Chromatography Forum

Hello,

I've a 5890 ECD for organochlorine pesticides and PCBs, with a DB-35ms column, all the peak has good shape except for PCBs which has a big tail.
The column is properly installed because all the other peaks are good.

But, after the analysis of dirty samples the shape of the PCBs are very good. But when I cut column and clean the injector the tails are again.

The injection is 2 µL in splitless mode.

Thank, Javier Camino

Your problem is inlet passivation. After cleaning, particularly when reusing a liner, there can be a problem with exposing active sites on the liner wall, which can cause tailing. There are some things you can do about it though.

Resilanization of the liner, (requires some work and practice).

Preconditioning the system by repeated injection of high level standards to saturate the active sites. Try this to see if the tailing diminishes.

Select a different liner / and always use a new liner after inlet maintenance.
My favorite for splitless work is the SGE Focusliner. E-mail
chromatography@fisher.co.uk to try one for free.

(No I don't work for them)

If nothing else works you could run PCB on a 5-phase column which is less polar.