Fluorescent Determination of Flumequine Using a Novel Tryptophan (Trp)—Zeolitic Imidazolate Framework-8 (ZIF-8)—Terbium (III) Visual Probe

Flumequine, a quinolone antibacterial drug, has been widely used in aquiculture. However, excess use of flumequine may lead to antibiotic residues in animals and its rapid determination remains a challenge. In this study, a visual lanthanide metal–organic frame probe of Trp@ZIF-8/Tb3+ was used for the determination of flumequine. The probe was stepwise synthetized by tryptophan (Trp), zeolitic imidazolate framework-8 (ZIF-8), and terbium (III). In the presence of flumequine, the fluorescence of Tb3+ in Trp@ZIF-8/Tb3+ was sensitized. The fluorescence method was fast, requiring only 40 s, the detection range was wide from 0.03 to 1.53 μM, and the detection limit was 0.018 μM. Moreover, the Trp@ZIF-8/Tb3+ probe had good specificity and strong anti-interference ability, which was used for flumequine determination in milk, tap water, and serum. Furthermore, the Trp@ZIF-8/Tb3+ probe provided a method for the rapid determination of flumequine on test strips: The color changed from blue to green with increasing concentration. Hence, the developed Trp@ZIF-8/Tb3+ probe offers an efficient and convenient method for flumequine determination.