Liquid chromatographic determination of trace levels of nitrophenols in water samples after dispersive magnetic solid phase extraction

Nitrophenols in the environment: An update on pretreatment and analysis techniques since 2017

Nitrophenols, a versatile intermediate, have been widely used in leather, medicine, chemical synthesis, and other fields. Because these components are widely applied, they can enter the environment through various routes, leading to many hazards and toxicities. There has been a recent surge in the development of simple, rapid, environmentally friendly, and effective techniques for determining these environmental pollutants. This review provides a comprehensive overview of the latest research progress on the pretreatment and analysis methods of nitrophenols since 2017, with a focus on environmental samples. Pretreatment methods include liquid-liquid extraction, solid-phase extraction, dispersive extraction, and microextraction methods. Analysis methods mainly include liquid chromatography-based methods, gas chromatography-based methods, supercritical fluid chromatography. In addition, this review also discusses and compares the advantages/disadvantages and development prospects of different pretreatment and analysis methods to provide a reference for further research.

Polyaniline-co-polyindole functionalized magnetic porous carbon derived from MIL-53(Fe) for separation/enrichment of nitrophenols pollutants before determination with high-performance liquid chromatography-ultraviolet detection

Herein, a novel polyaniline-co-polyindole functionalized magnetic porous carbon derived from MIL-53(Fe) was prepared and employed as an excellent nano-adsorbent to preconcentrate trace amounts of nitro-phenols in water and wastewater samples. Briefly, magnetic MIL-53(Fe) was synthesized by the addition of magnetite nanoparticles, terephthalic acid, and FeCl3 to the reaction medium. The magnetic MIL-53(Fe) was pyrolyzed under nitrogen protection to obtain a magnetic porous carbon nanocomposite, and finally, the nanomaterial was functionalized with polyaniline-co-polyindole via oxidation polymerization. The obtained nano-adsorbent was characterized via X-ray diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, and transmission and scanning electron microscopies. After that, the fabricated nano-material was utilized as an excellent nano-adsorbent for the preconcentration of trace nitro-phenols (2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol) in environmental water, and wastewater samples. The detection limits were obtained from 0.1 to 0.15 μg/L after performing the optimization process. The new method was in the range of 0.4-300 μg/L. The proposed method exhibited a good precision from 3.2% to 9.6% for within-day assay, and 5.2%-13.2% for between-day assay at three concentration levels (1, 50, and 250 μg/L). Eventually, this method was utilized to preconcentrate/determine the target analytes in three water, and wastewater samples, satisfactory (relative standard deviations, 5.4%-9.3%; relative recovery, 88%-109%).

A novel poly(2-mercaptobenzothiazole) coated magnetic nanoadsorbent derived from ZIF-8 for preconcentration/determination of palladium and silver

Herein, a novel poly(2-mercaptobenzothiazole) coated magnetic nanoadsorbent derived from zeolitic-imidazole framework-8 (ZIF-8) was synthesized and then employed for the extraction/preconcentration of trace amounts of palladium and silver in various real matrixes. In this way, magnetite was fabricated first, and then functionalized with tetraethyl orthosilicate. After that, the synthesized magnetite@silica was coated with the ZIF-8 to obtain magnetic ZIF-8. Afterward, the magnetic ZIF-8 was pyrolyzed under the protection of a nitrogen atmosphere to get a magnetic carbon nanoadsorbent. Finally, the magnetic carbon was functionalized with a conductive polymer (poly-2-mercaptobenzothiazole). Fabrication of the nanoadsorbent was affirmed with scanning and transmission electron microscopies, elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The method is linear from 0.25 to 200 μg L^-1 for silver, and from 0.5 to 250 μg L^-1 for palladium. The detection limits are 0.07 and 0.15 μg L^-1 for Ag and Pd, respectively. The precision was evaluated at three concentration levels (1, 75, 200 μg L^-1, n = 5) and all the relative standard deviation (RSD) values were lower than 10.3%. In the end, the new method was utilized for the preconcentration/determination of trace amounts of palladium and silver in various real matrixes, satisfactorily (relative recovery: 86% to 104%; RSD%: 4.0-9.5%).

Determination of phenols in natural and waste waters by capillary electrophoresis after preconcentration on magnetic nanoparticles coated with aminated hypercrosslinked polystyrene

An efficient sorbent for magnetic solid-phase extraction was developed from Fe₃ O₄ nanoparticles covered with aminated hypercrosslinked polystyrene. The sorbent has a saturation magnetization of 47 emu/g and a surface area of 509 mg/g and was tested for the extraction of 11 phenols from aqueous media. The optimum conditions were as follows: pH 3; adsorbent mass, 20.0 mg; adsorption time, 30 min; eluent (acetone) volume, 0.5 mL; and desorption time, 5 min. The enrichment factor after desorption reached 1595-1716 and the maximum adsorption capacity was 501-909 mg/g. Capillary electrophoresis was applied successively to separate 11 phenols after solid-phase extraction. The best separation was achieved using a fused silica capillary and borate buffer (pH 10.7) as a supporting electrolyte. After optimization, the linearity range was from 0.2 to 950 μg/L, and the limits of detection were 0.05-0.2 μg/L. The relative standard deviation varied from 6.1 to 8.7% (C = 1 μg/L) and from 2.9 to 3.5% (C = 500 μg/L). The determination of phenols is complicated in eutrophic water and spring water with a high content of humic and fulvic acids.

Dispersive solid-phase extraction of buprenorphine from biological fluids using metal-organic frameworks and its determination by ultra-performance liquid chromatography

In this work, various types of metal-organic frameworks were synthesized, and their affinities toward buprenorphine were evaluated using dispersive solid-phase extraction. The extracted buprenorphine was determined by ultra high performance liquid chromatography-ultraviolet detection system. The highest extraction recovery was observed by employing zeolitic imidazole framework-67. Then, a facile and fast extraction method was designed for the extraction and purification of the target drug. Optimization of the extraction method was carried out by the design of experiment approach. A linearity range of 1-1000 μg/L with the limit of detection of 0.15 μg/L and relative standard deviations (50 μg/L, n = 5) of 3.4% was obtained for standard sample analysis. Under optimized experimental and instrumental conditions, the relative recoveries were in the range of 95 to 111%. Eventually, zeolitic imidazole framework-67 was successfully employed for the extraction and determination of buprenorphine in the biological fluids with satisfactory results.