By Anonymous on Thursday, December 18, 2003 - 07:11 am:
Is it common for a UV detector to continually drift downwards when changed to a low wavelength (ie 190nm )- especially when it is nearing the end of its life? I am using C18 and water/mecn isocratically.
Thanks
By NV on Friday, December 19, 2003 - 06:19 am:
No, there is possiblity of response of analyte get lower.
Baseline Drift downwards due to following reason
1.Solvent used for mobile phase preparation
is not of HPLC Grade.
2.Mobile phase is not filter through 0.22 or 0.45
micron filter.
3.Column not equilibirate with mobile phase.
4.Lamp illumination is not reached to full
intensity.
5.Fluctuation in pump flow.
By bill tindall on Friday, December 19, 2003 - 04:38 pm:
I assume you mean the absorbance is becoming smaller with time. If this is the case, I would expect that something is getting cleaned out of the system that absorbs at 190. Have you pumped something else before switching to this analysis. It can take many hours to clean something like acetate out of a system so that its presence is undetectable at 190.
When the lamp is dyeing the siganl at 190 will often get noisy and death at 190 will likely occure way sooner that it will be a problem at 250 nm.