Rapid estimation of hemoglobin A2 without chromatography or electrophoresis.

Hemoglobin A2 is batch fractionated with diethylaminoethyl Bio-Gel A (Bio-Rad Laboratories) equilibrated with a tris(hydroxymethyl)aminomethane HCl buffer (pH 7.68, 8.75 mmol/liter, 6.36 mmol of CL- per liter). Hemoglobin A1 and F become bound to the resin, allowing the separation and quantitation of A1. Hemoglobin S alters the equilibrium condition, but adjustments are easily made so that A2 can be separated in the presence of S. The procedure is simpler than electrophoretic or chromatographic methods, requires 5 min, is accurate (A2 fraction is at least 94% A2, less than 6% A1), precise (SD +/-0.24 for duplicates), and has a normal limit of 2.6 +/-1.02%.