In the routine clinical diagnosis of haemoglobin variants, intact haemoglobin molecule is analysed using gel electrophoresis and/or Bio-Rad D-10 HPLC. Mass spectrometry has been used in recent years to identify the haemoglobin variants. Unlike routine proteomics experiments using one proteolytic enzyme, we are trying to use multiple proteases to analyse haemoglobin variants at their residue levels in a single step.