Trace analysis of quercetin in tea samples by HPLC-DAD system by means of a new nanocomposite including magnetic core-shell

Fe3O4@SiO2/GO/HKUST-1 nanocomposite for quercetin extraction and preconcentration followed by its determination using HPLC

Quercetin, a key flavonoid found in many fruits and vegetables, offers notable health benefits, including antioxidant, antiviral, and antitumor properties. Yet, isolating it from complex plant materials is challenging. This research aimed to develop a selective and efficient sorbent to clean up real sample matrices and pre-concentrate quercetin, enhancing its detection using high-performance liquid chromatography (HPLC). Several metal organic frameworks (MOFs) were synthesized and initially, their abilities to sorption of quercetin from aqueous and alcohol media were examined. Among them, HKUST-1 showed the best performance. To improve the efficiency of this MOF, its composite with graphene oxide (GO) was prepared (Fe3O4@SiO2/GO/HKUST-1) and was employed for quercetin extraction through magnetic dispersive micro solid-phase extraction. The effect of different parameters was examined and the kinetic, thermodynamic, and isotherm of the sorption process was studied. The related results showed the system followed the pseudo-second-order kinetic model, with the Temkin and Langmuir isotherm models applicable in aqueous and methanol solutions, respectively. The method enabled rapid preconcentration and clean up within 20 min, with a 99.6% adsorption efficiency using just 5 mg of sorbent. The nanocomposite demonstrated an adsorption capacity of 29.3 mg/g and effectively extracted quercetin from red onion samples, achieving recovery rates between 75% and 98% for HPLC-diode array detector analysis. PRACTICAL APPLICATION: Quercetin is a common polyphenolic compound, which is widely found in plant materials such as onions. Owing to its medicinal effects including anti-inflammatory, anti-oxidant, anti-cancer, cardioprotective, anti-bacterial, anti-viral, and anti-allergic features, it has widespread usage in pharmacology and preparation of food preservers. In this study, Fe3O4@SiO2/GO/HKUST-1 nanocomposite was synthesized for extraction and preconcentration of quercetin from an onion sample. Very low amounts of this sorbent indicated high adsorption percentage and adsorption capacity for quercetin. This method was simple, fast, cost-effective, precise, and accurate, which exhibited a potential for extraction of quercetin in a large scale.

Application of magnetic solid-phase extraction for sensitive determination of anticancer drugs in urine by means of diamino benzidine tetrachlorohydrate modified magnetic nanoparticles

BACKGROUND

The analysis of drug active molecules and residues in the treatment of cancer is important for the sustainability of human life and therapeutic effects. For this purpose, a new magnetic sorbent was developed to use in solid phase extraction prior to conventional high-performance liquid chromatography (HPLC) analysis of Paclitaxel (PAC) and Gemcitabine (GEM) molecules.

METHODS

In this study, a separation and pre-concentration approach based on magnetic solid phase extraction (MSPE) was proposed for PAC and GEM by means of using a newly synthesized magnetic sorbent. After the MSPE procedure, an HPLC system with a diode array detector (DAD) was used to analyze trace amounts of PAC and GEM anticarcinogenic drugs in urine samples. Surface modification of magnetic Fe₃O₄ nanoparticles was carried out by diaminobenzidinetetrachloro hydrate (DABTC) for the first time and a useful sorbent was obtained for MSPE experiments.

RESULTS

In the proposed method, PAC and GEM molecules were retained on the c in the presence of a pH 5.0 medium and desorbed to 300 μL of acetonitrile: methyl alcohol (1:1) eluent phase before HPLC-DAD analysis. Under the optimized conditions, the limit of detection (LOD) values for PAC and GEM were 1.38 and 1.44 ng mL^-1 while the enhancement factor for PAC and GEM were 139.5 and 145.3, respectively. The relative standard deviations (RSD %) for PAC and GEM were below 3.50% in inter-day repeated experiments by means of model solutions containing 100 ng mL^-1 drug active ingredients.

CONCLUSIONS

Synthesis and characterization of DABTC-Fe₃O₄ nanoparticles were performed using suitable methodologies. Optimization of MSPE was done step by step. And finally, the developed method was successfully applied to urine samples with quantitative recoveries in the range of 99.0% and 105.0%.

Magnetic nanofluid based on green deep eutectic solvent for enrichment and determination of chloramphenicol in milk and chicken samples by high-performance liquid chromatography-ultraviolet: Optimization of microextraction

In this work, magnetic nanofluid based on a deep eutectic solvent that constricts through a simple and easy route, and subsequently applied for the preconcentration and microextraction of chloramphenicol (CAP) as a hazardous drug from milk and chicken samples via syringe-to-syringe microextraction prior to its determination by high-performance liquid chromatography-ultraviolet (HPLC-UV). In addition, the optimum conditions of effective factors were searched by the central composite design (CCD), and subsequently, at their optimum value, the figures of merit were evaluated. Also, the suggested method illustrated a low limit of detection (0.2 ng mL^-1), a low limit of quantitation (0.67 ng mL^-1), and a good linear range with an R² of 0.996. The CAP relative recoveries in milk and chicken samples were 90.3%-95.1%, with relative standard deviations lower than 4.2%. The current enhancement technique is simple, easy, and rapid, which makes it suitable for quantification of CAP by HPLC-UV at trace levels in complicated materials with reliable and reproducible results.

