Rapid Determination of Tetracycline Antibiotics in Milk by HPLC Using an On-line Clean-up System

Abstract

A rapid and simple method for the analysis of four kinds of tetracycline antibiotics (TCs), oxytetracycline, tetracycline, chlortetracycline and doxycycline, was established by HPLC using an on-line clean-up system. Co-existing substances in milk were removed by a precolumn head-cut-loading method. TCs retained in the precolumn were rapidly loaded on an analytical column after changing the eluent. The co-existing substances retained in the precolumn was removed by back-flash washing. Sodium octanesulfonate was effective as a counter ion in the mobile phase for separation of TCs on the analytical column. Determination of TCs in milk by this method could be carried out only after deproteinization with 20% trifluoroacetic acid. Recoveries of TCs from milk fortified at 0.03, 0.05, 0.1, 0.5 and 1.0mg/L ranged from 80.2 to 104.3%. Detection limits were 0.01mg/L for all four TCs.