During electroporation of bacterial cells (I work with Mycobacterium tuberculosis, but I think this applies to E. coli as well), sometimes I get sparking. I've read this is due to salts present, either in the DNA sample or the bacteria.
I use the Qiagen plasmid prep kit, which includes EB (Elution Buffer). This contains Tris-Cl. Could this be contributing to the sparking? Can you explain how this works? Does eluting with water instead of EB reduce chances of sparking?