kmata,
This test is based on cation-exchange HPLC (a technique for separating molecules based on the distribution and quantity of positively charged sites on the surface of the molecule). Patients with sickle cell anemia have one of several variants of hemoglobin that are different from hemoglobin found in normal patients. Since these variants are slightly different in shape as well as the magnitude of positive charge under a defined set of conditions, these variants can be separated and detected based on the rate at which they pass through a cation exchange column. Bio-Rad (
http://bio-rad.com) sells equipment and analysis kits for this application. You might find more about this application there.