Based On Low Dimensional VgC 3 NResearch And Application Of High-efficiency Sample Processing Technology For 4 /Fe 3 O 4 Nanocomposites

Analytical chemistry is a significant instrument and widely used in a number of scientific fields such as environmental monitoring, food industry, epidemiology,biomedical sciences, and pharmaceutical chemistry. A complete analytical strategic method requires a lot of steps, starting from sample collection and ending with final result analysis report,to speak in general terms,the general steps of analytical process include sample preparation, separation, and quantification of analytes, clean-up, pre-concentration, fractioning of samples are some of time-consuming and vulnerable to mistakes, because a great deal of target analytes will be lost in these tedious and inadequate sample pretreatment steps, besides, the direct determination of extremely low concentration of analytes could be difficult, owing to matrix interferences of insufficient sensitivity of analytical techniques. They are critical steps as many errors occurring in these process and would lead to imprecision and inaccuracy in final results.Therefore, the preliminary separation and preconcentration of trace analytes is usually required.Solid-phase extraction ?SPE? technique has attracted a great deal of attention owing to its high enrichment factor, low limit of detection and stable recovery. SPE based on the partition coefficient of the analytes between the mobile phase and the solid sorbent. Magnetic solid phase extraction ?MSPE? has attracted a lot of attention for its interesting procedure which the magnetic sorbents is dispersive in a large sample solution volumes and the analyte is separated by an external magnetic field ?magnet?,this new technique not only simplify the procedure of solid phase extraction but also increase the extraction efficiency.Velvet-like graphitic carbon nitride?v-g-C₃N₄?, a new two-dimensional ?2D? material was synthesized via a water-assisted, one-step thermal condensation of urea, consisting of conjugated planes containing tri-s-triazine repeating units stacked through van der Waals interactions, has attracted a great deal of attention owing to its unique physicochemical properties. The strong covalent bonds between the carbon and the nitrogen atoms in v-g-C₃N₄ impart great Physicochemical stability to the material all owing it to withstand acids, alkalis and high temperatures. Compared to the complex structure of some sorbents, the simple 2D structure of V-g-C₃N₄ is beneficial for fast adsorption and desorption of molecules with concurrent high recovery and low solvent consumption. The g-C₃N₄ sheets have a double-sided polyaromatic scaffold structure with a large ?-electron system which provides it with a strong affinity for aromatic compounds that are commonly present in pollutants and biomolecules. However, the direct use of V-g-C₃N₄ sheets as SPE sorbents has several problems. The small sized nanoparticle may escape from the SPE column, and the good dispersity of V-g-C₃N₄ may make it difficult to separate from the solution. To solve the problem and maintain the advantageous properties, immobilizing Fe₃O₄ particles on the surface of the nanosheets is an effective solution, as they can then be easily separated from the solution with an external magnet for sample elution and material reuse. The use of a magnetic material in SPE has been referred to as magnetic solid phase extraction?MSPE?.Moreover, the existing hydroxyl group on hydrolyzed Fe₃O₄ particles can provide hydrogen bonding interaction with the target compounds for enhancing the adsorption. On the other hand, the MSPE procedure could be improved to increase the extraction efficiency and reduce time.For these significant advantages, Magnetic velvet-like graphitic carbon nitride?V-g-C₃N₄/Fe₃O₄? was used for rapid 1 min extraction of flavonoids from different tea extracts by co-solvent enhanced adsorptive magnetic solid phase extraction. The improvement can increase the efficiency and selectivity of MSPE so that the rapid extraction of target analytes can be achieved. To verify the improved efficiency of this method,four flavonoids including quercetin, apigenin, kaempferol and myricetin were used as the model analytes. The adsorption conditions were optimized by a statistical method known as response surface methodology ?RSM?, and all contributing factors were investigated. Because the amounts of flavonoids is different in different tea extracts, the amounts of sorbent used for MSPE of the flavonoids were optimized. This enhanced adsorptive MSPE method provides a rapid and effective extraction of this kind of compounds. The synergistic effects improved the extraction rate of flavonoids with excellent reproducibility ?88.2-107.2%?, sensitivity ?limits of detection LOD S/N=3?: 0.075-0. lmg/mL) and recoveries ?88.2-107.2%?-. This study demonstrated the potential to apply this method for various target analytes from complex sample matricesIn order to further efficiency of enrichment and preconcentration, porous V-g-C₃N₄/Fe₃O₄ was synthesis by co-precipitation method. Some of polychlorinated biphenyls ?CBs? were selected as model compounds to evaluate the possible application of this nanosheet composite. The advantages of this nanocomposite such as large surface area, good dispersity, low solvent consumption, rapid analyte adsorption ?30 s?and reusability make it a good sorbent. Factors affecting extraction efficiency were systematically investigated and optimized by response surface methodology ?RSM?.Under optimal experimental conditions, the limits of detection ?LODs S/N = 3? of the developed method for CBs investigated were in the range of 9.0×10-6-5.8 × 10-5 ug/mL. This method was then used for the analysis of four real water samples. Good spiked recoveries over the range of 80.1 -118.4%, and RSDs ?n = 5? of 0.02-3.7% were obtained. This work demonstrated the potential of using. this nanocomposite for adsorption, pre-concentration, or even removal of different carbon-based aromatic compounds or other hydrophobic pollutants.