Keto acid profiling analysis as ethoxime/tert-butyldimethylsilyl derivatives by gas chromatography–mass spectrometry

Organic acids, including keto acids, are key intermediates of central pathways in cellular metabolism. In this study, a comprehensive and reliable method was developed and optimized for the simultaneous measurement of 17 keto acids in various biological samples. The keto acids were converted to solvent extractable forms by ethoximation followed by tert-butyldimethylsilylation for direct analysis by gas chromatography–mass spectrometry in selected ion monitoring mode. The proposed method was precise (0.05–8.3, % RSD) and accurate (−10.5 to 5.3, % RE) with low limit of detection (0.01–0.5 ng/mL) and good linearity (r > 0.995) in the range of 0.01–5.0 μg/mL. This was suitable for profiling analysis of targeted keto acids in human plasma, urine and rat brain tissue.