Decarboxylation of [1-13C]Leucine by Peroxyl Radicals

The decarboxylation of [1-13C]leucine by peroxyl radicals (ROO.) has been studied by using combined gas chromatography/isotope ratio mass spectrometry (GC/IRMS) to follow the production of 13CO2. Peroxyl radicals were obtained by thermal decomposition of a water soluble azo initiator, 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH). The decarboxylation rates measured by GC/IRMS were dependent on [1-13C]leucine and AAPH concentrations. The leucine partial order was found to be constant over a 60 min. period (0.6) but the AAPH partial order was found to be variable during the same period, from 1.0 (t = 0) to 0.50 (t = 60 min.). The identification of the products of reaction between leucine and peroxyl radicals requires the use of combined gas chromatography/mass spectrometry using the selected-ion monitoring mode. Methyl-3 butanoate was identified from comparison of its mass spectrum with that of a standard. © 1997 John Wiley & Sons, Ltd.