# Most negative and most positive value for proton chemical shifts

What are the most negative and the most positive values for proton chemical shifts recorded till present?

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I suspect the most positive values can be found in superacidic media such as $\ce{HF - SbF5}$, which contain extremely poorly solvated, essentially bare $\ce{H^+}$ ions. –  Nicolau Saker Neto Aug 22 at 14:08
What are the values? –  Marko Aug 22 at 15:28