- 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
- Aqueous salt buffer
- 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|
- 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.