Chromatography Forum

CPG, you had stop and go oscillations due to the lamp, yet there was enough light output during an oscillation phase to produce such large peaks as Conny sees them?

CPG, you had stop and go oscillations due to the lamp, yet there was enough light output during an oscillation phase to produce such large peaks as Conny sees them?

HB - in my case when I saw the oscillations in the baseline upon initial equilibration before starting the sequence, I didn't go further and inject any samples/standards. I fixed the problem.

I have also seen small oscillations which, when compared to the size of the sought-for peak, were negligible.

What I would like to know is, whether anybody has seen oscillations due to a dying lamp (not due to electrical interference, etc.) which still had enough light output to create huge absorbances (peaks). Also what would cause a dying lamp to oscillate in repetition?
Conny, don´t you have a new lamp? (The trouble is, by the time the new lamp is put in the air problem could have resolved itself).

Yes, I have had a lamp go intermittently bad on me while still producing enough power to generate peaks of interest. While the only chromatogram we've seen is during a run, we can consider that the chromatographer has run a 'flow-off' situation with similar events. The easiest solution is flushing the flow cell and re-evaluating the error, although I consider a bubble in the flow cell a rather unlikely occurence. Based on what I've seen, a lamp power fluctuation is the cause, and it is very easy to swap a lamp and re-evaluate a problem. If the problem "goes away" after swapping the lamp, it is a throw away excuse that the "air bubble" went away following the lamp replacement.

bisnettrj2, ok, I see that this has to be approached differently if I am not to go away from this discussion with another myth engrained in my head:
What was the S/N ratio of your "peaks of interest" during a bad phase of the lamp?
I still don´t know about the oscillations.