A Polyclonal Antibody-based Immunoassay for Determination of Growth Stimulant Ractopamine: Comparative Study with Recent Advances in Immunoassay Methods

Ractopamine is a β-adrenergic agonist approved for use as a growth promoter in swine and cattle in the USA, Canada and Australia etc. but not in the European Union, China, or Taiwan. Here, we report the development of a polyclonal antibody-based enzyme-linked immunosorbent assay (ELISA) for ractopamine. Rabbits immunized with ractopamine-succinate-ovalbumin were utilized for polyclonal antibody generation. The calibration graphs of ractopamine showed linearity over the concentration ranges 0.3-24.3 μg/kg, whereas IC50 was 3.2 μg/kg, allowing the analysis of urine and serum samples without the need for sample clean-up. This paper also deals with the extraction of hydrochloric acid respect to meat and feed samples. It appears that the limit of determination of this assay for urine, serum and meat matrix was estimated to be 0.3 μg/kg, and for feed samples was 4 μg/kg. The results obtained a rapid, sensitive and specific assay to detect positive samples in routine analysis. Simultaneously, recent advances in immunoassay methods for ractopamine residues are reviewed herein, that can be considered as a basis for further research aimed at identifying the most efficient approaches for the analysis of ractopamine.