Colorimetric detection of the β-agonist ractopamine in animal feed, tissue and urine samples using gold–silver alloy nanoparticles modified with sulfanilic acid

ABSTRACT

A highly sensitive, selective and simple method was proposed for colorimetric detection of ractopamine on the basis of the interaction between ractopamine and sulfanilic acid-modified gold–silver alloy nanoparticles (AuAgNPs). The AuAgNPs were prepared by the reduction of HAuCl₄ and AgNO₃ with sodium citrate in aqueous medium and further modified by sulfanilic acid. The interaction of ractopamine with sulfanilic acid induced rapid aggregation of sulfanilic acid-modified AuAgNPs along with an optical colour change, leading to precise quantification which could be detected by absorptiometry. Under the optimum conditions, the absorbance ratio (A₆₀₀/A₄₃₅) of sulfanilic acid-modified AuAgNPs exhibited a linear relationship with the concentration of ractopamine in the range of 4.5–31.6 ng/mL. The detection limit of ractopamine was 1.5 ng/mL. The established novel colorimetric detection method showed high selectivity towards ractopamine. The method was successfully applied to detect ractopamine in spiked pork, swine feed and swine urine samples with excellent recoveries from 94.4% to 112.5%. These results demonstrated that the proposed new method has a good potential for practical applications.

KEYWORDS:

• Gold–silver nanoparticles
• ractopamine
• sulfanilic acid
• colorimetric detection

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 31060210], [grant number 31460422];Natural Science Foundation of Jiangxi Province [grant number 20143ACB20006], [grant number 20171BAB204029];the Research Projects of State Key Laboratory of Food Science and Technology of Nanchang University [grant number SKLF-KF-201607], [grant number SKLF-ZZA-201612], [grant number SKLF-ZZB-201707].