Heating and convection associated with alkaline electrophoresis

Alkaline version of the single-cell gel electrophoresis (Comet assay) is widely used in toxicological, environmental, and monitoring studies to assess the DNA damage levels in individual cells. The change in the temperature of the electrophoretic solution is one of the reasons leading to interlaboratory variation of Comet assay results. In this work, changes of surface temperature of the solution during electrophoresis were studied using technique of real-time thermal imaging. It has been found that the electrophoresis is accompanied by nonuniform temperature rise in different areas of the electrophoretic chamber. The maximum of heating was observed in the central region of the chamber, where temperature increased by an average of 7°C. The minimum temperature rise in other parts of the chamber was about 5°C. After removing the solution, the temperature on the surface of slides was higher than that on the surface of the solution. We believe that (1) nonuniform heating of the electrophoretic solution and convection could be the reasons responsible for the variability of results both in inter- and intralaboratory studies; (2) the spatial distribution of heating of the solution depends on the size and configuration of the electrophoretic chambers used.