Oxacillin residues in milk after drying off with Stapenor® Retard TS†

Abstract

Milk samples from 28 cows were analysed for residues of oxacillin after drying off with Stapenor^® Retard TS (oxacillin). Analysis was performed with an automated HPLC system consisting of an on-line solid-phase extraction and photochemical post-column derivatization with UV-detection at 300 nm. Although the time interval between treatment and parturition was less than the demanded 55 days, the maximum residue limit of 30 µg kg^–1 was only exceeded in one case, in which the withdrawal time was 28 days.