Citrate buffer without citric acid? - (Jun/13/2011 )

I want to make citrate buffer (pH 3.8). As I understand you need both trisodium citrate and citric acid to prepare this buffer. However we do not have citric acid on hand and I think in the past this buffer was prepared without citric acid. Do you really need citric acid? Wouldn't it be just as affective to pH with HCl?

The difficulty of using HCl is that you (in addition to your buffer) have also made salt from the sodium chloride formed. This may or may not be an issue in your application, but you should be aware of its presence.

Yeah, I thought about that! But the ionic strength in my experiments is already going to be quite high so I don't think a little extra should be a problem. Perhaps trying it both ways would give me more peace of mind...

as long as the addition of a little additional salt won't have an adverse effect on your system then you can take trisodium citrate and adjust the pH with acid. keep in mind that the citrate concentration will change with the addition of the acid so adjust the pH before bringing to final volume.