Godin:Protocols/Buffer Solutions
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Materials
- Potassium Chloride (KCl) (BP366 - Fisher Scientific)
- MW = 74.55 g/mol
- Lithium Chloride (LiCl) (L121 - Fisher Scientific)
- MW 42.39 g/mol
- HEPES buffer (BP310 - Fisher Scientific)
- MW = 283.3 g/mol
- EDTA (431788 - Aldrich Chemistry)
- MW = 292.24 g/mol
- Potassium hydroxide (KOH) from Science Store
- MW = 56.11 g/mol
- HEPES (BP310 - Fisher Scientific)
- Filtered deionized water
- Vacuum filtration system (1 μm pore size)
- pH/conductance meter
Preparation
- Aqueous salt buffer (pH 8.0)
- Partially fill a clean receptacle to slightly less than the final desired volume.
- Measure out salt and buffer powder (and optionally 1 mM EDTA) and add to DI water (see table 1 below).
- Fill to final desired volume with DI water.
- Add magnetic stir bar and mix until completely dissolved.
- Bring the solution to the desired pH by adding 2 M KOH dropwise while monitoring with a pH meter.
- Obtain a conductance measurement.
Solution | Volume | Mass of salt (g) | Mass of buffer (g) | Mass EDTA (g) |
1 M KCl, 10 mM HEPES | 500 mL | 37.275 | 1.417 | 0.146 |
2 M KCl, 10 mM HEPES | 500 mL | 74.55 | 1.417 | 0.146 |
3 M KCl, 10 mM HEPES | 500 mL | 111.827 | 1.417 | 0.146 |
1 M LiCl, 10 mM HEPES | 500 mL | 21.197 | 1.417 | 0.146 |
3.6 M LiCl, 10 mM HEPES | 500 mL | 76.31 | 1.417 | 0.146 |
4 M LiCl, 10 mM HEPES | 500 mL | 84.788 | 1.417 | 0.146 |
*To make aqueous salt buffer - pH 10.0 "HEPES" should be replaced by "Sodium Bicarbonate (NaHCO3)". Fore this purpose 0.42 g should be added to 500 mL of the solution.
- 2 M KOH (100 mL)
The following should be performed in the fume hood wearing full PPE
- Measure 11.2220 g of KOH
- Add 100 mL of deionized water.