Chromatography Forum

Ok, so here is my problem. My PFPD signal will max out after a full calibration (10 samples, 3 injections each) and will not return to normal noise conditions. I have checked all the settings/components that I can think of;
1) injection volume is 1 microliter
2) split is correct
3) calibration looks good
4) column is clean (ran calibration again after cleaning and replacing parts)
5) injection port is clean
6) detector housing is clean
7) voltages are good (I even tried changing them to no avail)

My first thought was that everything was just dirty, so I cleaned everything (injector/detector) and replaced consumables. Signal was still high.
Second thought was to replace the combustor. Signal returned to normal but after a new calibration with new standards, the signal maxed again and would not return.
It is not likely that I am injecting to high a concentration as I have done this calibration numerous times before without problems.

Any ideas?

Thanks.

It sounds as if when you refer to "signal" that you actually mean baseline - the signal is the peak height.

What is the composition of your calibration standards ?

What mode are you running ? sulfur ?, nitrogen, other ?

What GC is this on ?

What are all the temperatures, gas flows etc ?

Peter