Rapid analysis of ractopamine in pig tissues by dummy-template imprinted solid-phase extraction coupling with surface-enhanced Raman spectroscopy

•A SERS method was developed for the rapid analysis of ractopamine.•Ritodrine used as the dummy-template of ractopamine for molecularly imprinted polymer.•The dummy-template MIP showed high selectivity to ractopamine used for SPE.•The method was successfully applied for the rapid analysis of ractopamine in pig tissues.

Ritodrine has similar skeleton structure to ractopamine and it was selected as the dummy-template molecule to synthesize the molecular imprinted polymers (MIPs). The MIPs exhibited better selectivity to ractopamine than to the dummy-template molecule: the imprint factor for ractopamine was 8.9, while 7.6 for ritodrine. The MIPs were used as sorbents in solid-phase extraction for selective enrichment of ractopamine, and some key parameters were optimized. After that, a rapid surface-enhanced Raman spectroscopy method was developed for analysis of ractopamine and isoxuprine in pig tissue samples. Under the optimal conditions, good linearity was achieved in the range of 20.0–200.0 μg/L for ractopamine and isoxsuprine at 842 cm−1 and 993 cm−1, respectively. The limits of detection were 3.1–4.3 μg/L, which were lower than the maximum allowed by U. S. Food and Drug Administration. The recoveries of ractopamine and isoxsuprine were 72.4–79.7% and 71.0–78.2% for the spiked pork and pig liver, respectively, while the relative standard deviations ranging from 7.4% to 13.0%. The results suggest that the proposed method is sensitive and selective, and it has good potential on the quantitative analysis of trace amounts of β-agonists in complex samples.

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