RNA Loading Buffer PLUS is used as a tracking dye during RNA electrophoresis. It also contains intercalating dye Ethidium bromide for post-electrophoresis visualisation. The RNA loading dye has a slight negative charge and will migrate the same direction as RNA, allowing the user to monitor the progress of molecules moving through the gel. The rate of migration varies with gel composition. RNA Loading Buffer PLUS contains the denaturing agent formamide and urea, which allows RNA fragments to separate according to size even during non-denaturing electrophoresis.