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Okay thank you I think I was on the wrong way with my mind...

Yeah, Im searching for an answer to this question. Wikipedia says that CO2 has no influence to HEPES. I expect that cause I use a saturated Carbogen-Solution. So I get a HCO3-/CO2 buffer for a physilogical pH. Because of the metabolism the CO2 concentration changes. So that I also use HEPES-buffer. So all in all my question is where do I find a reference for "Hepes is a well buffer, even if the CO2 concentration is changig" I cant use Wikipedia in my references and the references which are named in the article of wikipedia doesnt include the information, although it is said in wikipedia. Im searching for a Paper where somebody investigated the buffer-capacity of HEPES in relation to the CO2-concentration.

Hey, I made during my practical year in the pharmacology some experiments and now I have to write a Master Thesis. Now I have a question to clear: I used a Krebs-Ringer Solution (contains also bicarbonat) and gassed the solution with Carbogen ( 5% CO2 95% O2) for 30 minutes. After that I added a HEPES-buffer. The buffer is for a physiological pH of 7,4. My cells consumpted during my experiments more or less O2, so that I gassed before with the Carbogen. I got the protokol by my professor and didnt asked a question. Now while writing I read the following: HEPES is widely used in cell culture, largely because it is better at maintaining physiological pH despite changes in carbon dioxide concentration (produced by cellular respiration) when compared to bicarbonate buffers, which are also commonly used in cell culture. (https://en.wikipedia.org/wiki/HEPES) Yeah I know that wikipedia is not the right site to get information. So I checked the references but I didnt find a sentence in Pubmed or else that says that Hepes buffers independently of the CO2 concentration. Is this right? Where do I find a source ? Thanks for helping