In recent years the use of ractopamine (RAC), originally synthesized for the treatment of respiratory diseases, is on the rise as a dietary supplement in animals. The excessive use of RAC has some adverse effects on human health. Hence, the demand for simple, easy-to-use, and expendable devices for RAC recognition, even in remote areas, is felt more than ever before. This need prompted us to devise a straightforward colorimetric system for RAC recognition based on the etching effect of RAC on AgNPrs. This nanoprobe is a very advanced materials with great optical properties and stability, which could be used unprecedentedly without any combination or reagents for RAC recognition. Considering the needs and advantages, a simple colorimetric chemosensor for the quantification of RAC was designed and applied to a chicken sample. The designed chemosensor was integrated with an optimized microfluidic paper-based colorimetric device (μPCD), creating a suitable tool for the determination of RAC based on a time/color pattern. The analytical metrics for this simple colorimetric chemosensing regime comprise a best colorimetric LLOQ of 100 μM in solution with 10 μM of μPCD, a spectroscopic LLOQ of 10 nM, and a broad linearity range of 0.1-10 000 μM, which are outstanding compared with other colorimetric techniques. The main remarkable features of this study include the first utilization of AgNPrs with high stability and excellent optical properties without any reagent as an optical sensing probe and optimized μPCD toward RAC recognition and the innovative time/color semi-analytical recognition method. Moreover, the prepared portable μPCD modified with AgNPrs could be a prized candidate for commercialization due to the benefits of the low-cost materials used, like paper and paraffin, and the simple instructions for μPCD preparation. This report could be a pioneering work, inspiring simple and effective on-site semi-analytical recognition devices for harmful substances or illegal drugs, which simply consist of a piece of lightweight paper and one drop of the required reagent.
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