A pH buffer is a substance that acts as a weak acid and/or a weak base so that the pH of the solution to which it is added will be resistant to a change in pH in response to various insults. This occurs through accepting or donating hydrogen ions, which are ultimately responsible for establishing pH.
the most common buffer used in media is sodium bicarbonate. The pH of sodium bicarbonate-containing media is sensitive to the amount of carbonic acid formed from the relative amounts of CO2 in the atmospheric conditions immediately surrounding the culture dish. The pH of the media can be maintained as long as levels of CO2 remain constant in the incubators; however, this can be problematic with repeated incubator openings/closings for cell observation as well as for manipulations performed at room atmosphere.
the point where equilibration is reached and equal portions of acid and conjugate base exist in solution, thus providing the highest buffering capacity (ability to resist pH change).In aqueous solution, carbonic acid exists in equilibrium with carbon dioxide, and the concentration of H2CO3 is much lower than the concentration of CO2. In many analyses, H2CO3 includes dissolved CO2 (referred to as CO2(aq)). In this system, carbon dioxide (CO2) combines with water (H2O) to form carbonic acid (H2CO3), which in turn rapidly dissociates to form hydrogen ions (H+) and bicarbonate (HCO3- )
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