By David Batchelor on Thursday, May 20, 2004 - 07:36 pm:

I need to transfere a HPLC assay for a tripeptide (gly-pro-Glu) from a standard hplc with uv detection to an HPLC/MS method.
The current technique uses a acetonitrile/0.1%TFA gradient on a phenomenex aqua Synergi Hydro RP column. However when try to change the conditions to a MS compatable acid (acetic or formic) the GPE fails to bind. Does any on know or suggest an alternative stratgy.
Thanks

-------------------------------------------------------------------------------------------------------
By jean paul on Friday, May 28, 2004 - 09:30 am:

Maybe you can try an other type of column, read the example of glutathione in J Chromatogr B
STEGHENS JP., FLOURIE F., ARAB K., COLLOMBEL C.
Fast liquid chromatography-mass spectrometry glutathione measurement in whole blood: micromolar GSSG is a sample preparation artifact.
J Chromatogr B, 2003, 25, 798(2):343-9.

-------------------------------------------------------------------------------------------------------
By MG on Tuesday, June 1, 2004 - 06:36 am:

If you are using positive ion mode, the TFA may be okay, depending on the detection limit you need, but you will get more sensitivity with acetic or formic acid. I admit that I also try to avoid TFA use when possible. An alternative for retention of polar compounds is hydrophilic interaction chromatography (HILIC). Search the forum and you'll find several discussions of HILIC.