Phosphorus-doped deep eutectic solvent-derived carbon dots-modified silica as a mixed-mode stationary phase for reversed-phase and hydrophilic interaction chromatography.

In this work, phosphorus-doped carbon dots (P-DESCDs) were successfully prepared using choline chloride/lactic acid type deep eutectic solvent and phosphoric acid as ingredients, and (3-aminopropyl) trimethoxysilane was used as a bridge to graft P-DESCDs onto the silica surface to obtain a new mixed-mode stationary phase (Sil-P-DESCDs) for reversed-phase and hydrophilic interaction liquid chromatography. The successful preparation of the stationary phase was confirmed by laser scanning confocal microscopy, elemental analysis, and Fourier transform infrared spectrometry. Interestingly, the doping of phosphorus greatly improved the separation performance and hydrophilicity of the Sil-P-DESCDs column. The Sil-P-DESCDs column was found to have certain hydrophobicity, hydrogen bonding ability and shape selectivity by Tanaka and Engelhardt standard test mixtures, and a series of hydrophilic and hydrophobic compounds such as alkylbenzenes, polycyclic aromatic hydrocarbons, sulfonamides, aromatic amines, phenols, flavonoids, nucleoside bases, and alkaloids. In addition, the effects of mobile phase ratio, column temperature, flow rate, salt concentration, and pH on the retention of analytes on Sil-P-DESCDs columns were investigated. Finally, the Sil-P-DESCDs column was applied to the qualitative and quantitative analysis of calcein-7-glucoside in the real sample of medicinal Astragalus pellets, and it was found at a concentration of 0.02 mg/mL.

Preparation of magnetic nitrogen-doped porous carbon by incomplete combustion with solvothermal synthesis for magnetic solid-phase extraction of benzoylurea insecticides from environmental water.

In this work, magnetic nitrogen-doped porous carbon (Fe3O4@N-PC) was prepared via incomplete combustion coupled with solvothermal synthesis for extraction of four benzoylureas (BUs) insecticides. Among them, nitrogen-doped porous carbon was produced through incomplete combustion of filter paper loaded with mixture formed by Zn(NO3)2·6H2O and polyethyleneimine solution, and magnetic nanoparticles were further introduced by solvothermal method. Compared with magnetic porous carbon (Fe3O4@PC), the surface hydrophilicity of Fe3O4@N-PC was improved by virtue of the doping of nitrogen atoms, and the dispersion of Fe3O4 was more uniform, which greatly exposed the adsorption site. The characterization of Fe3O4@N-PC were carried out by TEM, XRD, elemental analysis, XPS, BET and magnetic hysteresis curve. Besides, Fe3O4@N-PC was successfully used as magnetic solid-phase extraction (MSPE) adsorbent, which showed excellent enrichment factors and extraction recoveries toward polar BUs insecticides due to the polar surface and introduction of Lewis-basic nitrogen. The optimum amount of Fe3O4@N-PC adsorbent, extraction time, pH value, desorption solvent, desorption time and PEI concentration for BUs insecticides extraction were determined to be 3 mg, 10 min, 8, acetone/acetic acid (19:1, V/V), 6 min and 60 g L-1, respectively. Under this experimental condition, the enrichment factors ranged from 182 to 192 with good intra- and inter-day relative standard deviations (RSDs). The calibration lines were linear over the concentration in the range of 1-800 µg L-1, the limit of detection (LOD) and limit of quantification (LOQ) were 0.3 µg L-1 as well as 1 µg L-1, respectively. The recoveries for spiked sample ranged from 90.7 to 107.3% in spiked Yellow River water with the RSDs less than 7.0%. The results showed that the established MSPE strategy based on Fe3O4@N-PC could be used for the detection of trace BUs in complex samples.

Deep eutectic solvents-derivated carbon dots-decorated silica stationary phase with enhanced separation selectivity in reversed-phase liquid chromatography.

In this work, deep eutectic solvents-based carbon dots (DESCDs) were prepared and bonded to the silica surface for the first time to form a new hydrophobic chromatographic stationary phase (Sil-DESCDs). The successful preparation of DESCDs and Sil-DESCDs were demonstrated by a series of characterizations including transmission electron microscopies, laser scanning confocal microscope, Fourier transform infrared spectrometry, elemental analysis, etc. Retention behavior of Sil-DESCDs was evaluated using Tanaka and Engelhardt standard test mixtures. The results showed that this new stationary phase had excellent separation performance for polycyclic aromatic hydrocarbons, flavonoids, aromatic amines and phenolic compounds. Excellent separation selectivity for the 3-phenylene ring isomers including phenanthrene and anthracene, the 4-phenylene ring isomers including pyrene, triphenylene, chrysene and 1,2-benzanthracene was also obtained. Especially, prednisolone and hydrocortisone, which have very similar structures, can be separated using pure water as the mobile phase. In addition, the flavonoids in Astragalus extracts including calycosin-7-glucoside, ononin, calycosin and formononetin were determined using this new column, their concentrations were 0.050, 0.031, 0.023 and 0.034 mg/mL, respectively.