RESUMEN
Objective To evaluate the accuracy of different methods in detecting free amino acids in plasma.Method 40 blood samples from healthy volunteers were analyzed by an automatic amino acid analyzer ( Li+system) and the results compared with previous reports using other analyzers.Results The results ob-tained by this analyzer for major amino acids [asparagine (Asn), glutamic acid (Glu), glutamine (Gln), valine (Val), tyrosine (Tyr), phenylalanine (Phe), ornithine (Orn), arginine (Arg)] were similar with those previously reported using other amino acid analyzers ( all P>0.05 ) and liquid chromatography tandem-mass spectrometry (LC-MS/MS) (all P>0.05).Except for Glu and Tyr, the results for major amino acids showed large deviation compared to the results from high performance liquid chromatography ( HPLC) ( all P<0.05).Conclusion The amino acid analyzer (Li+) and LC-MS/MS (iTRAQ kit) could accurately detect free amino acids in plasma.