Colorimetric detection of ractopamine and salbutamol using gold nanoparticles functionalized with melamine as a probe

A highly selective and sensitive method is developed for colorimetric detection of ractopamine and salbutamol using gold nanoparticles (AuNPs) functionalized with melamine (MA), respectively. The presence of these beta-agonists induces the aggregation of gold nanoparticles through hydrogen-bonding interaction that was accompanied by a distinct change in color and optical properties, which could be monitored by a UV-vis spectrophotometer or even naked eyes. This process caused a significant decrease in the absorbance ratio (A(670) (nm)/A(520) (nm)) of melamine-gold nanoparticles (MA-AuNPs), and the color changed from wine red to blue. The systems exhibited a wide liner range, from 1 x 10(-10) M to 5 x 10(-7) mol/L with a correlation coefficient of 0.995 for ractopamine, and 1 x 10(-10) M to 1 x 10(-5) mol/L with a correlation coefficient of 0.996 for salbutamol, with measuring the absorbance ratio (A(670) (nm)/A(520) (nm)). The detection limit of these beta-agonists is as low as 1 x 10(-11) mol/L. Particularly, the developed method has been applied to the analysis of real swine feed samples and has achieved satisfactory results. (C) 2013 Elsevier B.V. All rights reserved.