Abstract:

A method was established for the determination of 5 penicillin residues in milk and pork by solid-phase extraction
and high performance liquid chromatography-tandem mass spectrometry (SPE-HPLC-MS-MS). The samples were extracted
with acetonitrile, purified on a Bond Elut C18 column by solid-phase extraction, and finally detected by HPLC-MS-MS and
quantified by an external standard method. As a result, the method showed a good linearity with a correlation coefficient
higher than 0.999 in the range from 2.0 to 200 μg/L for 5 penicillin compounds. The average recoveries of these five
penicillins in milk were in the range of 85.2% to 122.7% with relative standard deviations (RSDs) of 3.43% to 16.8% (n =
6). As for pork samples spiked at 50 and 100 μg/kg, the average recoveries were between 94.3% and 116.4% except for ampicillin
with RSDs of 1.62% to 5.09%. The limit of quantification (LOQ) was in the range of 1.0–2.0 μg/kg. In conclusion, the method is
convenient, rapid, accurate and sensitive so that it can be applied to determinate penicillin residues in milk and pork.

Key words: solid-phase extraction, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS), penicillins, milk, pork