PURPOSE: To reduce the interference between dye and biological organic molecule by adding a sample of the molecule to solution containing charged paint to prepare load solution, and applying a voltage across one direction of a gel.

CONSTITUTION: Paint charged to positive is selected, for example, from paints having brilliant green, methyl blue, and neutral paint is selected, for example, from paint containing Acramin yellow, Sudan III. Biological organic molecule having negative charge and containing amino acid, DNA, protein is added to the solution containing neutral or positive charged dye and buffer, and a sample is disposed on a separate gel. A voltage is applied across one direction of the gel. Thus, the dye and molecule can be separately driven.