Negative peaks

[sarex]

Can anyone advise on why we get negative peaks on our solvent front with a reverse phase assay method when the sample solvent is mobile phase. Wavelength is 210nm and mobile phase is 0.4% THF, 1.0% Isopropyl Alcohol, 98.6% water plus TFA to pH 2.6
Is it the TFA that causes this problem ?.

Any hints would be appreciated. Thanks.

Sarex

[GoldLeader]

Sarex-
Log in to www.waters.com. On their home page search window type " HPLC Troubleshooting". The second result that comes up will be for their Information Center for a publication by Dr. Uwe Neue (#WA 20769). You can download the whole thing in pdf. There is a chapter in there taht describes your situation very closely. Hope it helps.
-Gold Leader

btw- I'm not associated with Waters in any way...