aged UV lamp

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7 posts Page 1 of 1
Hi,
I need your help.

i transfer a method to my lab and the S/N for the LOQ's of the two peaks i'm interesting in, are 3 and 8 respectively.The limit is 10.
I run in a Agilent 1260 DAD with max cell cartridge.
The UV lamp has 5000h.
Do you believe that if i change the lamp with a new one (i dont have one now), the limit is fisible?
The current PtoP noise is about 0.02 for this analysis, not too much for MeOH/H2O at 228nm.
I know nobody can tell for sure but i want your opinion.
Myself, i dont think that the noise will be sagnificant improved or the signal(height) of the peaks.

Help me for this one,

Thanks
What is your injection volume?

Is it possible the cell is dirty?

5000h is nearing the lifetime of the lamp, so if it is unsteady it could be introducing a little noise, if the peaks are small enough it could be a problem.

Are you using the background wavelength and if so how far above the 228 wavelength is it?

Another thing that can cause some noise is a bad degasser or slightly leaking check valve, any pulse in the flow can introduce noise.
The past is there to guide us into the future, not to dwell in.
Thanks for the answer,

I think the noise is ok for the circumstances.
i wonder if the new lamp will increase the signal, the height of my peaks.
New lamp will not increase the heights of the peaks. What detector was used for the method development? Using VWD instead of DAD can improve S/N. What about the peak broadening (plate number, tailing)? The higher the efficiency, the higher the peaks.
If you do a noise and drift test of the detector and it passes, then lamp is not likely to be the problem. In addition to try VWD in stead of DAD, you can also try premixing the mobile phases and not use the online mixing function of the pump.
Have you run an intensity test on the lamp?

One of out LCMS systems recently had bad looking UV data. Intensity test failed dismally (lamp was old) Put in new lamp and everything looked good again.
Most of the D2 lamps have a lifetime of 2,000 hours, not 5,000! You certainly need to run a proper intensity check and also wavelength calibration. That hour value sounds incorrect (someone may have forgotten to reset it last time they changed the bulb).

You also left out the signal bandwidth value for your 228 nm wavelength. Bandwidth values are just as important as the wavelength and w/o such basic info, it is not possible to compare signals.
7 posts Page 1 of 1

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