Abstract
Liquid ionization (LI) mass spectrometry, providing mostly MH+ ions of components in a solution, was applied to screening inborn errors of metabolism using urines of newborn babys without any pretreatment.
Urinary samples of healthy babys exhibited MH+ ions of urea at m/z 61 and of creatinine at m/z 114 and their related ions at m/z 121, 174, 181, 227, and so on. In contrast, the patient's urines exhibited abnormally abundant peaks of components, such as amino acids and/or organic acids, due to the errors of metabolism. All urines of babys suffering from phenyl-ketonuria clearly showed the peak at m/z 166 corresponding to phenylalanine as far as examined. Some of the other peaks at m/z 90, 104, 116, 130, 136, 141, 146, 154, 247, were observed in the mass spectra in common. The peaks assumed to be amino acids (m/z 76, 90, 104, 116, 146) were also observed in the mass spectrum of hypertyrosinemia, which is one of inborn disorders in amino acid metabolism. In the case of glycerol kinase deficiency, the peaks of glycerol (m/z 93) and 3-hydroxybutanoic acid (m/z 105) were clearly exhibited in the mass spectrum, where ammonium adduct ions with them were also observed at m/z 110 and 122 of rather intense peaks than that of MH+ ions. In the case of methylmalonic acidemia, methyl-malonic acid (m/z 119) was rather concentrated in the urine, but weakly observed by means of the direct measurement.
Clear distinction was found between the mass spectra of normal and abnormal urines, although the direct analysis of urines provided rather weak peaks for organic acids. LI-MS is considered to be useful for analysis of biomedical samples like urine.
