Inthong TMatayatsuk Phechkrajang CWilairat PChaikum NMahidol University. National Doping Control Centre2019-06-202019-06-202019-06-202015https://repository.li.mahidol.ac.th/handle/20.500.14594/44137Recent advances in doping analysis (22) : Proceedings of the Manfred-Donike-Workshop ; 32nd Cologne Workshop on Dope Analysis ; 30th March to 4th April 2014, page 79-83Metipranolol is a beta-blocker in the WADA list of substances prohibited in particular sports. It is converted to deacetylmetipranolol by the first pass metabolism and the parent compound is not excreted. A standard methanolic solution of metipranolol can be converted to deacetylmetipranolol during prolonged storage at -20°C. Spiking blank urine with this aged standard can lead to misinterpretation of the form of metipranolol in a suspected urine sample since the normal GC-MS screening procedure for derivatized beta-blockers cannot separate this metabolite from the parent compound. A specific Ge-temperature program is required. However a LC-MS/MS method can separate metipranolol and its metabolite.engMahidol UniversitydeacetylmetipranololmetipranololProceeding PosterNational Doping Control Centre Mahidol University