I use 18% tris-tricine SDS-PAGE gel (ethylene glycol added) for separating protein samples. I use 0.1M Tris, 0.1M tricine, 0.4% SDS buffer for running the gel. I run the gel at constant voltage of 125-150 V. The current increases gradually, sometimes to about 300 mA and the gel gets heated. Why is the current too high? (It should be around 80-90 mA, I read somewhere.) What is the problem with the system and how do I troubleshoot?
The electric resistance will increase during the time of running. Therefor the current will be increased until the voltage is constant. To run the gels at constant voltage will give you a constant separation time and speed. The other way is to run the gels at constant current, here the voltage will be increased.
You have to make sure, that your gel is properly cooled at 15 °C. Higher temperatures will destroy the glass plates, at temperatures below 15 °C SDS will crystallize.
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