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
  1. Partially fill a clean receptacle to slightly less than the final desired volume.
  2. Measure out salt and buffer powder (and optionally 1 mM EDTA) and add to DI water (see table 1 below).
  3. Fill to final desired volume with DI water.
  4. Add magnetic stir bar and mix until completely dissolved.
  5. Bring the solution to the desired pH by adding 2 M KOH dropwise while monitoring with a pH meter.
  6. Obtain a conductance measurement.
Solution Volume Mass of salt (g) Mass of buffer (g) Mass EDTA (g)
1 M KCl, 10 mM HEPES500 mL37.2751.4170.146
2 M KCl, 10 mM HEPES500 mL74.551.4170.146
3 M KCl, 10 mM HEPES500 mL111.8271.4170.146
1 M LiCl, 10 mM HEPES500 mL21.1971.4170.146
3.6 M LiCl, 10 mM HEPES500 mL76.311.4170.146
4 M LiCl, 10 mM HEPES500 mL84.7881.4170.146
  • 2 M KOH (100 mL)

The following should be performed in the fume hood wearing full PPE

  1. Measure 11.2220 g of KOH
  2. Add 100 mL of deionized water.
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