Application of micro-nanostructured magnetite in separating tetrabromobisphenol A and hexabromocyclododecane from environmental water by magnetic solid phase extraction

Two typical brominated flame retardants (BFRs), namely, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD), were persistent organic pollutants widely detected in various environmental media. This study aimed to successfully synthesize micro-nano-structured magnetite particles (MNMPs) with surface modification by citric acid molecules. The synthesized composites served as an adsorbent for extracting TBBPA and HBCD from environmental water samples followed by gas chromatography–mass spectrometry analysis. The obtained MNMPs were characterized in terms of crystal structure, morphology, size distribution, hydrophobic and hydrophilic performance and magnetism. The results indicated that the MNMPs exhibited high surface area, good dispersibility, and strong magnetic responsiveness for separation. The parameters affecting the extraction efficiency were optimized, including sample pH, amount of sorbents, extraction time and desorption conditions. Under the optimum conditions, the recovery was 83.5 and 107.1%, limit of detection was 0.13 and 0.35μg/mL (S/N = 3), and limit of quantification was 0.37 and 0.59 μg/mL (S/N = 10) for TBBPA and HBCD respectively. The relative standard deviations obtained using the proposed method were less than 8.7%, indicating that the MNMP magnetic solid-phase extraction method had advantages of simplicity, good sensitivity and high efficiency for the extraction of the two BFRs from environmental water.

Three-dimensional assembly and disassembly of Fe3O4-decorated porous carbon nanocomposite with enhanced transversal relaxation for magnetic resonance sensing of bisphenol A

The design and construction of a novel magnetic resonance sensor (MRS) is presented for bisphenol A (BPA) detection. The MRS has been built based on the core component of magnetic Fe₃O₄ nanoparticles (~ 40 nm), which were uniformly distributed in nanoporous carbon (abbreviated as Fe₃O₄@NPC). The synthesis was derived from the calcination of the metal organic framework (MOF) precursor of Fe-MIL-101 at high temperature. Fe₃O₄@NPC was confirmed with enhanced transversal relaxation with r₂ value of 118.2 mM^-1 s^-1, which was around 1.7 times higher than that of the naked Fe₃O₄ nanoparticle. This enhancement is attributed to the excellent proton transverse relaxation rate of Fe₃O₄@NPC caused by the reduced self-diffusion coefficient of water molecules in the vicinity of Fe₃O₄ nanoparticles in the nanoporous carbon. BPA antibody (Ab) and antigen (Ag)-ovalbumin (OVA) were immobilized onto the Fe₃O₄@NPC to form Ab-Fe₃O₄@NPC and Ag-Fe₃O₄@NPC, respectively. These two composites can cause the three-dimensional assembly of Fe₃O₄@NPC via immunological recognition. The presence of BPA can compete with antigen-OVA to combine with Ab-Fe₃O₄@NPC, thereby breaking the assembly process (disassembly). The difference in the change of the T₂ value before and after adding BPA can thus be used to monitor BPA. The proposed MRS not only revealed a wide linear range of BPA concentration from 0.05 to 50 ng mL^-1 with an extremely low detection limit of 0.012 ng mL^-1 (S/N = 3), but also displayed high selectivity towards matrix interferences. The recoveries of BPA ranged from 95.6 to 108.4% for spiked tea π, and 93.4 to 104.7% for spiked canned oranges samples, respectively, and the RSD (n = 3) was less than 4.4% for 3 successive assays. The versatility of Fe₃O₄@NPC with customized relaxation responses provides the possibility for the adaptation of magnetic resonance platforms for food safety development. The magnetic Fe3O4 nanoparticles are uniformly dispersed in the nanoporous carbon (Fe3O4@NPC), which derived from the calcinating of the metal organic framework (MOF) precursor of Fe-MIL-101. And the magnetic Fe₃O₄@NPCs are adopted for the construction of magnetic resonance sensor (MRS) for bisphenol A (BPA) detection.

An environmentally friendly and novel amine-based liquid phase microextraction of quercetin in food samples prior to its determination by UV-vis spectrophotometry

A novel and environmentally-friendly method, which includes determination of trace amounts of quercetin in samples by using UV-vis spectrophotometry after enrichment with amine-based liquid phase microextraction (LPME), has been developed. As extraction solvent, N,N-dimethyl-n-octylamine has been used and the quercetin concentration in extraction phase was determined by UV-vis spectrophotometry at 382.5 nm. Important analytical parameters such as pH, extraction solvent type and volume, sample volume, extraction time were optimized by the method. Quercetin in the sample solution was extracted to 200 μL of N,N-dimethyl-n-octylamine phase at pH 4.0. The detection limit (LOD) and the quantitation limit (LOQ) values for quercetin were calculated as 0.07 μg·mL^-1 and 0.24 μg·mL^-1, respectively. Accuracy studies for the food samples was carried out by addition and recovery experiments. The developed method has been successfully applied to different food samples including spinach, green pepper, red onion and dill weed.