Correlation of ELISA and LC–MS/MS methods in determination of urinary ractopamine residual concentrations in treated pigs

Molecularly imprinted polymers (MIPs) for selective adsorption of ractopamine hydrochloride (RAC) were synthesised by an in situ method, in which salbutamol (SAL) was used as the dummy-template to avoid the template leakage. Scanning electron microscopy (SEM), mercury porosimerty and Fourier transform infrared spectroscopy (FTIR) were used to investigate the physical and morphological characteristics of the dummy-template MIPs. The test of adsorption selectivity indicated that the dummy-template MIPs exhibited high selectivity to RAC. The saturated adsorption capacity for RAC on dummy-template MIPs was 90.9 μg g−1. Based on the dummy-template polymers, a liquid chromatography–mass spectrometry (LC–MS) method was developed for the selective analysis of RAC in real pork samples. The averages of intra- and inter-day accuracy ranged from 78.9% to 92.2% and from 90.7% to 93.1%, respectively. The RSD% of repeatability ranged from 1.9% to 6.3%, and the RSD% of intermediate precision ranged from 3.5% to 9.2%, while the limit of detection (LOD) was 0.02 μg kg−1.