I am having an issue with measuring the pH of my media.

I use D-MEM/F12 media (without buffer) and try to adjust it to pH = 7.4.

Since I incubate it @ 37C / 5% CO2, I added 2.5 g/L of NaHCO3 (based on

https://www.phe-culturecollections.org.uk/news/ecacc-news/co2-concentration-and-ph-control-in-the-cell-culture-laboratory.aspx)

However, the rapid change of pH due to air exposure prevents me from obtaining a reliable result. I did try to use 15ml open tubes for the incubation, which I tightly close before removing from the incubator to limit air exposure, but it does not seem to do the trick.

Any ideas/creative solutions?

Thanks