Development of a cloud point extraction method for the determination of phenolic compounds in environmental water samples coupled with high-performance liquid chromatography

Determination of photoinitiator 4-methylbenzophenone in milk by cloud point extraction

An efficient and easy sample pretreatment methodology was proposed for the detection of photoinitiator 4-methylbenzophenone from milk before high-performance liquid chromatography. Appropriate conditions for demulsification were studied. The parameters affecting cloud point extraction, such as concentration of Tween-20, electrolyte salt, equilibration temperature, and time, have been investigated. When the spiked level was 200-1000 μg/kg, the average addition standard recovery was 99.14-105.98% with the optimum cloud point extraction conditions (concentration of Tween-20, 138 g/L; mass of anhydrous sodium sulfate, 0.75 g; equilibration temperature, 65°C; equilibration time, 30 min). To decrease the detection limits, further work about the organic solvent, shaking time, and ultrasonic parameters was carried. When the spiked level was 10-100 μg/kg, the average addition standard recovery was 70.40-106.91% with the optimum cloud point extraction and enrichment conditions (optimum cloud point extraction conditions; volume of cyclohexane, 30 mL; shaking time, 20 min; time of ultrasonic, 20 min; temperature of ultrasonic bath, 45°C).

Graphene oxide reinforced polymeric ionic liquid monolith solid-phase microextraction sorbent for high-performance liquid chromatography analysis of phenolic compounds in aqueous environmental samples

A graphene oxide reinforced polymeric ionic liquids monolith was obtained by copolymerization of graphene oxide doped 1-(3-aminopropyl)-3-(4-vinylbenzyl)imidazolium 4-styrenesulfonate monomer and 1,6-di-(3-vinylimidazolium) hexane bihexafluorophosphate cross-linking agent. Coupled to high-performance liquid chromatography, the monolith was used as a solid-phase microextraction sorbent to analyze several phenolic compounds in aqueous samples. Under the optimized extraction and desorption conditions, linear ranges were 5-400 μg/L for 3-nitrophenol, 2-nitrophenol, and 2,5-dichlorophenol and 2-400 μg/L for 4-chlorophenol, 2-methylphenol, and 2,4,6-trichlorophenol (R(2) = 0.9973-0.9988). The limits of detection were 0.5 μg/L for 3-nitrophenol and 2-nitrophenol and 0.2 μg/L for the rest of the analytes. The proposed method was used to determine target analytes in groundwater from an industrial park and river water. None of the analytes was detected. Relative recoveries were in the range of 75.5-113%.

Imprinted silica nanoparticles coated with N-propylsilylmorpholine-4-carboxamide for the determination of m-cresol in synthetic and real samples

m-Cresol-imprinted silica nanoparticles coated with N-propylsilylmorpholine-4-carboxamide have been developed that contain specific pockets for the selective uptake of m-cresol. Silica nanoparticles were synthesized by a sol-gel process followed by functionalization of their surface with N-propylsilylmorpholine-4-carboxamide. The formation of m-cresol-imprinted silica nanoparticles was confirmed by UV-Vis spectrophotometry, infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. Electron microscopic studies revealed the formation of monodispersed imprinted silica nanoparticles with spherical shape and an average size of 83 nm. The developed nanoparticles were filled in a syringe and used for the extraction of m-cresol from aqueous samples followed by quantification using high-performance liquid chromatography with diode array detection. Various adsorption experiments showed that developed m-cresol-imprinted silica nanoparticles exhibited a high adsorption capacity and selectivity and offered a fast kinetics for rebinding m-cresol. The chromatographic quantification was achieved using mobile phase consisting of acetonitrile/water (70:30 v/v) at an isocratic flow rate of 1.0 mL/min using a reversed-phase C18 column and detection at λmax = 275 nm. The limits of detection and quantification were 1.86 and 22.32 ng/mL, respectively, for the developed method. The percent recoveries ranged from 96.66-103.33% in the spiked samples. This combination of this nanotechnique with molecular imprinting was proved as a reliable, sensitive and selective method for determining the target from synthetic and real samples.

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

Here in, magnetic nanoparticles combined with graphene oxide adsorbent were fabricated via a microwave-assisted synthesis method, and used in the solid-phase extraction of three phenolic compounds (phenol, 4-nitrophenol, and m-methylphenol) in environmental water samples. Various instrumental methods were employed to characterize the magnetic nanoparticles modified with graphene oxide. The influence of experimental parameters, such as desorption conditions, amount of adsorbent, extraction time, and pH, on the extraction efficiency was investigated. Owing to the high surface area and excellent adsorption capacity of the prepared material, satisfactory extraction was achieved. Under optimum conditions, a linear response was observed in the concentration range of 1.000-100.0 μg/L for phenol, 0.996-99.6 μg/L for 4-nitrophenol, and 0.975-97.5 μg/L for m-methylphenol, with correlation coefficients in the range of 0.9995-0.9997. The limit of detection (signal-to-noise ratio of 3) of the method varied between 0.5 and 0.8 μg/L. The relative standard deviations were <5.2%. The recovery percentages of the method were in the range of 89.1-104.3%. The results indicate that the graphene oxide-modified magnetic nanoparticles possess high adsorptive abilities toward phenolic compounds in environmental water samples.