[rj1027]

I am working in a Bio-Chem lab right now and came across a problem all week. I was told to make AMS buffer and titrate it to a pH of 6.6 at 14C. Then I run it through a Toyo column for chromatography. (The column is in a fridge at 4 C). The eluent to come out needs to be  pH of 6.6 in order for us to load the column with our enzyme. So obvioulsy I bring the eluent back up to the conditions it was made at 14C. The pH is 6.6 but when i leave the eluent out for about 30 min, the pH drops to 6.48. Why? I know that pH is effected by Temp but by this much?

[Mitch]

Did you keep your buffer solutions sealed? If you didn't CO2 from the ambient air will dissolve into your sample and lower the pH.

[rj1027]

how much will ambient effect the pH?

[kevins]

What is the temperature of you measured for the buffer at 6.48?
What is the composition of AMS buffer ?
Have you condition the column before you pass the buffer?

[jdurg]

Did you keep your buffer solutions sealed? If you didn't CO2 from the ambient air will dissolve into your sample and lower the pH.

If it's a buffer solution, I don't think enough CO2 from the atmosphere could dissolve in the buffer to lower the pH by 0.12 points.  Especially since it's a buffer solution and carbonic acid is incredibly weak.