Dear María José España many thanks for sharing this very interesting technical question with the RG community. There are a few relevant literature references about this topic available. A detailed protocol for the preparation of stock solutions of cobalt(II) chloride hexahydrate (CoCl2 x 6H2O) in growth media is described in the following article:

Effect of cobalt(II) chloride hexahydrate on some human cancer cell lines

Article Effect of cobalt(II) chloride hexahydrate on some human canc...

Luckily this article has been posted by the authors as public full text on RG. Thus you can freely download it as pdf file.

Also please have a look at the following study which has been published Open Access:

CoCl2, a Mimic of Hypoxia, Induces Formation of Polyploid Giant Cells with Stem Characteristics in Colon Cancer

(see attached pdf file)

in this study the authors used stock solutions of cobalt(II) chloride in water. The authors mention CoCl2, but the anhydrous material is not very common in medical / biological studies. I would suggest to use the hexahydrate instead and recalculate the amount accordingly.

The third paper I would like to suggest to you is a potentially useful review article:

The use of cobalt chloride as a chemical hypoxia model

Article The use of cobalt chloride as a chemical hypoxia model: Coba...

This review has not yet been posted as public full text on RG. However, one of the authors has an RG profile (https://www.researchgate.net/profile/Maria-Chanez-Cardenas). You can easily send her a message via RG and request the full text. Normally authors respond quite rapidly to such full text requests.

Good luck with your research work and best wishes, Frank Edelmann

I really appretiate your answer Frank T. Edelmann! I was having trouble finding a paper with the tecnical details of how to use this compound in vitro.