25 mm HEPES/NH4OH (pH 8.0) - (Oct/02/2013 )

Hi, I want to make a buffer but I am not sure about the 25 mm HEPES/NH4OH (pH 8.0):

25 mm HEPES/NH4OH (pH 8.0), 20 mm KCl, 200 mm
NaCl, and 1% DMSO

I looked around for the a specific HEPES ammonia buffer but it is not available.  I am assuming that the buffer is made of 25 mM HEPES and 25mM NH4OH but I am not sure and I want to do it right.  Any ideas on how to make this 25 mm HEPES/NH4OH (pH 8.0)?

Thanks, FreddieP

I'd suggest that you start by making a 1 M HEPES NH4OH pH 8.0 solution. Then you can easily make your more complex buffer by using this stock solution.

To make 100 ml of the 1 M buffer, add 0.1 moles of HEPES to 70 ml of water. Add sufficient concentrated NH4OH to bring the pH to 8.0. The HEPES may not fully dissolve until you are near the correct pH.  Finally, bring the volume up to 100 ml.

To make 1 liter of your final solution, add 25 ml of your HEPES buffer, 20 ml of 1 M KCl, and 40 ml of 5 M NaCl, and bring the volume to 1 liter.

Great! that really helps alot. Thanks, FreddieP