Abstract
An application of liquid ionization (LI) mass spectrometry to the profiling of urinary organic acids due to several inherited metabolic disorders is described. A solid-phase extraction technique using DOWEX 50W-X8 was developed to remove urea and cationic species from urine matrix. This preliminary sample treatment was quite effective to detect urinary organic acids for LI mass spectrometry. LI mass spectra for dicarboxylic acidurias clearly exhibited the peaks of adipic (m/z 147), suberic (m/z 175), and sebacic (m/z 203) acids due to the disease. Those for lactic and methylmalonic acidurias exhibited the intense peaks of lactic (m/z 91) and methylmalonic (m/z 119) acids, respectively. For phenylketonuria, the peaks corresponding to phenylacetic (m/z 137) and phenyllactic (m/z 167) acids, which are diagnostic metabolites, were intensely observed. All mass spectra for the urine samples of the patients were quite indicative of the individual metabolic diseases. Furthermore, a principal component analysis was examined to classify the spectral patterns using 40 peaks selected. The mass spectra of patients with five kinds of metabolic diseases were differentiated from those of healthy newborns by the principal component plots.
