Analysis of urinary organic acids by Plasmaspray liquid chromatography/mass spectrometry

High-performance liquid chromatography is being used increasingly as a screening method to detect organic acid-urias, an important group of inherited metabolic disorders. Analysis is hampered by lack of a suitable specific detection system. We have carried out preliminary investigations to assess the potential value of liquid chromatography/mass spectrometry with a plasmaspray interface. Spectra of standard acids yielded intense [M-H]- ions with little fragmentation. Organic acids could not be identified in urine samples from healthy neonates because of poor sensitivity. However, urine from a baby with the inherited disorder methylmalonic aciduria showed a distinct peak of methylmalonic acid, easily identified owing to its high sample concentration.