Determination of monophosphate nucleotides by capillary electrophoresis inductively coupled plasma mass spectrometry

A preliminary study of a modified microconcentric nebulizer (CEI-100, CETAC) as the sample introduction device of capillary electrophoresis inductively coupled plasma mass spectrometry (CE-ICP-MS) for the determination of monophosphate nucleotides is described. The monophosphate nucleotides studied include adenosine 5'-monophosphate (AMP), guanosine 5'-monophosphate (GMP), uridine 5'-monophosphate (UMP) and inosine 5'-monophosphate (IMP). The species studied were well separated using a 70 cm length x 75 mum id fused silica capillary while the applied voltage was set at -22 kV and a 20 mmol l(-1) ammonium citrate/citric acid buffer (pH 4.0) containing 0.1% m/v cationic polymer (hexadimethrine bromide, Polybrene) was used as the electrophoretic buffer. The electroosmotic flow was reversed by flushing the fused silica capillary with 0.2% m/v Polybrene to accelerate separation. The detection limit of various species studied was in the range of 0.036-0.054 mug P ml(-1), which corresponded to the absolute detection limit of 1.1-1.6 pg P based on the injection volume of 30 nl. We determined the concentrations of nucleotides in two IG-enriched monosodium glutamates purchased from the local market. The recovery was in the range of 100-112% for various species, and the concentrations of IMP and GMP in these samples were in the range of 0.15-0.18% m/m.