Isn't IUPAC an international body and everyone respects their decisions for element names?

@funso, the single electrode charges are a can of worms...perhaps not very well understand despite seemingly easy. We will have to look the actual literature not these elementary websites which are making claims without any solid reference.

In each case, the sign is "absolute" electrostatic sign whether we are talking about isolated electrodes or we are talking about connected electrodes. Measuring the single electrode potential is an ill-posed problem.

Right, earlier we were talking about isolated electrodes. When we connect two electrodes, the Fermi levels of the two metals determines which one will acquire a net positive charge and which one will be net negative.

@funso I expanded the answer.

Scientific humbleness requires that someone else associate it with your name. Good scientists are often humble people. The fake ones have to beat their drum.

Long time ago, someone advised me that don't trust any paper until and unless we read 11-12 papers. People make mistakes in papers or forget to write more details, and it is not uncommon being unable to reproduce data.

You are right, the second curve is dubious. Authors say they use the first derivative. I tried to take the first and second derivative of the second curve...nothing clear. Try writing to the author (corresponding author) or search better papers.

One could have dessicated the tissues in an ordinary clean glass container. If you were measuring a specific phosphorous atom containing molecule, then it is a different story. Using HF is a very bad idea for a simple analysis. Geochemists need it because they have to dissolve silicate rocks. Boric acid serves to complex the fluoride ion. It should have never be used without formal training from the research institute. Typically the Environment Health and Safety Department in universities provides the requisite training and paper work.

It is not clear if you were just interested in phosphorous content, would not you be using acid digestion followed by an elemental analysis technique like inductively coupled plasma-optical emission spectrometry (ICP-OES) or ICP-Mass Spectrometry (ICP-MS)? Is this the instrument you are talking about. Were you doing direct infusion? Anyway, no mass spectrometer is designed to handle insoluble particles in a fluid. Secondly, there was no need to use glass fiber. The anger of the research staff is well-justified.

The question is still unclear!

This is exactly what you are asking "I am trying to find the pH at which [H2PO−4] is maximum by only knowing the pKas." Did you even check alpha plots or check the expressions for alphas. It is unfortunate with anonymous downvoting that we never know if an Einstein thinks the answer is wrong or a high-school student "thinks" the approach is wrong.