[Cell-biology] pH adjustments

alice508 from u.washington.edu via cellbiol%40net.bio.net (by alice508 from u.washington.edu)
Thu Nov 20 17:21:44 EST 2008

I would appreciate any suggestions for help with adjusting the pH of my media or working solution.  I am  
adding BSA to study the effects on my conditionally immortalized cells grown in RPMI media with 2% FBS 
and have had difficulties with pH adjustment.  I initially tried adding the BSA to media to make a working 
solution then adding it to my plates, but the amount of working solution is quite significant and causes 
the media to immediately turn yellow.  I then tried to adjust the pH of the working solution with sodium 
bicarbonate, but the amount needed was about 1:1 and diluted the media too much.  I then tried making 
the working solution with sterile water, then using 1N NaOH to adjust the pH to about 7.6 (which is the 
pH of the media) and the amount needed was acceptable.  However, when I placed this media into 37 
degrees incubator with 5% C02, at 24 hours, the pH of this changed to orange/yellow and the pH 
dropped to 6.8.  Any suggestions on how to get the pH within physiological range accounting for the 
C02 and temperature changes as well as amount needed to get the pH right without diluting the media?  
Thank you!

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