Like every other separation system, electrophoresis has its optimal working concentration. If the sample concentration is too high, then the gel-buffer cannot hold the pH-value anymore. This gel is shortly before burning!
Protein concentrations: Not more than 1 ug/ ul when Coomassie stained! Dilute 1:50 when silver staining follows the SDS-electrophoresis
As a sufficient pre-test the protein test-stick “Albym-Test” (Boehringer) can be used; available in every pharmacy (for urinary proteins).