Quantitation of penicillin G in medicated premix feeds by micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary chromatographic (MECC) method for quantitation of penicillin G in medicated premix feeds was compared with the AOAC microbiological cylinder plate method. Feed was extracted according to the AOAC method, enabling comparison of both methods with the same extract. The MECC method detected penicillin G within 20 min, using a 150 mM sodium dodecyl sulfate (SDS)-20 mM sodium borate run buffer and a UV photodiode array detector at 210 nm. Recoveries from 5 replicates of medicated feed containing 117 g penicillin G/kg and then spiked to give a concentration of 176 g/kg were 98.4-108%, with a relative standard deviation (RSD) of 3.76% for the MECC method, and 102-104% with RSD of 1.06% for the AOAC microbiological cylinder plate method. Using a 5-point calibration curve, the MECC method detected and quantitated penicillin G in medicated premix feeds within 3 h, versus 24 h for the AOAC microbiological cylinder plate method.