Instrument-free detection of natamycin in beer and wastewater based on Eu-MOF ratiometric fluorescence response

Abstract

Excessive intake of natamycin (NAT) is harmful to human health, so it is of great significance and necessity to effectively detect the content of NAT in food. In this study, we synthesized a dual-emission fluorescence probe, Eu@UiO-66(OH)2/(COOH)2, which exhibited emission peaks at 439nm and 614nm. This probe was obtained through the europium post-modification of UiO-66 type metal-organic frameworks (Eu-MOFs), which consisted of two types of ligands, 2, 5-dihydroxyterephthalic acid and pyromellitic acid. As expected, this probe Eu@UiO-66(OH)2/(COOH)2 can specifically respond to NAT with distinguishable ratiometric fluorescence changed from purple-red to blue with low limit of detection (0.15μM, approximately 0.10mg/kg), wide linear range (0-100μM), fast response (less than 1min), good selectivity and interference resistance. Based on the ratiometric fluorescence responsiveness, Eu@UiO-66(OH)2/(COOH)2 had been successfully used for the quantitative detection of NAT in wastewater, beer, yoghurt, and juice, demonstrating good recovery through smartphone-based colorimetric analysis. Thus, this work provides a ratiometric fluorescent probe for rapid, instrument-free and on-site detection of NAT in real samples such as beverage and environmental water.