Fraud monitoring using a new disposable photoluminescence sensor in milk

Abstract

A new, sensitive, and room-temperature On/Off photoluminescence sensor was developed for rapid, low-cost and convenient on-site determination of melamine (MEL) in dairy products using dithizone (Dz)-capped Eu3+ doped lithopone (LIT) particles (Dz/Eu3+-LIT) with the help of Pb2+ ions as the fluorescent probe. The interaction of Pb2+ ions with Dz led to form a rigid structure on the surface of Dz/Eu3+-LIT and turned on the luminescence intensity of the particles. The sensing mechanism is based on a simple complex formation strategy that quenches the luminescence signal of Pb2+-Dz/Eu3+-LIT complex by interaction with MEL. Polyvinyl alcohol (PVA) was used as the supporting material for the sensing particles and glutaraldehyde (GA) modifier was used to give the support insolubility property and make it suitable for water-based applications. The potential interferences including amino acids, ions, and other components had no significant effect on the luminescence quenching of the sensor. Under optimum conditions, there was a good linear relationship between the signal intensity of the probe and MEL concentration in the range of 10 to 1000 μg L-1 with a limit of detection (LOD) of 2.95 μg L-1. The relative standard deviation (RSD%) for 5 replicate measurements of MEL solution (50 μg L-1) was obtained 2.23 %. The developed method was applied to the determination of MEL concentrations in raw milk and milk infant powder and recovery values ranging from 98.9 to 102.1 % were obtained.