Dear Ben,
You don't say in your note, but are you filtering your buffers (with
dedicated glassware)?
I encountered a triplet or quartet of peaks when I used 0.1% TFA buffers as
well as the TEAc buffers. I spent almost a month eliminating sources.
I tracked the ghost source to the disposable filter I was using for the
buffers. When I switched from nylon to polypropylene, I lost the peaks.
(One test is to send Buffer A through the same filter several times to see
whether an increase in the size of the ghost peaks results.)
You can also try filtering the ACN/H2O buffer first which might reduce the
amount of material extracted by the subsequent filtration of the no/low
organic buffer.
Good hunting.
Jim Farmar
MicroChemistry/NYBC