[kirsch]

Hello all,

Do buffers in 18 M-ohm water have any shelf-life issues?  In particular, I'm preparing several solutions of citrate+phosphate+TRIS (each solution will contain all three salts) and will adjust pH to various values using NaOH and HBr. 

I'd like to prepare these solutions a day or two before my experiment and leave them sitting in volumentric flasks.  Any issues with doing so?

thanks,

chris

[Arkcon]

As a general rule, buffer stored for a couple of days in sealed glassware will not change much.  But  it really does depend on your application, local environment, and the pH of the buffer.  If your application is sensitive to traces of ions, or traces of oxidation products, then you might see a difference after storage.  A very moist, humid climate can allow microbes to grow in buffer very rapidly, especially if the pH is close to neutral.  As a tip, measure and record the pH when you've prepped your buffer, then remeasure just before use, and record the result.  Try to see if there is a significant pH shift, over time, and adjust your storage to avoid it.

[kirsch]

very helpful--thanks!