Please
First, i need to make a pH 7.4 phosphate buffer (0.1M), for a microbiology experiment, but i am missing KH2PO4, NaH2PO4 and Na2HPO4. . I have K2HPO4 and NaOH, how can i use these two product s,???
Second, what is the molarity of the final solution when done what follows:
Phosphate buffer solution pH 7.4.
Add 250.0 ml of 0.2 M potassium dihydrogen phosphate R
to 393.4 ml of 0.1 M sodium hydroxide
Thanks
Just a note: if you add HCl to K2HPO4, it will give you the desired pH, but you will not have just phosphate buffer; instead, you will have phosphate buffered saline, containing a significant amount of KCl. Using phosphoric acid instead of HCL will avoid this problem, but your final phosphate concentration will no longer be 0.1M. The best way is to mix a 0.1M solution of phosphoric acid with a 0.1M solution of K2HPO4 until you get the desired pH.
You will need either, Phosphoric or Hydrochloric acid to adjust to pH 7.4 if you only have dipotassium hydrogen phosphate.
The molarity of the final solution you mentioned will be 0.078 M.
However, it seems that this is not the answer that you are looking for and I would suggest reading up on pH, pKa, concept of weak acids and bases and their salts, Henderson–Hasselbalch equation because you will need these concepts if you plan to stay in the field of biological sciences.
fthank you, so i can combine K2HPO4 and NaOH to prepare phosphate buffer (0.1M) ?? but how I can calculate the sample size (mass and volume of K2HPO4 and NaOH)
No. Adding NaOH to K2HPO4 will not work. You need to make a 0.1M K2HPO4 solution and add HCl gradually and monitor pH until you reach pH7.4
Just a note: if you add HCl to K2HPO4, it will give you the desired pH, but you will not have just phosphate buffer; instead, you will have phosphate buffered saline, containing a significant amount of KCl. Using phosphoric acid instead of HCL will avoid this problem, but your final phosphate concentration will no longer be 0.1M. The best way is to mix a 0.1M solution of phosphoric acid with a 0.1M solution of K2HPO4 until you get the desired pH.
I have all NaH2PO4 and Na2HPO4 and NaCl. how to make standard PBS of pH 7.4?
Hi, Naimi,
This protocol might help: https://www.aatbio.com/resources/buffer-preparations-and-recipes/pbs-phosphate-buffered-saline
Hope this helps.
Best,
Arizaldo
Add 29.1 ml of 0.1 molar NaOH to 50 ml 0.1 molar potassium dihydrogen phosphate to obtain a pH=7 and the add the same NaOH gradually to ajust the pH to 7.4
Or to 100 ml of 0.1 molar (M) KH2PO4, add 78.2 ml of 0.1 M NaOH this way you get a value very close to pH =7.4
https://en.wikipedia.org/wiki/Phosphate-buffered_saline. please check this link, it may help. Thanks
http://www.drugfuture.com/Pharmacopoeia/EP7/DATA/40103E.PDF
A reference from EUROPEAN PHARMACOPOEIA 7.0
@Naimi Mostefa
In preparing Phosphate buffer solution with a pH = 7.4.
Add 250.0 mL of 0.2 M potassium dihydrogen phosphate R to
393.4 mL of 0.1 M sodium hydroxide.
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