Both DEA and TEA are rather inert to oxygen chemically. They are strongly alkaline and very mildly chelating. TEA is used as a base in developers.
DEA is a mild silver halide solvent.
You can do searches for Sodium Hexametaphosphate and buy it in a lifetime supply on Ebay. 1 lb. is $8 3 lb. is $13 10 lb. is $27. I have to use it out in the desert where I live or I get calcite bits on my negs after they dry.
Maybe I should point out that you had reason for your answer. Both TEA and DEA react with air, but not oxygen (readily). It is the Carbon Dioxide that they react with, gradually forming the carbonate salt.
This will drag the pH more acidic.
See 'Complex Phosphates' here:
It may be tripolyphosphate has sesquicarbonate added to reduce alkalinity. I can see no obvious reason why tripolyphosphate should not work provided it does not affect the pH.
110 feet down is still about 800 feet above sea level where I live.
Just a general note.
Our atmosphere is acidic and oxidizing due to the CO2 and O2 in it. Any alkaline solution left out in the open will react with CO2 and form a salt while decreasing in pH. Any reducing solution left out in the air will oxidize. This goes for the solids as well as the solutions I might add.
Therefore, developer, which is an alkaline solution of reductants goes bad when exposed to air. The CO2 makes it more acidic and the O2 oxidizes the reducing agents including HQ, Metol, Phenidone, Glycin and etc.