Confirmation of Residual Lasalocid Sodium in Commercial Chicken Liver by Thermospray Liquid Chromatography/Tandem Mass Spectrometry

The residual lasalocid sodium (LS) of commercial chicken tissues purchased in the Tokyo area in 1988 was examined by high performance liquid chromatography (HPLC) with fluorescence detection. The compound was detected at the level of 0.06ppm in one sample (liver) out of 31. This sample was further examined to confirm the presence of LS by using HPLC combined with tandem mass spectrometry (MS/MS), in which the selected reaction moniotoring (SRM) technique was used. The parent ion was selected at m/z 337 and the daughter ions at m/zz 237, 281 and 319. The SRM chromatograms of the LS-containing sample and LS authentic standard showed the same retention times and single peaks. The signal-to-noise ratios were better than 10 between SRM profiles of a positive sample and a negative sample. The compound was confirmed to be LS by the above-mentioned results.