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Mass spectrometric characterization of efaproxiral (RSR13) and its implementation into doping controls using liquid chromatography atmospheric pressure ionization-tandem mass spectrometry

Reputable Mentor II
Reputable Mentor II
Thevis M, Krug O, Schänzer W.
J Mass Spectrom. 2006 Mar;41(3):332-8.
Efaproxiral (2-[4-[[(3,5-dimethylanilino)carbonyl]methyl]phenoxyl]-2-methylpropionic acid, formerly referred to as RSR13) is prohibited in sports according to the World Anti-Doping Agency (WADA). The drug as well as structurally related compounds and a stable isotope-labeled derivative have been synthesized to elucidate the fragmentation pathway of efaproxiral, using electrospray ionization (ESI) and tandem mass spectrometry by employing a novel linear ion trap--orbitrap hybrid mass spectrometer--in positive and negative ionization modes. The elimination of 2-methyl acrylic acid (-86 u) has been identified as a major fragmentation process in both charge states. Negative ionization and collision-induced dissociation (CID) caused an additional release of carbon dioxide (-44 u), and positive ionization the loss of formic acid (-46 u). Efaproxiral was incorporated into an existing screening procedure for doping controls using solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry, enabling a limit of detection of 2.5 ng/ml and interday precisions ranging from 7.9 to 13.0%.
Institute of Biochemistry and the Competence Center for Preventive Anti-Doping Research, German Sport University Cologne, Carl-Diem Weg 6, 50933 Cologne, Germany.
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