Development of a Time-Resolved Fluoroimmunoassay for the Rapid Detection of Methyl-3-Quinoxaline-2-Carboxylic Acid in Porcine Tissues

A time-resolved fluoroimmunoassay for the specific determination of methyl-3-quinoxaline-2-carboxylic acid in animal tissues, a marker residue of olaquindox, was developed. The IC50 of the assay was found to be 1.46 +/- 0.19ng/mL of methyl-3-quinoxaline-2-carboxylic acid in phosphate-buffered saline samples and the detection limit was 0.16 +/- 0.03ng/mL. For porcine liver and muscle samples spiked with 5, 10, and 15ng/g, the recovery ranges were 95.7-112.3% and 98.5-116.2% and the coefficients of variation were 9.3-11.5% and 8.9-14.2%, respectively. The time-resolved fluoroimmunoassay results correlated well with high performance liquid chromatography results (correlation coefficients of 0.991 for liver and 0.988 for muscle). This study suggests that this method is simple, fast, and sensitive for the high-throughput determination of methyl-3-quinoxaline-2-carboxylic acid in animal tissues.