How to describe a situation in which you "throw things at the wall and see what sticks" in a master thesis For context, i'll describe the problem. I'm working in chromatography, and the first part of the work was to do TLC experiments to narrow mobile phase compositions for separation of valuable components of plant extracts through column chromatography. In these experiments, we found that there were impurities that could not be moved by ANY type of mobile phase. We tried several procedures, but none were effective, we just abandoned this problem because something else became evident. 

I'm now writing the description of the events in my thesis, and I have a whole subsection with a structure of "we tried this, here is a picture, you can see it did not work", repeated something like 5 or 6 times. Those SHOULD have worked, but they didn't. Imagine having a car in which the engine chugs and does not start, you replace the whole engine, and then the car continues to not start.

I am therefore stuck in a situation in which I can only describe an additional two procedures as "throwing stuff at the wall and seeing what sticks". I am however pretty sure you can't actually write that on a thesis. How should I express this?
It would be best to explain why such experiments were conducted along with supporting concepts that you would like to verify. It ought not to look like a random set of trials.

You may write something like this:


  Concept X follows from [explanation of X]. This concept formed the hypothesis Y to justify the following experiments. ... Although the experimental results were negative, it would be of worth to note them here as to why they were so.