Chromatography Forum

I'm running method 8270 and just cleaned my source and replaced my column. Autotune and DFTPP tune look fine.
However when I recalibrated, the RFs for several basic compounds were extremely low at low concentrations.... For ex. Di-n-octyl phthalate has an RF of 0.371 at 2 ug/L and that jumps to almost 0.800 at 80 ug/L. Could it be column placement in the transfer line?

That wouldn't be impossible, but whenever I have low-end sensitivity problems I tend to suspect the inlet and the front of the column.

Depending upon the instrument, if the placement is a question you could verify by inspection (the Agilent 5973 and later models makes this pretty east). With the 5972s and 5971s, I've seen column broken off in the interface, so that when you slid the column in and then pulled it back a mm or so (at least how most folks handle this installation) you don;t end up with the column where you thought and have issues similar to what you're seeing.

Thanks for your reply. I am running a 5973, however its not every low mass compound that's ehibiting this behavior. Low weight acids (2-methylphenol, phenol) and PAHs are fine. Phthaltes, toluenes and anilines are my worst responders.