Chromatography Forum

I have an FPD detector on a 6890 Agilent gc, and the FPD signal seems to be too high, resulting in the results I am getting to be high. Any suggestions?

Thanks

Signal too high ?? Do you mean background ?
Which element are you looking at ? Sn, S or P ?

Starting with the basics , you do know if running Sulfur that the response is non linear ? It is possible to have a linearisation module for some systems (not sure about 6890) but most GC data systems will happily integrate using a non linear/quadratic curve

Check your filters as well. A longpass filter will let some things through, resulting in higher noise while the narrow bandpass filter would shut out anything unwanted. Of course this depends on what you're looking for. In addition, check your photomultiplier tube for water buildup.

Thank you for the responses. We are checking for Phosphorus compounds, and the output signal of the detector is higher than what it normally is. Normally the output signal is around 40 and it is at 55 now. I did not see any water build up in photomultiplier tube. I would not mind if the signal was high normally, but I thought maybe it could help explain our spike being higher than usual.

maybe your o-rings need replacement?

The o rings are brand new so that wouldn't be it. The air supplying the gc somewhat contaminated, and replacing that has helped but not solved it completely.

If an instrument is fed with contaminated gas or air it takes a while (sometimes for ever) for the plumbing to clean out after the feed contamination is resolved.

Peter