User:Madeleine Y. Bee/Notebook/Single Molecule Fluorescence/2013/05/30

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May 30, 2013

KP Buffer Calculations

Goal: Make a 0.05M buffer solution of KH2PO4 and K2HPO4 with a pH of 7.4
To be used in the Modifying Silica-Coated AuNP with thiol DNA procedure, detailed on 05/24/2013

  • KH2PO4 (base)
    • FW: 136.09g/mol
  • K2HPO4 (acid)
    • FW: 174.20g/mol
    • pKa: 6.82 (use pKa closest to desired pH since phosphoric acid has 3 pKa's-1 for each dissociation constant)


7.4=6.8+log([base]/[acid])
0.6=log([base]/[acid])
3.9811=[base]/[acid]

[base]+[acid]=0.05
[base]=0.05-[acid]

3.9811=(0.05-[acid])/[acid]
[acid](3.9811+1)=0.05
[acid]=0.01M
[base]=0.05-[acid]=0.04M

0.01M×174.2g/mol=1.7486g K2HPO4
0.04M×136.20g/mol=5.4436g KH2PO4
Make one liter of solution
Divide all quantities by two for half liter of solution



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