High frequency noise late in chromatograms

[QZ]

Hi All,

I am having recurring, intermittent, problems with high frequency noise showing up at later retention times (higher temps) in my chromatograms. I have also run through the temperature program without injecting a sample and I see the same behavior, so I don't believe it to be sample related. Could it be related to detector gas purity or transient leaks?

The time/temp at which the noise occurs varies a bit, but is always at least 5 minutes in.

Here are the conditions:

HP 5890GC
Rtx5 column (0.53mm, 0.3 um, 15m)
Injector 250C
FID at 350C
Ramp 25 C/min (start at 50C for 0.5 min)
Final temp 225C

Any thoughts on troubleshooting this vexing issue would be apprecaited.

Thanks.

[GasMan]

QZ

I would put my money on a leak which is dependent on temperature. To rule out detecor gases or detector problems, remove the column from the detector and cap off the detector inlet line. Leave the carrier gas running through your column, assuming that it is not hydrogen. Start a new run, and if you still have problems then it must be detector related.

[WK]

QZ
Do you run many samples one after the other? If so does the noise occur mainly in the first run?
You will get noise late on in the first run from material condensed on the column when it was left idle.