Determination of ractopamine in pig hair using liquid chromatography with tandem mass spectrometric detection

A quantitative analytical procedure for the determination of ractopamine in pig hair has been developed and validated. The hair samples were washed and incubated at 75 °C with isoxuprine and hair extraction buffer. The drug present was quantified using mixed solid-phase extraction and liquid chromatography with tandem mass spectrometric detection. The limit of quantization (LOQ) was 10 pg/mg and the intra-day precision at 25 pg/mg and 750 pg/mg was 0.49% and 2.8% respectively. Inter-day precision was 0.88% and 3.52% at the same concentrations. The hair extraction percentage recovery at 25 pg/mg and 50 ng/mL was 99.47% and 103.83% respectively. The extraction percentage recovery at 25 pg/mg and 50 ng/mg was 93.52% and 100.26% respectively. Our results showed that ractopamine residues persist in hair in 24 days of withdrawal and also showed the possibility to test ractopamine from pig hair samples.