What inference can be made from the fact that there is no reversal in how three components eluate?
Question 1
Yes, of course! Something that is &quot;relatively&quot; non-polar would travel further with a non-polar mobile phase because it would have less attraction to the stationary phase. While a polar substance would not travel as far with the mobile phase because it would have a greater attraction to the stationary phase.
Question 2
Now, that depends. Are you also changing the stationary phase? Exactly how polar is the new polar-mobile phase? It would really depend on which phase the solutes have a greater attraction to.
Question 3
You are on your way. Quantitative HPLC is the bane of my existence. There's a million factors to consider, such as column temperature, flow rate of the solvent, particle size, polarity and charge. Usually, it takes a bit of experimentaton to reach a perfect combination that allows complete separation of whatever it is you're interested in. Usually, your best bet in identifying a compound at a particular point is to run a little bit of pure sample on its own. In the end, above all else, you need to find a combination that doesn't result in chemicals overlapping with each other.
In qualitative chromatography, as long as you can resolve all possible signals, you've done well enough.