pH drift of "physiological buffers" and culture media used for cell incubation during in vitro studies.

In pharmacological or toxicological studies performed at room atmosphere comparison of various media used for cell incubation revealed discrepancies among results due to pH instability when these media contain bicarbonate. With the classically used protocols, a relatively fast and notable rise of the pH of such media has been observed, and values higher than 8.5 could be reached after 1 h of incubation. A less important rise in pH was also observed for media containing low amounts of sodium bicarbonate, e.g., Hank's formula-derived media. Because Hepes-buffered media or media with abnormal osmolarity cannot always be used for such studies, our choice of media is limited.