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With Council Regulation 2821/98 zinc bacitracin, spiramycin, tylosin and virginiamycin, and with Commission Regulation 2788/98 olaquindox, were banned from animal feed as feed additives. To control the compliance of the ban a single multi-analyte liquid chromatography-mass spectrometry (LC-MS) method for their detection and quantification in animal feed was developed. A 2.5 g aliquot of feedstuff was extracted with 10 ml of methanol/water (70/30, v/v), and 3 ml of this extract was applied on an OASIS((R)) column after dilution with 27 ml of water. Elution was performed with 2 ml of acetonitrile/water (50150, v/v) and the eluant diluted to acetonitrile/water (30/70, v/v). An amount of 20 mul was injected onto a Kromasil C-18 liquid chromatography column. A gradient program, consisting of a mixture of acetonitrile and water (both containing 0.3% formic acid) was used for the separation of the compounds. The method was validated according to the draft SANCO 1085/2000. The detection capability of the method for all compounds was <1 mg kg(-1). (C) 2003 Elsevier Science B.V. All rights reserved.