Xylene cyanol

Xylene cyanol can be used as an electrophoretic color marker, or tracking dye, to monitor the process of agarose [gel electrophoresis] and polyacrylamide gel electrophoresis. Bromophenol blue and orange G can also be used for this purpose.
Once mixed with the sample, the concentration of xylene cyanol is typically about 0.005% to 0.03%.

Migration speed

In 1% agarose gels, xylene cyanol migrates at about the same rate as a 4 to 5 kilobase pair DNA fragment, although this depends on the buffer used. Xylene cyanol on a 6% polyacrylamide gel migrates at the speed of a 140 base pair DNA fragment. On 20% denaturating polyacrylamide gel electrophoresis, xylene cyanol migrates at about the rate of 25 bases oligonucleotide.