraction.