ABSTRACT
A new detection platform based on a hydroxylated covalent organic framework (COF) integrated with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was constructed and used for detecting adrenergic receptor agonists (ARAs) residues in milk. The hydroxylated COF was prepared by polymerization of tris(4-aminophenyl)amine and 1,3,5-tris(4-formyl-3-hydroxyphenyl)benzene and applied to solid-phase extraction (SPE) of ARAs. This hydroxylated COF was featured with hierarchical flower-like morphology, easy preparation, and copious active adsorption sites. The adsorption model fittings and molecular simulation were applied to explore the potential adsorption mechanism. This detection platform was suitable for detecting four α2- and five ß2-ARAs residues in milk. The linear ranges of the ARAs were from 0.25 to 50 µg·kg-1; the intra-day and the inter-day repeatability were in the range 2.9-7.9% and 2.0-10.1%, respectively. This work demonstrates this hydroxylated COF has great potential as SPE cartridge packing, and provides a new way to determine ARAs residues in milk.
Subject(s)
Milk , Solid Phase Extraction , Tandem Mass Spectrometry , Solid Phase Extraction/methods , Milk/chemistry , Animals , Tandem Mass Spectrometry/methods , Hydroxylation , Metal-Organic Frameworks/chemistry , Adsorption , Adrenergic Agonists/chemistry , Adrenergic Agonists/analysis , Limit of Detection , CattleABSTRACT
A fluorometric and colorimetric dual-modal nanoprobe (denoted as Fe2+-Phen/SiNPs) has been developed for selective and sensitive determination of nitrite (NO2-). The mechanism is based on fluorescence quenching between silicon nanoparticles (SiNPs) and Fe(II)-phenanthroline complex (Fe2+-Phen) via inner filter effect and redox. With the addition of increasing NO2-, Fe2+ is oxidized to Fe3+, recovering the fluorescence of SiNPs. Meanwhile, the color of the system gradually changes from orange-red to colorless, which enables colorimetric measurement. The NO2- concentration shows a wide linear relationship with fluorescence intensity from 0.1 to 1.0 mM (R2 = 0.9955) with a detection limit of 2.4 µM in the fluorometric method (excitation wavelength: 380 nm). By contrast, the linear range of the colorimetric method ranges from 0.01 to 0.35 mM (R2 = 0.9953) with a limit of detection of 6.8 µM (proposed selective absorbance: 510 nm). The probe has been successfully applied to nitrite determination in water, salted vegetables, and hams demonstrating broad application prospects for the determination of nitrite in complicated matrices.
