Thiol-disulfide exchange chromatography was performed on a normal control, a β-thalassemia intermedia patient who had been splenectomized, an HbH patient who had been splenectomized, and a patient with homozygous HbCS/CS. The unbound fraction was analyzed by SDS-PAGE and the α^CS was identified at a position consistent with a molecular weight of 19 kD. Note the presence of globin bands at the bottom of the gel. These have previously been shown to be α^A in β-thalassemia intermedia and β^A in HbH.2