pH Variation of DMEM
(Transferred from old blog)
Aim: Determine how quickly DMEM pH changes once removed from the incubator
Methods and Materials:
• non-sterile complete Dulbecco’s Modified Eagle’s Medium (DMEM) supplemented with 10% FBS
• 6 and 24 well cell culture plates
• 37 ºC 5% CO2 incubator
2 mL and 5 mL DMEM were placed in a 24 and 6 well plate, respectively. Both plates were incubated overnight to reach equilibrium. Both plates were then removed and the pH measured every ten minutes.
Results:
It is clear that the pH of DMEM changes quickly upon removal from the incubator. DMEM contains a buffer that uses CO2; in the incubator there is 5% CO2 compared to a fraction of percent in the air. Once removed from the incubator the dissolved CO2 in the media is released to the surroundings to go towards equilibrium, causing a pH change in the media. The fact that DMEM becomes more basic on the bench (23 ºC and about 0.03% CO2) correlates to rapid membrane discoloration on the bench compared to incubated samples, as membranes are more stable in acidic.