I am designing a world in which the biological solvent is an ammonia-water mixture and need help finding out which blood pigments (Hemoglobin, Hemocyanin etc.) would be immune to the negative effects of ammonia. I couldn't find anything about this specifically on google, so I've decided to ask.
I've come to the conclusion that none of the blood pigments we have on earth have immunity to ammonia poisoning. In fact, an ammonia-water solvent with any significant amount of ammonia isn't something that is possible in an organism unless they have completely different biochemistry from us (though our bodies do produce very small amounts of ammonia, it is processed into urea in the liver). Ammonia, when mixed with water, becomes ammonium hydroxide. Ammonium hydroxide is a caustic. Caustics destroy proteins, as shown in this link.
Basically, in order for an ammonia-water solvent to be possible, your lifeforms would need to have completely different biology from anything we have on earth.
However, that is from a purely scientific standpoint. I don't know the ins and outs of your world, or how scientifically accurate you want it to be, but you could create some component of a lifeform that counteracts the toxicity of ammonium hydroxide. Ammonium hydroxide is a fairly alkaline chemical, which is in large part the reason it's a caustic, so having another acidic chemical could help to counteract this. Or you could have a chemical that prevents ammonia and water from creating ammonium hydroxide.
These are just suggestions, however, and you can choose to ignore the chemistry if you want. This is worldbuilding, after all, not a science convention.