Acid electrophoresis (pH 6.0) is used to confirm or rule out the presence of hemoglobins D and G that migrate with hemoglobin S in alkaline electrophoresis (pH 8.6). Hb A and F migrate from the center-point of application toward the cathode, with Hb F migrating the furthest.
Relative migrations of hemoglobin variants on acid electrophoresis can be seen below. The application point is indicated by the arrow. In this image, hemoglobin D is now separated out from hemoglobin S. However, because it migrates with Hb A in acid electrophoresis, further testing would be needed to identify Hb D.