1. Food processing effects on residues: penicillins in milk and yoghurt Analytica Chimica Acta Volume 483, Issues 1-2, 25 April 2003, Pages 73-79 doi:10.1016/S0003-2670(02)01405-8 2. Identification of metabolites of ampicillin using liquid chromatography/thermospray mass spectrometry and fast atom bombardment tandem mass spectrometry Biomed Environ Mass Spectrom. 1989 Nov;18(11):983-94. 10.1002/bms.1200181106