We've seen problems due to preservatives used in the commercial buffers used to calibrate the pH meter as well. It is usually something like a phenyl phenylate compound, which is very lipophilic. A way around that is to prepare your buffers from scratch by using pH buffer capsules. They're prepared in 100 mL organic free water and have to be remade about every 2-3 week before biological growth occurs.

Anything that touches any glassware that contacts the organic or the aqueous part of the mobile phase could bring in a contaminant.


Tom Waeghe
Agilent Technologies
thomas_waeghe@agilent.com