Sulfonic acid-functionalized covalent organic frameworks as the coating for stir bar sorptive extraction of fluoroquinolones in milk samples

Sulfonic acid-functionalized covalent organic frameworks (COF-SO3) as a coating of stir bar sorptive extraction (SBSE) for capturing three fluoroquinolones from milk have been developed. The COF-SO3 material was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. Milk without any typical treatments like protein precipitation and defatting was only diluted five times with water for test. Combined with high-performance liquid chromatography (HPLC), a SBSE-HPLC method was established for detecting fluoroquinolones in milk samples. The corresponding wide linear ranges (4.00-500.0 mu g L-1), low detection limits (1.20-2.62 mu g L-1), good test repeatability (RSD < 5.2%), and acceptable enrichment factors (56.2-61.5) were implemented for three fluoroquinolones. The analytical method was applied to determine trace targets and provided satisfactory results. Furthermore, the research displayed satisfied reproducibility for bar-to-bar (RSD < 6.5%) and batch-to-batch (RSD < 8.6%) tests.

Automated summary

Sulfonic acid-functionalized covalent organic frameworks (COF-SO3) have been developed as a coating for stir bar sorptive extraction (SBSE) to capture fluoroquinolones from milk. The method showed wide linear ranges, low detection limits, good test repeatability, and acceptable enrichment factors for the targeted compounds. The analytical method was successfully applied to determine trace targets in milk samples.