Santos, LS (Santos, Leonardo S.). Univ Talca, Inst Quim Recursos Nat, Lab Asymmetr Synth, Talca, ChileDirect infusion electrospray ionization tandem mass spectrometry in the negative ion mode with single reaction monitoring is show to allow high selectivity and sensitivity in the quantification of taurine in energetic drinks. The method is also simple and rapid (less than 2 min run time), with high recovery and repeatability. Commercially available energetic drinks were found to contain taurine in concentrations quite different (lower or higher) from the declared amounts.