PBS is often used as an extraction solvent for human fecal metabolites in NMR studies. I've noticed that many studies use (at differing molar concentrations) either:
- Na2HPO4 / NaH2PO4
or
- K2HPO4 / NaH2PO4
or
- K2HPO4/ KH2PO4
The first one I listed seems to be the most common choice.
I understand that the two salts (an acid an a base) are used at various ratios to get a neutral or close to neutral pH, but can someone please help me understand the reasoning behind these choices?
The advantages/disadvantages of these different combinations, and more specifically, between Na2HPO4 or K2HPO4?
Thank you.
Hey,
PBS (phosphate buffered saline) is typically chosen to work at physiological pH levels and consist of a buffer salt, the phosphate, and salt to add ion strength. Depending on your requirements certain recipes might be used. If only the pH is to be managed the phosphate combination should not matter at all and salt is not required. Also, sodium salts tend to be less expensive compared to potassium salts and may therefore be preferred. For other experiments, for instance antibodies, typically PBS with KH2PO4, Na2HPO4 and NaCl is used, some protocols may even require further additives like Mg(Cl)2.
In the end it depends on your system and a suitable buffer may be chosen according to the closest literature.
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