Capillary zone electrophoresis/mass spectrometry of 5-aminolaevulinic acidand porphobilinogen

A capillary zone electrophoresis/electrospray ionisation mass spectrometry (CZE/ESI-MS) method has been developed for the separation and detection of 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG), Capillaries were 70 cm long with an inner diameter of 75 mu m and outer diameter of 375 mu m. The buffer used was aqueous ammonium acetate (50mM, pH 5.2) with a co-axial 'make-up' how of methanol/aqueous 0.1% formic acid (1:1 v/v) at a flowrate of 6 mu L/min. A voltage of 20 kV was used for CZE and an ESI voltage of 3 .5 kV, Full scan data was acquired over the range m/z 100-500 in positive i on mode, from which selected ion electropherograms were extracted; at m/z 1 32 for the protonated molecular ion of ALA and m/z 210 for the methylenepyr rolenine fragment ion of PBG. The protonated molecular ion of PBG, m/z 227, was found to be too facile to monitor, easily losing ammonia in the electr ospray source and better sensitivity was achieved by monitoring the resulti ng fragment ion, The detection limits were circa 100 attomoles of ALA and 1 0 attomoles of PBG at a signal-to-noise ratio (S/N) better than 10, providi ng sufficient sensitivity for clinical use and offering advantages over exi sting techniques, Copyright (C) 2000 John Wiley & Sons, Ltd.