Recently I checked the acsf pH before and after 95% O2/ 5% CO2 buffering and found pH value is 7.8 (7.8) and 7.6 (after) with 26mM NaHCO3 and 5% CO2. Does anyone know how to calculate the buffer ability of CO2-NaHCO3 pair? And what's the pH range of your acsf before and after buffering?
The pH can be adjusted with HCl before carbogenation to ensure you are starting in the physiological range. If the pH is still high after carbogenation, try lowering NaHCO3 from 26mM to 24mM. That is what I use. Alternately, you can get better buffering by using a formulation with HEPES and NaHCO3. A small amount of HEPES will lower the pH. For example, you can add 5 mM HEPES to your existing formula.
Hi, Jonathan. How's everthing going. I saw your cutting slice paper. Thanks for nice suggestion. The reason we check the pH is that we found the slice look good righ after putting into recording chamber but getting worse within about 20 min. Actually I did adjust pH with HCl before buffering. And when I rechecked the pH during the experiments. The pH still is about 7.6. It is weired. Let me try HEPES first to see whether it will keep slice better during the recording.
I tested and found that 24mM NaHCO3 was better than 26mM...the pH was closer to 7.4 with carbogenation. The temperature also can affect the pH even with constant carbogenation, At room temp with bubbling my aCSF is 7.4 but when the temp is raised to 32*C (like in the initial recovery chamber step) the pH increases to 7.5 or so. I am thinking to further adjust my recipe to make it 7.3 at room temp and 7.4 at 32*C just to be safe. That can be done by either adding more HEPES or lowering the NaHCO3 even further.
Hello Wenting. We have a similar problem at my lab. How do you solved it ?
Cheers.
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