The is a document, ICHQ2, that has guidance for validation of analytical assays.  Your problem is a little tricky because you are using extracts.  It sounds like you are looking to define a pattern that is specific for different tissue types.  I think specificity is the most important parameter in that case - you need to insure that you can distinguish the tissue types.  Accuracy implies a quantitative measurement but it could also be accuracy at identifying tissue types in a blinded test.  Precision is a quantitative measurement, I dont think it would apply.   Detection limit usually only applies for assays for components that you expect to be at very low concentrations or where you have to prove absence of an impurity.  I would recommend showing the robustness of this type of assay- different people doing the experiment, different lots of gel, different extracts from the same tissue, from different animals.

Very useful, thanks Paul

I recommend ICH Q2(r1) for validation.  In addition, you will want to include electric charge(s) in the 'robustness' section.  During 'specificity' include the various analytes you wish to detect in your extract as well as a 'spiked' sample versus a blank.