A member of my lab made up DEPC treated PBS (pH 7.5) by adding 1mL of DEPC to 1L PBS, shaking to dissolve and then autoclaving. After a few days, the pH of the DEPC treated PBS was significantly more acidic (pH around 5). My question is whether the DEPC itself caused the solution to become acidic, or if this is from another cause? I can't seem to find a helpful answer online. I know that DEPC treated water can acidify as it is not that stable of a pH and it sensitive to being exposed to air, etc to form weak acids, but I didn't know if this is also true for PBS. Any insight would be great.
Similar question already discussed in Research gate 2 years back by Moumita Sarkar .
Virendra Kumar Saxena, I did see this post from January 2017, but Moumita's question had to do with DEPC treated WATER. I can understand why the pH of water would drop drastically, especially MilliQ water. I do not understand why the pH of a buffered solution, in this case PBS, would drift so much from around neutral to acidic. But perhaps my perception of the stability of the pH of a PBS solution is a bit too naive?
Two remarks: pH in milliQ water is impossible to determine. You assme that it is 7 but standard Phmeters detect only ions. Pure water have almost no ions (10-7 H+ and same amount of OH-) then they cannot detect accurately 10-7 M. When you add DEPC perhpahs, only perhaps. pHmeter readings may be reliable. I say perhaps because it all will depend on the concentration.
Second remark: What is pH of PBS before and immediately after adding DEPC (at the unknown concentration)? WIthout this piece of data it is impossible to answer. By the way I am assuming that PBS has the right pH (this does not always is the case if many people in the lab or if "old"...).
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