If you still have to learn that the PO4 with three H substituents will behave different chemically and chromatographically than a PO4 with one H substituent, and one long carbon chain substituent, + that large other residue, then I recommend you hit the books. I have no inclination to give a course in basic organic or analytical chemistry here.
Apparently we are having communication problems...
My question to you was: please explain what "grave" differences (such as the difference between Cl2 and Cl- you mention earlier) exist in the chemical and/or physical properties of phosphate when incorporated in an analyte that invalidate generalizing the knowledge of free phosphate chemistry to it.
Again, this is limited to the differences in chemical and/or physical properties that would affect chromatographic performance.
Here is the statement you made earlier that initiated this last discussion
"For the few physical and chemical similarities there are many grave differences in the P species"