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Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: Embryopirate on October 15, 2019, 06:44:46 PM

Title: help with pH of my embryo culture media with henderson hasselbalch eq
Post by: Embryopirate on October 15, 2019, 06:44:46 PM

Hello, I've been trying to calculate what my pH should be under 5% and 6% CO2 gas in an incubator at 39°C.

The media is PZM3, and is mainly bicarbonate buffered.

NaCl                   (108 mM)
KCl                     (10 mM)
KH2PO4              (.35 mM)
MgSO4·7H2O      (.40 mM)
NaHCO3              (25.07 mM)
Na-pyruvate        (.2 mM)
Ca-(lactate)2·5H2O (2 mM)
L-Glutamine          (1 mM)
Hypotaurine          (5 mM)
Basal Medium Eagle amino acids
Minimum Essential Medium nonessential amino acids
Gentamicin
Fatty acid-free BSA

The media should be around 7.3 at 5%, but I've been struggling to prove this with the henderson-hasselbalch equation and ideal gas law equations. I'm also at sea level.

I've seen the pKa used for HCO3 and CO2 to be 6.1, but I must be doing the rest wrong since I'm getting 8.4 ??? I would greatly appreciate some help with this and figuring out the difference in pH at 5% and 6% CO2.

Thank you in advance, and sorry for formatting

Title: Re: help with pH of my embryo culture media with henderson hasselbalch eq
Post by: AWK on October 16, 2019, 02:38:46 AM

H-H simplified method for such a complex mixture is rather not applicable.

Title: Re: help with pH of my embryo culture media with henderson hasselbalch eq
Post by: Embryopirate on October 16, 2019, 07:00:20 AM

Quote from: AWK on October 16, 2019, 02:38:46 AM

H-H simplified method for such a complex mixture is rather not applicable.

oh man... that explains one reason I'm having so much trouble. If only my major professor would take that as an answer  :-\

From what I've gathered, it's mainly for my buffers like sodium bicarbonate. Which would be my conjugate acid, and the conjugate base would be carbon dioxide.
pH = 6.1 + log(HCO3 / (0.03 * PaCO2))
Is this applicable for my buffers? and CO2 in solution?

Title: Re: help with pH of my embryo culture media with henderson hasselbalch eq
Post by: AWK on October 16, 2019, 11:37:44 AM

It is not possible to calculate the exact pH of the buffer without knowing exactly the concentration of all the ingredients. The formula you are trying to apply is a modified H-H equation adapted to blood pH (you only need to correctly insert pCO2 in mmHg).
A pH of about 5.5-6.0 can be expected with the medium composition given unless the amino acid mixtures added are buffered.