Figure 1

Ion exchange chromatogram/negative ion mass spectra of plasma from a patient with diabetic ketoacidosis (top) and a patient with acidosis of unknown aetiology (bottom). Liquid chromatography/electrospray ionisation mass spectrometry was performed on a Hewlett-Packard Series 1100 liquid chromatography system directly coupled to a Series 1100 Mass Spectrometer fitted with electrospray ionisation and operating in 'negative ion' mode (Agilent Technologies UK Ltd, Wokingham, Berkshire, UK). The extracted ion currents are shown.