Abstract: Wash solution and method for purifying sequencing reaction product. The wash solution comprises an effective amount of guanidine in a low ionic solution to reduce or eliminate the presence of dye terminators in a sequencing reaction product. In its method aspects, the present invention comprises the addition of the wash solution to the sequencing reaction product prior to filtration, followed by filtration to reduce or eliminate unincorporated dye terminators. The purified sequencing products can then be resuspended and transferred to an appropriate substrate for sequencing or further preparation. Dye blobs formed from unincorporated dye terminators no longer interfere with the electropherograms generated upon electrophoresis of the sample.