Abstract: To explore the characteristics of both qualitative and quantative analysis,by Gas Chromatography-Mass Spectrometry (GC-MS),of the four urinary markers,lactate, uracil,orotate and hippurate,for ornithine transcarbamylase deficiency (OTCD).Urea in urine samples was decomposed with urease,and heptadecanoiate was added as internal standard,then protein was denatured with ethanol and removed by centrifugation. After evaporation, the residue was trimethylsilylly derivatized by BSTFA/TMCS, and analyzed by GC-MS.The results showed that the markers can be separated well in total ion currency profiles,with indentifications confirmed by mass spectrums.Quantitative analysis revealed that the significantly elevated levels of lactate, uracil and orotate in urine from OTCD patient were droped to normal or nearly normal levels,together with large amount of hippurate excretion in the urine,after clinical therapeutic measures,including introduction of benzoic acid,were performed.These findings suggest that GC-MS analysis of the urinary markers is a valuable tool for the diagnosis and evaluation of the therapeutic effect of OTCD.

Key words: Ornithine Transcarbamylase Deficiency, Gas Chromatography, Mass Spectrometry