2014 Volume 35 Issue 3 Pages 117-123
Keto acids are known to be key intermediates in various metabolic pathways. The development of an accurate method for the determination of keto acids is therefore important for diagnosing metabolic disorders as well as elucidating cellular metabolic processes in the TCA cycle, glycolysis and amino acid biosynthesis. In this study, we have developed a comprehensive and reliable LC-MS/MS method for the analysis of biological samples using a pre-column derivatization process. Ten keto acids, including α- and β-keto acids, were converted to the corresponding O-(2,3,4,5,6-pentafluorobenzyl)oxime derivatives and analyzed by LC-MS/MS. Oxaloacetic acid, which is generally considered to be unstable, was also successfully derivatized under mild reaction conditions. The pretreatment procedure used in this study was simple and did not require any difficult extraction or evaporation processes. The separation and detection of the derivatized keto acids was achieved using an LC-MS/MS system in multiple reaction monitoring mode. This newly developed method was applied to the analysis of keto acids in rat plasma, and showed good reproducibility (1.1–4.7% as CV) and recovery (96–109%) rates. This method also exhibited a low limit of detection in the range of 0.01–0.25 μM and good linearity (r2 > 0.997) over a wide concentration range of up to 300 μM. Based on these performance characteristics, this method could be readily applied to the comprehensive analysis of keto acids in biological samples.