Simultaneous immunodetection of ionophore antibiotics, salinomycin and narasin, in poultry products and milk

Abstract

Rabbit polyclonal antibodies were generated against the ionophore antibiotic salinomycin (SAL) as a determinant of the BSA–SAL conjugate. The homologous ELISA format was found to be preferred for similar recognition of SAL and narasin (NAR) with IC₅₀ values of 0.55 and 0.57 ng mL⁻¹, respectively. Both analytes could be determined in the range of 0.1–2.7 ng mL⁻¹ (IC₂₀–IC₈₀) with a detection limit of 0.03 ng mL⁻¹. To analyze matrices, individual pretreatment of samples was required. For chicken muscles, simple buffer extraction was sufficient to recover 87–110% of ionophores. Extraction with acetonitrile followed by evaporation of the solvent was best for recovering 67–108% SAL and NAR from egg homogenate. A feature of the extraction of ionophores from milk was the elimination of fat-mediated interference by organic solvation. It was found that the absence of Na⁺ and K⁺ ions during reconstitution of sample extracts was a key factor contributing to the increase in the average recovery of ionophores from 32% to 93%. Thanks to this special pretreatment and improved recovery, the developed immunoassay method was suitable for the analysis of ionophore antibiotics SAL and NAR in a milk matrix, which has not been previously reported.