Thimerosal is an organic mercury compound that is metobolised to a low molecular weight compound (the ethylmercury kation) , which is an excellent inhibitor of many enzymes. It works against nearly everything, but not against bacterial endospores, in the microgram per ml range. It is somewhat outfashioned, due to the heavy metal character of the compound.

Thymol is a phenol and for may applications not sufficiently active. In addition, it has a considerable vapour pressure and a charcateristic smell. I do nor recommend for conservation of solutes and similar.

Sodium azide reasonably active (should be used at 0.1 g per 100 ml or somewhat lower) , is very cheap, and easy to wash out of suspensions. It inhibits everything that lives on respiration via cytochrome c- oxidase. Do not use it in acidic solutions. You could produce the free acid, which is volatile and highly toxic.

Overall, everything that is meant to do conservation jobs, must necessarily be toxic. That's the idea. Personally, I normally use sodium azide to prevent growth on material that can neither be sterile-filtered or autoclaved (essentially only column chromatogrophy material).

I think that azide is just cheaper.

Overall I think any could be appropriate, comes down to personal preference. If i had to guess why Sodium Azide is more often used, its relatively safe, cheap, and above all else lasts forever in a bottle stored away in a cupboard. I believe the others could break down over time (organic compounds).

Sodium Azide: Disrupts Cytochrome oxidase, which many prokaryotes and most (if not all) eukaryotes have in some form of homolog structure.

Thymol: I believe interrupts glucose uptake

Thiomersal: Not sure how this one works; organic mercury, my organic teacher always told me to stay away from these.

Umm.... just so you know sodium azide is very toxic. Not safe. That's partly why it's a preservative.

Yes you are correct, all the substances listed are toxic to humans.

Thimerosal is an organic mercury compound that is metobolised to a low molecular weight compound (the ethylmercury kation) , which is an excellent inhibitor of many enzymes. It works against nearly everything, but not against bacterial endospores, in the microgram per ml range. It is somewhat outfashioned, due to the heavy metal character of the compound.

Thymol is a phenol and for may applications not sufficiently active. In addition, it has a considerable vapour pressure and a charcateristic smell. I do nor recommend for conservation of solutes and similar.

Sodium azide reasonably active (should be used at 0.1 g per 100 ml or somewhat lower) , is very cheap, and easy to wash out of suspensions. It inhibits everything that lives on respiration via cytochrome c- oxidase. Do not use it in acidic solutions. You could produce the free acid, which is volatile and highly toxic.

Overall, everything that is meant to do conservation jobs, must necessarily be toxic. That's the idea. Personally, I normally use sodium azide to prevent growth on material that can neither be sterile-filtered or autoclaved (essentially only column chromatogrophy material).

I have also come across 20% ethanol as a preservative for affinity purification resins, including protein A-Sepharose, which I prefer to use when possible.

Thank you all very much for your answers!

I want to use NaN3 as preserver for non-covalent BSA aggregates. In the future, I will want to use that aggregates for evaluate innate immune response in another laboratory.

Do you know, if NaN3 at 0.02% can interfere in that experiment?

Can you recommend me another preservative for storage 6 months?

Well there is another newer guy on the block: Proclin, available from Sigma: 

"Unlike other biocides, ProClin products present no health hazards, toxicology problems, or disposal issues at recommended usage levels."

http://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/SAFC/General_Information/1/efficacy-vs-thimerosal-and-sodium-azide.pdf