We would need some quantitative analysis technique. I am not aware of anyone offering this here.

My extractiton with titration is enough for that when done correctly. There is another possibility I am aware of - An1cca's Mescaline quantification in live cacti using TLC. Both techniques seem to have similar effort per specimen, though TLC may be a bit more pricey.

I can imagine cooperation with someone or more people willing to analyze the cactuses, but the community here seems to be too small to organize such project :/

But yes, I will send some samples for qualitative analysis to endlessness when I find something interesting.